Research Supporting Performance Cooling

Out of the initially identified 6982 search records, 15 studies were deemed eligible for meta-analysis. Our results showed that precooling significantly improved time trial (TT) performance (SMD, -0.37, p < 0.01, I2 = 0%) and time to exhaustion (TTE) performance in the heat (SMD, 0.73, p < 0.01, I2 = 50%). Further subgroup analyses revealed that external precooling is more effective in improving TT performance (SMD, -0.43, p = 0.004, I2 = 0%) and TTE performance (SMD, 1.01, p < 0.001, I2 = 48%), particularly in running-based performances (TT, SMD, -0.41, p = 0.02, I2 = 0%; TTE, SMD, 0.85).

Rectal temperature was ~0.5 °C (0.9 °F) lower during exercise in the heat after the precooling intervention, and participants exercised 18 min longer compared with no cooling. Because precooling delayed the onset of hyperthermia without affecting post-exercise cooling rates, it appears that a relatively short bout of precooling may be a useful strategy for delaying, or possibly even preventing, exertional heat illness.

Method: A systematic review and meta-analysis of randomized controlled trials investigating the effects of precooling strategies on endurance performance in hot conditions. Fifteen studies involving trained and elite endurance athletes (runners, cyclists, triathletes) were included. Cooling interventions primarily involved external precooling methods (e.g., ice vests, cold water immersion) compared against no-cooling control conditions. Performance outcomes included time trial performance and time to exhaustion.

Results: Precooling resulted in a statistically significant improvement in endurance performance compared to control. Time-trial completion times improved and time to exhaustion was prolonged. Subgroup analysis showed external cooling methods such as ice vests were particularly effective.

Conclusion: Precooling, particularly through external cooling methods such as ice vests, significantly enhances endurance performance in hot environments. Benefits appear to be driven largely by reductions in skin temperature and improvements in thermal comfort.

Method: A meta-analysis examining pre-cooling and per-cooling (cooling during exercise) strategies across 28 controlled studies performed in hot environments (>30 °C). Included studies assessed endurance performance in trained and elite endurance athletes using cooling methods such as ice vests, cold water immersion, and ice ingestion.

Results: Cooling strategies improved endurance performance by ~6–10% overall. Both precooling and per-cooling independently enhanced performance, with per-cooling via ice vests during exercise showing the largest mean effect. Performance improvements occurred without meaningful differences in final core temperature, suggesting perceptual and skin-temperature mechanisms as primary drivers.

Conclusion: Both precooling and cooling during exercise significantly improve endurance performance in the heat. Ice vest–based cooling during activity is one of the most effective per-cooling strategies available to athletes.

Method: Nine trained male endurance runners completed 5-km treadmill time trials in hot conditions (33 °C) under three conditions: precooling via cold-water immersion, mid-exercise cooling via facial water spray, and no cooling control. Physiological and perceptual measures were recorded alongside performance.

Results: Both precooling and mid-exercise cooling significantly improved 5-km performance times compared to control (~2–3% faster). Precooling reduced core temperature prior to exercise, whereas facial water spray did not. Despite this, performance improvements were similar between cooling conditions.

Conclusion: Endurance running performance in the heat can be improved through both precooling and simple in-exercise cooling methods. Performance benefits appear to be mediated primarily through perceived thermal comfort rather than absolute changes in core temperature.

Method: This systematic review and meta-analysis examined 28 studies assessing precooling and per-cooling strategies in hot environments (>30°C). Studies included endurance athletes performing cycling, running, and time-to-exhaustion trials. Cooling methods included ice vests, cold water immersion, and cold fluid ingestion. Performance outcomes and physiological measures were compared to non-cooled controls.

Results: Cooling improved endurance performance by ~6–10% overall. Per-cooling (cooling during exercise) showed slightly larger average effects than precooling alone. Ice vest use during exercise was among the most effective interventions identified.

Conclusion: Both pre-exercise and during-exercise cooling improve endurance performance in the heat, with per-cooling strategies — particularly ice vest use — delivering the greatest performance benefits.

Method: Trained cyclists completed cycling time-to-exhaustion tests in hot laboratory conditions with or without a precooling protocol involving ice vests. Skin and core temperatures were continuously monitored. Cardiovascular responses and perceptual ratings were recorded.

Results: Precooling significantly increased time to exhaustion. Skin temperature reductions were substantial, while core temperature differences were moderate. Athletes reported improved thermal comfort and lower RPE. Performance gains were attributed primarily to delayed onset of thermal discomfort and reduced cardiovascular strain.

