THE EFFECTS OF CONTRAST WITH COMPRESSION THERAPY ON MUSCLE RECOVERY POST EXERCISE

This study investigated the effect of combing contrast with compression therapy as a post exercise recovery modality. Previous research indicates that contrast and compression alone can potentially enhance recovery but the combination of the two is yet to be explored. Ten recreationally trained males between 18 and 35 were recruited (years 21.25 ± 2.12; height 182.1 ± 8.5 cm; weight 88.04 ± 19.49 kg) in a randomized control trial with a repeated measure (within subject) crossover design. The conditions were randomly assigned by dominant/non-dominant arm and contrast with compression (CwC) or control (CON) in which one arm was used for each condition. Participants completed 30 eccentric elbow flexor repetitions and were subsequently tested at six timepoints (pre, immediate post, 1 h, 24 h, 48 h, and 72 h) for power, strength, swelling, range of motion (ROM), and perceived soreness. The CwC condition received treatment after post testing, at 24 h and 48 h; the CON condition did not receive any treatment. CwC resulted significantly improved recovery in power, strength, and swelling (p ≤ 0.05). However, no difference was seen in ROM and perceived soreness. Conclusion: CwC can be used as a post exercise recovery technique to improve muscular performance and reduce swelling in recreationally trained individuals.

athletes. Full recovery between bouts of exercise, practice or competition allows athletes to be able to perform at a higher level in subsequent bouts. However, athletes training and competition schedules often do not allow them to fully recover between bouts of exercise resulting in decreased levels of performance and increasing the risk of injury 1-4 . Along with a drop off in performance, incomplete recovery can lead to overtraining, which is caused by an imbalance of energy expenditure load and recovery 5 . Consequently, athletes often take part in various recovery therapies / techniques in the hopes of accelerating recovery 6,7 . Two common forms of recovery therapies are contrast therapy (alternated exposure to hot and cold) and compression therapy.
Intense exercise through game-play, weight training, or unaccustomed exercise can cause a disruption in the muscle tissue called exercise induced muscle damage (EIMD) which can lead to hindered functional activity, delayed on set muscle soreness (DOMS), loss in range of motion (ROM), and inflammation / swelling [8][9][10] . EIMD is primarily caused by eccentric muscle contractions, i.e. when a muscle is forcibly lengthened. This type of contraction can be stimulated through resistance training but often occurs in sports during tasks such as landing, decelerating and changing direction. These eccentric muscle contractions can subsequently cause a disruption in the sarcomeres which damages the excitation and contraction coupling system and leads to a less efficient muscle contraction 10,11 . Eccentric exercise has been shown to result in muscle soreness, swelling, and loss of range of motion, power and strength loss; these signs typically start at 24 h and peak between 24-72 h but can be seen for up to 11 days 12 . One study reported a differences in recovery of eccentric exercises between upper body and lower body exercises, claiming that upper body exercises give more pronounced symptoms of DOMS compared to the lower body 13 .
Compression garment therapy has been widely studied and been shown to improve the rate the recovery 3,14 . This therapy can take form of a single sleeve 15 , a garment for the legs 3 , or a whole body suit 14 which can be used before, during, or after an activity 16 .
Compression of a muscle has been linked to increase venous pump which allows blood to be returned to the heart at a faster rate and waste products to then be removed 14 . Blood flows at higher velocity due to the decreased diameter of the vessels as explained by the Bernoulli's principle. The use of these garments can also aid in recovery of muscle function such as strength and power while reducing swelling, and perceptual pain 16 . Compression garments can vary in pressure depending on the brand and size and are usually worn for extended periods of time, which often make them impractical. However, smaller bouts of compression therapy are being used as a more efficient post exercise recovery. Pneumatic compression sleeves can offer more compression along with sequential compression that starts at the distal end of an extremity and pulses up to the core, which helps aids in further blood return and waste products/metabolites to the core. The effectiveness of using this device in the biceps brachii when receiving the treatment for multiple days has been shown to decrease swelling, DOMS and increase range of motion after heavy eccentric exercise 17 .
Cold-water-immersion (CWI) and hot-water-immersion have been used as single modalities to accelerate recovery after intense exercise 18 . CWI has been shown to decrease muscle temperature, which decreases blood flow by constricting the vessel, therefore it reduces edema by slowing down inflammation mediators (e.g leukocytes), which leads to less swelling. Furthermore, it acts as a local anesthetic by decreasing the activation threshold of the tissues nociceptors and the conduction speed of pain nerve signals 19 . A meta-analysis has shown that pain measures after using CWI below 15° C after exercise can lower the perception of DOMS from 24-96 h compared to a control 20 . On the other hand, heat vasodilates the vessels, increasing the blood flow which removes metabolites, damaged tissues and free radicals 6,21 .
The combination of both hot and cold-water therapies is known as contrast water therapy (CWT). CWT is a common tool that is used to recover from an intense workout bout and it has been shown to decrease the time to baseline in athletic performance 1, [22][23][24] . CWT works by hyper reactive vasodilation during the heating phase and vasoconstriction during the cold phase, which in turn helps increase circulation, removing metabolites and free radicals, decreasing inflammatory response, and slowing the metabolic process down 18,22,25 . The use of CWT alone has been proven to be superior to passive recovery but has reported little difference compared to compression, stretching, cold water immersion and active recovery 7 . Furthermore, the effects of contrast water therapy at various ratios and temperatures have been looked at with varying degrees of significance with the most common being 1:1, at cold (15° C) to hot (38° C) from 10-14 min 7,18,22,26 . It has also been reported that there doesn't seem to be a dose response when comparing CWT at 6, 12 and 18 min 23 .
Compression therapy and CWT aren't alone in their attempt to shorten recovery time as massage therapy 27 , CWI 20 , stretching 28 , and active recovery 29 all being used in athletic fields. A meta-analysis performed in 2018 suggested that massage therapy was most effective at reducing DOMS and perceived fatigue with CWI and compression garments also positively effects these variables, but gave no inclination to athletic performance 6 . The potential of combining modalities for greater recovery effect has started to receive some attention. For example, a study looked at combining compression therapy with cryotherapy (cryocompression) 4 and yielded closer to baseline scores in 24 and 48 h in power and soreness measures. Pairing cryotherapy with compression may increase the effects of both therapies as compression therapy may mitigate the vasoconstriction that is associated with cryotherapy while maintaining beneficial neurological and metabolic changes.
To our knowledge no research has been performed to determine the potential benefits of combined contrast and compression therapy (CwC) as a post exercise therapeutic intervention. Therefore, we explored the use of CwC when used once a day for three day in 10 min bouts. With the lack of definitive knowledge of a superior modality for recovery, the need to enhance what has already been studied should be explored. With greater recovery from exercise it will allow for better day to day training, workouts or game performances and could improve the efficiency of a program and sport performance 30 . Thus, the purpose of this study was to determine the effects of contrast with compression on performance and recovery parameters following a heavy eccentric exercise bout. We hypothesized that CwC will lead to shorter recovery times in both muscular performance and other recovery parameters measured.

