What are the Physiological Mechanisms for Post-Exercise Cold Water Immersion in the Recovery from Prolonged Endurance and Intermittent Exercise?

Muscle Cooling Before and in the Middle of a Session: There Are Benefits on Subsequent Localized Endurance Performance in a Warm Environment

ABSTRACT

Baláš, J, Kodejška, J, Procházková, A, Knap, R, and Tufano, JJ. Muscle cooling before and in the middle of a session: there are benefits on subsequent localized endurance performance in a warm environment. J Strength Cond Res 38(3): 533-539, 2024-Localized cold-water immersion (CWI) has been shown to facilitate recovery in the middle of a session of exhaustive repeated forearm contractions. However, it has been suggested that these benefits may be attributed to "precooling" the muscle before an activity, as opposed to cooling a previously overheated muscle. Therefore, this study aimed to determine how precooling and mid-cooling affects localized repeated muscular endurance performance in a warm environment. Nineteen subjects completed a familiarization session and 3 laboratory visits, each including 2 exhaustive climbing trials separated by 20 minutes of recovery: PRE CWI (CWI, trial 1; passive sitting [PAS], trial 2); MID CWI (PAS, trial 1; CWI, trial 2); and CONTROL (PAS, trial 1; PAS, trial 2). Climbing trial 1 in PRE CWI was 32 seconds longer than in CONTROL ( p = 0.013; d = 0.46) and 47 seconds longer than in MID CWI ( p = 0.001; d = 0.81). The time of climbing trial 2 after PAS (PRE CWI and CONTROL) was very similar (312 vs. 319 seconds) irrespective of the first trial condition. However, the time of the second trial in MID CWI was 43 seconds longer than in PRE CWI ( p < 0.001; d = 0.63) and 50 seconds longer than in CONTROL ( p < 0.001; d = 0.69). In warm environments, muscle precooling and mid-cooling can prolong localized endurance performance during climbing. However, the effectiveness of mid-cooling may not be as a "recovery strategy" but as a "precooling" strategy to decrease muscle temperature before subsequent performance, delaying the onset of localized heat-induced neuromuscular fatigue.

Mechanism involved of post-exercise cold water immersion: Blood redistribution and increase in energy expenditure during rewarming

Thermogenesis is well understood, but the relationships between cold water immersion (CWI), the post-CWI rewarming and the associated physiological changes are not. This study investigated muscle and systemic oxygenation, cardiorespiratory and hemodynamic responses, and gastrointestinal temperature during and after CWI. 21 healthy men completed randomly 2 protocols. Both protocols consisted of a 48 minutes heating cycling exercise followed by 3 recovery periods (R1-R3), but they differed in R2. R1 lasted 20 minutes in a passive semi-seated position on a physiotherapy table at ambient room temperature. Depending on the protocol, R2 lasted 15 minutes at either ambient condition (R2_AMB) or in a CWI condition at 10°C up to the iliac crest (R2_CWI). R3 lasted 40 minutes at AMB while favoring rewarming after R2_CWI. This was followed by 10 minutes of cycling. Compared to R2_AMB, R2_CWI ended at higherV ˙ O2 in the non-immersed body part due to thermogenesis (7.16(2.15) vs. 4.83(1.62) ml.min-1.kg-1) and lower femoral artery blood flow (475(165) vs. 704(257) ml.min-1) (p < 0.001). Only after CWI, R3 showed a progressive decrease in vastus and gastrocnemius medialis O2 saturation, significant after 34 minutes (p < 0.001). As blood flow did not differ from the AMB protocol, this indicated local thermogenesis in the immersed part of the body. After CWI, a lower gastrointestinal temperature on resumption of cycling compared to AMB (36.31(0.45) vs. 37.30(0.49) °C, p < 0.001) indicated incomplete muscle thermogenesis. In conclusion, the rewarming period after CWI was non-linear and metabolically costly. Immersion and rewarming should be considered as a continuum rather than separate events.

Influence of physical post-exercise recovery techniques on vagally-mediated heart rate variability: A systematic review and meta-analysis

In sports, physical recovery following exercise-induced fatigue is mediated via the reactivation of the parasympathetic nervous system (PNS). A noninvasive way to quantify the reactivation of the PNS is to assess vagally-mediated heart rate variability (vmHRV), which can then be used as an index of physical recovery. This systematic review and meta-analysis investigated the effects of physical recovery techniques following exercise-induced fatigue on vmHRV, specifically via the root mean square of successive differences (RMSSD). Randomized controlled trials from the databases PubMed, WebOfScience, and SportDiscus were included. Twenty-four studies were part of the systematic review and 17 were included in the meta-analysis. Using physical post-exercise recovery techniques displayed a small to moderate positive effect on RMSSD (k = 22, Hedges' g = 0.40, 95% confidence interval [CI] = 0.20-0.61, p = 0.04) with moderate heterogeneity. In the subgroup analyses, cold water immersion displayed a moderate to large positive effect (g = 0.75, 95% CI: 0.42-1.07) compared with none for other techniques. For exercise type, physical recovery techniques performed after resistance exercise (g = 0.69, 95% CI: 0.48-0.89) demonstrated a larger positive effect than after cardiovascular intermittent (g = 0.52, 95% CI: 0.06-0.97), while physical recovery techniques performed after cardiovascular continuous exercise had no effect. No significant subgroup differences for training status and exercise intensity were observed. Overall, physical post-exercise recovery techniques can accelerate PNS reactivation as indexed by vmHRV, but the effectiveness varies with the technique and exercise type.

Effect of foam rolling recovery on pain and physical capacity after resistance exercises: A randomized crossover trial

OBJECTIVES

To compare the effects of passive recovery (PR), active recovery (AR), and recovery through self-massage with the aid of foam rolling (FRR) on pain and physical capacity in healthy volunteers after a resistance exercise (RE) session.

METHODS

The sample of this randomized crossover trial comprised 37 physically healthy men who underwent three sessions of RE (squat, leg press, and leg extension), involving four sets of 10 repetitions with 80% of 10MR, with an interval of seven days between sessions. PR consisted of sitting for 20min, AR included a cycle ergometer for 20min at 50% maximum heart rate, and FRR involved 10 repetitions per target body area, followed by 1min rest. Variables of physical capacity (strength, power, agility, joint range of motion, flexibility, speed, and fatigue resistance) were assessed 1h after RE, whereas pain was assessed 24h, 48h, and 72h after RE.

RESULTS

In the dominant lower limb, the percentage of strength decreased (p < 0.001) by 16.3% after RE but improved (p < 0.001) by 5.2% after AR and FRR in relation to PR. Similar results were observed in the non-dominant lower limb. Agility was enhanced (p < 0.001) by 3.6% in AR and 4.3% in FRR compared with the baseline assessment. The recoveries for the other physical variables were similar. Only FRR reduced (p < 0.001) pain at 24h (22.8%), 48h (39.2%), and 72h (59.7%) compared to PR.

CONCLUSIONS

Self-massage using a foam roll reduced pain and improved agility and muscle strength during recovery after exercise.

TRIAL REGISTRATION NUMBER

NCT04201977.

Enhancing physiological recovery and subsequent exercise performance in the heat using a phase-change material cooling blanket

This study aimed to assess the effect of a phase-change material (PCM) cooling blanket for cooling between exercise bouts on recovery of physiological parameters and subsequent exercise performance in the heat. Eighteen male volunteers were recruited to participate in human trials involving two exhaustive treadmill running bouts (Bout1 for 3 km and Bout2 for 1.5 km) in a climate chamber (temperature = 33 °C; relative humidity = 40%). Participants were randomly subjected to one of two cooling conditions for a 10-min period between exercise bouts: CON: natural cooling; 10-min PCM: with a PCM cooling blanket for 10 min. Several physiological parameters including mean skin temperature (Tskin), oral temperature (Toral), core temperature (Tcore), heart rate (HR), mean arterial pressure (MAP), respiratory rate (RR), peripheral capillary oxygen saturation (SpO2), average running speed and rating of perceived exertion (RPE) scale score were analyzed. The results showed that compared to the CON group, participants in the 10-min PCM group had a significant lower Tskin, Tcore, HR and RR at post-cooling, as well as greater reductions in mean skin temperature (ΔTskin) and core temperature (ΔTcore) from post-Bout1 to post-cooling. Additionally, the 10-min PCM group exhibited significantly lower peak Tcore, peak HR and RPE scale score during Bout2, while the average running speed during Bout2 was significantly higher. The present study suggests that cooling with a PCM cooling blanket can enhance physiological recovery and subsequent exercise performance in the heat.

Energetic responses of head-out water immersion at different temperatures during post-exercise recovery and its consequence on anaerobic mechanical power

PURPOSE

While exercise recovery may be beneficial from a physiological point of view, it may be detrimental to subsequent anaerobic performance. To investigate the energetic responses of water immersion at different temperatures during post-exercise recovery and its consequences on subsequent anaerobic performance, a randomized and controlled crossover experimental design was performed with 21 trained cyclists.

METHOD

Participants were assigned to receive three passive recovery strategies during 10 min after a Wingate Anaerobic Test (WAnT): control (CON: non-immersed condition), cold water immersion (CWI: 20 ℃), and hot water immersion (HWI: 40 ℃). Blood lactate, cardiorespiratory, and mechanical outcomes were measured during the WAnT and its recovery. Time constant (τ), asymptotic value, and area under the curve (AUC) were quantified for each physiologic parameter during recovery. After that, a second WAnT test and 10-min recovery were realized in the same session.

