Effects of 10 Weeks of Periodized Resistance Training on Sarcopenia Classification in Older Women

Sarcopenia is defined as the progressive, age related loss of lean muscle mass, which in turn has been associated with osteoporosis, decreases in physical function, and loss of independence. Newly established sarcopenia classification criteria include measures of appendicular lean mass (ALM), grip strength, and gait speed. Periodized resistance training (PRT) has been investigated in older adults, however the impact of PRT, particularly daily undulating periodized resistance training (DUP) on current sarcopenia classification criteria is unknown. The aim of this randomized controlled trial was to investigate the effects of a 10-week DUP intervention on sarcopenia classification in older women. Inactive women (n=25) aged 72.3±4.6 years, who were sarcopenic or symptomatic, were randomized to a DUP group or an active control group (CON) and trained three days per week for 10 weeks. Measures of ALM, grip strength, and gait speed were recorded at baseline and post-intervention and sarcopenia was classified using established criteria. Other measures included upper and lower body strength, and global physical functioning. A McNemar’s test found no significant withinor between-group changes in sarcopenia classification. Mixed models analyses found both groups significantly improved gait speed (DUP: p=0.001, CON: p<0.001) but DUP significantly increased grip strength compared to CON (p=0.036). There were no significant changes in ALM for either group. Both groups significantly improved upper and lower body strength (p<0.001) and global physical function (DUP: p=0.039, CON: p=0.008). Results indicate DUP increases strength and function, but does not significantly alter sarcopenia classification compared to CON. However, results are limited by sample size and demonstrate the need for future research to investigate trials in larger samples with longer durations.


LIST OF TABLES
. Daily undulations of program variables Table 2. Baseline characteristics of participants Table 3. Baseline and post intervention changes in sarcopenia classification using different national and international sarcopenia classification criteria

INTRODUCTION
The aging process contributes to multiple changes within the human body including muscle fiber atrophy, a loss of type 2 muscle fibers, and fatty infiltration of skeletal muscle Kostek & Delmonico, 2011). Sarcopenia, known as the age-related loss of skeletal muscle mass, can negatively affect physical functioning and muscular strength. Indeed, following age 50 years, muscle mass decreases ~1-2% per year and muscle strength decreases at rates 2 to 5 times faster than muscle mass.
These decreases have been observed in both men and women of varying ethnicities Delmonico et al., 2009;Visser et al., 2005). The atrophy of skeletal muscle fibers and subsequent loss of muscle mass that occur during the development of sarcopenia coupled with rapidly decreasing muscular strength places older individuals at risk for injury and/or disability (Yang, Ding, Luo, Hao, & Dong, 2014).
Furthermore, the estimated healthcare costs directly associated with sarcopenia in 2000 were $18.5 billion, with more than $7 billion attributed to older women (Janssen, Shepard, Katzmarzyk, & Roubenoff, 2004). A greater percentage of the older population is female, and they are at a greater risk of developing sarcopenia because women live longer, typically have lower amounts of lean mass and lower physical activity levels in old age when compared to men (Administration on Aging, 2014; . Additionally, estimates indicate that there will be 80 million U.S. adults over the age of 65 by 2050, which is double the estimated 40 million adults in 2010 (US Department of Health & Human Services, 2006). The already significant health care costs, increased risk for older women and estimated population increases indicate that sarcopenia is a serious public health issue, and intervention strategies are necessary to attenuate the loss of physical functioning, lean mass and muscular strength in older women.
Current sarcopenia classification criteria have been established by the European Working Group on Sarcopenia in Older People (EWGSOP) , the International Working Group (IWG) , and the Foundation for the National Institutes of Health Sarcopenia Project (FNIHSP) . These criteria include diagnostic cut points for appendicular lean mass (ALM), gait speed (GS), and/or grip strength (GR), however cut-points do not agree between criteria. This lack of consensus between classification criteria may result in large variability in sarcopenia classification depending on the set of criteria used. That variation could result in inconsistent clinical classification of sarcopenia, the inability to compare research using different sets of classification criteria, and could lead to problems with identifying individuals for interventions.
Previously investigated treatment approaches for sarcopenia include diet and supplementation, hormonal therapies, and resistance training (RT) Katsanos et al., 2008;.
Resistance training has been previously documented as an effective method of increasing lean mass, strength, and physical functioning in post-menopausal women and appears to be the most promising treatment method for sarcopenia Peterson, Sen, & Gordon, 2011;. Despite previous research, the effects of RT on sarcopenia classification remain widely uninvestigated. Periodized resistance training (PRT) programs use pre-planned variations of acute training program variables (exercise selection, order, intensity, volume, and rest) and has been shown to be superior to conventional RT . A further subset of PRT is daily undulating periodization (DUP), which modifies program variables on a daily basis and has been shown to be superior to other forms of PRT . To date, DUP has not been investigated in older women who are sarcopenic or symptomatic and it is unclear if a DUP intervention would provide necessary increases in ALM, GS, and GR measures to alter sarcopenia classification by current criteria. Therefore, the primary aim of this study was to investigate the effects of DUP on sarcopenia classification in older women with sarcopenia or symptoms of sarcopenia. The secondary aim of this study was to evaluate the effects of DUP on individual measures of strength and global physical function.

Design
This study utilized a randomized controlled trial design among a cohort of 25 older, community dwelling women who met any component of sarcopenia classification criteria. The study evaluated the effects of a 10-week DUP intervention as a method of changing sarcopenia classification within the cohort. Secondary aims were to examine the effects of a 10-week DUP intervention on strength and physical functioning outcomes. Data were collected at four time points; baseline, mid-point, post intervention, and 6-months post intervention.

Participants and setting
Participants were recruited from the local community surrounding the University of Rhode Island through a variety of methods including posters, newspaper advertisements, talks at senior centers and community centers, and word of mouth.
All components of the study took place within the Kinesiology department at the University of Rhode Island, Kingston, Rhode Island, USA.

Screening for eligibility and enrollment
Initial screening was conducted via telephone interview to include women who were postmenopausal, aged 65-84 years, not involved in a regular exercise program, and met at least one component of either EWGSOP , IWG , or FNIHSP  sarcopenia classification criteria (i.e. low grip strength, low gait speed, etc.) Reasons for study exclusion included failure to provide informed consent, inability to speak and read English, significant cognitive impairment, and the inability to safely engage in a mild to moderate intensity exercise. Participants with recent major joint, vascular, abdominal or thoracic surgery were excluded, as well as participants who had physician diagnosed cardiovascular or pulmonary disease or an implanted pacemaker or defibrillator. Uncontrolled diabetes, blood pressure, or anemia was reason for exclusion as were any medication changes within three weeks or changes to lipid lowering medication within six months.
Following the telephone interview, initially eligible participants visited the University of Rhode Island for an information session and a question and answer session with primary investigators. Participants then provided written informed consent and a teach-back process was also employed to ensure that participants understood the consent form. Participants then completed a four-meter gait speed test, a handgrip strength test, a single chair stand test and a body composition test using an InBody 570 multi-frequency bioelectrical impedance analysis (BIA) device (Biospace Co, Ltd, Korea). Participants' ALM, GS, and GR data were then evaluated using EWGSOP, IWG, and FNISHP criteria to determine sarcopenia status. The primary investigators then reviewed participants based on inclusion and exclusion criteria and sarcopenia status and determined study eligibility. All participants selected to participate in the study obtained pre-participation medical clearance from their physician. This study was approved by the Institutional Review Board of the University of Rhode Island.