Contrast Water Therapy (CWT) on recovery:
A meta-analysis was conducted by Bieuzen et al. 7  CWT also reduced CK concentrations in the blood indicating reduced muscle damage.
Vaile et al. 22 conducted a study on recreationally trained athletes in which they acted as their own controls in a cross over design with a six-week wash-out period. This study compared CWT to a passive control after a heavy eccentric workout bout and tracked various variables related to muscle damage. Five sets of 10 eccentric bilateral leg presses at 140% 1RM to induce muscle damage, after which they entered one of the two recovery techniques: a passive recovery for 15 min, or CWT for 15 min using a cold-hot ratio of 1:2 (8-10° C to 40-42° C). Measures were taken immediately after treatment along with, 24, 48 and 72 h post recovery and the measurements taken were isometric front-squat strength, lower body power during a jump squat while lifting using 30% of their maximal load, CK, thigh volume using a tape measure, and VAS for perceived soreness. Results showed that CWT resulted in smaller loss of isometric strength (p < 0.05), power (p < 0.006), and smaller increase in thigh volume (p < 0.01); however, there was no significance reported in perceived pain. The author speculated both hot and cold increases the sympathetic drive of the nervous system and the pumping effect could circulate blood around the body with the use of vasoconstriction and vasodilation, which will also help with further metabolite clearance.
Vaile et al. 18 conducted another study looking at three different hydrotherapy techniques and a control group. Participants were randomly assigned to one of the four groups: 1) CWI (15° C, n = 12), 2) hot water immersion (38° C, n = 11), 3) CWT with a ratio of 1:1 (CWT, 15° C: 38° C, n = 15), 4) passive control (CON) all hydrotherapy modalities required full body submersion and for 14 minutes total. Muscle damage was induced by 5 sets of 10 repetitions of eccentric bilateral leg presses at 120% of their 1RM. Measures included isometric squat (force plat form), peak power (jump squat), blood markers (CK, LDH), thigh circumference (tape measure), and perceived soreness (VAS). All three water therapies faster recovery in isometric force compared to CON but only CWI and CWT improved recovery in dynamic power and decreased swelling (p < 0.05).
Versey et al. 23 compared the duration of CWT on recovery on running performance.
There were four recovery techniques: a control, and three CWT groups at 6,12 and 18 min (15-38° C). Participants were long distance runners used to covering > 60 km/week and were not used to hydrotherapy. It was a crossover design counterbalanced at least 4 days apart. Two hours was given between the first workout and the second and running performance (3000m), pain to pressure threshold, perceived exertion, heart rate and leg girth were also taken during this study for measurements. This study reported that 6 min of CWT induced a faster running time on the second trial than control (87% probability, 0.8 ± 0.8% mean ± 90% CL); however, 12 min (34%, 0.0 ± 1.0%) and 18 min (34%, -0.1 ± 0.8%) had no effect.
This implies that CWT does not have a dose response to running performance in a cold environment but implies 6 min of CWT is significantly better than 12 min, 18 min and a control. However, with the small sample size for each group it is hard to draw any real conclusion. Therefore, Versey et al. 1 employed a similar study design but on 5 min cycling performance and peak power and did not see a dose response when comparing 6, 12, and 18 min of CWT to a control. This time, the 5 min timed bike trial did not differ between conditions. The total work performed in the 5-min time-trials after 6 min of CWT was greater than control (75% probability; 1.5 ±2.1%, mean ± 90% CL) and CWT18 (99%, 2.5 ± 1.2%), but not 12 min of CWT. Exercise bout of one 15-s sprint total work was greater in 6 min CWT (75%, 2.0 ± 2.7%) and 12 min of CWT (94%, 3.0 ± 2.2%) than control. The total work performed in the 15 s sprints after 6 mins of CWT and 12 mins of CWT was greater than control (6 min: 87%; 3.0 ± 3.1%, 12 min: 95%; 4.3 ± 3.4%), with 12 min of CWT also being greater than 18 min (78%, 1.9 ± 2.2%). These finding suggests that psychologically non-athletes feel more recovered using CWT, but it may not offer many benefits after a 1h time point.
Robey et al. 31 compared CWT to static stretching and a control and saw no differences amongst the three groups. Recovery procedures were administered at three time points (immediate post, 24 h and 48 h). They used a strenuous stair-climbing run (up and down) as the protocol to induce muscle damage, but muscle damage (CK), perceived soreness, peak torque and rowing ergometer (2 km times) showed no significant differences between groups. This may have been because the muscle damaging protocol did not stimulate much damage.
French et al. 8 looked at compression garments (CG) and CWT compared to CON in recreationally trained athletes with >1 year of resistance training and >4 years training in their given sport (soccer and rugby). The CB group switch from a cold bath (8-10° C) and a hot bath (37-40° C) at a ratio of 3:1 starting and ending with cold. The compression group wore commercially available compression shorts for 12 hours post exercise. The muscle damaging exercise used was six reps and ten sets of parallel back squats with a load relative to 100% body mass. At the end of every set a single 5 s eccentric back squat against a load relative to the participant's predicted 1 repetition max was implemented and then followed by 2 min of rest. Interestingly this study suggests that none of these recovery methods prove superior when evaluating power, strength, speed, ROM, circumference, perceived soreness, agility and CK.