RESULTS

Regardless the water immersion temperature, water immersion increased [Formula: see text] (+ 18%), asymptote ([Formula: see text]+ 16%, [Formula: see text] + 13%, [Formula: see text] + 17%, HR + 16%) and AUC ([Formula: see text]+ 27%, [Formula: see text] + 18%, [Formula: see text] + 20%, HR + 25%), while decreased [Formula: see text] (- 33%). There was no influence of water immersion on blood lactate parameters. HWI improved the mean power output during the second WAnT (2.2%), while the CWI decreased 2.4% (P < 0.01).

CONCLUSION

Independent of temperature, water immersion enhanced aerobic energy recovery without modifying blood lactate recovery. However, subsequent anaerobic performance was increased only during HWI and decreased during CWI. Despite higher than in other studies, 20 °C effectively triggered physiological and performance responses. Water immersion-induced physiological changes did not predict subsequent anaerobic performance.

Effect of CO2 and H2 gas mixture in cold water immersion on recovery after eccentric loading

Background

The findings of previous studies support the efficacy of cold water immersion (CWI) with carbon dioxide (CO2) in enhancing muscle blood flow and maintaining aerobic performance efficiency. We hypothesize that the addition of hydrogen gas (H2), known for its antioxidant properties and role in inflammation regulation, to C-CWI can enhance recovery after eccentric exercise.

Subjects

and Methods: Thirty-four healthy subjects performed a knee-extensor eccentric exercise. They were randomly allocated into four groups: control, CWI, CO2-rich CWI (C-CWI), and CO2 + H2 gas mixture CWI (CH-CWI). In the three CWI groups, all subjects were immersed in the appropriate bath at 20 °C for 20 min immediately after 60 repetitions of eccentric exercise. Before exercise and after 48 h of recovery, the subjects' maximal voluntary isometric contraction torque (MVC-ISO), maximal voluntary concentric (MVC-CON) contraction torque, countermovement jump (CMJ) height, knee flexion range of motion (ROM), muscle soreness, and muscle thickness were measured.

Results

In the CH-CWI group only, the MVC-ISO, CMJ height, and ROM did not decrease significantly post-exercise, whereas all of these decreased in the other three groups. Muscle soreness at palpation, contraction, and stretching significantly increased post-exercise in all groups. Echo intensity and tissue hardness did not increase significantly in the CH-CWI group.

Conclusions

CH-CWI stimulated recovery from impairments in MVC-ISO torque, CMJ height, knee-flexion ROM, tissue hardness, and echo intensity. These findings indicate that CH-CWI can promote recovery after eccentric exercise.

Repeated cold-water immersion improves autonomic cardiac modulation following five sessions of high-intensity interval exercise

PURPOSE

The study aimed to investigate the effect of repeated cold-water immersion (CWI) after high-intensity interval exercise sessions on cardiac-autonomic modulation, neuromuscular performance, muscle damage markers, and session internal load.

METHODS

Twenty-one participants underwent five sessions of high-intensity interval exercise (6-7 bouts of 2 min; pause of 2 min) over a two-week period. Participants were allocated randomly into either a group that underwent CWI (11-min; 11 °C) or a group that performed passive recovery after each exercise session. Before the exercise sessions were performed, countermovement jump (CMJ) and heart rate variability were recorded (i.e., rMSSD, low and high frequency power and its ratio, SD1 and SD2). Exercise heart rate was calculated by recording the area under the curve (AUC) response. Internal session load was evaluated 30 min after each session. Blood concentrations of creatine kinase and lactate dehydrogenase were analyzed before the first visit and 24 h after the last sessions.

RESULTS

The CWI group presented higher rMSSD than the control group at each time point (group-effect P = 0.037). The SD1 was higher in CWI group when compared to the control group following the last exercise session (interaction P = 0.038). SD2 was higher in CWI group compared to the control group at each time point (group-effect P = 0.030). Both groups presented equal CMJ performance (P > 0.05), internal load (group-effect P = 0.702; interaction P = 0.062), heart rate AUC (group-effect P = 0.169; interaction P = 0.663), and creatine kinase and lactate dehydrogenase blood concentrations (P > 0.05).

CONCLUSION

Repeated post-exercise CWI improves cardiac-autonomic modulation. However, no differences in neuromuscular performance, muscle damage markers, or session internal load were demonstrated between the groups.

Cold-water immersion and whole-body cryotherapy attenuate muscle soreness during 3 days of match-like tennis protocol

PURPOSE

This study aimed to investigate the effect of whole-body cryotherapy (WBC), cold-water immersion (CWI) and passive recovery (PAS) on tennis recovery.

METHODS

Thirteen competitive male tennis players completed three consecutive match-like tennis protocols, followed by recovery (WBC, CWI, PAS) in a crossover design. Five tennis drills and serves were performed using a ball machine to standardize the fatiguing protocol. Maximal voluntary contraction (MVC) peak torque, creatine kinase activity (CK), muscle soreness, ball accuracy and velocity together with voluntary activation, low- and high-frequency torque and EMG activity were recorded before each protocol and 24 h following the third protocol.

RESULTS

MVC peak torque (- 7.7 ± 11.3%; p = 0.001) and the high- to low-frequency torque ratio (- 10.0 ± 25.8%; p < 0.05) decreased on Day 1 but returned to baseline on Day 2, Day 3 and Day 4 (p = 0.052, all p > 0.06). The CK activity slightly increased from 161.0 ± 100.2 to 226.0 ± 106.7 UA L-1 on Day 1 (p = 0.001) and stayed at this level (p = 0.016) across days with no differences between recovery interventions. Muscle soreness increased across days with PAS recovery (p = 0.005), while no main effect of time was neither observed with WBC nor CWI (all p > 0.292). The technical performance was maintained across protocols with WBC and PAS, while it increased for CWI on Day 3 vs Day 1 (p = 0.017).

CONCLUSION

Our 1.5-h tennis protocol led to mild muscle damage, though neither the neuromuscular function nor the tennis performance was altered due to accumulated workload induced by consecutive tennis protocols. The muscle soreness resulting from tennis protocols was similarly alleviated by both CWI and WBC.

TRIAL REGISTRATION

IRB No. 2017-A02255-48, 12/05/2017.

Active recovery vs hot- or cold-water immersion for repeated sprint ability after a strenuous exercise training session in elite skaters

This study compared the acute effects of three recovery methods: active recovery (AR), hot- and cold-water immersion (HWI and CWI, respectively), used between two training sessions in elite athletes. Twelve national-team skaters (7 males, 5 females) completed three trials according to a randomized cross-over study. Fifteen minutes after an exhaustive ice-skating training session, participants underwent 20 min of HWI (41.1 ± 0.5°C), 15 min of CWI (12.1 ± 0.7°C) or 15 min of active recovery (AR). After 1 h 30 min of the first exercise, they performed a repeated-sprint cycling session. Average power output was slightly but significantly higher for AR (767 ± 179 W) and HWI (766 ± 170 W) compared to CWI (738 ± 156 W) (p = 0.026, d = 0.18). No statistical difference was observed between the conditions for both lactatemia and rating of perceived exertion. Furthermore, no significant effect of recovery was observed on the fatigue index calculated from the repeated sprint cycling exercises (p > 0.05). Finally, a positive correlation was found between the average muscle temperature measured during the recoveries and the maximal power output obtained during cycling exercises. In conclusion, the use of CWI in between high-intensity training sessions could slightly impair the performance outcomes compared to AR and HWI. However, studies with larger samples are needed to confirm these results, especially in less trained athletes.

Acute Performance, Daily Well-Being, and Hormone Responses to Water Immersion After Resistance Exercise in Junior International and Subelite Male Volleyball Athletes

ABSTRACT

Horgan, BG, Tee, N, West, NP, Drinkwater, EJ, Halson, SL, Colomer, CME, Fonda, CJ, Tatham, J, Chapman, DW, and Haff, GG. Acute performance, daily well-being and hormone responses to water immersion after resistance exercise in junior international and subelite male volleyball athletes. J Strength Cond Res XX(X): 000-000, 2023-Athletes use postexercise hydrotherapy strategies to improve recovery and competition performance and to enhance adaptative responses to training. Using a randomized cross-over design, the acute effects of 3 postresistance exercise water immersion strategies on perceived recovery, neuromuscular performance, and hormone concentrations in junior international and subelite male volleyball athletes (n = 18) were investigated. After resistance exercise, subjects randomly completed either 15-minute passive control (CON), contrast water therapy (CWT), cold (CWI), or hot water immersion (HWI) interventions. A treatment effect occurred after HWI; reducing perceptions of fatigue (HWI > CWT: p = 0.05, g = 0.43); improved sleep quality, compared with CON (p < 0.001, g = 1.15), CWI (p = 0.017, g = 0.70), and CWT (p = 0.018, g = 0.51); as well as increasing testosterone concentration (HWI > CWT: p = 0.038, g = 0.24). There were trivial to small (p < 0.001-0.039, g = 0.02-0.34) improvements (treatment effect) in jump performance (i.e., squat jump and countermovement jump) after all water immersion strategies, as compared with CON, with high variability in the individual responses. There were no significant differences (interaction effect, p > 0.05) observed between the water immersion intervention strategies and CON in performance (p = 0.153-0.99), hormone (p = 0.207-0.938), nor perceptual (p = 0.368-0.955) measures. To optimize recovery and performance responses, e.g., during an in-season competition phase, postresistance exercise HWI may assist with providing small-to-large improvements for up to 38 hours in perceived recovery (i.e., increased sleep quality and reduced fatigue) and increases in circulating testosterone concentration. Practitioners should consider individual athlete neuromuscular performance responses when prescribing postexercise hydrotherapy. These findings apply to athletes who aim to improve their recovery status, where postresistance exercise HWI optimizes sleep quality and next-day perceptions of fatigue.