Periodized Daily Undulating Resistance Training Intervention
Participants in the periodized daily undulating resistance training intervention (DUP) group followed a program designed to target the entire body and trained three non-consecutive days per week for 45 minutes per session. The training program incorporated exercises that progressed in complexity (e.g. leg press to deadlifts) and included the use of selectorized RT equipment and free weights. This program modified program variables on daily basis and incorporated periods of low intensity work in an attempt to maintain participant interest in the program and prevent overtraining. Higher intensity periods were also programmed to stimulate increases in muscular strength and hypertrophy. A depiction of the daily program variations is presented in Table 1. Participants began every training session with a dynamic warmup and finished every session with a stretching cool down session. National Strength and Conditioning Association Certified Strength and Conditioning Specialists instructed and supervised all training sessions.

Active Control Group
The active control group (CON) underwent identical screening and testing processes as the DUP group; however, during the 10-week intervention this group met three times per week for 45 minutes per session and completed a program composed of exercises ranging from light to vigorous intensities (stretching, Tai Chi, aerobics, calisthenics). Through the combination of warm up, moderate and vigorous intensity activity, and cool down the program approached the 150 minutes per week of moderate intensity physical activity for adults recommended by the ACSM (American College of Sports Medicine, 2009). These activities, while beneficial to overall health, have not been shown to produce adaptations similar to those experienced in RT. This style of control group was implemented to potentially reduce attrition and to provide a benefit for the "control" group.

Measures
The primary outcome measure was sarcopenia classification. Secondary outcome measures were body composition, chest, leg and grip strength, and global physical functioning. Sarcopenia classification was conducted at baseline and postintervention. Secondary measures were assessed at four time points: baseline, 5-weeks, post intervention, and 6-months post intervention. All testing was conducted during the same time of day for all time points.

Anthropometrics
Height was measured to the nearest 0.1 cm without shoes using a Seca wall mounted stadiometer and body weight was measured to the nearest 0.1 kg using a Seca balance beam scale (Seca, Chino, CA). Both height and weight were measured in duplicate and the averages were used to calculate body mass index (BMI).

Body Composition
Overall body composition was estimated using dual-energy x-ray absorptiometry (DXA) using fan-beam technology on a GE Lunar iDXA machine (GE, Waukesha, WI). Participants reported to testing in a fasted state (~12 hours) and wore surgical scrubs during the test. Standardized positioning procedures were followed and a licensed radiology technician performed all tests . Appendicular lean mass, total body fat mass, and percent fat were measured. Appendicular lean mass was considered the sum of non-bone lean mass in both arms and legs. Total body lean mass was defined as lean soft tissue mass plus total body bone mineral content.

Physical Functioning
Physical functioning was measured using several low burden tests. The Established Populations for Epidemiologic Studies of the Elderly short physical performance battery (SPPB) includes a standing balance test, a four-meter gait usual speed test, and timed five-chair stand test, and was conducted to assess each participant's global physical functioning (Guralnik et al., 1994). The best gait speed score measured in the SPPB was used for sarcopenia classification.
To further evaluate physical functioning participants completed a 400-meter walk test, which is a valid and reproducible measure of physical functioning (Simonsick, Montgomery, Newman, Bauer, & Harris, 2001). Participants also completed a timed up and go (TUG) test to measure physical functioning and mobility (Whitney, Lord, & Close, 2005). The TUG test was conducted according to standardized protocol; participants were asked to rise from a 46-cm high chair, walk forward eight feet at their usual walking pace, turn 180° around a cone, walk back to the chair and sit down. Measures were taken in duplicate, with the best score recorded.

Grip Strength
Grip strength is a simple, safe, and effective method of predicting total body strength and future disability (Laukkanen, Heikkinen, & Kauppinen, 1995;. Handgrip strength was measured in both hands with the participant in a seated position using a handgrip dynamometer and standardized protocols (Jamar Hydraulic Dynamometer, J.A. Preston, Corp., Jackson, MS) (Bellace, Healy, Besser, Byron, & Hohman, 2000). Two trials per hand were completed and the highest score measured was used for sarcopenia classification.

Muscle Strength
All participants completed a familiarization with leg press and chest press machines one week prior to strength testing. The familiarization included a dynamic warm-up, determination of proper seat and handle positions and instructions regarding proper exercise and breathing technique. Participants then completed a set of 3-5 repetitions on each machine using a load determined by the participant to be comfortable, then a second set of 3-5 repetitions at an increased intensity, followed by 1-3 sets of progressively increasing intensity until the participant reached 80-90% of their maximal effort as rated on the Borg CR-10 scale (Borg, 1998).
Maximal leg press and chest press strength were assessed using previously published methods on Cybex seated leg press and chest press machines (Cybex International Inc., Medway, MA) LeBrasseur, Bhasin, Miciek, & Storer, 2008). Participants completed a dynamic warm-up prior to strength testing. The leg press test required the participant to extend their knees from a starting position of ~90 degrees until the legs are fully extended, but not locked at the knees.
The chest press test required the participant hold on to handles perpendicular to the chest, located at the height of the sternum and extended their elbows completely and return to the starting position in a controlled manner. Participants followed a standard strength testing protocol and were given three minute rest periods between attempts .

Sarcopenia Classification
Following baseline testing, anthropometric, gait speed, grip strength, and ALM data were used to determine sarcopenia classification by EWGSOP , IWG , and FNIHSP  criteria published previously. Following post-intervention testing, participants were reevaluated by the same classification criteria to determine any within group or between group changes in sarcopenia status as a result of the intervention.

Nutritional Risk
The Dietary Screening Tool (DST) was used to assess the participants' nutritional risk. The DST is a valid and reliable measure of dietary quality among older community-dwelling adults (Bailey et al., 2009). Based on DST scores (0-100) participants were categorized based on nutritional risk levels: at risk (<60), possible risk (60-75), and not at risk (>75).

Sample Size
Between-group changes for the primary outcome variable of sarcopenia classification were estimated to calculate sample size. Data from Mason et al. (2013) were adjusted to reflect the duration of our study. Those estimates indicated an expected between group difference in sarcopenia classification of 1.41±1% following a 10-week intervention. Based on those estimations, a minimum of 10 participants per group was required to provide sufficient statistical power (0.80) to measure between group changes in sarcopenia classification.

Randomization
Following the completion of baseline testing participants were randomized into a resistance training intervention group (RTI) or a control group (CON) using a random number generator using Random Allocation Software (Isfahan University of Medical Sciences, Isfahan, Iran).

