Influence of cold-water immersion on limb blood flow after resistance exercise

A evidence-based approach to selecting post-exercise cryostimulation techniques for improving exercise performance and fatigue recovery: A systematic review and meta-analysis

Rationale

Cryostimulation involves using water environments and low temperatures as intervention mediums, with main methods including CWI (cold water immersion), CWT (contrast water therapy), and WBC (whole-body cryostimulation). Previous systematic reviews focused on the effect of cryostimulation on muscle fatigue and sports performance. However, studies on the selection of different cryostimulation methods and their intervention effects present inconsistent results.

Introduction

To systematically review and methodologically appraise the quality and effectiveness of existing intervention studies that the effects of various cryostimulation methods, including CWI, CWT, and WBC, on exercise performance and fatigue recovery.

Methods

Following PRISMA guidelines, we conducted searches in PubMed, Embase, The Cochrane Library, Web of Science, and EBSCO databases to gather randomized controlled trials or self-controlled trials involving CWI/CWT/WBC and their effects on exercise performance or fatigue recovery. The search period ranged from November 2013 to November 2, 2023. Literature screening was performed using EndNote X9.1, and the quality of included studies was assessed using the Cochrane risk of bias assessment tool. Meta-analysis was conducted using RevMan 5.3 software.

Results

This study included a total of 18 articles, included a total of 499 healthy participants, comprising 479 males and 20 females. Among them, participants underwent cryostimulation, including 102 using CWT, using CWI, and 58 using WBC. Compared to the control group, cryostimulation can significantly alleviate muscle pain intensity (SMD -0.45, 95% CL -0.82 to 0.09, P = 0.01). Specifically, CWI significantly reduced muscle pain intensity (SMD = -0.45, 95% CI: 0.820.09, P = 0.01), WBC significantly decreased C-reactive protein levels (SMD = -1.36, 95% CI: 2.350.36, P = 0.008). While, CWT showed no significant differences from the control group in exercise performance and fatigue recovery indicators (P > 0.05).

Conclusion

Cryostimulation can significantly reduce muscle pain intensity and perceived fatigue. Specifically, CWI significantly alleviates muscle pain intensity, WBC significantly lowers markers of inflammation caused by fatigue after exercise, in contrast, CWT does not significantly improve exercise performance and fatigue recovery. After exercise, compared with rest, using cryostimulation may have more noticeable benefits for muscle fatigue and muscle pain, with recommendations prioritizing WBC and CWI particularly for addressing inflammation and muscle pain. However, all cryostimulation may have no significant influence on exercise performance.

Thermo-haemodynamic coupling during regional thigh heating: Insight into the importance of local thermosensitive mechanisms in blood circulation

A positive relationship between local tissue temperature and perfusion exists, with isolated limb-segment hyperthermia stimulating hyperaemia in the heated region without affecting the adjacent, non-heated limb segment. However, whether partial-limb segment heating evokes a heightened tissue perfusion in the heated region without directly or reflexly affecting the non-heated tissues of the same limb segment remains unknown. This study investigated, in 11 healthy young adults, the lower limb temperature and haemodynamic responses to three levels of 1 h upper-leg heating, none of which alter core temperature: (1) whole-thigh (WTH; water-perfused garment), (2) quadriceps (QH; water-perfused garment) and (3) partial-quadriceps (PQH; pulsed shortwave diathermy) heating. It was hypothesised that perfusion would only increase in the heated regions. WTH, QH and PQH increased local heated tissue temperature by 2.9 ± 0.6, 2.0 ± 0.7 and 2.9 ± 1.3°C (P < 0.0001), respectively, whilst remaining unchanged in the non-heated hamstrings and quadriceps tissues during QH and PQH. WTH induced a two-fold increase in common femoral artery blood flow (P < 0.0001) whereas QH and PQH evoked a similar ∼1.4-fold elevation (P ≤ 0.0018). During QH and PQH, however, tissue oxygen saturation and laser-Doppler skin blood flow in the adjacent non-heated hamstrings or quadriceps tissues remained stable (P > 0.5000). These findings in healthy young humans demonstrate a tight thermo-haemodynamic coupling during regional thigh heating, providing further evidence of the importance of local heat-activated mechanisms on the control of blood circulation.

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.

Effect of heat stress on heat shock protein expression and hypertrophy-related signaling in the skeletal muscle of trained individuals

Muscle mass is balanced between hypertrophy and atrophy by cellular processes, including activation of the protein kinase B-mechanistic target of rapamycin (Akt-mTOR) signaling cascade. Stressors apart from exercise and nutrition, such as heat stress, can stimulate the heat shock protein A (HSPA) and C (HSPC) families alongside hypertrophic signaling factors and muscle growth. The effects of heat stress on HSP expression and Akt-mTOR activation in human skeletal muscle and their magnitude of activation compared with known hypertrophic stimuli are unclear. Here, we show a single session of whole body heat stress following resistance exercise increases the expression of HSPA and activation of the Akt-mTOR cascade in skeletal muscle compared with resistance exercise in a healthy, resistance-trained population. Heat stress alone may also exert similar effects, though the responses are notably variable and require further investigation. In addition, acute heat stress in C2C12 muscle cells enhanced myotube growth and myogenic fusion, albeit to a lesser degree than growth factor-mediated hypertrophy. Though the mechanisms by which heat stress stimulates hypertrophy-related signaling and the potential mechanistic role of HSPs remain unclear, these findings provide additional evidence implicating heat stress as a novel growth stimulus when combined with resistance exercise in human skeletal muscle and alone in isolated murine muscle cells. We believe these findings will help drive further applied and mechanistic investigation into how heat stress influences muscular hypertrophy and atrophy.NEW & NOTEWORTHY We show that acute resistance exercise followed by whole body heat stress increases the expression of HSPA and increases activation of the Akt-mTOR cascade in a physically active and resistance-trained population.