Effects of cooling glove on the human body's recovery after exercise and improvement of exercise ability

BACKGROUND

After high-intensity exercises, the body's core temperature increases, affecting the body's metabolism, increasing thermal stress and muscle fatigue. The most popular technique to maximize post-workout recovery is cryotherapy. However, the cooling effect may vary depending on the body part being cooled since body tissues do not process the same perfusion.

OBJECTIVE

This study investigates the effects of hand cooling on human body functional recovery and exercise ability improvement by comparing normal rest and rest with hand cooling gloves after high-intensity exercise.

METHODS

Thirty healthy subjects participated in this study wherein they exercised and used normal rest for one session and hand cooling rest for the next. Blood lactate concentration, heart rate recovery rate, VO2 max measurement, and the degree of recovery of muscle strength, muscular endurance, and muscle fatigue were investigated in both groups to determine the efficacy of hand cooling gloves for postexercise recovery.

RESULTS

When hands were cooled after exercise, blood lactate concentration and body temperature significantly decreased, and cardiopulmonary function, muscle strength, and muscular endurance significantly recovered.

CONCLUSION

Using hand cooling gloves after exercise could attenuate core temperature elevation and improve postexercise recovery. It could also effectively improve athletic performance without using large-scale facilities.

Effects of a Graphene Heating Device on Fatigue Recovery of Biceps Brachii

Far-infrared (FIR) is considered to be an ideal method to promote fatigue recovery due to its high permeability and strong radiation. In this paper, we report a flexible and wearable graphene heating device to help fatigue recovery of human exercise by using its high FIR divergence property. This study compares two different fatigue recovery methods, graphene far-infrared heating device hot application and natural recovery, over a 20 min recovery time among the male colleges' exhaustion exercise. Experimental results show that the achieved graphene device holds excellent electro-thermal radiation conversion efficiency of 70% and normal total emissivity of 89%. Moreover, the graphene FIR therapy in our work is more energy-efficient, easy to use, and wearable than traditional fatigue recovery methods. Such an anti-fatigue strategy offers new opportunities for enlarging potential applications of graphene film in body science, athletic training recovery, and wearable devices.

The effect of cold water immersion on the recovery of physical performance revisited: A systematic review with meta-analysis

This review evaluated the effect of CWI on the temporal recovery profile of physical performance, accounting for environmental conditions and prior exercise modality. Sixty-eight studies met the inclusion criteria. Standardised mean differences were calculated for parameters assessed at <1, 1-6, 24, 48, 72 and ≥96 h post-immersion. CWI improved short-term recovery of endurance performance (p = 0.01, 1 h), but impaired sprint (p = 0.03, 1 h) and jump performance (p = 0.04, 6h). CWI improved longer-term recovery of jump performance (p < 0.01-0.02, 24 h and 96 h) and strength (p < 0.01, 24 h), which coincided with decreased creatine kinase (p < 0.01-0.04, 24-72 h), improved muscle soreness (p < 0.01-0.02, 1-72 h) and perceived recovery (p < 0.01, 72 h). CWI improved the recovery of endurance performance following exercise in warm (p < 0.01) and but not in temperate conditions (p = 0.06). CWI improved strength recovery following endurance exercise performed at cool-to-temperate conditions (p = 0.04) and enhanced recovery of sprint performance following resistance exercise (p = 0.04). CWI seems to benefit the acute recovery of endurance performance, and longer-term recovery of muscle strength and power, coinciding with changes in muscle damage markers. This, however, depends on the nature of the preceding exercise.

Effects of Cold-Water Immersion Compared with Other Recovery Modalities on Athletic Performance Following Acute Strenuous Exercise in Physically Active Participants: A Systematic Review, Meta-Analysis, and Meta-Regression

BACKGROUND

Studies investigating the effects of common recovery modalities following acute strenuous exercise have reported mixed results.

OBJECTIVES

This systematic review with meta-analysis and meta-regression compared the effects of cold-water immersion (CWI) against other common recovery modalities on recovery of athletic performance, perceptual outcomes, and creatine kinase (CK) following acute strenuous exercise in physically active populations.

STUDY DESIGN

Systematic review, meta-analysis, and meta-regression.

METHODS

The MEDLINE, SPORTDiscus, Scopus, Web of Science, Cochrane Library, EmCare, and Embase databases were searched up until September 2022. Studies were included if they were peer reviewed, published in English, included participants who were involved in sport or deemed physically active, compared CWI with other recovery modalities following an acute bout of strenuous exercise, and included measures of performance, perceptual measures of recovery, or CK.

RESULTS

Twenty-eight studies were meta-analysed. CWI was superior to other recovery methods for recovering from muscle soreness, and similar to other methods for recovery of muscular power and flexibility. CWI was more effective than active recovery, contrast water therapy and warm-water immersion for most recovery outcomes. Air cryotherapy was significantly more effective than CWI for the promotion of recovery of muscular strength and the immediate recovery of muscular power (1-h post-exercise). Meta-regression revealed that water temperature and exposure duration were rarely exposure moderators.

CONCLUSION

CWI is effective for promoting recovery from acute strenuous exercise in physically active populations compared with other common recovery methods.

PROTOCOL REGISTRATION

Open Science Framework: https://doi.org/10.17605/OSF.IO/NGP7C.

Cold water immersion after a soccer match: Does the placebo effect occur?

Although cold water immersion (CWI) is one of the most widely used post-exercise strategies to accelerate recovery processes, the benefits of CWI may be associated with placebo effects. This study aimed to compare the effects of CWI and placebo interventions on time course of recovery after the Loughborough Intermittent Shuttle Test (LIST). In a randomized, counterbalanced, crossover study, twelve semi-professional soccer players (age 21.1 ± 2.2 years, body mass 72.4 ± 5.9 kg, height 174.9 ± 4.6 cm, V ˙ O_2max 56.1 ± 2.3 mL/min/kg) completed the LIST followed by CWI (15 min at 11°C), placebo (recovery Pla beverage), and passive recovery (Rest) over three different weeks. Creatine kinase (CK), C-reactive protein (CRP), uric acid (UA), delayed onset muscle soreness (DOMS), squat jump (SJ), countermovement jump (CMJ), 10-m sprint (10 mS), 20-m sprint (20 mS) and repeated sprint ability (RSA) were assessed at baseline and 24 and 48 h after the LIST. Compared to baseline, CK concentration was higher at 24 h in all conditions (p < 0.01), while CRP was higher at 24 h only in CWI and Rest conditions (p < 0.01). UA was higher for Rest condition at 24 and 48 h compared to Pla and CWI conditions (p < 0.001). DOMS score was higher for Rest condition at 24 h compared to CWI and Pla conditions (p = 0.001), and only to Pla condition at 48 h (p = 0.017). SJ and CMJ performances decreased significantly after the LIST in Rest condition (24 h: -7.24%, p = 0.001 and -5.45%, p = 0.003 respectively; 48 h: -9.19%, p < 0.001 and -5.70% p = 0.002 respectively) but not in CWI and Pla conditions. 10 mS and RSA performance were lower for Pla at 24 h compared to CWI and Rest conditions (p < 0.05), while no significant change was observed for 20 mS time. These data suggests that CWI and Pla intervention were more effective than the Rest conditions in recovery kinetics of muscle damage markers and physical performance. Furthermore, the effectiveness of CWI would be explained, at least in part, by the placebo effect.

Time-specific effects of acute eccentric exercise on myostatin, follistatin and decorin in the circulation and skeletal muscle in rats

Myostatin (MSTN), an important negative regulator of skeletal muscle, plays an important role in skeletal muscle health. In previous study, we found that the expression of MSTN was different during skeletal muscle injury repair. Therefore, we explored the expression changes of MSTN at different time points during skeletal muscle injury repair after eccentric exercise. In addition, MSTN is regulated by follistatin (FST) and decorin (DCN) in vivo, so our study examined the time-specific changes of FST, DCN and MSTN in the circulation and skeletal muscle during skeletal muscle injury repair after eccentric exercise, and to explore the reasons for the changes of MSTN in the process of exercise-induced muscle injury repair, to provide a basis for promoting muscle injury repair. The rats performed one-time eccentric exercise. Blood and skeletal muscle were collected at the corresponding time points, respectively immediate after exercise (D0), one day (D1), two days (D2), three days (D3), seven days (W1) and fourteen days (W2) after exercise (n=8). The levels of MSTN, FST, DCN in serum and mRNA and protein expression in muscle were detected. MSTN changes in the blood and changes in DCN and FST showed the opposite trend, except immediately after exercise. The change trends of mRNA and protein of gastrocnemius DCN and MSTN are inconsistent, there is post-transcriptional regulation of MSTN and DCN in gastrocnemius. Acute eccentric exercise might stimulate the secretion of DCN and FST into the circulation and inhibit MSTN. MSTN may be regulated by FST and DCN after acute eccentric exercise.