Statistical Analysis
Continuous variables for primary and secondary outcomes were assessed for normality using Shapiro-Wilk tests. Outliers were identified using box plots and Tukey's method. Any influential outliers were excluded from analyses. Baseline characteristics were reported using descriptive statistics presented as means ± standard deviation. Due to the paired nature of the data, changes in sarcopenia classification between groups were measured using McNemar's tests. Within and between group changes for all continuous variables were measured using mixed models analyses.
Attrition rate was reported using descriptive statistics. The alpha was set at p<0.05 for all analyses. Analyses were performed using SAS version 9.3 (SAS Institute Inc, Cary, NC).

RESULTS
A total of 160 participants were initially screened for study inclusion, 61 participants signed informed consent and underwent secondary screening, and 25 Caucasian women aged 72.3±4.6 years met all inclusion and exclusion criteria and were enrolled in the study ( Figure 1). All data points determined to be outliers did not influence significance, and were included in analyses. The baseline physical characteristics of the participants are shown in Table 2. There were no changes in nutritional risk measured by the DST. As shown in Table 3, there were no significant within or between group changes in sarcopenia classification, by any set of criteria.
Participants in DUP experienced reversals in sarcopenia classification by IWG (n=1) and FNIHSP (n=2) criteria. One participant in DUP also transitioned from sarcopenia to pre-sarcopenia by EWGSOP criteria. The two changes in FNIHSP and one change EWGSOP classification were due to improvements in grip strength by the participants.
The one change by IWG criteria was due to an improvement in gait speed. Participants in CON experienced reversals in sarcopenia classification by EWGSOP (n=1) and IWG (n=2) criteria. The two participants who reversed their IWG classification did so by improvements in gait speed. Those same two participants were also considered sarcopenic by EWGSOP criteria at baseline, and maintained that classification post intervention. The one participant who reversed their EWGSOP sarcopenia classification did so by improvements in ALM/ht 2 . No participants in CON met FNIHSP criteria at baseline or post-intervention. Table 4, both DUP (p<0.001) and CON (p>0.001) showed significant improvements in gait speed, and chest and leg press strength. Post intervention both DUP (p=0.001) and CON (p=0.046) experienced significant improvements in 400-meter walk time. Post intervention DUP also showed a mean increase in grip strength of 2.45 kilograms, which was significantly greater than CON (p=0.024).

DISCUSSION
These results present, for the first time, the effects of a 10-week periodized daily undulating resistance training intervention on sarcopenia classification in postmenopausal women who presented with sarcopenia or symptoms of sarcopenia based on newly established classification criteria. Our results indicate that when compared to an active control group, 10-weeks of DUP does not elicit significant changes in sarcopenia classification within a sample of older, post-menopausal women.
However, these results support the use DUP as a method of increasing muscular strength and physical functioning. Moreover, when compared to an active control group, DUP will significantly increase grip strength in older sarcopenic women.
Although our primary hypothesis was not supported, we present findings that indicate 10 weeks of DUP or general exercise can significantly increase upper and lower body strength and physical functioning in older women with sarcopenia or symptoms of sarcopenia.
Other research investigating interventions for sarcopenia includes that of Mason et al. (2013), who investigated the effects of 12-months of aerobic exercise in 76 post-menopausal women classified as sarcopenic using IWG lean mass cut points.
Although those results were significant, they are quite small, and indicate that regular aerobic training can attenuate further loss of lean mass, but not increase ALM over time. Additionally, the women in that study did not undergo physical function testing, therefore the assessment of sarcopenia was not by full IWG criteria. Nonetheless, our results agree with those of Mason et al. (2013) suggesting that regular physical activity could be beneficial for lean mass maintenance in those who are not sarcopenic.
However, in older women with sarcopenia, treatments other than aerobic exercise are likely required to increase lean mass to the point of reversing sarcopenia classification.
Additionally, a recent study by Hassan et al. (2016) investigated the effects of six months of RT on sarcopenia classification in 42 adults aged 85.9±7.5 years, living in nursing homes. Sarcopenia was classified using EWGSOP criteria and post-intervention there were no changes in sarcopenia classification in the intervention group. That study also found significant increases in grip strength in their intervention group compared to the control group (p=0.002). Our results are similar to those of Hassan et al. (2016), as we did not find any significant changes in sarcopenia classification post-intervention. However, that study only had six participants considered sarcopenic at baseline compared to our five participants in the DUP group who met EWGSOP criteria at baseline. While our findings agree that RT is effective at slowing the progression of sarcopenia, we also present the findings that 10-weeks of general exercise attenuates the loss of ALM. However, our results and those of Furthermore our findings indicate that increases in muscular strength, as measured by grip strength, were primarily responsible for changes in classification in the DUP group. While improvements in physical function, measured by gait speed, were responsible for the majority of changes in classification by the CON group.
These results suggest that DUP or general exercise can improve sarcopenia classification, albeit through different channels. Our results also align with the recent findings of  who found that a sample of 23 older women experienced significant increases in gait speed following eight weeks of RT. The novel finding of that study was that the improvements in gait speed were associated with increases in lower body muscular strength and not muscle mass. Our results corroborate those findings as both the DUP and CON group experienced significant increases in both leg press strength and gait speed, while maintaining baseline levels of lean mass. Our results present the new findings that DUP is a viable method of increasing gait speed and grip strength, independent of lean mass gains, and contributes to the body of literature regarding treatment methods for sarcopenia.
The unexpected strength increases of the CON group may be explained by  who found that 12 weeks of aerobic training produced a significant (p<0.05) 55±7% increase in knee extensor power compared to baseline measures in a sample of seven older women aged 71±2 years. A further study by Konopka et al. (2010) found that following 12 weeks of aerobic training a sample of nine older women maintained their overall body mass levels, and experienced small (0.5 kg) but significant increases in lean body mass. Furthermore, those researchers also found that following training participants had significantly lower levels of myostatin mRNA expression, which they hypothesized, was partially responsible for the increases in lean mass. While the mechanisms of myostatin expression in relation to aging are not completely understood, research has shown that inhibition of myostatin can lead to increases in lean mass in post-menopausal women (Attie et al., 2013;White & LeBrasseur, 2014). While Konopka et al. (2010) had a relatively small sample size, the finding of decreased myostatin expression following aerobic exercise may partially explain the maintenance of lean mass in our CON group and present a possible avenue for future research investigating myostatin suppression and its effects on sarcopenia.
Furthermore, our results suggest that the FNIHSP criteria is more conservative with sarcopenia classification than the EWGSOP and IWG criteria. The EWGSOP and IWG criteria classified a combined 14 participants as sarcopenic at baseline, while the FNIHSP criteria only found two DUP participants to be weak with low lean mass at baseline. Interestingly, both participants that met FNIHSP criteria had BMIs >30, which is consistent with the results of  who found individuals who met FNIHSP criteria to be heavier with larger BMIs compared to those who met EWGSOP or IWG criteria. Consequently, the FNIHSP criteria may be more appropriate for obese populations, while the EWGSOP and IWG criteria identify more individuals as sarcopenic and may be better suited for those with BMIs <30.
Considering the maintenance of ALM experienced by both groups, future research should investigate the potential effects of interdisciplinary interventions on sarcopenia classification, particularly the combined effects of DUP and a diet or supplementation intervention. A recent study by Bauer et al. (2015) found that after 13 weeks of whey protein and vitamin D supplementation, older, sarcopenic men and women experienced significant (p=0.045) increases in ALM when compared to a control group. Moreover, Cangussu et al. (2015) found that older, post-menopausal women who supplemented with vitamin D experienced significant (p<0.0001) improvements in chair stand tests compared to a control group. Based on those results, supplementation could provide older sarcopenic women with significant increases in ALM and physical function. Supplement induced increases in ALM combined with DUP induced increases in strength and physical function could present a strong method of altering sarcopenia classification in older women.
This pilot study has demonstrated the feasibility of delivering a 10-week DUP intervention to a group of older, post-menopausal women who had sarcopenia or symptoms of sarcopenia at baseline. Additionally this study had high external validity, as the RT equipment used is common among most fitness centers, and training three days per week is a feasible task for older adults. Attendance for the DUP group averaged 85.2±7.8%, while the CON group averaged 82.6±7.2%.
Additionally, only three participants were lost to follow up (12% attrition). This indicates that it is feasible and safe to deliver a three-day per week, DUP intervention to older sarcopenic women without any injury or undue attrition.
This study had several limitations including sample size and intervention duration. Having a sample size of 25 participants limited our ability to measure between group differences and gauge the success of the intervention. The cohort was also 100% Caucasian, which enhances the applicability of results to that population, but limits applicability of results to those of differing race. Furthermore, only seven participants in each group met sarcopenia classification criteria at baseline. The small exposure to cases of sarcopenia may have limited the ability to measure changes in sarcopenia classification, which was also a limitation of Hassan et al. (2016).
Additionally, the use of an active control group may have influenced the results of