Compression Therapy on recovery
A systematic review with meta-analysis by Marques-Jimenez et al. 16   Kraemer et al. 15 used a between group design to compare a CG in the form of an arm sleeve to a CON after an eccentric exercise. The CG was worn continuously for 108 h and at 72 h the CG experienced less of a decrease in strength and power compared to the CON group. Furthermore, significantly less swelling (circumference) and change in passive elbow flexion was seen in the CG.
Combing cold and compression therapy (i.e. cryocompression) is a colloquial method used in the field but DuPont et al. 4 was the first to study this by looking at its effects on recovery compared to a CON group from 16 resistance trained men. Testing took place, before, immediately after and 1, 24  thought to reduce edema, which also lowered the perceived pain felt by the experiment group due to less pressure on the nerve endings. Also, it is thought that compression acts like a "dynamic cast" that helps with muscular repair by holding the muscle in place to allow the sarcomeres to re-align after exercise.
Hill et al. 35 compared a lower leg CG to a CON group on 24 marathon runners postrace. The CON group wore the garment for 72 h while the control group did a fake ultrasound test to act as a placebo. The CG group only showed significance in lower perceived soreness at 24 h (p ≤ 0.05) compared to the CON group but no differences were seen in max voluntary isometric contractions (MVIC).
CWT and compression conclusion: Alone, there is mixed evidence supporting CWT, but several meta-analyses showed that it increases recovery parameters.
However, there are a lot of studies that do not provide enough EIMD to draw conclusion especially when performed in an athletic population using game-play stimuli. Research on low intensity and long duration compression has been conducted yielding favorable results for recovery. However, when compared to PC it was shown to be inferior when comparing swelling, DOMS and range of motion but there is little evidence to show that when used alone it can improve performance. Furthermore, when PC in combined with cold therapy one study showed that it can improve power output.