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.

Effect of hot water immersion on acute physiological responses following resistance exercise

Purpose: Hot water immersion (HWI) is a strategy theorised to enhance exercise recovery. However, the acute physiological responses to HWI following resistance exercise are yet to be determined. Methods: The effect of HWI on intramuscular temperature (IMT), muscle function, muscle soreness and blood markers of muscle cell disruption and inflammatory processes after resistance exercise was assessed. Sixteen resistance trained males performed resistance exercise, followed by either 10 min HWI at 40°C or 10 min passive recovery (PAS). Results: Post-intervention, the increase in IMT at all depths was greater for HWI compared to PAS, however this difference had disappeared by 1 h post at depths of 1 and 2 cm, and by 2 h post at a depth of 3 cm. There were no differences between groups for muscle function, muscle soreness or any blood markers. Conclusion: These results suggest that HWI is a viable means of heat therapy to support a greater IMT following resistance exercise. Recovery of muscle function and muscle soreness is independent of acute changes in IMT associated with HWI.

Practical internal and external cooling methods do not influence rapid recovery from simulated taekwondo performance

Background/Objectives

The influence of post-exercise cooling on recovery has gained much attention in the empirical literature, however, data is limited in regards to optimizing recovery from taekwondo performance when combat is repeated in quick succession within the same day. The aim of this study was therefore to compare the effects of external and internal cooling after simulated taekwondo combat upon intestinal temperature (T_int), psychomotor skills (reaction time, response time, movement time), and neuromuscular function (peak torque, average power, time to reach peak torque).

Methods

Using a randomized counterbalanced crossover design, 10 well-trained male taekwondo athletes completed four recovery methods on separate occasions: passive recovery (CON), a 5-minute thermoneutral water immersion (35°C) (TWI), a 5-min cold water immersion (15°C) (CWI), and ice slurry ingestion (-1°C) (ICE; consumed every 5 min for 30 min). Heart rate (HR), blood lactate (Blac) concentrations, and T_int were determined at rest, immediately after combat, and at selected intervals during a 90-min recovery period. Neuromuscular functional (measured with isokinetic dynamometer) and psychomotor indices were assessed at baseline and after the recovery period.

Results

ICE led to a significantly lower T_int at 30 min (P<0.01) and 45 min (P<0.01) after simulated combat; 15-30 min after cessation of ingesting ice slurry, compared with the CON and TWI conditions, respectively. However, there were no differences in T_int across time points between the other conditions (P>0.05). Psychomotor skills and neuromuscular function indices returned to baseline values after the 90 min recovery period (P>0.05) with no differences observed between conditions (P>0.05).

Conclusion

The present findings suggest that internal (ICE) and external (CWI) recovery methods appear to have little impact on physiological and functional indices over the time course required to influence repeated taekwondo combat performance.

Can muscle typology explain the inter-individual variability in resistance training adaptations?

Considerable inter-individual heterogeneity exists in the muscular adaptations to resistance training. It has been proposed that fast-twitch fibres are more sensitive to hypertrophic stimuli and thus that variation in muscle fibre type composition is a contributing factor to the magnitude of training response. This study investigated if the inter-individual variability in resistance training adaptations is determined by muscle typology and if the most appropriate weekly training frequency depends on muscle typology. In strength-training novices, 11 slow (ST) and 10 fast typology (FT) individuals were selected by measuring muscle carnosine with proton magnetic resonance spectroscopy. Participants trained both upper arm and leg muscles to failure at 60% of one-repetition maximum (1RM) for 10 weeks, whereby one arm and leg trained 3×/week and the contralateral arm and leg 2×/week. Muscle volume (MRI-based 3D segmentation), maximal dynamic strength (1RM) and fibre type-specific cross-sectional area (vastus lateralis biopsies) were evaluated. The training response for total muscle volume (+3 to +14%), fibre size (-19 to +22%) and strength (+17 to +47%) showed considerable inter-individual variability, but these could not be attributed to differences in muscle typology. However, ST individuals performed a significantly higher training volume to gain these similar adaptations than FT individuals. The limb that trained 3×/week had generally more pronounced hypertrophy than the limb that trained 2×/week, and there was no interaction with muscle typology. In conclusion, muscle typology cannot explain the high variability in resistance training adaptations when training is performed to failure at 60% of 1RM. KEY POINTS: This study investigated the influence of muscle typology (muscle fibre type composition) on the variability in resistance training adaptations and on its role in the individualization of resistance training frequency. We demonstrate that an individual's muscle typology cannot explain the inter-individual variability in resistance training-induced increases in muscle volume, maximal dynamic strength and fibre cross-sectional area when repetitions are performed to failure. Importantly, slow typology individuals performed a significantly higher training volume to obtain similar adaptations compared to fast typology individuals. Muscle typology does not determine the most appropriate resistance training frequency. However, regardless of muscle typology, an additional weekly training (3×/week vs. 2×/week) increases muscle hypertrophy but not maximal dynamic strength. These findings expand on our understanding of the underlying mechanisms for the large inter-individual variability in resistance training adaptations.