Conclusion: Ice vest precooling meaningfully extends how long athletes can sustain high-intensity effort in the heat, driven primarily by skin temperature reductions and improved perceived comfort rather than core temperature changes alone.

Method: Competitive cyclists completed 20-km time trials in the heat following either no cooling or external cooling via an ice vest and cold towels. The crossover design ensured each athlete experienced both conditions. Performance time and physiological markers were measured.

Results: Cyclists completed the time trial significantly faster after precooling. Core temperature rise was slower in the cooling condition. Thermal comfort scores improved markedly.

Conclusion: External cooling via an ice vest enhances self-paced endurance cycling performance in the heat. The combination of ice vest and surface cooling produces meaningful and practical performance improvements in competitive cyclists.

Method: This review evaluated cooling methods used in endurance running events in hot climates. It included studies using ice vests, cold water immersion, and evaporative cooling garments. Outcomes included time-trial performance and physiological strain.

Results: External cooling garments consistently improved running performance in hot environments. Improvements were most pronounced in events longer than 5 km. The authors emphasized that cooling vests effectively reduce cardiovascular strain and perceived exertion. Benefits were greater in longer-duration events where heat accumulation plays a larger role in fatigue.

Conclusion: Cooling vests are particularly valuable for longer endurance running events in the heat, where sustained thermal management provides compounding performance benefits throughout the race.

Ten well-trained runners did two 100-minute treadmill runs, one at ~66℉ and one at 93℉. In both, they drank enough water to replace ~90% of sweat loss and took in 60 grams of glucose (20 grams every 20 minutes). Even while maintaining hydration, heat shaved ~20% off the rate at which runners burned the carbs they drank. Total carbohydrate use was similar across conditions, but in the heat, more of it came from their own glycogen stores and fat oxidation dropped by ~27%. Core temperature and heart rate were, unsurprisingly, higher in the heat, and blood lactate and glucose ran higher too, consistent with a shift toward more glycolytic metabolism.

A study exposed adults ranging from 20 to 79 years old to six hours of extreme heat. Each participant spent six hours in an environmental chamber set to 109°F and 25% relative humidity. Every hour consisted of 50 minutes of seated rest followed by 10 minutes of treadmill walking at three metabolic equivalents.

Average core temperature rose by a range from 0.6°F to as much as 3°F.  Age explained part of that difference. The older the participants were, the less they sweated.  

Heat vulnerability appears to accumulate gradually across adulthood. . The age-related decline in thermoregulation looked gradual rather than catastrophic. Higher cardiorespiratory fitness appeared to provide some additional physiological reserve against the heat as you get older.

Method: A controlled laboratory study evaluated four cooling vest technologies — a phase change material (PCM) vest, an evaporative cooling vest, a fan-assisted airflow vest, and a ventilated mesh-based design — using a thermal manikin under simulated heat-stress conditions. Each vest was tested across multiple metabolic heat production levels and compared for core temperature regulation, skin temperature, heat storage, and thermal comfort.

Results: All cooling vest designs reduced thermal strain compared to no cooling; however, substantial differences emerged as metabolic rate increased. Mesh and airflow-assisted vests maintained lower simulated core and skin temperatures across moderate-to-high workloads. Traditional PCM-only vests showed diminished cooling effectiveness once phase-change capacity was exhausted and demonstrated heat retention effects at higher metabolic rates. The fan-assisted mesh vest consistently demonstrated the lowest heat storage and best thermal comfort scores at higher intensities.

Conclusion: While all cooling vest technologies provided some degree of heat mitigation, ventilated mesh-based and airflow-assisted cooling vests were most effective, particularly during moderate-to-high intensity activity. Cooling vests designed to allow heat to escape rather than trap it are better suited for sustained exertion in hot environments.

Method: A systematic review and meta-analysis of studies examining the effects of cooling vests on perceptual responses, thermophysiological behavior, and sports performance in heat-exposed adults. Following PRISMA guidelines, 711 studies were screened; 10 met criteria for the systematic review and 8 for meta-analysis. Outcomes included test time, peak power, skin temperature, core temperature, and perceptual scores.

Results: Application of cooling vests showed significant improvements in test time and substantial increases in peak power. Skin temperature was significantly reduced across studies. Core temperature changes were generally small or non-significant. Thermal and exertional perception improved significantly with cooling vest use, indicating reduced perceived strain during heat exposure.

Conclusion: Cooling vests appear to be an ergogenic tool under heat stress, improving perceptual comfort, lowering skin temperature, and enhancing performance metrics like test time and peak power. However, their effect on core temperature appears limited.