CON. However in an invited commentary Booth & Lees contend that interventions
investigating exercise should include active control participants rather than traditional sedentary controls (Booth & Lees, 2006). Moreover, the intervention duration of 10weeks may have impacted our ability to observe lean mass increases that would alter sarcopenia classification, as research indicates that muscle hypertrophy typically begins 6-8 weeks after onset of training, which limited the amount of time for measureable hypertrophy to occur (Deschenes & Kraemer, 2002). However, previous studies have experienced significant increases in lean mass in 8 and 10 weeks, albeit in larger samples, indicating the potential for measurable hypertrophy in shorter duration interventions . Future research should seek to investigate longer duration DUP interventions in larger samples of older women with higher prevalence's of sarcopenia at baseline. Nonetheless, our results indicate that 10-weeks of DUP improved strength and physical function, and attenuated the age related loss of muscle mass in this sample.

CONCLUSION
In conclusion, this study presents novel new information regarding the use and feasibility of DUP as a potential treatment for sarcopenia in older, post-menopausal women. Our results indicate that through either general exercise or DUP, older women with sarcopenia or symptoms of sarcopenia can significantly increase their strength and physical functioning. Although, to garner maximum strength benefits older women should engage in DUP rather than general exercise. These results provide a new substrate from which future research can build upon to further investigate which forms of treatment provide the greatest change in sarcopenia classification in older women.    Table 3. Baseline and post intervention changes in sarcopenia classification using different national and international sarcopenia classification criteria.

Introduction
The term sarcopenia, originally coined in 1989 by Dr. Irwin Rosenberg, originates from the Greek language and translates to "poverty of the flesh" (Rosenberg, 1989). Sarcopenia has been reported as a global public health problem, and results in a gradual, age-accelerated loss of skeletal muscle mass, which can negatively affect physical functioning and muscular strength (Chen et al., 2014;Cherin, Voronska, Fraoucene, & de Jaeger, 2014;Cruz-Jentoft et al., 2014;Diz et al., 2016;W. Kemmler et al., 2015;Tichet et al., 2008). While sarcopenia is related to aging, several mechanisms are associated with this multifactorial process. Factors including decreased levels of physical activity, hormonal changes, altered nervous system activity, muscle fiber atrophy, loss of type 2 muscle fibers, and fatty infiltration of skeletal muscle all contribute to the accelerated loss of skeletal muscle Karakelides & Nair, 2005;Kostek & Delmonico, 2011). Following age 50 muscle mass decreases at a rate of 1-2% per year . Evidence suggests this progressive muscular atrophy contributes to rapid declines in muscle strength, power, and physical function; placing older individuals at risk for injury and/or disability Choi, 2013;Visser et al., 2005;Yang, Ding, Luo, Hao, & Dong, 2014).
Furthermore, Jannssen et al. (2004) estimated that the healthcare costs directly associated with sarcopenia in 2000 were $18.5 billion, with more than $7 billion attributed to older women. Those estimates, coupled with the projected increase in the older population indicate that appropriate diagnostic and treatment strategies need to be developed in order to combat sarcopenia in older adults (Administration on Aging, 2014). Moreover, women typically live longer than men and therefore may have an increased risk of functional impairment as they age (Barford, Dorling, Davey Smith, & Shaw, 2006;. Periodized resistance training (PRT) is a form of RT program design that has elicited greater performance gains when compared to traditional RT programming (Kraemer et al., 2003;Monteiro et al., 2009;O'bryant, Byrd, & Stone, 1988). While RT in older adults has been researched previously, no study has investigated if an intervention using a specific form of PRT: daily undulating periodized resistance training (DUP), would elicit changes in sarcopenia classification in older women considered sarcopenic by current criteria.

Sarcopenia in Older Women
Recent population estimates indicate a greater percentage of the older population is female, and they have a longer life expectancy and are at a greater risk of physical disability compared to men (Administration on Aging, 2014; Carrière et al., 2005). Additionally, compared to men, women typically have lower amounts of lean mass and lower levels of physical activity in old age, resulting in an increased risk of developing sarcopenia . As shown in a study by , 67% of women over the age of 50 are not active enough to achieve a reduction in chronic disease risk. Moreover, hormonal changes due to menopause result in decreases in lean mass accompanied by increases in fat mass, independent of age Orsatti et al., 2016). While men also experience decreases in testosterone that contribute to losses of muscle mass, women begin to experience changes in estrogen up to 10 years prior to the onset of menopause, contributing to pre-menopausal declines in muscle mass, bone mass, and strength (Brown, 2008;Burger, Hale, Robertson, & Dennerstein, 2007;Delmonico & Beck, 2015). Due to the increased risk of sarcopenia in older women detection and intervention strategies are critical to prevent and treat sarcopenia in this population.
In a study assessing 18,913 older U.S. and English men and women, U.S. women experienced the steepest decline in measures of activities of daily living and physical function when compared to other study participants at eight years of follow up (Bendayan et al., 2016). Those researchers also determined that activities incorporating climbing stairs, kneeling down, or crouching were the first to decline among their cohort. That study indicates that as women in the U.S. age, they will likely experience declines in the ability to perform activities of daily living, therefore treatment strategies are necessary to regain physical function in older women.
Sarcopenia has also been associated with an increased risk of all-cause mortality. A recent meta-analysis by Chang & Lin (2016) analyzed 10 longitudinal studies with 3,797 men and women with an average follow up of 4.17 years.
Sarcopenia was classified using three different sets of criteria including EWGSOP criteria. With non-sarcopenic participants considered the referent group there was there was a significantly increased risk of all-cause mortality in those considered to have sarcopenia (HR:1.87, 95% CI: 1.61-2.18). The finding that sarcopenia increased the risk of all-cause mortality underscores the impact of sarcopenia in older adults.
Therefore, prevention and treatment of this condition is necessary in this population.
The body of evidence within the literature indicates that sarcopenia is a significant public health issue, especially in older women. As the population over 65 grows, it can be inferred that the prevalence of sarcopenia, the risk of all cause mortality, and healthcare expenses within this population will also increase. Therefore it is imperative that intervention strategies be developed to help attenuate the loss of physical functioning, lean mass and muscular strength in older women.

