Core Temperature Responses to Cold-Water Immersion Recovery: A Pooled-Data Analysis

Influence of acute and chronic therapeutic cooling on cognitive performance and well-being

PURPOSE

Research regarding the effect cold-water immersion (CWI) has on cognitive performance often uses excessive cooling protocols (>1-hour) to measure the detrimental impact prolonged cold exposure has on cognition. Previous studies have not considered shorter CWI protocols, similar to that used in recovery and wellness practices (∼10 min).

AIMS

To investigate a more ecologically valid CWI protocol on cognition, well-being and sleep in an acute and chronic manner. It was hypothesised that a therapeutic CWI protocol would improve well-being, and sleep and have no detrimental effect on cognition.

METHODS

Thirteen healthy participants (20.85±2.15 years), (169.96±7.77 cm), (72.03±14.92 kg), (27.67±9.55 BF%) volunteered to complete a 4-week CWI protocol. Participants were immersed in cold water (10.42±0.59 °C) 3-times a week for 4-weeks. Cognitive performance (Stroop & TMT), well-being (WEMWBS, PSWQ, GAD-7, SHS) and sleep (PSQI) were measured acutely and chronically over the 4-week protocol along with thermoregulatory measures (Tsk, Tco, thermal comfort).

RESULTS

Results show that CWI had no detrimental impact on cognitive performance, with Stroop performance & well-being seeing no differences acutely or chronically. Alternatively, the trail making test showed significant improvement from baseline (TMT-A 15.17±4.81-seconds, TMT-B 39.68±15.12-seconds) to week-3 (TMT-A 11.06±3.29-seconds, TMT-B 26.18±10.23-seconds). A reduction in sleep disturbances was seen from baseline scores of 7.85±3.44 AU to the end of week-3 measures 5.75±3.77 AU.

CONCLUSION

Therapeutic cooling can improve sleep quality when utilised in short frequent doses (3 times per week, for 4-weeks) and is not detrimental to cognitive performance, improving certain aspects of executive function.

Cold for centuries: a brief history of cryotherapies to improve health, injury and post-exercise recovery

For centuries, cold temperatures have been used by humans for therapeutic, health and sporting recovery purposes. This application of cold for therapeutic purposes is regularly referred to as cryotherapy. Cryotherapies including ice, cold-water and cold air have been popularised by an ability to remove heat, reduce core and tissue temperatures, and alter blood flow in humans. The resulting downstream effects upon human physiologies providing benefits that include a reduced perception of pain, or analgesia, and an improved sensation of well-being. Ultimately, such benefits have been translated into therapies that may assist in improving post-exercise recovery, with further investigations assessing the role that cryotherapies can play in attenuating the ensuing post-exercise inflammatory response. Whilst considerable progress has been made in our understanding of the mechanistic changes associated with adopting cryotherapies, research focus tends to look towards the future rather than to the past. It has been suggested that this might be due to the notion of progress being defined as change over time from lower to higher states of knowledge. However, a historical perspective, studying a subject in light of its earliest phase and subsequent evolution, could help sharpen one's vision of the present; helping to generate new research questions as well as look at old questions in new ways. Therefore, the aim of this brief historical perspective is to highlight the origins of the many arms of this popular recovery and treatment technique, whilst further assessing the changing face of cryotherapy. We conclude by discussing what lies ahead in the future for cold-application techniques.

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.

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.

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.

Don't Lose Your Cool With Cryotherapy: The Application of Phase Change Material for Prolonged Cooling in Athletic Recovery and Beyond