The Influence of Ambient Temperature Changes on the Indicators of Inflammation and Oxidative Damage in Blood after Submaximal Exercise

Physical activity has a positive effect on human health and well-being, but intense exercise can cause adverse changes in the organism, leading to the development of oxidative stress and inflammation. The aim of the study was to determine the effect of short-term cold water immersion (CWI) and a sauna bath as methods of postexercise regeneration on the indicators of inflammation and oxidative damage in the blood of healthy recreational athletes. Forty-five male volunteers divided into two groups: 'winter swimmers' who regularly use winter baths (n = 22, average age 43.2 ± 5.9 years) and 'novices' who had not used winter baths regularly before (n = 23, mean age 25 ± 4.8 years) participated in the study. The research was divided into two experiments, differing in the method of postexercise regeneration used, CWI (Experiment I) and a sauna bath (Experiment II). During Experiment I, the volunteers were subjected to a 30-min aerobic exercise, combined with a 20-min rest at room temperature (RT-REST) or a 20-min rest at room temperature with an initial 3-min 8 °C water bath (CWI-REST). During the Experiment II, the volunteers were subjected to the same aerobic exercise, followed by a RT-REST or a sauna bath (SAUNA-REST). The blood samples were taken before physical exercise (control), immediately after exercise and 20 min after completion of regeneration. The concentrations of selected indicators of inflammation, including interleukin 1β (IL-1β), interleukin 6 (IL-6), interleukin 8 (IL-8), interleukin 8 (IL-8), interleukin 10 (IL-10), transforming growth factor β1 (TGF-β1) and tumor necrosis factor α (TNF-α), as well as the activity of indicators of oxidative damage: α1-antitrypsin (AAT) and lysosomal enzymes, including arylsulfatase A (ASA), acid phosphatase (AcP) and cathepsin D (CTS D), were determined. CWI seems to be a more effective post-exercise regeneration method to reduce the inflammatory response compared to a sauna bath. A single sauna bath is associated with the risk of proteolytic tissue damage, but disturbances of cellular homeostasis are less pronounced in people who regularly use cold water baths than in those who are not adapted to thermal stress.

Acute Inflammatory, Anthropometric, and Perceptual (Muscle Soreness) Effects of Postresistance Exercise Water Immersion in Junior International and Subelite Male Volleyball Athletes

ABSTRACT

Horgan, BG, West, NP, Tee, N, Drinkwater, EJ, Halson, SL, Vider, J, Fonda, CJ, Haff, GG, and Chapman, DW. Acute inflammatory, anthropometric, and perceptual (muscle soreness) effects of postresistance exercise water immersion in junior international and subelite male volleyball athletes. J Strength Cond Res 36(12): 3473-3484, 2022-Athletes use water immersion strategies to recover from training and competition. This study investigated the acute effects of postexercise water immersion after resistance exercise. Eighteen elite and subelite male volleyball athletes participated in an intervention using a randomized cross-over design. On separate occasions after resistance exercise, subjects completed 1 of 4 15-minute interventions: control (CON), cold water immersion (CWI), contrast water therapy (CWT), or hot water immersion (HWI). Significance was accepted at p ≤ 0.05. Resistance exercise induced significant temporal changes (time effect) for inflammatory, anthropometric, perceptual, and performance measures. Serum creatine kinase was reduced ( g = 0.02-0.30) after CWI ( p = 0.007), CWT ( p = 0.006), or HWI ( p < 0.001) vs. CON, whereas it increased significantly ( g = 0.50) after CWI vs. HWI. Contrast water therapy resulted in significantly higher ( g = 0.56) interleukin-6 concentrations vs. HWI. Thigh girth increased ( g = 0.06-0.16) after CWI vs. CON ( p = 0.013) and HWI ( p < 0.001) and between CWT vs. HWI ( p = 0.050). Similarly, calf girth increased ( g = 0.01-0.12) after CWI vs. CON ( p = 0.039) and CWT ( p = 0.018), and HWI vs. CON ( p = 0.041) and CWT ( p = 0.018). Subject belief in a postexercise intervention strategy was associated with HSP72 ("believer">"nonbeliever," p = 0.026), muscle soreness ("believer">"nonbeliever," p = 0.002), and interleukin-4 ("nonbeliever">"believer," p = 0.002). There were no significant treatment × time (interaction effect) pairwise comparisons. Choice of postexercise water immersion strategy (i.e., cold, contrast, or hot) combined with a belief in the efficacy of that strategy to enhance recovery or performance improves biological and perceptual markers of muscle damage and soreness. On same or subsequent days where resistance exercise bouts are performed, practitioners should consider athlete beliefs when prescribing postexercise water immersion, to reduce muscle soreness.

Functional Impact of Post-exercise Cooling and Heating on Recovery and Training Adaptations: Application to Resistance, Endurance, and Sprint Exercise

The application of post-exercise cooling (e.g., cold water immersion) and post-exercise heating has become a popular intervention which is assumed to increase functional recovery and may improve chronic training adaptations. However, the effectiveness of such post-exercise temperature manipulations remains uncertain. The aim of this comprehensive review was to analyze the effects of post-exercise cooling and post-exercise heating on neuromuscular function (maximal strength and power), fatigue resistance, exercise performance, and training adaptations. We focused on three exercise types (resistance, endurance and sprint exercises) and included studies investigating (1) the early recovery phase, (2) the late recovery phase, and (3) repeated application of the treatment. We identified that the primary benefit of cooling was in the early recovery phase (< 1 h post-exercise) in improving fatigue resistance in hot ambient conditions following endurance exercise and possibly enhancing the recovery of maximal strength following resistance exercise. The primary negative impact of cooling was with chronic exposure which impaired strength adaptations and decreased fatigue resistance following resistance training intervention (12 weeks and 4–12 weeks, respectively). In the early recovery phase, cooling could also impair sprint performance following sprint exercise and could possibly reduce neuromuscular function immediately after endurance exercise. Generally, no benefits of acute cooling were observed during the 24–72-h recovery period following resistance and endurance exercises, while it could have some benefits on the recovery of neuromuscular function during the 24–48-h recovery period following sprint exercise. Most studies indicated that chronic cooling does not affect endurance training adaptations following 4–6 week training intervention. We identified limited data employing heating as a recovery intervention, but some indications suggest promise in its application to endurance and sprint exercise.

Angiostatic freeze or angiogenic move? Acute cold stress prevents angiokine secretion from murine myotubes but primes primary endothelial cells for greater migratory capacity

The skeletal muscle tissue can adapt to exercise and environmental stressors with a remarkable plasticity. Prolonged cold stress exposure has been associated to increased skeletal muscle capillarization. Angioadaptation refers to the coordinated molecular and cellular processes that influence the remodeling of skeletal muscle microvasculature. Two cell types are central to angioadaptation: the myocytes, representing an important source of angiokines; and the skeletal muscle endothelial cell (SMECs), targets of these angiokines and main constituents of muscle capillaries. The influence of cold stress on skeletal muscle angioadaptation remains largely unknown, particularly with respect to myocyte-specific angiokines secretion or endothelial cell angioadaptive responses. Here, we use an in vitro model to investigate the impact of cold stress (28°C versus 37°C) on C2C12 myotubes and SMECs. Our main objectives were to evaluate: 1) the direct impact of cold stress on C2C12 cellular expression of angiokines and their release in the extracellular environment; 2) the indirect impact of cold stress on SMECs migration via these C2C12-derived angiokines; and 3) the direct effect of cold stress on SMECs angioadaptive responses, including migration, proliferation, and the activation of the vascular endothelial growth factor receptor-2 (VEGFR2). Cold stress reduced the secretion of angiokines in C2C12 myotubes culture media irrespective their pro-angiogenic or angiostatic nature. In SMECs, cold stress abrogated cell proliferation and reduced the activation of VEGFR2 despite a greater expression of this receptor. Finally, SMECs pre-conditioned to cold stress displayed an enhanced migratory response when migration was stimulated in rewarming conditions. Altogether our results suggest that cold stress may be overall angiostatic. However, cold stress accompanied by rewarming may be seen as a pro-angiogenic stressor for SMECs. This observation questions the potential for using pre-cooling in sport-performance or therapeutic exercise prescription to enhance skeletal muscle angioadaptive responses to exercise.

A combination of cherry juice and cold water immersion does not enhance marathon recovery compared to either treatment in isolation: A randomized placebo-controlled trial

Purpose

Cherry juice (CJ) and cold water immersion (CWI) are both effective recovery strategies following strenuous endurance exercise. However, athletes routinely combine recovery interventions and less is known about the impact of a combined CJ and CWI protocol. Therefore, this study investigated the effects of combining CWI and CJ (a “cocktail” (CT)) on inflammation and muscle damage following a marathon.

Methods

A total 39 endurance trained males were randomly assigned to a placebo (PL), CWI, CJ, or CT group before completing a trail marathon run. Muscle damage (creatine kinase (CK)), muscle function (maximal voluntary isometric contraction (MVIC)), and inflammation (interleukin-6 (IL-6); C-reactive protein (CRP)) were measured at baseline, immediately after marathon (only IL-6), 24 h, and 48 h after marathon.

Results

There were no statistically significant differences between groups and no group × time interaction effects for any of the dependent variables. Confidence intervals (CI) illustrated that CT had unclear effects on inflammation (IL-6; CRP) and MVIC, but may have increased CK to a greater extent than PL and CJ conditions.

Conclusion

There is no evidence of an additive effect of CJ and CWI when the treatments are used in conjunction with each other. On the contrary, combining CJ and CWI may result in slightly increased circulating CK.