Dynapenia vs Sarcopenia
Dynapenia, in contrast to sarcopenia, is defined as the age related loss of muscular strength that is not associated with any neurological or muscular disease (Clark & Manini, 2012;Mitchell et al., 2015). Dynapenia is distinct from sarcopenia, however these two conditions are similar as research indicates that muscular strength and muscle mass are closely related (Clark & Manini, 2008;Reed, Pearlmutter, Yochum, Meredith, & Mooradian, 1991). Similar to sarcopenia, dynapenia is a multifactorial process influenced by changes to the nervous system and the muscular system. Clark & Manini (2008) argue that decreased strength (dynapenia) may have a greater influence on physical functioning in older individuals than decreased muscle mass (sarcopenia). Those researchers contend that future research should focus on methods of preventing the loss of strength rather than muscle mass. However, the term sarcopenia is more widely recognized within the literature than dynapenia, and current sarcopenia classification criteria include measures of muscular strength.
Furthermore, current criteria have been developed to be comprehensive clinical assessments, as individual diagnoses of low mass or low strength may be of limited clinical value Delmonico & Beck, 2015). Clark & Manini (2008) clearly demonstrate that muscular strength is vital to maintaining physical function and completing activities of daily living. While there are various methods of assessing muscular strength in older individuals, few are as easy and portable to assess as grip strength. Isometric handgrip strength is related to lower body power and has also been shown to be a valid clinical marker of mobility (Lauretani et al., 2003). Additionally, research has shown a linear relationship between handgrip strength and future disability for activities of daily living (Al Snih, Markides, Ottenbacher, & Raji, 2004). Due to the ease, affordability, and validity of this measure, handgrip strength is present in some sarcopenia classification criteria.
However, this measure is not without limitations. Despite being a valid predictor of total body strength and future disability, grip strength may not be a valid measure for older individuals with hand ailments such as arthritis (Erol, Ceceli, Uysal Ramadan, & Borman, 2016;.

Importance of Gait Speed
Ambulation is a vital component of activities of daily living and its importance in overall physical functioning cannot be understated. Indeed some researchers suggest that gait speed should be considered the "sixth vital sign" and assessed clinically along with breathing, temperature, heart rate, pain, and color (Fritz & Lusardi, 2009). A study by Studenski et al. (2011) examining gait speed and survival in 34,485 older adults found that lower levels of gait speed were associated with increased risk of mortality. Additionally, those researchers determined an overall hazard ratio of 0.88 (95% CI: 0.87-0.90) for each 0.1-meter per second (m/s) increase in gait speed. The results of that study suggest that older adults with poor gait speed and therefore reduced physical function are at a greater risk of all-cause mortality.
Gait speed is also easy and inexpensive to measure, with the only requirements being a stopwatch and a pre-measured distance. Test distances for gait speed have varied from 2 to 40 meters in length, however for patient and clinician practicality and feasibility, it is recommended that tests not exceed 10 meters in distance (Middleton, Fritz, & Lusardi, 2015). While protocols for specific tests may vary, gait speed tests are a validated method of assessing overall physical function in older adults.
Considering the immense importance of gait speed in relation to physical function and mortality including this measure in routine medical assessments would allow clinicians to monitor gait speed trajectory and determine if an individual's gait speed is improving or deteriorating.
Consequently, while the term sarcopenia by definition refers to the age related loss of muscle mass; some current sarcopenia classification criteria include measures of muscle mass, strength, and physical function. These criteria allow for a more comprehensive evaluation of individuals' overall health and physical function and may be beneficial for the detection of functional impairment in older individuals, regardless of the underlying mechanism or terminology.