Exercise induced Muscle damage
The DOMS model is explained by McArdle et al. 9 as to be caused by unaccustomed exercise using eccentric muscle actions; for example running downhill (working the quadriceps) or lowering weights slowly during resistance training. Eccentric exercises are usually followed by reduced muscle force and the release of cytosolic enzymes (creatine kinase) and myoglobin. Damage is also seen in the contractile myofibrils and non-contractile structures (tendons). The increase of metabolites in the muscle causes even more damage and lack of force. Starting around 24 h the feeling of DOMS will appear and is the result of inflammation, tenderness and pain. Lastly, as the inflammation process begins the muscles start to heal and adapt, therefore making them more resistant to damage from subsequent exercise.
Proske et al. 10 summarized eccentric exercise such as mechanisms, adaptions and clinical applications. Eccentric exercise causes muscle damage observed through microscopic examinations that show sarcomeres out of lines with one another, Z-line streaming, over-extended sarcomeres, regional disorganization of the myofilaments and t-tubule damage. When someone is unaccustomed to this kind of exercise they will start to feel DOMS (i.e. soreness starting at 24 h after exercise which peaks 2-3 days after exercise). However, if one was to perform the same exercise a week or two later they will not be as sore due to adaptations of the muscle to stop further damage and this is known as the repeated bout effect. It has been theorized that there are two reasons behind muscle damage; one is a disruption in the sarcomeres and the other is damage to the excitation and contraction coupling system. Excitation and contraction coupling system is the link between the excitation of a neuron to stimulate an action potential in the muscle fiber sarcolemma which causes a muscle to contract through the release of calcium.
Clarkson 11 reports that eccentric actions performed at long muscle length cause more damage than when shortened. When the muscle is extended and under force it is thought that the weakest sarcomeres become passive and put more strain on the others.
The reason for the inability to extend the arm may be explained by swelling, a change in properties of supporting connective tissue, and/or non-neurally mediated contractures.
Twenty-six female students performed 70 eccentric contractions on the elbow flexors and compared the results to their other arm. Swelling peaks significantly (P < 0.01) at 24 h up to 96 h, the resting angle of the elbow joint decreased significantly after and peaked at day 4, a loss in strength was seen after exercise and peaked at 24 h but still showed significant decreases after 11 day (-20%), tenderness at the mid-belly peaked at 48 h post and returned to baseline after 7 days, and pain/soreness was seen at 24 h, peaked at 72 h and no longer existed at day 8. Therefore, eccentric exercises where effective in producing tenderness, swelling, muscle shortening, and strength loss. The study showed that pain is not necessarily related to strength as no pain was felt immediately after the exercise but there was a big reduction in isometric strength post exercise and at 24 h 12 .

Variables chosen:
Huw et al. 37  with an external load of 30% (p < 0.001) and lower body at 0%. Power losss after muscle damage has also been shown in many recovery studies and vary in efficacy to return power to its pre EIMD state within 72 h 1,2,31, 3,4,7,14,16,22,25,26 . Power is an essential factor for athletic performance, therefore, the lack of power after EIMD can affect an athlete ability to perform at their peak 38 .
Strength decreases after muscle damage can be as much as a 60% from baseline and is prevalent even before soreness is perceived 11 . Due to disruption in the sarcomere placement, and sensitivity to contract through the excitation and contraction coupling theory, strength is often used to measure muscular recovery 4,14,16,39 .
Lau et al. 40  Swelling is often used when looking at muscular recover due to the inflammation that occurs at a given sight. Swelling is mostly measured as circumference 1, 8,12,15,18,22 due to the feasibility of a tape measure, but intramuscular swelling can also be seen using ultrasound 7,14 . Due to the necrosis of some muscle fibers during repeated eccentric contractions there is an inflammatory response consisting of leukocytes and neutrophils that cause edema 9 .
Many studies use ROM 8,12,26 when looking at muscular recovery from an exercise and when they are specifically looking at the bicep this can be achieved by measuring the passive flexion and active flexion of the arm as shown by Kuligowski et al. 24 . It was once thought that muscle pain was the reason for decreased angle of a joint but there has been no correlation 10,12 .
Lactate acid is the result of energy produced by the anaerobic glycolytic pathway. As hydrogen ions build up, we start to fatigue due to metabolic acidosis (increased pH) in short term high intensity exercise. Lactate is correlated with glycolysis therefore exercise that requires high amounts of glycolysis with cause more lactate to be produced 29 .