Method: This study evaluated multiple cooling vest designs based on different heat-extraction concepts (e.g., phase change, evaporative, airflow/ventilated mesh) using human and manikin thermal analysis. Testing focused on materials and configurations that influence heat transfer, skin temperature, and comfort — characteristics relevant to wearable cooling garments.

Results: Vest designs that enhance ventilation and airflow performed better at sustaining heat dissipation under simulated metabolic heat loads compared with solid-phase cooling materials alone. Evaporative and mesh-based designs demonstrated superior thermal performance under high-intensity simulation. Phase change materials showed limitations under continuous high metabolic output.

Conclusion: Cooling vest effectiveness strongly depends on design and heat-extraction concept. Vest technologies that emphasize ventilation and airflow (e.g., mesh, active cooling) are superior for sustained high-intensity activity compared to traditional phase change material approaches.

Method: Eight well-trained male athletes completed two bouts of intermittent high-intensity cycling in 33 °C heat, separated by a 15-minute break. During the break, participants either wore an ice-based cooling vest or rested without cooling. Power output, heart rate, skin temperature, and perceptual responses were assessed.

Results: Wearing a cooling vest during the break resulted in higher mean power output (~5%) during the second exercise bout. Skin temperature and heart rate were significantly lower, and athletes reported improved thermal comfort and reduced perceived exertion. Core temperature changes were modest.

Conclusion: Cooling vest use during short recovery periods improves subsequent endurance performance in the heat. Performance benefits are likely driven by reduced skin temperature and perceptual strain rather than core body cooling alone.

Method: Eight non–heat-acclimated male athletes completed a laboratory-based intermittent cycling protocol in 33 °C heat, consisting of two 30-min bouts separated by a 15-min halftime. In a randomized crossover design, participants either wore a cooling vest with ice packs during halftime or wore an identical-weight vest without ice. Mean/max power output, rectal/core temperature, skin temperatures, heart rate, and perceptual responses (thermal sensation, thermal comfort, RPE) were recorded.

Results: Mean power output in the second half was significantly greater in the cooling vest condition vs. control (3rd trial: 589 ± 58 W vs. 561 ± 53 W; 4th trial: 584 ± 58 W vs. 561 ± 53 W). Skin temperature and perceived exertion were meaningfully reduced.

Conclusion: Using a cooling vest during a short mid-exercise break in the heat improved subsequent intermittent cycling performance, primarily by lowering skin temperatures and enhancing thermal comfort.

Method: Forty-seven physically active males completed a 45-min treadmill protocol designed to simulate soccer match demands, then underwent a 15-min recovery period. Participants were assigned to either a cool vest intervention group (wearing a cooling vest during recovery) or a control group (passive rest without cooling). Skin temperature and tympanic (core) temperature were measured at multiple points before, during, and after the protocol.

Results: The cooling vest intervention group exhibited significantly lower skin temperatures at 10 min post-exercise compared with the control group (31.46 ± 0.67 °C vs. 32.40 ± 1.04 °C; p = 0.003). Tympanic temperature was also reduced in the cooling vest group.

Conclusion: Applying a cooling vest during a short recovery window (15 min) after intense exercise reduces both skin and core temperatures, suggesting meaningful benefits for thermoregulatory recovery.

Method: Well-trained athletes performed cycling tests in hot conditions with and without wearing an ice vest during warm-up. Core temperature, skin temperature, heart rate, and power output were measured. The protocol simulated competition heat stress conditions.

Results: Precooling via ice vest lowered starting skin temperature and slowed the rise in core temperature during exercise. Athletes maintained higher mean power output in later stages of the trial. Perceived exertion was reduced despite similar final core temperatures. The cooling effect improved pacing strategy and allowed athletes to work harder for longer before heat fatigue set in.

Conclusion: Wearing an ice vest during warm-up is an effective precooling method that delays heat accumulation and helps athletes sustain higher power outputs across the full duration of competition in hot conditions.

Method: This systematic review assessed per-cooling strategies used during endurance exercise. Studies included cycling and running protocols in heat stress conditions. Cooling garments, including ice vests, were compared to control trials.

Results: Pre-cooling improved endurance performance by sustaining higher work rates. Ice vest strategies were effective when airflow was present. Core temperature differences were small but skin cooling was substantial. The review highlighted improved pacing tolerance as the key mechanism.

Conclusion: Per-cooling via ice vest during exercise enables athletes to maintain higher sustained work rates by managing skin temperature and reducing perceptual heat strain — even when core temperature changes are minimal.