Strenuous exercise can result in muscle damage in both recreational and elite athletes, and is accompanied by strength loss, and increases in soreness, oxidative stress, and inflammation. If the aforementioned signs and symptoms associated with exercise-induced muscle damage are excessive or unabated, the recovery process becomes prolonged and can result in performance decrements; consequently, there has been a great deal of research focussing on accelerating recovery following exercise. A popular recovery modality is cryotherapy which results in a reduction of tissue temperature by the withdrawal of heat from the body. Cryotherapy is advantageous because of its ability to reduce tissue temperature at the site of muscle damage. However, there are logistical limitations to traditional cryotherapy modalities, such as cold-water immersion or whole-body cryotherapy, because they are limited by the duration for which they can be administered in a single dose. Phase change material (PCM) at a temperature of 15°C can deliver a single dose of cooling for a prolonged duration in a practical, efficacious, and safe way; hence overcoming the limitations of traditional cryotherapy modalities. Recently, 15°C PCM has been locally administered following isolated eccentric exercise, a soccer match, and baseball pitching, for durations of 3-6 h with no adverse effects. These data showed that using 15°C PCM to prolong the duration of cooling successfully reduced strength loss and soreness following exercise. Extending the positive effects associated with cryotherapy by prolonging the duration of cooling can enhance recovery following exercise and give athletes a competitive advantage.

Combining cooling or heating applications with exercise training to enhance performance and muscle adaptations

Athletes use cold water immersion, cryotherapy chambers, or icing in the belief that these strategies improve postexercise recovery and promote greater adaptations to training. A number of studies have systematically investigated how regular cold water immersion influences long-term performance and muscle adaptations. The effects of regular cold water immersion after endurance or high-intensity interval training on aerobic capacity, lactate threshold, power output, and time trial performance are equivocal. Evidence for changes in angiogenesis and mitochondrial biogenesis in muscle in response to regular cold water immersion is also mixed. More consistent evidence is available that regular cold water immersion after strength training attenuates gains in muscle mass and strength. These effects are attributable to reduced activation of satellite cells, ribosomal biogenesis, anabolic signaling, and muscle protein synthesis. Athletes use passive heating to warm up before competition or improve postexercise recovery. Emerging evidence indicates that regular exposure to ambient heat, wearing garments perfused with hot water, or microwave diathermy can mimic the effects of endurance training by stimulating angiogenesis and mitochondrial biogenesis in muscle. Some passive heating applications may also mitigate muscle atrophy through their effects on mitochondrial biogenesis and muscle fiber hypertrophy. More research is needed to consolidate these findings, however. Future research in this field should focus on 1) the optimal modality, temperature, duration, and frequency of cooling and heating to enhance long-term performance and muscle adaptations and 2) whether molecular and morphological changes in muscle in response to cooling and heating applications translate to improvements in exercise performance.

Exploring the Efficacy of a Safe Cryotherapy Alternative: Physiological Temperature Changes From Cold-Water Immersion Versus Prolonged Cooling of Phase-Change Material

PURPOSE

To evaluate the effectiveness between cold-water immersion (CWI) and phase-change-material (PCM) cooling on intramuscular, core, and skin-temperature and cardiovascular responses.

METHODS

In a randomized, crossover design, 11 men completed 15 min of 15°C CWI to the umbilicus and 2-h recovery or 3 h of 15°C PCM covering the quadriceps and 1 h of recovery, separated by 24 h. Vastus lateralis intramuscular temperature at 1 and 3 cm, core and skin temperature, heart-rate variability, and thermal comfort were recorded at baseline and 15-min intervals throughout treatment and recovery.

RESULTS

Intramuscular temperature decreased (P < .001) during and after both treatments. A faster initial effect was observed from 15 min of CWI (Δ: 4.3°C [1.7°C] 1 cm; 5.5°C [2.1°C] 3 cm; P = .01). However, over time (2 h 15 min), greater effects were observed from prolonged PCM treatment (Δ: 4.2°C [1.9°C] 1 cm; 2.2°C [2.2°C] 3 cm; treatment × time, P = .0001). During the first hour of recovery from both treatments, intramuscular temperature was higher from CWI at 1 cm (P = .013) but not 3 cm. Core temperature deceased 0.25° (0.32°) from CWI (P = .001) and 0.28°C (0.27°C) from PCM (P = .0001), whereas heart-rate variability increased during both treatments (P = .001), with no differences between treatments.

CONCLUSIONS

The magnitude of temperature reduction from CWI was comparable with PCM, but intramuscular temperature was decreased for longer during PCM. PCM cooling packs offer an alternative for delivering prolonged cooling whenever application of CWI is impractical while also exerting a central effect on core temperature and heart rate.