Recovery from exercise is an important factor in the performance of successful resistance exercise training programs. Modalities have become an important part of the interventions that may assist in the recovery process from both the physiological and perceptual perspectives. The negative transient effects after exercise results in the reluctance or inability to continue or optimally perform a regular exercise program (Lee et al., 2012). Compression and contrast treatments of hot and cold have shown minimal effects on recovery from resistance exercise however contrast treatments did attenuate muscle soreness (French et al., 2008). Cold temperatures have been shown to constrict blood vessels and help flush toxins like H+ ions more rapidly from the muscles (Bailey et al., 2007; Eston and Peters, 1999), reduce inflammation (Pournot et al., 2011), reduce thermal strain (Vaile et al., 2008a), and reduce muscle soreness (Vaile et al., 2008b). However, a recent meta-analysis has shown cooling therapies effects on recovery from exercise to be minimal with only perceptual ratings showing improvements (Hohenauer et al., 2015). Thus, it appears that new cryo-technologies are needed to address the recovery processes following exercise.
The study of compression garments has increased dramatically since the early 1990s with our understanding of its effects. Compression has been shown to improve blood flow of oxygen rich blood back to the body (MacRae et al., 2011), reduced muscle vibration thereby providing stability to the muscle help prevent microtrauma to the muscles (MacRae et al., 2011), alleviate swelling and inflammation (Kraemer et al., 1998), increase muscle support (Kraemer et al., 2010a), and enhance proprioception (Shim et al., 2001). It has also been shown that compression can enhance recovery of muscle strength after a heavy resistance exercise workout (Goto and Morishima, 2014; Kraemer et al., 2010b). Recent data indicate that compression can significantly improve recovery from exercise induced damage with higher compressions having a greater effect (Hill et al., 2017).
However, very little research has been done to determine the benefits of combining cold and compression (i.e., cryocompression therapy) as a post exercise therapeutic intervention as most have used this for clinical/medical applications (Hoiness et al., 1998). Thus, there was a need for further work on cryocompression technologies that may assist in the recovery from exercise and allow for better day to day training performances and therefore improve the effectiveness of the training program. Thus the purpose of this study was to determine the effects of cryocompression on performance and recovery parameters following heavy resistance exercise.
Sixteen healthy recreational resistance exercise trained men were recruited to participate in the study. Subjects had been involved with resistance training for at least 6 months with regular barbell squats as part of their training 2 times per week. Each subject had to squat at least 1.0 X their body mass and groups were also matched on training status. The Ohio State University's Institutional Review Board for Human Research approved the study. The study's protocols, procedures, risks, and benefits were fully explained to each of the participants before they signed the approved informed consent document. Baseline measurements were obtained and used to match subject pairs for age (yrs), height (cm), body mass (kg), strength (1RM barbell back squat), body composition (7site skin fold), power (counter movement and squat jump), reaction time (Quick Board reaction test), and physical activity (International Physical Activity Questionnaire). From the matched pair participants were then randomly assigned to either the cryocompression (CRC) or the Control (CON) treatment groups. In subsequent analyses it was then demonstrated there were no significant differences between CRC and CON groups at baseline (see Table 1).
Participants were familiarized with the testing protocols on a familiarization day and then allowed to subsequently come in to the laboratory again and practice each test as much as they wanted until they were comfortable with the testing procedures. We have found this minimizes any potential learning effects. Baseline measurements were obtained and used for matching purposes as noted before. Additionally, participants in the CRC group were also sized for proper fit of the Cryocompression pants.
Participants reported to the laboratory on 3 consecutive days for testing (see experimental design in Figure 1). On day 1 (PERF), participants performed an acute bout of resistance exercise (AHRET) and then 20 minutes of their respective treatment immediately following exercise. Blood samples were obtained to indirectly measure muscular damage before (PRE), immediately after (IP), and +60min after exercise. Perceptual measures were obtained before (PRE), 20 minutes (+20min) after and 60 minutes (+60min) after exercise. Before all performance testing participants were taken through a simple warm-up procedure that consisted of walking on a treadmill for 5 minutes and lower body dynamic stretches. Performance tests were measured before (PRE) and 60 minutes (+60min) after the exercise bout.
Twenty-four hours and again forty-eight hours after the exercise bout participants again reported to the laboratory. Again, a blood sample and perceptual measures were obtained, 20 minutes of respective treatment was administered, and then participants warmed-up and performance testing was again conducted.
Cryocompression garment characteristics
Aquilo Sports (Louisville, KY, USA) developed a novel portable therapy system that combines cryo and compression in one recovery modality system. The system we used was comprised of a wearable 3-layer compression garment lined with polyurethane flow channels situated between an outer compression layer and a soft inner layer (skin contact), and a control unit for circulating cooled water through sealed flow channels at a regulated temperature (see Figure 2).
Garment characteristics were validated for the study with skin surface area temperature ([degrees]C) during the treatment and post-treatment (20 minutes) was validated using an infrared thermometer (Nubee NUB8500H, Duarte, CA, USA). In order to determine skin temperature during the treatment, the garment was briefly opened on one leg with three measurements simultaneously recorded (front quadricep, back quadricep, and gastrocnemius). Consecutive measurements were taken on alternating legs to reduce cooling loss each time the garment was opened. Quadricep, patella (knee), and gastrocnemius (calf) compression (mmHg) was measured throughout the lower body (Microlab PicoPress, Nicolo, Italy) by compression sensors placed at each location.
The pressure-flow relationship (H-Q curve) demonstrated the ability to generate flow up to 3 L * [min.sup.-1] at inlet pressure of 12 psi. The experimental garment achieved targeted compression metrics and skin temperature with uniform cooling (10-12[degrees] C) across the lower body (see Figure 3). No device failures, leaks, or deterioration occurred during endurance, durability, and robustness testing or in its use in the experimental study.
Acute bout of resistance exercise
The acute bout of heavy resistance exercise was designed to create muscular fatigue and moderate muscle tissue damage in the lower body musculature. It was a heavy resistance exercise protocol that many healthy recreationally resistance trained adults may perform during a typical workout. Therefore, participants performed barbell back squats for 4 sets of 6 repetitions at 80% of their one repetition maximum with 90 seconds rest between sets, followed by stiff legged deadlifts for 4 sets of 8 repetitions using 1.0 X body mass with 60 seconds rest between sets, followed by eccentric legs curls (Nordic hamstring curls) for 4 sets of 10 repetitions with 45 seconds rest between sets.
Blood draws and muscle damage biomarker
A trained phlebotomist collected blood from the antecubital vein in the arm at PRE, IP, +60min, +24H, and +48H into serum 10ml vacutainers. Blood was allowed to sit at room temperature between 30-60 minutes to clot and then centrifuged using a Sorvall Legend XT centrifuge (Thermo Fisher Scientific Inc., Waltham, MA, USA) at 3000 rpm for 10 minutes and aliquoted into labeled 1.5ml micro centrifuge tubes. Samples were immediately placed in--80[degrees] C freezers for storage. After all testing was complete, frozen samples were thawed once and analyzed.
Total serum creatine kinase (CK) concentrations were used as an indirect biochemical marker of muscle fatigue and damage (Brancaccio et al., 2010). Creatine kinase concentrations were determined using Sekusui's creatine kinase-SL enzymatic assay...