Modulation of Leukocyte Subsets Mobilization in Response to Exercise by Water Immersion Recovery

Purpose: To investigate the effect of different water immersion temperatures on the kinetics of blood markers of skeletal muscle damage and the main leukocyte subpopulations. Methods: Eleven recreationally trained young men participated in four experimental sessions consisting of unilateral eccentric knee flexion and 90 min of treadmill running at 70% of peak oxygen uptake, followed by 15 min of water immersion recovery at 15, 28 or 38°C. In the control condition participants remained seated at room temperature. Four hours after exercise recovery, participants completed a performance test. Blood samples were obtained before and immediately after exercise, after immersion, immediately before and after the performance test and 24 h after exercise. The number of leukocyte populations and the percentage of lymphocyte and monocytes subsets, as well as the serum activity of creatine kinase and aspartate aminotransferase were determined. Results: Leukocytosis and increase in blood markers of skeletal muscle damage were observed after the exercise. Magnitude effect analysis indicated that post-exercise hot-water immersion likely reduced the exercise-induced lymphocytosis and monocytosis. Despite reduced monocyte count, recovery by 38°C immersion, as well as 28°C, likely increased the percentage of non-classical monocytes in the blood. The percentage of CD25⁺ cells in the CD4 T cell subpopulation was possibly lower after immersion in water at 28 and 15°C. No effect of recovery by water immersion was observed for serum levels of creatine kinase and aspartate aminotransferase. Conclusions: Recovery by hot-water immersion likely attenuated the leukocytosis and increased the mobilization of non-classical monocytes induced by a single session of exercise combining resistance and endurance exercises, despite no effect of water immersion on markers of skeletal muscle damage. The monocyte response mediated by hot water immersion may lead to the improvement of the inflammatory response evoked by exercise in the skeletal muscle.

Cold Water Immersion Improves the Recovery of Both Central and Peripheral Fatigue Following Simulated Soccer Match-Play

The present study aimed to investigate the effect of cold water immersion (CWI) on the recovery of neuromuscular fatigue following simulated soccer match-play. In a randomized design, twelve soccer players completed a 90-min simulated soccer match followed by either CWI or thermoneutral water immersion (TWI, sham condition). Before and after match (immediately after CWI/TWI through 72 h recovery), neuromuscular and performance assessments were performed. Maximal voluntary contraction (MVC) and twitch responses, delivered through electrical femoral nerve stimulation, were used to assess peripheral fatigue (quadriceps resting twitch force, Q_tw,pot) and central fatigue (voluntary activation, VA). Performance was assessed via squat jump (SJ), countermovement jump (CMJ), and 20 m sprint tests. Biomarkers of muscle damages (creatine kinase, CK; Lactate dehydrogenase, LDH) were also collected. Smaller reductions in CWI than TWI were found in MVC (-9.9 ± 3%vs-23.7 ± 14.7%), VA (-3.7 ± 4.9%vs-15.4 ± 5.6%) and Q_tw,pot (-15.7 ± 5.9% vs. -24.8 ± 9.5%) following post-match intervention (p < 0.05). On the other hand, smaller reductions in CWI than TWI were found only in Q_tw,pot (-0.2 ± 7.7% vs. -8.8 ± 9.6%) at 72 h post-match. Afterwards, these parameters remained lower compared to baseline up to 48–72 h in TWI while they all recovered within 24 h in CWI. The 20 m sprint performance was less impaired in CWI than TWI (+11.1 ± 3.2% vs. +18 ± 3.6%, p < 0.05) while SJ and CMJ were not affected by the recovery strategy. Plasma LDH, yet no CK, were less increased during recovery in CWI compared to TWI. This study showed that CWI reduced both central and peripheral components of fatigue, which in turn led to earlier full recovery of the neuromuscular function and performance indices. Therefore, CWI might be an interesting recovery strategy for soccer players.

Comparison of 4 Different Cooldown Strategies on Lower-Leg Temperature, Blood Lactate Concentration, and Fatigue Perception After Intense Running

CONTEXT

Although active recovery (AR) and cold application is recommended, many people take a shower after exercise. Therefore, a direct comparison between a shower and other recommended methods (AR and/or cold-water immersion) is necessary. To compare immediate effects of 4 postexercise cooldown strategies after running.

DESIGN

A crossover design.

METHODS

Seventeen young, healthy males (23 y; 174 cm; 73 kg) visited on 4 different days and performed a 10-minute intense treadmill run (5 km/h at a 1% incline, then a belt speed of 1 km/h, and an incline of 0.5% were increased every minute). Then, subjects randomly experienced 4 different 30-minute cooldown strategies each session-AR (10-min treadmill walk + 10-min static stretch + 10-min shower), cold-water walk (10-min shower + 20-min walk in cold water), cold-water sit (10-min shower + 20-min sit in cold water), and passive recovery (10-min shower + 20-min passive recovery). Across the cooldown conditions, the water temperatures for immersion and shower were set as 18 °C and 25 °C, respectively. Lower-leg muscle temperature, blood lactate concentration, and fatigue perception were statistically compared (P < .001 for all tests) and effect sizes (ES) were calculated.

RESULTS

The cold-water walk condition (F135,2928 = 69.29, P < .0001) was the most effective in reducing muscle temperature after running (-11.6 °C, ES = 9.46, P < .0001), followed by the cold-water sit (-8.4 °C, ES = 8.61, P < .0001), passive recovery (-4.5 °C, ES = 4.36, P < .0001), and AR (-4.0 °C, ES = 4.29, P < .0001) conditions. Blood lactate concentration (F6,176 = 0.86, P = .52) and fatigue perception (F6,176 = 0.18, P = .98) did not differ among the 4 conditions.

CONCLUSIONS

While the effect of lowering the lower-leg temperature was different, the effect of reducing blood lactate concentration and fatigue perception were similar in the 4 cooldown strategies. We suggest selecting the appropriate method while considering the specific goal, available time, facility, and accessibility.

The Comparative Effect of Different Timings of Whole Body Cryotherapy Treatment With Cold Water Immersion for Post-Exercise Recovery

Despite several established benefits of Whole Body Cryotherapy (WBC) for post-exercise recovery, there is a scarcity of research which has identified the optimum WBC protocol for this purpose. This study investigated the influence of WBC treatment timing on physiological and functional responses following a downhill running bout. An additional purpose was to compare such responses with those following cold water immersion (CWI), since there is no clear consensus as to which cold modality is more effective for supporting athletic recovery. Thirty-three male participants (mean ± SD age 37.0 ± 13.3 years, height 1.76 ± 0.07 m, body mass 79.5 ± 13.7 kg) completed a 30 min downhill run (15% gradient) at 60% VO₂ max and were then allocated into one of four recovery groups: WBC1 (n = 9) and WBC4 (n = 8) underwent cryotherapy (3 min, −120°C) 1 and 4 h post-run, respectively; CWI (n = 8) participants were immersed in cold water (10 min, 15°C) up to the waist 1 h post-run and control (CON, n = 8) participants passively recovered in a controlled environment (20°C). Maximal isometric leg muscle torque was assessed pre and 24 h post-run. Blood creatine kinase (CK), muscle soreness, femoral artery blood flow, plasma IL-6 and sleep were also assessed pre and post-treatment. There were significant decreases in muscle torque for WBC4 (10.9%, p = 0.04) and CON (11.3% p = 0.00) and no significant decreases for WBC1 (5.6%, p = 0.06) and CWI (5.1%, p = 0.15). There were no significant differences between groups in muscle soreness, CK, IL-6 or sleep. Femoral artery blood flow significantly decreased in CWI (p = 0.02), but did not differ in other groups. WBC treatments within an hour may be preferable for muscle strength recovery compared to delayed treatments; however WBC appears to be no more effective than CWI. Neither cold intervention had an impact on inflammation or sleep.

Anaerobic performance after 3-day consecutive CO2-rich cold-water immersion in physically active males

Background Objective

We investigated the effects of a 3-day consecutive CO₂-rich cold (20 °C) water immersion (CCWI) following a high-intensity intermittent test (HIIT) on subjects' sublingual temperature (T_sub), blood lactate ([La]b), and heart rate (HR) compared to cold (20 °C) tap-water immersion (CWI) or passive recovery (PAS).

Methods

Thirty-two subjects were randomly allocated into three groups (CCWI, CWI, and PAS), each of which completed 4 consecutive days of cycling experiments. HR, T_sub, and [La]b were recorded on each day of exercise testing (immersion from Day 1 to Day 3 and Day 4). HIIT consisted of 8 sets of 20-sec maximum exercise at an intensity of 120% of VO₂max with 10-sec passive rest. The mean and peak power, and peak pedal repetitions (PPR) within HIIT were averaged and the decline in PPR (ΔPPR) from Day 1 to Day 4 was measured.

Results

In CCWI and CWI, HR declined significantly following each immersion, with CCWI showing the larger reduction (p < 0.001). At Day 2, CCWI showed a significantly lower [La]b compared to PAS (p < 0.01). The changes in mean and peak power from Day 1 to Day 4 did not differ among the groups (p = 0.302). ΔPPR of HIIT was significantly correlated with the HR and [La]b values after immersions (ΔPPR-HR: r² = 0.938, p < 0.001, ΔPPR-[La]b: r² = 0.999, p < 0.001).

Conclusions

These findings indicate that CCWI is a promising intervention for maintaining peak performance in high-intensity intermittent exercise, which is associated with a reduction in [La]b and HR.

Impact of Cold-Water Immersion Compared with Passive Recovery Following a Single Bout of Strenuous Exercise on Athletic Performance in Physically Active Participants: A Systematic Review with Meta-analysis and Meta-regression

Background

Studies investigating the effects of cold-water immersion (CWI) on the recovery of athletic performance, perceptual measures and creatine kinase (CK) have reported mixed results in physically active populations.