Sarcopenia Classification
Researchers have faced difficulties designing and justifying interventions strategies for older adults with sarcopenia in part due to the lack of consensus definition/diagnostic criteria for sarcopenia and inability to compare results of different studies (Cruz-Jentoft et al., 2014). In addition, sarcopenia lacks significant clinical endpoints (e.g. fracture risk for osteoporosis), making it difficult to pinpoint the onset of the condition . One of the earliest and most common methods of sarcopenia diagnosis is the skeletal muscle index (SMI) method (Baumgartner, Waters, Gallagher, Morley, & Garry, 1999). The SMI method is calculated by dividing ALM in kilograms by height in meters squared (kg/m 2 ), where ALM is measured via dual energy x-ray absorptiometry (DXA), and considered the sum of non-bone lean mass in both arms and legs. Baumgartner et al. (1998) first used the SMI method in the New Mexico Aging Process study. That study classified sarcopenia in an older population using sex specific SMI cut points that were two standard deviations below the mean SMI of a healthy young adult population from the Rosetta Study (Baumgartner et al., 1998;Gallagher et al., 1997). The inclusion of height in the SMI is beneficial as taller individuals often have more ALM. Indeed, further data from the New Mexico Aging Process Study showed that 38% of the variance in muscle mass measurements in older women was attributable to height differences, which demonstrates the need to account for skeletal size when assessing lean mass (Baumgartner et al., 1999).
Although the SMI method accounts for height and can be used with sex specific cut points, it is limited in that it doesn't account for fat mass and may fail to classify obese individuals as sarcopenic. This became evident when two separate studies analyzed data from the Health, Aging, and Body Composition (Health ABC) study. The first study by Newman et al. (2003) included data from 2,984 men and women aged 70-79 years. That study used two different methods of classifying sarcopenia in their cohort: the SMI method and a proposed new method of classifying sarcopenia using linear regression residuals. However in their use of the SMI method they did not compare participant data to that of a healthy reference population as Baumgartner et al. (1998) did, rather a participant was considered sarcopenic is their SMI value fell below the 20 th percentile of the sex-specific distribution of values within the Health ABC cohort. The residuals method also uses ALM in its sarcopenia classification however this method also accounts for fat mass. In order for those researchers to model the relationship between fat mass, height, and ALM, a linear regression was performed. The residuals of this regression were then used to determine sarcopenia classification. Any participant who fell below the 20 th percentile of the residuals of the Health ABC cohort was considered sarcopenic. This allowed for direct comparison with the SMI method using the 20 th percentile cut point.
The results of Newman et al.'s (2003) investigation indicated that when applying the SMI method to overweight and obese women 0.8% and 0%, respectively, of the population was considered sarcopenic. Conversely, the residuals method reported 21.7% and 21% sarcopenia prevalence's in overweight and obese women respectively. Furthermore, when assessed using the residuals method, women had higher adjusted odds of lower extremity functional limitation (OR: 1.9, 95% CI: 1.4-2.5), than when they were assessed with the SMI method (OR: 0.9, 95% CI: 0.7-1.2).
The second study using Health ABC data by Delmonico et al. (2007) included a sample of 2,976 older men and women aged 70-79 at baseline. Participant data were assessed using the SMI method and the 20 th percentile of the Health ABC population cut point and the 20 th percentile of linear regression residuals cut point. Those researchers found that after five years of follow up the residuals method predicted increased risk of lower extremity limitation (HR: 1.34, 95% CI: 1.11-1.61) while the SMI method initially predicted improvement in lower extremity (HR: 0.58, 95% CI: 0.48-0.72). However after adjustment for confounders including age, race, physical activity, and total body fat mass, the SMI results appeared to insignificantly predict future functional limitation (HR: 1.04, 95% CI: 0.82-1.31).
Those results demonstrate the limitations of using the SMI method to classify sarcopenia, especially in populations with a high prevalence of overweight and/or obese individuals. This also demonstrates the importance of including measures such as fat mass or percent body fat into classification criteria, and that the residuals method may offer better prediction of future incidence of functional limitations (Delmonico et al., 2007;Newman et al., 2003). Despite those findings some current They also include 20 th percentile cut points for the residuals method. To be considered pre-sarcopenic one must score below one of the established lean mass cut points presented in their criteria. In order to be considered sarcopenic one must score below the cut point for ALM and gait speed (<0.8 m/s), or grip strength (<20 kg). A severe sarcopenia classification would require one to score below the cut points for gait speed, grip strength, and ALM. Although they state that they have reached a consensus agreement on proper sarcopenia classification criteria, the EWGSOP includes various different methodologies of evaluating and quantifying lean mass, strength, and physical functioning. This does not appear to be true consensus criteria, rather a list of multiple suggested methodologies and cut points that can used to screen for sarcopenia. Nonetheless, the EWGSOP criteria are widely featured among the  (Bahat et al., 2016;Beaudart et al., 2014;Masanés et al., 2016;Patel et al., 2015;Wen, An, Chen, Lv, & Fu, 2015).
In contrast, the IWG criteria use a "yes" or "no" sarcopenia classification. To receive a "yes" classification one must score below a SMI cut point of 5.67 kg/m 2 and below a gait speed cut point of 1.0 m/s. The IWG also suggests the use of a single chair stand as an indicator of overall strength. While the chair stand is not included in the "yes" or "no" classification criteria it may be more indicative of overall strength and the ability to complete activities of daily living than grip strength alone (Delmonico & Beck, 2015;). There appears to be less variation in how to use the IWG criteria, as for women there is only one cut point for ALM and one cut point for gait speed. Interestingly, the SMI cut point of 5.67 kg/m 2 is the same cut point developed by Delmonico (2007) and Newman (2003) that represents the SMI of the lowest 20% of the Health ABC cohort.
The FNISHP criteria use a somewhat different method of stratifying sarcopenia classification. Those criteria use "weak with low lean mass" and "weak and slow with low lean mass" to classify sarcopenia. Those criteria also utilize a different variable to quantify lean mass: ALM divided by body mass index (BMI). stage, and that criteria has been shown to classify greater percentages of populations as sarcopenic than IWG or FNIHSP criteria . However the FNIHSP criteria has been shown to classify a greater percentage of obese participants as "weak with low lean mass" than other criteria, suggesting the adjustment of ALM by BMI may be an ideal method of classifying sarcopenia in overweight and obese populations .

Treatment for Sarcopenia
There are several treatment approaches available for sarcopenia. Treatments should focus around methods of maintaining or improving lean mass, physical functioning, and strength levels. The most common treatment methods include hormonal therapies, diet and supplementation approaches, physical activity, and RT.

Hormonal Treatments
Hormonal treatments for sarcopenia have been researched in males and females . The two most common therapies are testosterone and estrogen for males and females respectively. While some research indicates potential side effects, the market for testosterone replacement therapy is flourishing and it should be considered as a viable treatment option for older men with sarcopenia. The most common hormonal replacement therapy (HRT) for older women is estrogen and/or estradiol replacement therapy. While the research regarding HRT is encouraging, it remains inconclusive. Indeed some studies have reported negative side effects of HRT in women and that some women discontinued prescriptions due to side effects (Bjorn & Backsrom, 1999;Manson et al., 2003).
However, other studies have shown considerably beneficial effects of HRT in women including increases in lean body mass and reduction of risk for coronary heart disease (Grodstein, Manson, & Stampfer, 2006;Sorensen et al., 2001). Overall, HRT in women presents a potentially viable treatment method for sarcopenia in women, but more research is needed to determine potential side effects and the impacts they may have on older women.

Diet and Supplementation
Currently there is encouraging evidence regarding dietary protein intake as well as supplementation for lean mass maintenance in older men and women (Katsanos et al., 2008;. Several studies have suggested that daily intakes of 1.0-1.6 grams of protein per kilogram of body mass is necessary for maintenance of muscle mass in older adults (Bauer et al., 2013;Lancha Jr, Zanella Jr, Tanabe, Andriamihaja, & Blachier, 2016). However, some literature suggests that high dietary protein intake may lead to potential colon health issues and high protein diets may also be contraindicated in those with renal disease and Parkinson's disease (Fracasso, Morais, Gomez, Hilbig, & Rabito, 2013;Russell et al., 2011;Zeller, Whittaker, Sullivan, Raskin, & Jacobson, 1991). Supplementation research also presents a promising avenue for treatment of sarcopenia and is commonly paired with resistance training to assess the effects of supplements alone and combined with RT.
Studies that have examined the effects of creatine supplementation and protein supplementation, with and without RT have shown that when combined, supplementation and RT provide significant increases in lean mass, strength, and physical function in samples of older women (Francis et al., 2016;Gualano et al., 2014). However, Francis et al. (2016) did not measure or control for dietary protein intake and it is unclear if higher dietary protein intake may have affected those results.
Additionally, Gualano et al. (2014) conducted their study in older women with osteopenia and osteoporosis. While that was an older population, it is unclear if those benefits could be observed in women with sarcopenia. Therefore, dietary and supplementation approaches may treat sarcopenia and attenuate some of the decline in lean mass, more research is needed to assess potential side effects and ideal dosage strategies for older women with sarcopenia.