METHODOLOGY
Design: A randomized control trial with a repeated measure (within subject) crossover design was conducted. In this study, each of the 10 participants completed two subsequent single-arm elbow flexor workouts after which they received either CwC therapy or no treatment (see Figure 1). After each workout follow-up measurements of muscle performance, perceived soreness, ROM, and inflammation were taken at six time points (before, immediately after and 1, 24, 48, and 72 h after exercise).
Participants were recruited from The University of Rhode Island by flyers and word of mouth. To qualify to take part, participants had to be 18-35 years old, male, not on any anti-inflammatory drugs, and have had no upper extremity injury in the last 6 months.
Additionally, throughout the study participants were required to come to testing euhydrated, and refrain from exercise and alcohol throughout the study. Once participants attended a single information meeting and signed an informed consent they were then scheduled to participate in the study and were randomly assigned to a condition based off control/intervention and dominant/non-dominant arm in the first week; the second week would subsequently be the opposite (see Figure 1). All testing was completed in the Human Performance Lab at The University of Rhode Island.     As an additional measure of swelling, circumference measure was taken using a calibrated tape measure which was taken at the first point listed above. Once the standard 60" Gulick tape measure (Richardson, Frankfort, IL) was loosely around the arm at the correct point it was then recoiled with 4-ounce tension to give an accurate measurement in cm. During all circumference measures participants were told to relax their arm with the arm resting on their side but not in contact with the body.  Perceived soreness: DOMS is usually measured using subjective scales and tend to increase after EIMD. To measure muscle soreness, we used three separate visual analogue scales (VAS), in which the participant drew a line on a blank 10 cm chart rating their pain from no pain at all to the worst possible pain (see Figure 10). The first VAS scale was in a resting position on the Biodex with the upper arm rested on the pad at 45° shoulder flexion with the arm fully extended (see Figure 11) 17 . The second measurement looked at the arm in motion with the arm in the same position as the first one but this time they performed 2 controlled bicep curls with zero resistance to replicate movement of the muscle 18 . The final VAS was used for soreness of touch / palpation. In this test using a 1 cm 2 transducer was used to apply 1.5 kg of force (kgf) to the bicep using an algometer (Force Ten FDC Digital Force Gage, Wagner Instruments, Greenwich CT: 6). The anatomical position used was the same as stated for the circumference measure. The 1.5 kgf used in this test was determined by pilot testing of 5 participants where the force was bearable, but they could detect a small amount of discomfort. The force was applied at constant rate of ~0.5 kgf by a trained researcher (see Figure 12). Lastly, the algometer was used again to determine pain to pressure threshold (PPT). Pressure was applied at a rate of ~0.5 kgf per second and the participants were instructed to say stop when they no longer felt pressure and started to feel pain, in which the pressure was stopped, and the number recorded (kgf).    Figure 10. Relative intramuscular swelling. Asterisks represent significant difference from baseline for CON; plus symbols represent significant difference from baseline for CwC; dollar sign represents significant difference between conditions. Perceived soreness: There was a significant time effect over 72 h for resting (p = 0.004), motion (p < 0.001), and palpation (p = 0.017); but not in PPT (p = 0.640).
More specifically, for resting VAS, CON were significantly elevated to baseline (p = 0.034) at 72 h. Also, there were significant time effects in all timepoints in moving VAS in CON but only at 24 h for CwC (p = 0.002). There was no interaction effect in all VAS and PPT measures.  *+ * Figure 11. Range of motion. Asterisks represent significant difference from baseline for CON; plus symbols represent significant difference from baseline for CwC; dollar sign represents significant difference between conditions. Lactate: In the CON condition there was significant differences from baseline (p = 0.004) and when compared to CwC immediately post exercise. Both conditions returned close to baseline at 1 h. respectively. This is in-line with the 65% of max strength was seen post muscle damaging exercise in a previous study using the same protocol and population 44 .