Objectives

The purpose of this systematic review was to investigate the effects of CWI on recovery of athletic performance, perceptual measures and CK following an acute bout of exercise in physically active populations.

Study Design

Systematic review with meta-analysis and meta-regression.

Methods

A systematic search was conducted in September 2021 using Medline, SPORTDiscus, Scopus, Web of Science, Cochrane Library, EmCare and Embase databases. Studies were included if they were peer reviewed and published in English, included participants who were involved in sport or deemed physically active, compared CWI with passive recovery methods following an acute bout of strenuous exercise and included athletic performance, athlete perception and CK outcome measures. Studies were divided into two strenuous exercise subgroups: eccentric exercise and high-intensity exercise. Random effects meta-analyses were used to determine standardised mean differences (SMD) with 95% confidence intervals. Meta-regression analyses were completed with water temperature and exposure durations as continuous moderator variables.

Results

Fifty-two studies were included in the meta-analyses. CWI improved the recovery of muscular power 24 h after eccentric exercise (SMD 0.34 [95% CI 0.06–0.62]) and after high-intensity exercise (SMD 0.22 [95% CI 0.004–0.43]), and reduced serum CK (SMD − 0.85 [95% CI − 1.61 to − 0.08]) 24 h after high-intensity exercise. CWI also improved muscle soreness (SMD − 0.89 [95% CI − 1.48 to − 0.29]) and perceived feelings of recovery (SMD 0.66 [95% CI 0.29–1.03]) 24 h after high-intensity exercise. There was no significant influence on the recovery of strength performance following either eccentric or high-intensity exercise. Meta-regression indicated that shorter time and lower temperatures were related to the largest beneficial effects on serum CK (duration and temperature dose effects) and endurance performance (duration dose effects only) after high-intensity exercise.

Conclusion

CWI was an effective recovery tool after high-intensity exercise, with positive outcomes occurring for muscular power, muscle soreness, CK, and perceived recovery 24 h after exercise. However, after eccentric exercise, CWI was only effective for positively influencing muscular power 24 h after exercise. Dose–response relationships emerged for positively influencing endurance performance and reducing serum CK, indicating that shorter durations and lower temperatures may improve the efficacy of CWI if used after high-intensity exercise.

Funding

Emma Moore is supported by a Research Training Program (Domestic) Scholarship from the Australian Commonwealth Department of Education and Training.

Protocol registration

Open Science Framework: 10.17605/OSF.IO/SRB9D.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40279-022-01644-9.

Post‐Exercise Cold‐ and Contrasting‐Water Immersion Effects on Heart Rate Variability Recovery in International Handball Female Players

This study aimed to investigate the effect of water immersion (WI) on cardiac parasympathetic reactivation during recovery from handball training sessions in elite female players during a two-week training camp. On the first three days of both weeks, players completed a crossover design with one of three 60-min delayed post-exercise WI protocols or passive rest (PAS). Recovery interventions consisted of a period of 6-min cold-WI (10°C; CWI₆) and two contrasting periods cold- and hot-WI (36°C): one session included 3 min cold + 2 min hot + 3 min cold and the other session 5 × 2 min with cold at the very end. Short-term measures of heart rate variability (HRV) were collected before and after handball training sessions, and after WI. Derived parasympathetic HRV indices collected daily showed lower values post-training compared to pre-training values (p < 0.0001, large ES). Individual handball training sessions revealed similar clear depression of the vagal tone throughout the training camp. The comparison between each WI protocol and PAS revealed significant time × condition interaction particularly for CWI₆. All parasympathetic indices revealed higher post-recovery values in CWI₆ than PAS (p < 0.001 –p < 0.0001, with large ES ranging from 0.86 to 0.94). Surprisingly, 60-min delayed post-training WI revealed for most of parasympathetic HRV indices higher values than pre-training. This study highlighted that post-exercise parasympathetic disruption was exacerbated in response to handball training, and the 60-min delayed WI recovery interventions improved parasympathetic reactivity. Cardiac vagal tone can be highly improved with CWI₆ compared to PAS. For the purpose of HRV modulations, CWI₆ is recommended for short-term recovery.

Can Post-Exercise Hemodynamic Response Be Influenced by Different Recovery Methods in Paraplegic Sportsmen?

Post-exercise hypotension is of great clinical relevance and also in sports training settings, as recovery speed is important. The aim of this study was to compare the influence of different recovery methods on post-exercise hemodynamic response. Twelve male paraplegic sportsmen (25.40 ± 3.30 years) performed a strength training (ST) session using the bench press exercise. After the ST, three recovery methods were randomly performed over a 15-min period: passive recovery (PR), cold-water (CW) and dry needle (DN). Blood pressure (BP), heart rate (HR) and myocardial oxygen were measured before and post ST, as well as post the recovery method. Results: Dry needling induced lower systolic blood pressure (SBP) immediately after the treatment when compared with the other recovery methods, but the contrary was observed at 50 and 60-min post recovery, where records with DN exhibit higher mean values (η²p = 0.330). There were no differences in post-exercise diastolic BP and mean BP between recovery methods. There was a significantly higher HR after the PR method, when compared with CW and with DN (η²p = 0.426). The same was observed for double product and for myocardial oxygen, though with a larger effect size (η²p = 0.446). We conclude that dry needling seems to induce a faster SBP lowering immediately after the procedure but at 50-min post procedure the cold-water method showed better result. As for HR, both procedures (DN and CW) showed a better recovery when compared with passive recovery, along the several moments of measurement.

Effects of Light Pedaling Added to Contrast Water Immersion for Recovery after Exhaustive Exercise

For years, athletes and coaches have been looking for new strategies to optimize post-exercise recovery; it has recently been suggested that combining several methods might be a great option. This study therefore aimed to investigate the efficacy of contrast water therapy (CWT) used alone or associated with pedaling to recover from exhaustive exercise. After high-intensity intermittent exercise, 33 participants underwent 30 min of either (i) passive rest (PASSIVE), (ii) CWT with pedaling while in water (COMB) or (iii) classic CWT (CWT). Blood lactate concentration, countermovement jump height and perceived exhaustion were recorded before exercise, immediately after, after recovery interventions and after an additional 30 min of passive rest. Blood lactate concentration returned to initial values after 30 min of COMB (5.9 mmol/L), whereas in the other conditions even 60 min was not enough (10.2 and 9.6 mmol/L for PASSIVE and CWT, respectively, p < 0.05). Jump height was close to initial values after 30 min of CWT (37.3 cm), whereas values were still depressed after 60 min in the PASSIVE (36.0 cm) and COMB (35.7 cm) conditions (p < 0.05). Perceived exertion was still high for all conditions after 60 min. The present results are in favor of the utilization of CWT after exhaustive exercise, but the modality has to be chosen depending on what comes next (subsequent exercise scheduled in the following hours or further away).

Short-term effects of two different recovery strategies on muscle contractile properties in healthy active men: A randomised cross-over study

The aim of this study was to compare the immediate effects of cold-water immersion (CWI) and hot-water immersion (HWI) versus passive resting after a fatigue-induced bout of exercise on the muscle contractile properties of the Vastus Medialis (VM). We conducted a randomised cross-over study involving 28 healthy active men where muscle contractile properties of the VM wer recorded using Tensiomyography (TMG) before and after CWI, HWI or passive resting and up to one-hour post-application. The main outcomes obtained were muscle displacement and velocity of deformation according to limb size (Dmr and Vdr). Our results showed a significant effect of time (F(3.9,405) =32.439; p <0.001; η²_p =0.29) and the interaction between time and temperature (F(7.9,405) =5.814; p <0.001; η²_p=0.13) on Dmr but no for temperature alone (F(2,81) =2.013; p =0.14; η²_p=0.04) while for Vdr, both time (F(5.2,486) =23.068; p <0.001 η²_p = 0.22) and temperature (F(2,81) =4.219; p = 0.018; η²_p= 0.09) as well as the interaction (F(10.4,486) =7.784; p <0.001; η²_p =0.16) were found significant. Compared to CWI, HWI increased Dmr post-application and Vdr both post-application as well as 15 and 45' thereafter. These findings suggest that applying HWI could be a valid alternative to CWI to promote muscle recovery.

Athlete, coach and practitioner knowledge and perceptions of post-exercise cold-water immersion for recovery: a qualitative and quantitative exploration

This survey sought to establish current use, knowledge and perceptions of cold-water immersion (CWI) when used for recovery. 111 athletes, coaches and support practitioners completed the anonymous online survey, answering questions about their current CWI protocols, perceptions of benefits associated with CWI and knowledge of controlling mechanisms. Respondents were largely involved in elite sport at international, national and club level, with many having used CWI previously (86%) and finding its use beneficial for recovery (78%). Protocols differed, with the duration of immersion one aspect that failed to align with recommendations in the scientific literature. Whilst many respondents were aware of benefits associated with CWI, there remains some confusion. There also seems to be a gap in mechanistic knowledge, where respondents are aware of benefits associated with CWI, but failed to identify the underlying mechanisms. This identifies the need for an improved method of knowledge transfer between scientific and applied practice communities. Moreover, data herein emphasises the important role of the ‘support practitioner’ as respondents in this role tended to favour CWI protocols more aligned to recommendations within the literature. With a significant number of respondents claiming they were made aware of CWI for recovery through a colleague (43%), the importance of knowledge transfer and context being appropriately applied to data is as important as ever. With the firm belief that CWI is useful for recovery in sport, the focus should now be on investigating the psychophysiological interaction and correct use of this methodology.