Pre-cooling can be described as the rapid removal of heat from the body before exercise to create a larger heat storage capacity. Many pre-cooling techniques have been proven to be effective, ranging from whole body pre-cooling such as cold water immersion and cold air exposure to local cooling using cooling vests or cooling packs, or internal cooling strategies such as the ingesting of cold water or ice slurry. Furthermore, a combination of these cooling techniques (mixed method cooling) is often used. Taken together, the effects of pre-cooling greatly depend on the cooling strategy, exercise setting and ambient conditions. The optimal pre-cooling strategy to improve exercise performance includes a combination of external and internal cooling techniques, applied in a practical and time-efficient manner.

Method: Ten trained/highly trained male cyclists and/or triathletes completed two 20-km cycling time trials (CTT) before heat acclimation (HA) training sessions (10 × 60 min intermittent-heat exposure protocol in 36 °C, 50–80% relative humidity), and after. No cooling (CON) or crushed-ice was ingested 30 min prior to the CTTs.

Results: No meaningful direct relations were observed for 20-km CTT completion time between the post-HA precooling group (2663 ± 307 s) and the post-HA control group (2671 ± 370 s).

Conclusion: Ingestion of crushed ice only warranted "insufficient evidence exists to support a meaningful performance improvement in 20-km CTT in hot-humid conditions."

Method: Fifteen trained male cyclists and triathletes completed 800-kJ cycling time trials in 35 °C conditions before and after either ice-slurry precooling or 12 days of heat acclimation training. Performance times, core temperature, and perceptual measures were compared.

Results: Ice-slurry precooling produced performance improvements comparable to heat acclimation, with significantly faster post-intervention time trials. Precooling lowered pre-exercise core temperature, delayed sweating onset, and reduced thermal sensation during exercise.

Conclusion: Precooling using crushed ice is an effective strategy for improving cycling time-trial performance in the heat and may serve as a practical alternative to heat acclimation when preparation time is limited.

Method: Endurance-trained athletes performed exercise trials in heat comparing ice vest cooling, ice slurry ingestion, and control. Trials were randomized and conducted in controlled environmental chambers. Power output, core temperature, and perceptual strain were measured.

Results: Both external (ice vest) and internal cooling improved performance relative to control. External cooling was more effective at reducing skin temperature, while internal cooling influenced core temperature more directly. Combined strategies showed additive benefits.

Conclusion: Ice vest cooling and ice slurry ingestion each independently improve performance in the heat through complementary mechanisms — external cooling targets skin and peripheral temperatures while internal cooling targets core temperature. Athletes benefit most when both strategies are used together.

Method: Trained runners performed 5-km time trials in 33°C heat under precooling, mid-exercise cooling, and control conditions. Core temperature, skin temperature, and perceptual measures were tracked.

Results: Both cooling interventions improved performance by ~2–3%. Precooling lowered core temperature prior to exercise. Mid-exercise cooling reduced perceived exertion without significantly altering core temperature. Performance improvements were linked to thermal perception changes.

Conclusion: Cooling interventions improve running performance in the heat primarily by improving how athletes perceive thermal strain, rather than through direct core temperature reductions — underscoring the powerful role of perceived comfort in pacing and output.

Method: Cyclists and triathletes performed cycling time trials in 35°C heat before and after either ice slurry precooling or heat acclimation training. Core temperature and performance time were measured.

Results: Ice slurry precooling improved time trial performance similarly to heat acclimation. Core temperature was reduced at exercise onset. Thermal sensation was improved.

Conclusion: Precooling provided an effective short-term alternative to acclimation, making it a practical tool for athletes who compete in the heat without extended preparation time. Ice slurry ingestion is a low-cost, accessible strategy that delivers performance results comparable to structured heat adaptation protocols.

Method: This follow-up review examined endurance performance under various cooling protocols in hot conditions. Studies included trained endurance athletes. Performance, thermal strain, and perceptual outcomes were analyzed across sport disciplines.

Results: Cooling significantly enhanced endurance capacity across sports. External cooling via ice vests was particularly effective when combined with warm-up protocols. Performance gains occurred even when core temperature reductions were modest. Reduced thermal discomfort was a consistent finding across all interventions reviewed.

Conclusion: External cooling — especially ice vest use integrated into pre-competition warm-up — reliably improves endurance capacity across multiple sports. Athletes do not need dramatic core cooling to benefit; reductions in thermal discomfort alone are sufficient to drive measurable performance gains.