Effects of cutaneous administration of an over-the-counter menthol cream during temperate-water immersion for exercise-induced hyperthermia in men

Introduction: Hyperthermia impairs various physiological functions and physical performance. We examined the effects of cutaneous administration with an over-the-counter (OTC) analgesic cream containing 20% methyl salicylate and 6% L-menthol during temperate-water immersion (TWI) for exercise-induced hyperthermia. Methods: In a randomized crossover design, twelve healthy males participated in both of two experiments. Firstly, participants underwent a 15-min TWI at 20°C with (CREAM) or without (CON) cutaneous application of an analgesic cream. Cutaneous vascular conductance (CVC) was measured using laser doppler flowmetry during TWI. In a subsequent experiment, same participants performed a 30-min strenuous interval exercise in a heated (35°C) environment to induce hyperthermia (~39°C), which was followed by 15 min of TWI. Results: Core body temperature, as measured by an ingestible telemetry sensor, and mean arterial pressure (MAP) were measured. CVC and %CVC (% baseline) were higher during TWI in CREAM than in CON (Condition effect: p = 0.0053 and p = 0.0010). An additional experiment revealed that core body heat loss during TWI was greater in CREAM than in CON (Cooling rate: CON 0.070 ± 0.020 vs. CREAM 0.084°C ± 0.026°C/min, p = 0.0039). A more attenuated MAP response was observed during TWI in CREAM than in CON (Condition effect: p = 0.0007). Conclusion: An OTC analgesic cream containing L-menthol and MS augmented cooling effects when cutaneously applied during TWI in exercise-induced hyperthermia. This was, at least in part, due to the counteractive vasodilatory effect of the analgesic cream. The cutaneous application of OTC analgesic cream may therefore provide a safe, accessible, and affordable means of enhancing the cooling effects of TWI.

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.

Cool-Water Immersion Reduces Postexercise Quadriceps Femoris Muscle Perfusion More Than Cold-Water Immersion

PURPOSE

The muscle perfusion response to postexercise cold-water immersion (CWI) is not well understood. We examined the effects of graded postexercise CWI upon global and regional quadriceps femoris muscle perfusion using positron emission tomography and [15O]H2O.

METHODS

Using a matched-group design, 30 healthy men performed cycle ergometer exercise at 70% V̇O2peak to a core body temperature of 38°C, followed by either 10 min of CWI at 8°C, 22°C, or seated rest (control). Quadriceps muscle perfusion; thigh and calf cutaneous vascular conductance; intestinal, muscle, and local skin temperatures; thermal comfort; mean arterial pressure; and heart rate were assessed at preexercise, postexercise, and after CWI.

RESULTS

Global quadriceps perfusion was reduced beyond the predefined minimal clinically relevant threshold (0.75 mL per 100 g·min-1) in 22°C water versus control (difference (95% confidence interval (CI)), -2.5 (-3.9 to -1.1) mL per 100 g·min-1). Clinically relevant decreases in muscle perfusion were observed in the rectus femoris (-2.0 (-3.0 to -1.0) mL per 100 g·min-1) and vastus lateralis (-3.5 (-4.9 to -2.0) mL per 100 g·min-1) in 8°C water, and in the vastus lateralis (-3.3 (-4.8 to -1.9) mL per 100 g·min-1) in 22°C water versus control. The mean effects for vastus intermedius and vastus medialis perfusion were not clinically relevant. Clinically relevant decreases in thigh and calf cutaneous vascular conductance were observed in both cooling conditions.

CONCLUSIONS

The present findings revealed that less noxious CWI (22°C) promoted clinically relevant postexercise decreases in global quadriceps muscle perfusion, whereas noxious cooling (8°C) elicited no effect.

The Heat Shock Connection: Skeletal Muscle Hypertrophy and Atrophy

Skeletal muscle is an integral tissue system that plays a crucial role in the physical function of all vertebrates and is a key target for maintaining or improving health and performance across the lifespan. Based largely on cellular and animal models, there is some evidence that various forms of heat stress with or without resistance exercise may enhance skeletal muscle growth or reduce its loss. It is not clear whether these stimuli are similarly effective in humans or meaningful in comparison to exercise alone across various heating methodologies. Furthermore, the magnitude by which heat stress may influence whole body thermoregulatory responses and the connection to skeletal muscle adaptation remains ambiguous. Finally, the underlying mechanisms, which may include interaction between relevant heat shock proteins and intracellular hypertrophy and atrophy related factors, remain unclear. In this narrative mini-review we examine the relevant literature regarding heat stress alone or in combination with resistance exercise emphasizing skeletal muscle hypertrophy and atrophy across cellular and animal models, as well as human investigations. Additionally, we present working mechanistic theories for heat shock protein mediated signaling effects regarding hypertrophy and atrophy related signaling processes. Importantly, continued research is necessary to determine the practical effects and mechanisms of heat stress with and without resistance exercise on skeletal muscle function via growth and maintenance.

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.