The Effectiveness of Aquatic Plyometric Training in Improving Strength, Jumping, and Sprinting: A Systematic Review

CONTEXT

Aquatic plyometric training may provide benefits due to reduced joint loading compared with land plyometric training; however, the reduced loading may also limit performance gains.

OBJECTIVE

To systematically review the effect of aquatic plyometric training on strength, performance outcomes, soreness, and adverse events in healthy individuals.

EVIDENCE ACQUISITION

Five databases were searched from inception to June 2020. Quality assessment and data extraction were independently completed by 2 investigators. When similar outcome measures were used, standardized mean differences were calculated.

EVIDENCE SYNTHESIS

A total of 19 randomized controlled trials with 633 participants (mean age, range 14-30 y) were included. Aquatic plyometric training was most commonly performed in waist to chest deep water (12/19 studies), 2 to 3 times per week for 6 to 12 weeks (18/19 studies), with final program foot contacts ranging from 120 to 550. Meta-analyses were not completed due to the clinical and statistical heterogeneity between studies. Compared with land plyometric training, aquatic plyometric training exercises and dosage were replicated (15/16 studies) and showed typically similar performance gains (3/4 knee extensor strength measures, 2/4 leg extensor strength measures, 3/4 knee flexor strength measures, 7/10 vertical jump measures, 3/3 sprint measures). In total, 2 of 3 studies monitoring muscle soreness reported significantly less soreness following training in water compared with on land. Compared with no active training (no exercise control group or passive stretching), most effect sizes demonstrated a mean improvement favoring aquatic plyometric training (23/32 measures). However, these were not significant for the majority of studies measuring isokinetic knee strength, vertical jump, and sprinting. The effect sizes for both studies assessing leg press strength indicated that aquatic plyometric training is significantly more effective than no training.

CONCLUSION

Aquatic plyometric training appears similarly effective to land plyometric exercise for improving strength, jumping, and sprinting and may be indicated when joint impact loading needs to be minimized. However, the low quality of studies limits the strength of the conclusions.

Recovery From Eccentric Squat Exercise in Resistance-Trained Young and Master Athletes With Similar Maximum Strength: Combining Cold Water Immersion and Compression

The aim of this study was to investigate whether recovery from eccentric squat exercise varies depending on age and to assess whether the use of a mixed-method recovery (MMR) consisting of cold water immersion and compression tights benefits recovery. Sixteen healthy and resistance-trained young (age, 22.1±2.1years; N=8) and master male athletes (age, 52.4±3.5years; N=8), who had a similar half squat 1-repetition maximum relative to body weight, completed two identical squat exercise training sessions, separated by a 2-week washout period. Training sessions were followed by either MMR or passive recovery (PR). Internal training loads [heart rate and blood lactate concentration (BLa)] were recorded during and after squat sessions. Furthermore, maximal voluntary isometric contraction (MVIC) force, countermovement jump (CMJ) height, resting twitch force of the knee extensors, serum concentration of creatine kinase (CK), muscle soreness (MS), and perceived physical performance capability (PPC) were determined before and after training as well as after 24, 48, and 72h of recovery. A three-way mixed ANOVA revealed a significant time effect of the squat protocol on markers of fatigue and recovery (p<0.05; decreased MVIC, CMJ, twitch force, and PPC; increased CK and MS). Age-related differences were found for BLa, MS, and PPC (higher post-exercise fatigue in younger athletes). A significant two-way interaction between recovery strategy and time of measurement was found for MS and PPC (p<0.05; faster recovery after MMR). In three participants (two young and one master athlete), the individual results revealed a consistently positive response to MMR. In conclusion, master athletes neither reach higher fatigue levels nor recover more slowly than the younger athletes. Furthermore, the results indicate that MMR after resistance exercise does not contribute to a faster recovery of physical performance, neuromuscular function, or muscle damage, but promotes recovery of perceptual measures regardless of age.

Effects of Various Physical Interventions on Reducing Neuromuscular Fatigue Assessed by Electromyography: A Systematic Review and Meta-Analysis

Introduction: Various interventions have been applied to improve recovery from muscle fatigue based on evidence from subjective outcomes, such as perceived fatigue and soreness, which may partly contribute to conflicting results of reducing muscle fatigue. There is a need to assess the effectiveness of various intervention on reducing neuromuscular fatigue assessed by a quantitative outcome, such as electromyography (EMG). The objective of this review and meta-analysis was to evaluate the effectiveness of different interventions and intervention timing for reducing fatigue rates during exercise. Methods: The literature was searched from the earliest record to March 2021. Eighteen studies with a total of 87 data points involving 281 participants and seven types of interventions [i.e., active recovery (AR), compression, cooling, electrical stimulation (ES), light-emitting diode therapy (LEDT), massage, and stretching] were included in this meta-analysis. Results: The results showed that compression (SMD = 0.28; 95% CI = -0.00 to 0.56; p = 0.05; I ² = 58%) and LEDT (SMD = 0.49; 95% CI = 0.11 to 0.88; p = 0.01; I ² = 52%) have a significant recovery effect on reducing muscle fatigue. Additionally, compression, AR, and cooling have a significant effect on reducing muscle fatigue when conducted during exercise, whereas a non-effective trend when applied after exercise. Discussion: This meta-analysis suggests that compression and LEDT have a significant effect on reducing muscle fatigue. The results also suggest that there is a significant effect or an effective trend on reducing muscle fatigue when compression, AR, cooling, and ES are applied during exercise, but not after exercise.

Applying Heart Rate Variability to Monitor Health and Performance in Tactical Personnel: A Narrative Review

Human performance optimization of tactical personnel requires accurate, meticulous, and effective monitoring of biological adaptations and systemic recovery. Due to an increased understanding of its importance and the commercial availability of assessment tools, the use of heart rate variability (HRV) to address this need is becoming more common in the tactical community. Measuring HRV is a non-invasive, practical method for objectively assessing a performer's readiness, workload, and recovery status; when combined with additional data sources and practitioner input, it provides an affordable and scalable solution for gaining actionable information to support the facilitation and maintenance of operational performance. This narrative review discusses the non-clinical use of HRV for assessing, monitoring, and interpreting autonomic nervous system resource availability, modulation, effectiveness, and efficiency in tactical populations. Broadly, HRV metrics represent a complex series of interactions resulting from internal and external stimuli; therefore, a general overview of HRV applications in tactical personnel is discussed, including the influence of occupational specific demands, interactions between cognitive and physical domains, and recommendations on implementing HRV for training and recovery insights into critical health and performance outcomes.

Adaptations to Post-exercise Cold Water Immersion: Friend, Foe, or Futile?

In the last decade, cold water immersion (CWI) has emerged as one of the most popular post-exercise recovery strategies utilized amongst athletes during training and competition. Following earlier research on the effects of CWI on the recovery of exercise performance and associated mechanisms, the recent focus has been on how CWI might influence adaptations to exercise. This line of enquiry stems from classical work demonstrating improved endurance and mitochondrial development in rodents exposed to repeated cold exposures. Moreover, there was strong rationale that CWI might enhance adaptations to exercise, given the discovery, and central role of peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) in both cold- and exercise-induced oxidative adaptations. Research on adaptations to post-exercise CWI have generally indicated a mode-dependant effect, where resistance training adaptations were diminished, whilst aerobic exercise performance seems unaffected but demonstrates premise for enhancement. However, the general suitability of CWI as a recovery modality has been the focus of considerable debate, primarily given the dampening effect on hypertrophy gains. In this mini-review, we highlight the key mechanisms surrounding CWI and endurance exercise adaptations, reiterating the potential for CWI to enhance endurance performance, with support from classical and contemporary works. This review also discusses the implications and insights (with regards to endurance and strength adaptations) gathered from recent studies examining the longer-term effects of CWI on training performance and recovery. Lastly, a periodized approach to recovery is proposed, where the use of CWI may be incorporated during competition or intensified training, whilst strategically avoiding periods following training focused on improving muscle strength or hypertrophy.

Recovery during and after a simulated multi-day tennis tournament: Combining active recovery, stretching, cold-water immersion, and massage interventions

The aim of this study was to investigate the effects of a mixed-method recovery intervention (MMR) consisting of active recovery, stretching, cold-water immersion, and massage on physical, technical, physiological, and perceptual recovery during and after a five-day simulated tennis tournament. Nine competitive male tennis players (age, 24.6±4.2 years) with national ranking positions (German Tennis Federation) and Universal Tennis Ratings between approximately 11-13 participated in two singles tennis tournaments, which were separated by a three-month washout period. During the tournaments, participants played five two-and-a-half-hour competitive singles tennis match on five consecutive days. For the assignment to one of two groups, athletes were matched into homogeneous pairs according to their ranking. Then, within each pair, the players were randomly assigned to one of two groups. The first group performed MMR during the first tournament, whereas the other group used passive recovery (PAS). During the second tournament, recovery conditions were interchanged. Measures of physical and technical performance as well as physiological and perceptual responses (heart rate, blood lactate concentration, perceived exertion) were recorded during match-play sessions. Furthermore, muscle soreness, perceived recovery state, blood markers, countermovement jump height (CMJ), and repeated sprint ability (RSA) were determined before, during, and after the five-day tournament periods. Results showed significant changes over time (P < 0.05) in muscle soreness, perceived recovery state, creatine kinase, c-reactive protein, insulin-like growth factor 1, and countermovement jump height. However, no significant differences or recovery strategy x time interactions were noted either for tennis-specific performance (e.g. number of total points won) or any other of the measured parameters between MMR and PAS (P > 0.05). In conclusion, the repeated use of MMR during and after a five-day tennis tournament did not affect match performance, match load, or recovery from repeated days of tennis match play.

