Ice Slurry Ingestion Research Articles

Effect of cold beverages on whole-body heat exchange in young and older males during intermittent exercise in the heat.

To mitigate health risks associated with occupational heat stress, workers are advised to adhere to a work-rest regimen, and hydrate regularly. However, it remains unclear if beverage temperature influences whole-body heat exchange during work-rest cycles, and if responses differ in older workers who have a blunted heat loss capacity. Ten young (mean [SD]: 22 [3] years) and 10 older (60 [4] years) males performed four 15-min bouts of moderate-intensity cycling at a fixed rate of metabolic heat production (200 W·m-2), each interspersed by 15-min rest in dry heat (40°C, ~12% relative humidity). On separate days, participants consumed either ice-slurry (~0°C), standardized to provide a heat transfer capacity of 75 kJ·m-2, or an identical mass of warm fluid (37.5°C) before the first and third exercise bouts. Evaporative and dry heat exchange (direct calorimetry) and metabolic heat production (indirect calorimetry) were measured continuously to determine cumulative heat storage (summation of heat loss and heat gain) over the entire protocol. Rectal temperature was also measured continuously. Relative to warm fluid, ice-slurry ingestion reduced cumulative heat storage in young (69 [181] vs. 216 [94] kJ) and older males (90 [104] vs. 254 [140] kJ, main effect: p < 0.01), but was unaffected by age (p = 0.49). However, rectal temperature was unaffected by beverage temperature in both groups (all p ≥ 0.15). We show that cold fluid ingestion is an appropriate administrative control for both young and older males as it can mitigate increases in body heat content during moderate-intensity work-rest cycles in dry heat.

Effects of Heat Exposure and Ice Slurry Ingestion on Risk-Taking Behavior in Healthcare Workers.

Healthcare workers (HCWs) wearing personal protective equipment (PPE) experience physiological strain that can impair motor and psychological functions, potentially affecting patient care. We assessed the effects of heat exposure on maximal strength and risk-taking behavior among PPE-wearing HCWs and the efficacy of ice slurry to alleviate adverse effects. Seventeen HCWS completed two experimental trials in a crossover design, consuming 5 g·kg -1 of body mass of ambient drink (AMB) or ice slurry (ICE) before donning PPE and undergoing 2 h of simulated decontamination exercise (wet-bulb globe temperature (WBGT): 25.9°C ± 0.8°C, PPE microenvironment WBGT: 29.1°C ± 2.1°C). Body core temperature ( Tc ), heart rate (HR), chest skin temperature ( Tsk ), ratings of perceived exertion (RPE), thermal sensation (RTS), maximal voluntary contraction (MVC), risk-taking behavior (balloon analogue risk-taking task (BART)), and salivary cortisol were assessed. Predrinking to postdrinking ∆ Tc was greater in ICE (-0.2°C ± 0.1°C) than AMB (-0.0°C ± 0.1°C, P = 0.003). Post-drinking RTS was lower in ICE (2.7 ± 1.2) than AMB (4.1 ± 0.4, P < 0.001). ICE and AMB had similar Tc and HR (both P > 0.05), but Tsk was lower in ICE than AMB ( P = 0.049). A lower MVC (30.3 ± 6.7 vs 27.4 ± 4.9 kg, P = 0.001) and higher BART-adjusted total pump count (472 ± 170 vs 615 ± 174 pumps, P = 0.017) was observed pretrial to posttrial in AMB but absent in ICE (both P > 0.05). Salivary cortisol was similar between trials ( P = 0.42). Heat-exposed PPE-wearing HCWs had impaired maximal strength and elevated risk-taking behavior. This may increase the risk of avoidable workplace accidents that can jeopardize HCWs and patient care. Ice slurry ingestion alleviated these heat-related impairments, suggesting its potential as an ergogenic aid.

Ice slurry ingestion for enhanced occupant thermal comfort in warm/hot indoor environments: A comparative study with an energy-efficient desk fan

Ice slurry ingestion has been widely used as an effective pre-exercise cooling strategy for athletes to improve exercise performance while competing in the heat. Nonetheless, its potential to improve thermal comfort for office workers in various indoor environments has received little attention. In this study, two representative external and internal body cooling modalities, ice slurry ingestion (ICE) and desk fan (FAN), were used under free control in three warm/hot environments (30, 32, and 34 °C, RH = 50%). Throughout the heat exposure, the subjects' physiological responses (heart rate and local skin temperatures) were recorded, as well as their overall and local thermal perceptions. The subjects' usage behavior was recorded, including the fanning speed level and ice slurry ingestion rate. The results show that, when compared to the FAN condition, ICE resulted in significantly lower thermal sensation (decreased by 0.93 rating scale, p < 0.01) and sweat rate (38.3 ± 34.6 g/h, p < 0.01), as well as higher thermal comfort (increased by 1.17 rating scales, p < 0.05) at 34 °C. The total amount of ice slurry ingested by the subjects increased significantly with increasing air temperature, from 107.5 ± 64.1 g/h to 249.2 ± 84.1 g/h (p < 0.001). This study demonstrates the pronounced efficacy of ice slurry ingestion to sustain young female occupant thermal comfort at 30–34 °C indoor temperatures. Further research is still necessary to investigate the efficacy of ice slurry ingestion in higher indoor temperatures during extreme heatwaves, however.