Post-exercise Warm or Cold Water Immersion to Augment the Cardiometabolic Benefits of Exercise Training: A Proof of Concept Trial

We investigated whether substituting the final half within 60-min bouts of exercise with passive warm or cold water immersion would provide similar or greater benefits for cardiometabolic health. Thirty healthy participants were randomized to two of three short-term training interventions in a partial crossover (12 sessions over 14–16 days, 4 week washout): (i) EXS: 60 min cycling 70% maximum heart rate (HRmax), (ii) WWI: 30 min cycling then 30 min warm water (38–40°C) immersion, and/or (iii) CWI: 30 min cycling then 30 min cold water (10–12°C) immersion. Before and after, participants completed a 20 min cycle work trial, V.O₂max test, and an Oral Glucose Tolerance Test during which indirect calorimetry was used to measure substrate oxidation and metabolic flexibility (slope of fasting to post-prandial carbohydrate oxidation). Data from twenty two participants (25 ± 5 year, BMI 23 ± 3 kg/m², Female = 11) were analyzed using a fixed-effects linear mixed model. V.O₂max increased more in EXS (interaction p = 0.004) than CWI (95% CI: 1.1, 5.3 mL/kg/min, Cohen’s d = 1.35), but not WWI (CI: −0.4, 3.9 mL/kg/min, d = 0.72). Work trial distance and power increased 383 ± 223 m and 20 ± 6 W, respectively, without differences between interventions (interaction both p > 0.68). WWI lowered post-prandial glucose ∼9% (CI −1.9, −0.5 mmol/L; d = 0.63), with no difference between interventions (interaction p = 0.469). Substituting the second half of exercise with WWI provides similar cardiometabolic health benefits to time matched exercise, however, substituting with CWI does not.

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 Effects of Regular Cold-Water Immersion Use on Training-Induced Changes in Strength and Endurance Performance: A Systematic Review with Meta-Analysis

BACKGROUND

Cold-water immersion (CWI) is one of the main recovery methods used in sports, and is commonly utilized as a means to expedite the recovery of performance during periods of exercise training. In recent decades, there have been indications that regular CWI use is potentially harmful to resistance training adaptations, and, conversely, potentially beneficial to endurance training adaptations. The current meta-analysis was conducted to assess the effects of the regular CWI use during exercise training on resistance (i.e., strength) and endurance (i.e., aerobic exercise) performance alterations.

METHODS

A computerized literature search was conducted, ending on November 25, 2019. The databases searched were MEDLINE, Cochrane Central Register of Controlled Trials, and SPORTDiscus. The selected studies investigated the effects of chronic CWI interventions associated with resistance and endurance training sessions on exercise performance improvements. The criteria for inclusion of studies were: (1) being a controlled investigation; (2) conducted with humans; (3) CWI performed at ≤ 15 °C; (4) being associated with a regular training program; and (5) having performed baseline and post-training assessments.

RESULTS

Eight articles were included before the review process. A harmful effect of CWI associated with resistance training was verified for one-repetition maximum, maximum isometric strength, and strength endurance performance (overall standardized mean difference [SMD] = - 0.60; Confidence interval of 95% [CI95%] = - 0.87, - 0.33; p < 0.0001), as well as for Ballistic efforts performance (overall SMD = - 0.61; CI95% = - 1.11, - 0.11; p = 0.02). On the other hand, selected studies verified no effect of CWI associated with endurance training on time-trial (mean power), maximal aerobic power in graded exercise test performance (overall SMD = - 0.07; CI95% = - 0.54, 0.53; p = 0.71), or time-trial performance (duration) (overall SMD = 0.00; CI95% = - 0.58, 0.58; p = 1.00).

CONCLUSIONS

The regular use of CWI associated with exercise programs has a deleterious effect on resistance training adaptations but does not appear to affect aerobic exercise performance.

TRIAL REGISTRATION

PROSPERO CRD42018098898.

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.

Intramuscular Temperature Changes in the Quadriceps Femoris Muscle After Post-Exercise Cold-Water Immersion (10°C for 10 min): A Systematic Review With Meta-Analysis

Post-exercise cold-water immersion (CWI) is a widely accepted recovery strategy for maintaining physical performance output. However, existing review articles about the effects of CWI commonly pool data from very heterogenous study designs and thus, do rarely differentiate between different muscles, different CWI-protocols (duration, temperature, etc.), different forms of activating the muscles before CWI, and different thickness of the subcutaneous adipose tissue. This systematic review therefore aimed to investigate the effects of one particular post-exercise CWI protocol (10°C for 10 min) on intramuscular temperature changes in the quadriceps femoris muscle while accounting for skinfold thickness. An electronic search was conducted on PubMed, LIVIVO, Cochrane Library, and PEDro databases. Pooled data on intramuscular temperature changes were plotted with respect to intramuscular depth to visualize the influence of skinfold thickness. Spearman's rho (r_s) was used to assess a possible linear association between skinfold thickness and intramuscular temperature changes. A meta-analysis was performed to investigate the effect of CWI on pre-post intramuscular temperature for each measurement depth. A total of six articles met the inclusion criteria. Maximum intramuscular temperature reduction was 6.40°C with skinfold thickness of 6.50 mm at a depth of 1 cm, 4.50°C with skinfold thickness of 11.00 mm at a depth of 2 cm, and only 1.61°C with skinfold thickness of 10.79 mm at a depth of 3 cm. However, no significant correlations between skinfold thickness and intramuscular temperature reductions were observed at a depth of 1 cm (r _s = 0.0), at 2 cm (r _s = -0.8) and at 3 cm (r _s = -0.5; all p > 0.05). The CWI protocol resulted in significant temperature reductions in the muscle tissue layers at 1 cm (d = -1.92 [95% CI: -3.01 to -0.83] and 2 cm (d = -1.63 [95% CI: -2.20 to -1.06]) but not at 3 cm (p < 0.05). Skinfold thickness and thus, subcutaneous adipose tissue, seems to influence temperature reductions in the muscle tissue only to a small degree. These findings might be useful for practitioners as they demonstrate different intramuscular temperature reductions after a specific post-exercise CWI protocol (10°C for 10 min) in the quadriceps femoris muscle.