Range of motion:
While this is the first study that tracked the rate of recovery after use of CwC therapy, several previous studies have independently investigated recovery after CWT and compression therapy. A meta-analysis by Bieuzen et al. 7  those two modalities could be more efficient, however this is the only study we found investing this modality.
Decreased strength and power could be attributed to a disruption in the excitationcontraction coupling which means that's less calcium is released per action potential 47 .
Decreased strength could also be due to a change in the length tension relationship or to overstretched and misaligned sarcomeres that would provide a fewer number of cross-bridges 11,16 . Lastly, as these mechanisms are damaged it may cause some neural factors to inhibit full stimulation of the muscle to protect it from further damage, this is called central modulation 16 . In this study we believe that the contrast offered a pumping action in the vessels which helped increase blood flow to clear metabolites, repair muscle and slow down the metabolic process 7,21 . This may be amplified using compression which reduces the inflammatory response which in turn attenuates further ultrastructural damage and restore central factors that result in reduced voluntary activation 2 .
Swelling: In the present study, there were significant changes observed between conditions in intramuscular swelling using ultrasound but not in circumference measures. It is important to note that ultrasound is the "gold standard" when measuring muscular swelling as it gives a clearer picture of the muscle and allows for more accurate readings compared to a tape measure. These two results may not correlate due to the tester error or due to small amounts of swelling in bicep brachii was hard to detect by using the whole circumference of the arm. Ultrasound swelling has been used in a previous study 14 but due to the cost of this measure several previous studies have used circumference measures 1,18 .
In line with our results Vaile et al. 18 showed similar findings when using CWT for 14 min once a day at post, 24, 48, and 72 h. After a muscle damaging protocol, mid-thigh girth as measured through circumference, was significantly lower in 24, 48, 72 h (p < 0.01). Furthermore, Winke et al. 17 compared wearing a mild compression sleeve for 108 h to 20 min per day of PC in the upper arm. They reported that the magnitude swelling in the PC group was significantly lower (p = 0.012) over 108 h, which suggests intermittent compression at higher intensities could be more beneficial.
Due to the necrosis of some muscle fibers during repeated eccentric contractions there is an inflammatory response consisting of leukocytes and neutrophils that cause edema 9 . The CwC machine reduced the inflammation by compressing the upper arm which allowed smaller changes in osmotic pressure which diminishes fluid shifts to the interstitial space therefore causing less edema 6 . Again, this process seemed to be amplified by CWT which allowed an increased blood flow to clear metabolites, repair muscle and slowing down the metabolic process cause by the pumping effect during vasodilation and vasoconstriction 7,21 .

Range of Motion:
The exercise intervention caused significant reduction in ROM, active flexion and passive extension. However, in the present study, there were no significant changes observed between conditions for ROM and extension, but there were significant changes in flexion. The CON condition showed reduced ROM at 1 h but not in the CwC which shows that CwC may have short term benefits. It is evident in Figure. 11 that there was a reduction on ROM in both conditions and that CwC suggests closer to baseline scores, but more research needs to be done to see if there could be significant findings.
In line with these results Kraemer et al. 15 reported no significance in extension when the participants wore a compressive sleeve (10 mm Hg) for 108 h after an eccentric workout. Conversely, range of motion in the elbow flexor muscles had a significant main effect over 108 h in both elbow extension (p = 0.005) and elbow flexion (p = 0.002) when using PC once a day for 20 min over 5 days compared to continuous slight sleeve compression 17 . This shows that intermittent PC may offer superior benefits to range of motion however this was not back up with the combination on contrast and compression and requires more exploration.
Possible explanation for the significant interaction effect during elbow flexion reported in this study may be due to the reduced swelling of the bicep offered by CwC, limiting the amount of flexion possible by the participant. A loss in range of motion may also be due to the volume change of the muscle which adds increased tension on the connective tissue or damage to the connective tissue itself 10,11 . Other potential mechanisms for lower resting extension may be because of an increased calcium concentration in the damaged muscle that causes a low intense contraction 12 .