Physical Activity
Physical activity, often defined as aerobic exercise, has been shown to be excellent for overall health and wellbeing as well as preventing and treating other chronic diseases (Bonaiuti et al., 2002;Hirose, Hamajima, Takezaki, Miura, & Tajima, 2003;Thompson et al., 2003). Physical activity has also been shown to have positive effects on balance and reduction of fall risk in older adults (Buchner et al., 1997;Gregg, Pereira, & Caspersen, 2000). Despite those positive health benefits, evidence has shown that physical activity alone has little effect on muscular strength or mass. Some studies have found older adults to increase both strength and lean mass following aerobic exercise Konopka et al., 2010). However those studies had very small sample sizes and the aerobic training groups were not compared to other methods of training. Additionally, those studies were not conducted in a sarcopenic population, and therefore have very limited applicability. Furthermore, in a longitudinal study with five years of follow up, Marcell et al. (2014) found that 35 active, older women who participated in regular endurance exercise experienced significant decreases in strength, while maintaining baseline levels of lean mass.
Those results indicate that regular endurance exercise may help attenuate the loss of lean mass, yet do not prevent the age related loss of strength, which is included in sarcopenia classification criteria and associated with functional limitations.
Additionally, a study by Mason et al. (2013) examined the effects of diet, exercise, and diet and exercise combined on sarcopenia in 439 overweight and obese post-menopausal women over a 12-month study duration. The exercise group completed moderate to vigorous aerobic exercise five days per week for 45 minutes per session, and consisted of a combination of home and clinic based exercise. The diet intervention group set a weight loss goal of 10% of the baseline weight.
Sarcopenia was classified using the SMI method developed by Baumgartner (1998) and cut points utilized by IWG criteria. However there was no measurement of gait speed, which is a component of IWG criteria. Post-intervention the exercise group experienced a small yet significant 0.4% increase in SMI (p=0.004) compared to the control group. In contrast, the diet group experienced a significant (p=0.01) 3.2% decrease in SMI, while the diet and exercise combined group did not significantly change their SMI. That study indicates that regular aerobic exercise can attenuate the loss of lean mass with or without a weight loss intervention. However those results are limited by the lack of physical function assessment, and thus the effects of that intervention are inconclusive, as incomplete data prevented pre and post intervention sarcopenia classification by current criteria. Therefore, while beneficial for overall health, and potential lean mass maintenance, physical activity (aerobic exercise) does not appear to be a viable method of increasing muscle mass or strength; and altering sarcopenia classification.
Examining the effects of RT in older adults was a meta-analysis by . That analysis used 47 studies with a total of 1079 male and female subjects aged 50-92 years. The average study duration in that analysis was 17.6 weeks and subjects trained from one to three times per week. The intensity of training as well as volume (sets and repetitions) of exercises varied between studies, although most included measures of maximal leg press and/or chest press strength in their results.
Those researchers found upper and lower body strength measured by chest and leg press to increase by 24% and 29% respectively. However, those results are from combined pool estimates of strength, and the studies included had large variation in training program design and participants. Nonetheless, those results indicate that both upper and lower body strength are responsive to RT in older adults.
A further meta-analysis by  included 49 studies and 1,328 male and female participants with a mean age of 65.5 years. Study duration ranged from 10 to 52 weeks and resistance-training programs included communitybased programs, in home programs, and individual personal training programs. A weighted pooled estimate found a mean lean mass increase of 1.1 kg over a mean study duration of 20.5 weeks. Those results are encouraging and demonstrate the ability of older adults to experience muscular hypertrophy with RT. However, the variation in programming style and study duration may limit the applicability of these results and limit use in intervention design. Nonetheless, that study indicates that despite large variations in program design and training duration, older adults can experience increases in lean mass with RT. However information regarding ideal RT program design to increase lean mass in older adults is needed to apply these findings in a clinical setting.
Although results from   Gait speed is also responsive to resistance training. A study conducted by  included 90 older men and women aged 87±0.6 years who were randomized into four groups: exercise, exercise and supplement, supplement placebo, and control. The exercise group completed movements that trained the hip and knee extensors three days per week for 10 weeks. The exercise group experienced a significant 8.6% (p=0.009) increase in gait speed when compared to the inactive groups. Also of note, both the exercise and exercise plus supplement groups experienced significant increases in hip and knee strength (p<0.001). That study, while conducted in older adults, took place in 1994 prior to the development of current sarcopenia classification criteria. Therefore it is unclear if the participants were sarcopenic or had symptoms of sarcopenia (low gait speed, low strength, low ALM).
However it is evident that RT can positively influence gait speed in older adults.
Also supporting the use of resistance training to improve gait speed was a recent study by , who delivered an 8-week RT intervention to 23 healthy older women aged 69.6±6.4 years. Participants trained three days per week following a program designed to meet ACSM recommendations for muscle hypertrophy and strength. Following the training program participants' gait speed improved by 3.67% (p=0.03). Those results indicate that RT can result in significant improvements in gait speed time in older women. However that study used a 10-meter fast walking speed test, which may not be indicative of normal gait speed in older adults. Additionally, although the women included in that study were older and inactive, they were not evaluated for sarcopenia and it is unknown if similar results can be observed in older sarcopenic women.
Recent research has also compared the effects of aerobic and resistance training on strength in 93 older men and women. Participants aged 65-75 years, with sarcopenic obesity were randomized to four groups: aerobic training, resistance training, combined aerobic and resistance training, and a control group. Training groups trained two times per week for eight weeks and underwent post-intervention testing, and follow-up testing four weeks post intervention. Results indicated that the RT group experienced significant gains in grip strength (3.5 kg, p<0.05) that were maintained four weeks post intervention compared to all other groups (Chen, Chung, Chen, Ho, & Wu, 2017). Those results indicate that one-day of RT per week will not produce significant gains in grip strength, and that greater frequencies of RT are needed to increase grip strength. Moreover, that study further demonstrated the shortcomings of aerobic exercise at treating symptoms of sarcopenia. Additionally, although the participants in that study were assessed for sarcopenia at baseline there was no discussion regarding change in sarcopenia status post intervention.
Nonetheless, grip strength is included in current sarcopenia classification criteria, and that study demonstrated that RT is the most effective method of increasing grip strength in that population compared to other exercise modalities.
Further demonstrating the efficacy of RT as a treatment for sarcopenia was a recent study by Stoever et al. (2015). Those researchers investigated the effects of RT on 18 obese, older men with sarcopenia and 15 obese, older men without sarcopenia.
Sarcopenia was classified using the SMI method and participants completed a RT program two days per week for 16 weeks. Following the program the participants with sarcopenia had increased their grip strength by 12% and the non-sarcopenic participants maintained their baseline levels of strength. That study indicates that RT is effective at attenuating the age related loss of grip strength in non-sarcopenic men and improving grip strength in men with sarcopenia. Similar effects were seen in women in a study by , who found 20 older women to increase grip strength by 8% following one year of RT. However, that study was conducted in women without sarcopenia and it is unclear if those results can be duplicated in older women with sarcopenia.
While many RT studies vary in frequency, the most common frequency is three days per week. Farinatti et al. (2013)  Considering that gait speed is a component of current sarcopenia classification criteria and an important functional measure, future RT interventions should seek to program training three days per week in order to realize the greatest improvements in gait speed. Furthermore, that study incorporated a single set RT program, which has been shown to be inferior to multiple set RT programs for strength improvements (W. K. Kemmler, Lauber, Engelke, & Weineck, 2004). Therefore, in order for older women to experience maximum improvements in strength and functional performance they should partake in a multiple set RT program three days per week.