Post-exercise Cold Water Immersion Effects on Physiological Adaptations to Resistance Training and the Underlying Mechanisms in Skeletal Muscle: A Narrative Review

Post-exercise cold-water immersion (CWI) is a popular recovery modality aimed at minimizing fatigue and hastening recovery following exercise. In this regard, CWI has been shown to be beneficial for accelerating post-exercise recovery of various parameters including muscle strength, muscle soreness, inflammation, muscle damage, and perceptions of fatigue. Improved recovery following an exercise session facilitated by CWI is thought to enhance the quality and training load of subsequent training sessions, thereby providing a greater training stimulus for long-term physiological adaptations. However, studies investigating the long-term effects of repeated post-exercise CWI instead suggest CWI may attenuate physiological adaptations to exercise training in a mode-specific manner. Specifically, there is evidence post-exercise CWI can attenuate improvements in physiological adaptations to resistance training, including aspects of maximal strength, power, and skeletal muscle hypertrophy, without negatively influencing endurance training adaptations. Several studies have investigated the effects of CWI on the molecular responses to resistance exercise in an attempt to identify the mechanisms by which CWI attenuates physiological adaptations to resistance training. Although evidence is limited, it appears that CWI attenuates the activation of anabolic signaling pathways and the increase in muscle protein synthesis following acute and chronic resistance exercise, which may mediate the negative effects of CWI on long-term resistance training adaptations. There are, however, a number of methodological factors that must be considered when interpreting evidence for the effects of post-exercise CWI on physiological adaptations to resistance training and the potential underlying mechanisms. This review outlines and critiques the available evidence on the effects of CWI on long-term resistance training adaptations and the underlying molecular mechanisms in skeletal muscle, and suggests potential directions for future research to further elucidate the effects of CWI on resistance training adaptations.

In vivo Ca2+ dynamics during cooling after eccentric contractions in rat skeletal muscle

The effect of cooling on in vivo intracellular calcium ion concentration [Ca²⁺]_i after eccentric contractions (ECs) remains to be determined. We tested the hypothesis that cryotherapy following ECs promotes an increased [Ca²⁺]_i and induces greater muscle damage in two muscles with substantial IIb and IIx fiber populations. The thin spinotrapezius (SPINO) muscles of Wistar rats were used for in vivo [Ca²⁺]_i imaging, and tibialis anterior (TA) muscles provided greater fidelity and repeatability of contractile function measurements. SPINO [Ca²⁺]_i was estimated using fura 2-AM and the magnitude, location, and temporal profile of [Ca²⁺]_i determined as the temperature near the muscle surface post-ECs was decreased from 30°C (control) to 20°C or 10°C. Subsequently, in the TA, the effect of post-ECs cooling to 10°C on muscle contractile performance was determined at 1 and 2 days after ECs. TA muscle samples were examined by hematoxylin and eosin staining to assess damage. In SPINO, reducing the muscle temperature from 30°C to 10°C post-ECs resulted in a 3.7-fold increase in the spread of high [Ca²⁺]_i sites generated by ECs (P < 0.05). These high [Ca²⁺]_i sites demonstrated partial reversibility when rewarmed to 30°C. Dantrolene, a ryanodine receptor Ca²⁺ release inhibitor, reduced the presence of high [Ca²⁺] sites at 10°C. In the TA, cooling exacerbated ECs-induced muscle strength deficits via enhanced muscle fiber damage (P < 0.05). By demonstrating that cooling post-ECs potentiates [Ca²⁺]_i derangements, this in vivo approach supports a putative mechanistic basis for how postexercise cryotherapy might augment muscle fiber damage and decrease subsequent exercise performance.

Diving with hypertension and antihypertensive drugs

Hypertension is a common condition, which is highly prevalent amongst scuba divers. As a consequence, a substantial proportion of divers are hypertensive and/or on antihypertensive drugs when diving. In this article, we review available literature on the possible risks of diving in the presence of hypertension and antihypertensive drugs. Guidelines are presented for the diving physician for the selection of divers with hypertension suitable for diving, along with advice on antihypertensive treatment best compatible with scuba diving.

Water immersion methods do not alter muscle damage and inflammation biomarkers after high-intensity sprinting and jumping exercise

Purpose

The aim of this study was to compare the efficacy of three water immersion interventions performed after active recovery compared to active recovery only on the resolution of inflammation and markers of muscle damage post-exercise.