Predictive Ability of Body Fat Percentage and Thigh Anthropometrics on Tissue Cooling During Cold-Water Immersion

CONTEXT

Cold-water immersion (CWI) is a common aid in exercise recovery. The effectiveness of CWI depends on the magnitude of muscle and core cooling. Individual cooling responses to CWI vary and are likely influenced by the CWI dose and individual physiological characteristics.

OBJECTIVE

To evaluate body fat percentage and thigh anthropometric values as predictors of intramuscular and skin-cooling responses to CWI.

DESIGN

Descriptive laboratory study.

SETTING

Sports medicine research center.

PATIENTS OR OTHER PARTICIPANTS

Sixteen young adults (8 males, 8 females, age = 24.3 ± 1.84 years, height = 176.4 ± 12.7 cm, mass = 86.6 ± 29.4 kg).

INTERVENTION(S)

Body fat percentage was measured using a 3-site skinfold assessment. Thigh length, thigh circumference, anterior thigh adipose thickness, anterior thigh muscle thickness, and thigh volume were estimated using manual and ultrasound methods. Using sterile techniques, we placed thermocouple probes in the belly of the rectus femoris (2-cm deep to the subadipose tissue) and on the anterior midthigh surface. Participants cycled on an ergometer for 30 minutes at a target heart rate of 130 to 150 beats/min. Postexercise, participants were placed in CWI (immersion depth to the iliac crest; 10°C) until intramuscular temperature was 7°C below pre-exercise baseline temperature, with a maximum immersion duration of 30 minutes.

MAIN OUTCOME MEASURE(S)

Intramuscular rectus femoris and thigh skin temperatures measured postexercise, after 10 and 15 minutes of CWI, and post-CWI.

RESULTS

Body fat percentage significantly predicted the rectus femoris cooling magnitude and rate after 10 minutes of CWI, 15 minutes of CWI, and post-CWI (P < .001; R2 range = 0.58-0.67). Thigh anthropometric values significantly predicted the thigh skin-cooling rate post-CWI (P = .049; R2 = 0.46).

CONCLUSIONS

A simple 3-site skinfold assessment may improve the effective prescription of CWI by allowing estimation of the dose required for minimal muscle tissue cooling.

Cold Water Immersion as a Strategy for Muscle Recovery in Professional Basketball Players During the Competitive Season

CONTEXT

Despite prior studies that have addressed the recovery effects of cold-water immersion (CWI) in different sports, there is a lack of knowledge about longitudinal studies across a full season of competition assessing these effects.

OBJECTIVE

To analyze the CWI effects, as a muscle recovery strategy, in professional basketball players throughout a competitive season.

DESIGN

A prospective cohort design.

SETTING

Elite basketball teams.

PARTICIPANTS

A total of 28 professional male basketball players divided into 2 groups: CWI (n = 12) and control (n = 16) groups.

MAIN OUTCOME MEASURES

Muscle metabolism serum markers were measured during the season in September-T1, November-T2, March-T3, and April-T4. Isokinetic peak torque strength and ratings of perceived exertion were measured at the beginning and at the end of the season. CWI was applied immediately after every match and after every training session before matches.

RESULTS

All serum muscular markers, except myoglobin, were higher in the CWI group than the control group (P < .05). The time course of changes in muscle markers over the season also differed between the groups (P < .05). In the CWI group, ratings of perceived exertion decreased significantly from the beginning (T1-T2) to the end (T3-T4). Isokinetic torque differed between groups at the end of the season (60°/s peak torque: P < .001 and ηp2=.884; and 180°/s peak torque: P < .001 and ηp2=.898) and had changed significantly over the season in the CWI group (P < .05).

CONCLUSIONS

CWI may improve recovery from muscle damage in professional basketball players during a regular season.

Effect of the Depth of Cold Water Immersion on Sleep Architecture and Recovery Among Well-Trained Male Endurance Runners

Introduction: The aim of the present study was to investigate the effect of the depth of cold water immersion (CWI) (whole-body with head immersed and partial-body CWI) after high-intensity, intermittent running exercise on sleep architecture and recovery kinetics among well-trained runners. Methods: In a randomized, counterbalanced order, 12 well-trained male endurance runners ( V . O₂max = 66.0 ± 3.9 ml·min^-1·kg^-1) performed a simulated trail (≈18:00) on a motorized treadmill followed by CWI (13.3 ± 0.2°C) for 10 min: whole-body immersion including the head (WHOLE; n = 12), partial-body immersion up to the iliac crest (PARTIAL; n = 12), and, finally, an out-of-water control condition (CONT; n = 10). Markers of fatigue and muscle damage-maximal voluntary isometric contraction (MVIC), countermovement jump (CMJ), plasma creatine kinase [CK], and subjective ratings-were recorded until 48 h after the simulated trail. After each condition, nocturnal core body temperature (T _core) was measured, whereas sleep and heart rate variability were assessed using polysomnography. Results: There was a lower T _core induced by WHOLE than CONT from the end of immersion to 80 min after the start of immersion (p < 0.05). Slow-wave sleep (SWS) proportion was higher (p < 0.05) during the first 180 min of the night in WHOLE compared with PARTIAL. WHOLE and PARTIAL induced a significant (p < 0.05) decrease in arousal for the duration of the night compared with CONT, while only WHOLE decreased limb movements compared with CONT (p < 0.01) for the duration of the night. Heart rate variability analysis showed a significant reduction (p < 0.05) in RMSSD, low frequency (LF), and high frequency (HF) in WHOLE compared with both PARTIAL and CONT during the first sequence of SWS. No differences between conditions were observed for any markers of fatigue and muscle damage (p > 0.05) throughout the 48-h recovery period. Conclusion: WHOLE reduced arousal and limb movement and enhanced SWS proportion during the first part of the night, which may be particularly useful in the athlete's recovery process after exercise. Future studies are, however, required to assess whether such positive sleep outcomes may result in overall recovery optimization.

The cold truth: the role of cryotherapy in the treatment of injury and recovery from exercise

Cryotherapy is utilized as a physical intervention in the treatment of injury and exercise recovery. Traditionally, ice is used in the treatment of musculoskeletal injury while cold water immersion or whole-body cryotherapy is used for recovery from exercise. In humans, the primary benefit of traditional cryotherapy is reduced pain following injury or soreness following exercise. Cryotherapy-induced reductions in metabolism, inflammation, and tissue damage have been demonstrated in animal models of muscle injury; however, comparable evidence in humans is lacking. This absence is likely due to the inadequate duration of application of traditional cryotherapy modalities. Traditional cryotherapy application must be repeated to overcome this limitation. Recently, the novel application of cooling with 15 °C phase change material (PCM), has been administered for 3-6 h with success following exercise. Although evidence suggests that chronic use of cryotherapy during resistance training blunts the anabolic training effect, recovery using PCM does not compromise acute adaptation. Therefore, following exercise, cryotherapy is indicated when rapid recovery is required between exercise bouts, as opposed to after routine training. Ultimately, the effectiveness of cryotherapy as a recovery modality is dependent upon its ability to maintain a reduction in muscle temperature and on the timing of treatment with respect to when the injury occurred, or the exercise ceased. Therefore, to limit the proliferation of secondary tissue damage that occurs in the hours after an injury or a strenuous exercise bout, it is imperative that cryotherapy be applied in abundance within the first few hours of structural damage.

Changes in myocardial myosin heavy chain isoform composition with exercise and post-exercise cold-water immersion

This study investigated the changes in myocardial myosin heavy chain (MHC) isoforms, MHC-α and MHC-β composition in young healthy rodents following endurance training, with and without post-exercise cold-water immersion (CWI). Male rats were either trained on a treadmill for 10 weeks with (CWI) or without (Ex) regular CWI after each running session, or left sedentary (CON). Left ventricular mRNA of MHC-α, MHC-β, thyroid receptor α1 (TR-α1) and β (TR-β) were analyzed using rt-PCR and semiquantitative PCR analysis. MHC isoform protein composition was determined using SDS-PAGE electrophoresis. MHC-α isoform protein was predominant in all groups. The relative expression of MHC-β (%MHC-β) protein was not different between groups (CWI 34.7 ± 6.9%; Ex 32 ± 5.3%; CON 35.5 ± 10%; P = 0.7). MHC-β mRNA was reduced in Ex (0.7 ± 0.3-fold) compared to CWI (1.3 ± 0.2-fold; P < 0.001) and CON (1.01 ± 0.2-fold; P = 0.03). TRα1 mRNA was lower in CWI (0.4 ± 0.05-fold) than Ex (1.02 ± 0.3-fold) and CON (1.01 ± 0.2-fold) (P < 0.001 for both). CWI exhibited greater %MHC-β mRNA (56.8 ± 4.1%) than Ex (44.4 ± 7.7%; P = 0.001) and CON (48.5 ± 7.8%; P = 0.03). Neither exercise nor post-exercise CWI demonstrated a distinct effect on myocardial MHC protein isoform composition. However, CWI increased the relative expression of MHC-β mRNA compared with Ex and CON. Although this implicates a potential negative long-term impact of post-exercise CWI, future studies should include measures of cardiac function to better understand the effect of such isoform mRNA shifts following regular use of CWI.