Periodized Resistance Training
The aforementioned studies demonstrate the efficacy of RT in treating symptoms of sarcopenia and utilized what is considered conventional RT.
Conventional RT is commonly programmed using the progressive overload principle, which involves gradually increasing training workload (Hass, Feigenbaum, & Franklin, 2001). Conventional RT programs, especially those in older individuals are typically structured using baseline strength measures, and progressively increase the intensity of the movements for the duration of intervention (Farinatti et al., 2013;Ferri et al., 2003;Krist, Dimeo, & Keil, 2013). In programs of that style, the number of sets and repetitions is often held constant (fixed volume), and the only variations in the training program are increases in intensity when appropriate (Pollock, Graves, Swart, & Lowenthal, 1994). Other variations of conventional RT include programs where participants only complete one set of prescribed exercises per training session (single set) (Wolfe, LeMura, & Cole, 2004). These types of design limit the ability of the participants to obtain maximum benefits from a RT program, as different intensities and repetition ranges can be used to target muscular strength, hypertrophy, endurance, and power .
A different method of designing RT programs is periodization. Periodized resistance training (PRT) programs use pre-planned variations of acute training program variables. The program variables that are modified are exercise selection, exercise order, intensity, volume, and rest periods (Bartolomei, Stout, Fukuda, Hoffman, & Merni, 2015;. There are many different methods of designing PRT programs and few studies incorporate identical training programs, which limits the comparison of results within the literature. While conventional RT can certainly be beneficial for many populations, multiple studies have demonstrated the benefits of PRT over conventional RT . A meta-analysis by   between cycles (Conlon et al., 2016). The most common form of linear periodization is block periodization, which was first introduced in the 1970s by Verkhoshansky, who designed programs for track and field athletes (Yessis, 1982). Block periodization is commonly programmed using four-week training segments, called mesocycles. Each mesocycle targets a single training outcome variable or adaptation (i.e., muscular hypertrophy, strength, or power). Athletes seeking peak performance for individual competitions or competitive seasons often use linear/block PRT programs (Turner, 2011).
In a study by Botero et al. (2013), 23 post-menopausal women followed a linear PRT program two days per week for 12 months. Participants were inactive prior to study inclusion and followed a traditional linear model of periodization: progressive increases in intensity, and decreases in volume. Following intervention participants displayed significant increases in bench press (30.82%, p<0.05) and leg press (100.9%, p<0.05). Participants also displayed significant increases in lean mass (1.59%, p=0.009). That study supports the use of PRT; especially linear PRT due to the significant increases in strength and lean mass experienced by the participants.
However, that study did not include secondary test groups investigating other forms of RT in comparison to the PRT program or a control group. Additionally, due to the linear program design, participants had completed a strength cycle of training just prior to post-intervention testing, which may have influenced the final results.
Furthermore, that study claimed that long-term PRT prevents sarcopenia, which is a bold claim, however there is no indication that these researchers assessed sarcopenia by any criteria. While that study produced positive results, it suggests further research is needed investigating forms of PRT in post-menopausal women who have been screened for sarcopenia. Additionally, linear PRT programs, while beneficial for individuals of all sexes and ages, may not be ideal for those who are not training for a specific event or season, but rather seeking to improve and maintain strength, lean mass, and physical functioning, like older adults (Kraemer et al., 2004;Miranda et al., 2011).
Non-linear periodization still incorporates modifications of program variables similar to linear/block PRT programs, however non-linear PRT can be programmed so that participants train for separate outcomes (hypertrophy, strength, or endurance) on a daily or weekly basis, rather than a bi-weekly or monthly basis. This may be beneficial for those seeking a well-rounded training program that allows for continuous training of multiple outcomes. While there are not any set rules or guidelines one must follow to design non-linear PRT programs, a common method is weekly or daily undulations. The undulations signify modifications to program variables (exercise selection, order, intensity, volume, and rest periods). Individuals following weekly undulating PRT (WUP) programs will commonly train for a specific adaptation (i.e. strength) for one week, then train for a different adaptation (i.e. hypertrophy) the following week. Daily undulating PRT (DUP) programs simply incorporate modifications of training variables and targeted adaptation on a daily basis. These undulations are designed to provide periods of low intensity training, which allow adaptations to occur, decrease the risk of overtraining, and maintain interest in the program (Komi, 1986;).
Indeed, research shows that consistently high training intensities contribute to increased inflammatory markers and symptoms of delayed onset muscle soreness (Hasenoehrl et al., 2016;Nosaka, Newton, & Sacco, 2002). Additionally, in a joint consensus statement, the European College of Sport Science and the American College of Sports Medicine suggested that adjusting daily training intensities and volumes and/or allowing rest days is vital to preventing overtraining (Meeusen et al., 2013). Those organizations also recommended avoiding monotonous training programs and that one of the best methods of preventing overtraining syndrome is appropriately periodizing training programs and allowing adequate time for rest and recovery (Meeusen et al., 2006). Therefore a DUP program would provide the variations required to prevent excessive soreness, overtraining, and boredom, all of which may promote adherence to a training program. press and leg press strength, however the DUP group displayed significantly higher increases than the linear PRT group for both bench press (p=0.002) and leg press (p=0.001). However the studies by both  and  included college-aged men, and despite the potential benefits of DUP in older women,

Instructions:
While exercising we want you to rate your perception of exertion, i.e., how heavy and strenuous the exercise feels to you. The perception of exertion depends mainly on the strain and fatigue in you muscles and on your feeling of breathlessness or aches in the chest.
Look at this rating scale; we want you to use this scale from 1 to 10, where 1 means "no exertion at all" and 10 means "maximal or very, very strong exertion." For most people this is the most strenuous resistance exercise they have ever experienced.
Try to appraise your feeling of exertion as honestly as possible, without thinking about what the actual physical load is. Don't underestimate it, but don't overestimate it either. It's your own feeling of effort and exertion that's important, not how it compares to other people's. What other people think is not important either. In addition, this scale has no anchor. That is, if after giving a "10" on a previous rating, you decide that the current exercise is more strenuous, you may give a higher number (i.e. "11"0. Look at the scale and the expressions and then give a number.
Any questions?
How often do you drink some kind of juice at breakfast? ____ Never or Less than once a week ____ 1 or 2 times a week ____ 3 to 5 times a week ____ Every day or almost every day How often do you eat chicken or turkey? ____ Never or less than once a week ____ 1 or 2 times a week ____ More than 3 times a week How often do you drink a glass of milk?
____ Never or Less than once a week ____ 1 or 2 times a week ____ 3 to 5 times a week ____ Every day or almost every day ____ More than once every day Which of the following best describes your nutritional supplement use.
____ I don't use supplements ____ I use supplements other than vitamins and mineral ____ I use a multivitamin/mineral preparation (e.g. Centrum)