Methods

Nine physically active men (n = 9; age 20‒35 years) performed an intensive loading protocol, including maximal jumps and sprinting on four occasions. After each trial, one of three recovery interventions (10 min duration) was used in a random order: cold-water immersion (CWI, 10 °C), thermoneutral water immersion (TWI, 24 °C), contrast water therapy (CWT, alternately 10 °C and 38 °C). All of these methods were performed after an active recovery (10 min bicycle ergometer), and were compared to active recovery only (ACT). 5 min, 1, 24, 48, and 96 h after exercise bouts, immune response and recovery were assessed through leukocyte subsets, monocyte chemoattractant protein-1, myoglobin and high-sensitivity C-reactive protein concentrations.

Results

Significant changes in all blood markers occurred at post-loading (p < 0.05), but there were no significant differences observed in the recovery between methods. However, retrospective analysis revealed significant trial-order effects for myoglobin and neutrophils (p < 0.01). Only lymphocytes displayed satisfactory reliability in the exercise response, with intraclass correlation coefficient > 0.5.

Conclusions

The recovery methods did not affect the resolution of inflammatory and immune responses after high-intensity sprinting and jumping exercise. It is notable that the biomarker responses were variable within individuals. Thus, the lack of differences between recovery methods may have been influenced by the reliability of exercise-induced biomarker responses.

Electronic supplementary material

The online version of this article (10.1007/s00421-020-04481-8) contains supplementary material, which is available to authorized users.

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.

Changes in quadriceps femoris muscle perfusion following different degrees of cold-water immersion

We examined the influence of graded cold-water immersion (CWI) on global and regional quadriceps muscle perfusion with positron emission tomography (PET) and [¹⁵O]H₂O. In 30 healthy men [33 ± 8 yr; 81 ± 10 kg; 184 ± 5 cm; percentage body fat: 13 ± 5%; peak oxygen uptake (V̇o_2peak): 47 ± 8 mL·kg^-1·min^-1] quadriceps perfusion, thigh and calf cutaneous vascular conductance (CVC), intestinal, muscle, and local skin temperatures, thermal comfort, mean arterial pressure, and heart rate were assessed before and after 10 min of CWI at 8°C, 15°C, or 22°C. Global quadriceps perfusion did not change beyond a clinically relevant threshold (0.75 mL·100 g·min^-1) in any condition and was similar between conditions {range of differences [95% confidence interval (CI)]: 0.1 mL·100 g·min^-1 (-0.9 to 1.2 mL·100 g·min^-1) to 0.9 mL·100 g·min^-1 (-0.2 to 1.9 mL·100 g·min^-1)}. Muscle perfusion was greater in vastus intermedius (VI) compared with vastus lateralis (VL) (2.2 mL·100 g·min^-1; 95% CI 1.5 to 3.0 mL·100 g·min^-1) and rectus femoris (RF) (2.2 mL·100 g·min^-1; 1.4 to 2.9 mL·100 g·min^-1). A clinically relevant increase in VI muscle perfusion after immersion at 8°C and a decrease in RF muscle perfusion at 15°C were observed. A clinically relevant increase in perfusion was observed in VI in 8°C compared with 22°C water (2.3 mL·100 g·min^-1; 1.1 to 3.5 mL·100 g·min^-1). There were no clinically relevant between-condition differences in thigh CVC. Our findings suggest that CWI (8-22°C) does not reduce global quadriceps muscle perfusion to a clinically relevant extent; however, colder water increases (8°C) deep muscle perfusion and reduces (15°C) superficial muscle (RF) perfusion in the quadriceps muscle.NEW & NOTEWORTHY Using positron emission tomography, we report for the first time muscle perfusion heterogeneity in the quadriceps femoris in response to different degrees of cold-water immersion (CWI). Noxious CWI temperatures (8°C) increase perfusion in the deep quadriceps muscle, whereas superficial quadriceps muscle perfusion is reduced in cooler (15°C) water. Therefore, these data have important implications for the selection of CWI approaches used in the treatment of soft tissue injury, while also increasing our understanding of the potential mechanisms underpinning CWI.

Hot-water immersion does not increase postprandial muscle protein synthesis rates during recovery from resistance-type exercise in healthy, young males

The purpose of this study was to assess the impact of postexercise hot-water immersion on postprandial myofibrillar protein synthesis rates during recovery from a single bout of resistance-type exercise in healthy, young men. Twelve healthy, adult men (age: 23 ± 1 y) performed a single bout of resistance-type exercise followed by 20 min of water immersion of both legs. One leg was immersed in hot water [46°C: hot-water immersion (HWI)], while the other leg was immersed in thermoneutral water (30°C: CON). After water immersion, a beverage was ingested containing 20 g intrinsically L-[1-¹³C]-phenylalanine and L-[1-¹³C]-leucine labeled milk protein with 45 g of carbohydrates. In addition, primed continuous L-[ring-²H₅]-phenylalanine and L-[1-¹³C]-leucine infusions were applied, with frequent collection of blood and muscle samples to assess myofibrillar protein synthesis rates in vivo over a 5-h recovery period. Muscle temperature immediately after water immersion was higher in the HWI compared with the CON leg (37.5 ± 0.1 vs. 35.2 ± 0.2°C; P < 0.001). Incorporation of dietary protein-derived L-[1-¹³C]-phenylalanine into myofibrillar protein did not differ between the HWI and CON leg during the 5-h recovery period (0.025 ± 0.003 vs. 0.024 ± 0.002 MPE; P = 0.953). Postexercise myofibrillar protein synthesis rates did not differ between the HWI and CON leg based upon L-[1-¹³C]-leucine (0.050 ± 0.005 vs. 0.049 ± 0.002%/h; P = 0.815) and L-[ring-²H₅]-phenylalanine (0.048 ± 0.002 vs. 0.047 ± 0.003%/h; P = 0.877), respectively. Hot-water immersion during recovery from resistance-type exercise does not increase the postprandial rise in myofibrillar protein synthesis rates. In addition, postexercise hot-water immersion does not increase the capacity of the muscle to incorporate dietary protein-derived amino acids in muscle tissue protein during subsequent recovery.NEW & NOTEWORTHY This is the first study to assess the effect of postexercise hot-water immersion on postprandial myofibrillar protein synthesis rates and the incorporation of dietary protein-derived amino acids into muscle protein. We observed that hot-water immersion during recovery from a single bout of resistance-type exercise does not further increase myofibrillar protein synthesis rates or augment the postprandial incorporation of dietary protein-derived amino acids in muscle throughout 5 h of postexercise recovery.