Perceived soreness and PPT:
In the present study, there was a significant time effect for all perceived soreness measures but not PPT. We took a comprehensive approach and included resting, motion, palpation and PPT to analyze soreness, which are all used in current literature but are rarely seen together. The VAS and PPT differ as a VAS informs us of the severity of the pain felt after a set stimulus but PPT shows us the level of palpation a participant starts to feel pain.
In line with our result Vaile et al. 22 reported no difference between CWT and CON when subjects rated perceived soreness using VAS in a 72 h time frame. Conversely, CWT did show significance in all time points compared to CON in a meta-analysis at 6 h (6 trials), 24 h (13 trials), 48 h (10 trials) and 72 h (5 trials) 7 . As reported pain is a subjective measure that has a large degree of inter-person and inter-day variability, larger samples sizes (such as those of the meta-analysis) may be needed compared to other physiologically based measures used in the present study. When comparing PC to CON Winke et al. 17 reported no significance in palpation measures, but they did find significance using VAS during elbow extension in a rested position (p ≤ 0.05) 7 .
Also DuPont et al. 4 showed that cryocompression when used in recreationally trained athletes for 20 min, post, 24, and 48 h after exercise showed a main effect (p ≤ 0.05) in general soreness using a VAS over 48 h after eccentric exercise which leaves room for future exploration.
Cold water therapy appears to lower pain sensation through both an analgesic effect and reduced nerve conduction velocity. Also reducing edema through compression and CWT can reduce the pressure on pain receptors in the muscle 6,25 . In summary, our study does not back these theories and other studies up and this could be due to the subjective nature of VAS and the day to day variation.
Limitations: This study had several limitations including a non-athletic population.
The participants in the present were recreationally trained in a variety of activities. As the machine is intended to enhance muscular recovery in an athletic population it would be better served to do this study using the intended target population. However, controlling for exercise in an athletic population can be difficult due to their rigorous training and games schedules. Furthermore, muscle damage does not change between individuals and therefore we were still able to monitor recovery in our lab-based intervention. This study could have included a muscle damaging measure such as CK to measure the amount of damage in the muscle and track changes; CK has been used in multiple studies 2,4,15,48 . Also, compression was not measured in the CwC cuff, which makes it hard to draw conclusion as to how much pressure is needed to see a positive effect in performance and swelling measures. However, the external validity of this compression was still present as demonstrated by the strength, power and swelling measurements. Lastly, palpation VAS was administered at the midpoint between the acromion process and the olecranon process, which was meant to represent the location of the muscle belly. However, previous studies have reported that point tenderness is greatest at the myotendinous junction rather than the muscle belly 12 , therefore a location closer to the elbow creases may have yielded clearer results in perceived soreness.

Conclusion:
This study was the first to examine the effects of combing contrast with compression therapy (CwC) as a post exercise recovery modality. When CwC was used at three time points (immediately, 24 and 48 h post exercise) statistical analysis demonstrated improved recovery over at 72 h in strength, power and swelling. This information would benefit sports team coaches and athletic trainers in their attempt to decrease recovery time between training and game-play to maintain peak athletic performance. Future research should seek to investigate doing this in an athletic population, compare CwC to other recovery techniques, or measuring the amount of compression needed to cause an effect with contrast therapy. This study had many strengths such as the controls, a crossover design, and the use of multiple variables to measure muscle damage accurately. Therefore, CwC should be considered as a post exercise recovery modality for increased recovery after an intense exercise bout.

Consent Form for Research
We hope that you consider taking part in our study examining how contrast with compression therapy affects recovery from a bout of exercise. We believe that this study (detailed below) has potential to improve how sports medicine professionals treat their clients in order to help them recover from exercise and/or injury.

STUDY TITLE -
The effects of contrast therapy with compression on exercise recovery.

KEY INFORMATION
Important information to know about this research study: • The purpose of the study is to determine if contrast with compression (CwC) therapy improves an individual's recovery after a bout of exercise. • If you choose to participate, you will be asked to sign this informed consent document and then complete a total of 8 days of testing over a 3-week period. The anticipated total time commitment for this study is ~8 hr. • The first 4 days of testing will be used to test condition #1 (either CwC therapy or no therapy) while the last 4 days of testing will be used to test condition #2 (either CwC therapy or no therapy). The order of the conditions that you receive will be randomly assigned, but you will complete both conditions. • In the first week of testing you will be asked to attend 4  o Days 2-4 -Follow-up / recovery testing: ~30-45 min each day. • Risks or discomforts from this research include moderate muscle soreness from performing eccentric muscular contractions of the elbow flexor muscles. • The study will be used to determine whether contrast with compression therapy is a good alternative to other recovery modalities on the market. • You will be provided a copy of this consent form.
• Taking part in this research project is voluntary. You don't have to participate and you can stop it any time.

INVITATION
You are invited to take part in this research study. The information in this form is meant to help you decide whether or not to participate. If you have any questions, please ask.

Why are you being asked to be in this research study?
You are being asked to be in this study because you may be interested in participating in research related to kinesiology, physical therapy or sports medicine. To take part you must be between the ages of 18-35, male, and currently free from any elbow flexor injury in the past 6 months.

What is the reason for doing this research study?
There are many recovery methods employed in both athletic and physical therapy departments, which vary in degree of effectiveness. Combining contrast therapy with compression therapy may offer compounding benefits to recovery that provides a potent stimulus for recovery.