Males benefit more from cold water immersion during repeated handgrip contractions than females despite similar oxygen kinetics

The purpose of the present study was to assess the effect of different water immersion temperatures on handgrip performance and haemodynamic changes in the forearm flexors of males and females. Twenty-nine rock-climbers performed three repeated intermittent handgrip contractions to failure with 20 min recovery on three separate laboratory visits. For each visit, a randomly assigned recovery strategy was applied: cold water immersion (CWI) at 8 °C (CW8), 15 °C (CW15) or passive recovery (PAS). While handgrip performance significantly decreased in the subsequent trials for the PAS (p < 0.05), there was a significant increase in time to failure for the second and third trial for CW15 and in the second trial for CW8; males having greater performance improvement (44%) after CW15 than females (26%). The results indicate that CW15 was a more tolerable and effective recovery strategy than CW8 and the same CWI protocol may lead to different recovery in males and females.

Postexercise cooling impairs muscle protein synthesis rates in recreational athletes

Key points

Protein ingestion and cooling are strategies employed by athletes to improve postexercise recovery and, as such, to facilitate muscle conditioning. However, whether cooling affects postprandial protein handling and subsequent muscle protein synthesis rates during recovery from exercise has not been assessed.

We investigated the effect of postexercise cooling on the incorporation of dietary protein‐derived amino acids into muscle protein and acute postprandial (hourly) as well as prolonged (daily) myofibrillar protein synthesis rates during recovery from resistance‐type exercise over 2 weeks.

Cold‐water immersion during recovery from resistance‐type exercise lowers the capacity of the muscle to take up and/or direct dietary protein‐derived amino acids towards de novo myofibrillar protein accretion. In addition, cold‐water immersion during recovery from resistance‐type exercise lowers myofibrillar protein synthesis rates during prolonged resistance‐type exercise training.

Individuals aiming to improve skeletal muscle conditioning should reconsider applying cooling as a part of their postexercise recovery strategy.

Abstract

We measured the impact of postexercise cooling on acute postprandial (hourly) as well as prolonged (daily) myofibrillar protein synthesis rates during adaptation to resistance‐type exercise over 2 weeks. Twelve healthy males (aged 21 ± 2 years) performed a single resistance‐type exercise session followed by water immersion of both legs for 20 min. One leg was immersed in cold water (8°C: CWI), whereas the other leg was immersed in thermoneutral water (30°C: CON). After water immersion, a beverage was ingested containing 20 g of intrinsically (l‐[1‐¹³C]‐phenylalanine and l‐[1‐¹³C]‐leucine) labelled milk protein with 45 g of carbohydrates. In addition, primed continuous l‐[ring‐²H₅]‐phenylalanine and l‐[1‐¹³C]‐leucine infusions were applied, with frequent collection of blood and muscle samples to assess myofibrillar protein synthesis rates in vivo over a 5 h recovery period. In addition, deuterated water (²H₂O) was applied with the collection of saliva, blood and muscle biopsies over 2 weeks to assess the effects of postexercise cooling with protein intake on myofibrillar protein synthesis rates during more prolonged resistance‐type exercise training (thereby reflecting short‐term training adaptation). Incorporation of dietary protein‐derived l‐[1‐¹³C]‐phenylalanine into myofibrillar protein was significantly lower in CWI compared to CON (0.016 ± 0.006 vs. 0.021 ± 0.007 MPE; P = 0.016). Postexercise myofibrillar protein synthesis rates were lower in CWI compared to CON based upon l‐[1‐¹³C]‐leucine (0.058 ± 0.011 vs. 0.072 ± 0.017% h⁻¹, respectively; P = 0.024) and l‐[ring‐²H₅]‐phenylalanine (0.042 ± 0.009 vs. 0.053 ± 0.013% h⁻¹, respectively; P = 0.025). Daily myofibrillar protein synthesis rates assessed over 2 weeks were significantly lower in CWI compared to CON (1.48 ± 0.17 vs. 1.67 ± 0.36% day⁻¹, respectively; P = 0.042). Cold‐water immersion during recovery from resistance‐type exercise reduces myofibrillar protein synthesis rates and, as such, probably impairs muscle conditioning.

Protein ingestion and cooling are strategies employed by athletes to improve postexercise recovery and, as such, to facilitate muscle conditioning. However, whether cooling affects postprandial protein handling and subsequent muscle protein synthesis rates during recovery from exercise has not been assessed.

We investigated the effect of postexercise cooling on the incorporation of dietary protein‐derived amino acids into muscle protein and acute postprandial (hourly) as well as prolonged (daily) myofibrillar protein synthesis rates during recovery from resistance‐type exercise over 2 weeks.

Cold‐water immersion during recovery from resistance‐type exercise lowers the capacity of the muscle to take up and/or direct dietary protein‐derived amino acids towards de novo myofibrillar protein accretion. In addition, cold‐water immersion during recovery from resistance‐type exercise lowers myofibrillar protein synthesis rates during prolonged resistance‐type exercise training.

Individuals aiming to improve skeletal muscle conditioning should reconsider applying cooling as a part of their postexercise recovery strategy.

Effects of postexercise cooling on heart rate recovery in normotensive and hypertensive men

BACKGROUND

Postexercise heart rate recovery (HRR) is determined by cardiac autonomic restoration after exercise and is reduced in hypertension. Postexercise cooling accelerates HRR in healthy subjects, but its effects in a population with cardiac autonomic dysfunction, such as hypertensives (HT), may be blunted. This study assessed and compared the effects of postexercise cooling on HRR and cardiac autonomic regulation in HT and normotensive (NT) subjects.

METHODS

Twenty-three never-treated HT (43 ± 8 years) and 25 NT (45 ± 8 years) men randomly underwent two exercise sessions (30 min of cycling at 70% VO_2peak ) followed by 15 min of recovery. In one randomly allocated session, a fan was turned on in front of the subject during the recovery (cooling), while in the other session, no cooling was performed (control). HRR was assessed by heart rate reductions after 60 s (HRR60s) and 300 s (HRR300s) of recovery, short-term time constant of HRR (T30) and the time constant of the HRR after exponential fitting (HRRτ). HRV was assessed using time- and frequency-domain indices.

RESULTS

HRR and HRV responses in the cooling and control sessions were similar between the HT and NT. Thus, in both groups, postexercise cooling equally accelerated HRR (HRR300s = 39±12 versus 36 ± 10 bpm, P≤0·05) and increased postexercise HRV (lnRMSSD = 1·8 ± 0·7 versus 1·6 ± 0·7 ms, P≤0·05).

CONCLUSION

Differently from the hypothesis, postexercise cooling produced similar improvements in HRR in HT and NT men, likely by an acceleration of cardiac parasympathetic reactivation and sympathetic withdrawal. These results suggest that postexercise cooling equally accelerates HRR in hypertensive and normotensive subjects.

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.

Cold water immersion settings for reducing muscle tissue temperature: a linear dose-response relationship

BACKGROUND

Although cold water immersion (CWI) is widely accepted and integrated as a recovery modality in sports practice, questions regarding its proposed working mechanisms remain. This study systematically reviews the existing literature on one the proposed mechanisms of CWI, its effect on muscle tissue temperature, and subsequently tries to identify a dose-response relationship in order to describe an optimal dose.

EVIDENCE ACQUISITION

A systematic literature search (PubMed and Sport Discus) was conducted in October 2017. Dose-response relationships were analyzed using linear regression while controlling for possible confounders (muscle measurement depth and immersion position).

EVIDENCE SYNTHESIS

A total of 10 studies, with a total of 104 participants, were included utilizing 26 different CWI protocols. Muscle tissue temperatures were reduced significantly by 24 CWI protocols. A significant, relationship with a medium effect size (r=0.51) was identified between muscle tissue temperature and CWI. The most optimal dose-response relationship, with a large effect size, (r=0.87) was described for CWI protocols using full-body immersion at a measurement depth of 30 mm (y = 4.051 x + 0.535).

CONCLUSIONS

CWI can decrease muscle tissue temperature significantly if a minimum CWI dose of 1.1 is applied, corresponding with an immersion of 11 minutes with a water temperature of 10 °C.

Mild hypothermia affects the morphology and impairs glutamine-induced anabolic response in human primary myotubes

The specific impact of reduced temperature on skeletal muscle adaptation has been poorly investigated. Cold water immersion, one situation leading to decreased skeletal muscle temperature, is commonly proposed to reduce the perception of fatigue and muscle soreness after strenuous exercise. In contrast, it may impair long-term benefits of resistance exercise training on muscle strength and hypertrophy. To date, the physiological factors responsible for this blunted muscle adaptation remain unclear. Here, we used a cell culture model of human primary myotubes to specifically investigate the intrinsic behavior of muscle cells during mild hypothermia (MH). Newly formed myotubes were exposed to either 37°C or 32°C to evaluate the effect of MH on myotube size and morphology, protein synthesis, and anabolic signaling. We also compared the glutamine (GLUT)-induced hypertrophic response between myotubes incubated at 32°C or 37°C. We showed that 48 h exposure to MH altered the cellular morphology (greater myotube area, shorter myosegments, myotubes with irregular shape) and impaired GLUT-induced myotube hypertrophy. Moreover, MH specifically reduced protein synthesis at 8 h. This result may be explained by an altered regulation of ribosome biogenesis, as evidenced by a lower expression of 45S pre-ribosomal RNA and MYC protein, and a lower total RNA concentration. Furthermore, MH blunted GLUT-induced increase in protein synthesis at 8 h, a finding consistent with an impaired activation of the mechanistic target of rapamycin pathway. In conclusion, this study demonstrates that MH impairs the morphology of human myotubes and alters the hypertrophic response to GLUT.