What will be done during this research study?
After signing this informed consent document you will be asked to schedule your 8 days of testing over a 3-week period (this should take ~ 15 min).
All participants will complete an exercise day and 3 days of recovery testing after receiving contrast with compression (CwC) therapy as well as a separate exercise day and 3 days of recovery testing in which no recovery therapy is provided. However, the order of these two conditions will be randomly assigned to each participant. Details of each session are provided below:

Days 1 & 5 -Baseline Testing, Exercise Bout and Post-Exercise Testing:
On this day you will complete baseline testing which will consist of a range of motion test as well ultrasound measures of your biceps muscle, blood measures taken using the finger stick method, soreness measures using various scales and elbow flexor strength and power tests. You will then complete a bout of elbow flexor exercise using specialized equipment (e.g. 6 sets of 5 repetitions of eccentric / lower arm curls). Finally you will then repeat the testing you performed at baseline immediately after and 1 hr after the exercise. On the day that you are assigned to the CwC condition you will also receive 15 min of CwC prior to the 1 hr post testing. Your estimated time commitment for these days are ~2 hr each day.

Days 2, 3, 4 & Days 6, 7 & 8 -Recovery Testing
You will be asked to complete follow-up testing 24, 48 and 72 hr after the each exercise bout (Day 1 & Day 5) in order to monitor your recovery from the exercise. In each session you will be asked to repeat the same testing that you performed before the exercise, including measures of range of motion, ultrasound of your biceps muscle, blood measures taken using the finger stick method, soreness measures using various scales and elbow flexor strength and power tests. Each of these sessions should take ~ 30 min. Additionally, when assigned to the CwC condition additional CwC therapy sessions will be provided at 24 & 48 hr post-exercise How will my data be used?
Your data will coded so that you cannot be identified and results from analysis of your data will presented at scientific conferences and published in scientific journal without any individual identifiers.
What are the possible risks of being in this research study?
There are minimal risks to you from being in this research study but you may experience delayed onset muscle soreness after the exercise intervention but this should not affect your daily living.
What are the possible benefits to you?
You are not expected to get any benefit from being in this study.

What are the possible benefits to other people?
The results from this study will provide information that can potentially be used to improve the effectiveness of recovery programs that are designed to help people to recovery from exercise or injury.

What are the alternatives to being in this research study?
Instead of being in this research study you can decide not to take part in this study without any repercussions.

What will being in this research study cost you?
There is no cost to you to be in this research study.

Will you be compensated for being in this research study?
You will receive financial compensation of $150 in gift cards after completion of the study.

What should you do if you have a problem during this research study?
Your welfare is the major concern of every member of the research team. If you have a problem as a direct result of being in this study, you should immediately contact one of the people listed at the beginning of this consent form.

How will information about you be protected?
Reasonable steps will be taken to protect your privacy and the confidentiality of your study data. The data will be stored electronically through a secure server and will only be seen by the research team during the study. The only persons who will have access to your research records are the study personnel, the Institutional Review Board (IRB), and any other person, agency, or sponsor as required by law. The information from this study may be published in scientific journals or presented at scientific meetings but the data will be reported as group or summarized data and your identity will be kept strictly confidential.

What are your rights as a research subject?
You may ask any questions concerning this research and have those questions answered before agreeing to participate in or during the study.
For study related questions, please contact the investigator listed at the beginning of this form.
For questions concerning your rights or complaints about the research contact the Institutional Review Board (IRB) or Vice President for Research and Economic Development: • IRB: (401) 874-4328 / researchintegrity@etal.uri.edu.
• Vice President for Research and Economic Development: at (401) 874-4576 What will happen if you decide not to be in this research study or decide to stop participating once you start?
You can decide not to be in this research study, or you can stop being in this research study ("withdraw') at any time before, during, or after the research begins for any reason. Deciding not to be in this research study or deciding to withdraw will not affect your relationship with the investigator or with the University of Rhode Island (list others as applicable).
You will not lose any benefits to which you are entitled.

Documentation of informed consent
You are voluntarily making a decision whether or not to be in this research study.
Signing this form means that (1) you have read and understood this consent form, (2) you have had the consent form explained to you, (3) you have had your questions answered and (4) you have decided to be in the research study. You will be given a copy of this consent form to keep. My signature certifies that all elements of informed consent described on this consent form have been explained fully to the subject. In my judgment, the participant possesses the capacity to give informed consent to participate in this research and is voluntarily and knowingly giving informed consent to participate.