Ad libitum ice slurry ingestion and half-marathon performance in a hot environment: A study comparing the effects of the amount and moment of ingestion between ice slurry and water at 37 °C

Ice slurry ingestion during prolonged exercises may improve performance in hot environments; however, the ideal amount and timing of ingestion are still uncertain. We determined whether ad libitum ice slurry ingestion influences physiological and perceptual variables and half-marathon performance while comparing the effects of the amount and moment of ingestion between ice slurry and water at 37 °C. Ten trained participants (28 ± 2 years; mean and SD) were required to run two half marathons while consuming either ice slurry (-1 °C; Ad-1) or water (37 °C; 37 CE) ad libitum. They then performed two other half marathons where, during one, they were required to ingest an amount of water equivalent to the amount consumed during the Ad-1 trial (Pro37), and in the other, to ingest ice slurry in the amount consumed during the 37 CE trial (Pro-1). During the half marathons, dry-bulb temperature and relative humidity were controlled at 33.1 ± 0.3 °C and 60 ± 3%, respectively. Ad-1 ingestion (349.6 ± 58.5 g) was 45% less than 37 CE ingestion (635.5 ± 135.8 g). Physical performance, heart rate, perceived exertion, body temperatures, and thermal perception were not influenced by the temperature or amount of beverage ingestion. However, a secondary analysis suggested that lower beverage ingestion was associated with improved performance (Ad-1 + Pro37 vs. 37 CE + Pro-1: −4.0 min, Cohen's d = 0.39), with a significant relationship between lower beverage ingestion and faster running time (b = 0.02, t = 4.01, p < 0.001). In conclusion, ice slurry ingestion does not affect performance or physiological or perceptual variables during a half marathon in a hot environment. Preliminary evidence suggests that lower beverage ingestion (ice slurry or warm water) is associated with improved performance compared to higher ingestion.

Compromised heat loss leads to a delayed ice slurry induced reduction in heat storage.

Compromised heat loss due to limited convection and evaporation can increase thermal strain. We aimed to determine the effectiveness of ice slurry ingestion to reduce thermal strain following hyperthermia in a state of compromised heat loss. Twelve healthy males (age: 25 ± 4y) underwent hot water immersion to elevate rectal temperature (Trec) by 1.82 ± 0.08°C on four occasions. In the subsequent 60-min of seated recovery, participants ingested either 6.8 g·kg-1 of ice slurry (-0.6°C) or control drink (37°C) in ambient conditions (21 ± 1°C, 39 ± 10% relative humidity), wearing either t-shirt and shorts (2 trials: ICE and CON) or a whole-body sweat suit (2 trials: ICE-SS and CON-SS). Trec and mean skin temperature (Tsk) were recorded and a two-compartment thermometry model of heat storage was calculated. Heat storage was lower in ICE compared with CON at 20-40min (p ≤ 0.044, d ≥ 0.88) and for ICE-SS compared with CON-SS at 40-60 min (p ≤ 0.012, d ≥ 0.93). Trec was lower in ICE compared with CON from 30-60min (p ≤ 0.034, d ≥ 0.65), with a trend for a reduced Trec in ICE-SS compared with CON-SS at 40min (p = 0.079, d = 0.60). A greater Tsk was found in ICE-SS and CON-SS compared with ICE and CON (p < 0.001, d ≥ 3.37). A trend for a lower Tsk for ICE compared with CON was found at 20-40min (p ≤ 0.099, d ≥ 0.53), no differences were found for ICE-SS vs CON-SS (p ≥ 0.554, d ≤ 0.43). Ice slurry ingestion can effectively reduce heat storage when heat loss through convection and evaporation is compromised, relevant to those wearing personal protective equipment or those with compromised sweat loss. Compromised heat loss delays the reduction in heat storage, possibly related to ice slurry ingestion not lowering Tsk.

Rectal and gastrointestinal temperature differ during passive heating and subsequent recovery

We aimed to compare rectal temperature (Trec) and gastro-intestinal temperature (TGI) during passive heating and subsequent recovery with and without ice slurry ingestion. Twelve males (age: 25 ± 4 years, body mass index: 25.7 ± 2.5 kg m−2) were immersed in hot water on two occasions (Trec elevation: 1.82 ± 0.08°C). In the subsequent 60-min recovery in ambient conditions, participants ingested either 6.8 g kg−1 of ice slurry (−0.6°C, ICE) or control drink (37°C, CON). During passive heating, Trec was lower than TGI (P < 0.001), in the recovery, Trec was higher than TGI (P < 0.001). During passive heating, mean bias and 95%LoA (Limits of Agreement) were −0.10(±0.25)°C and −0.12(±0.36)°C for CON and ICE, respectively. In the recovery, mean bias and 95%LoA were 0.30(±0.60)°C and 0.42(±0.63)°C for CON and ICE, respectively. Trec and TGI differed during both heating and recovery, and less favourable agreement between Trec and TGI was found in the recovery from passive heating with or without ice slurry ingestion.

Effects of ice slurry ingestion on body temperature and softball pitching performance in a hot environment: a randomized crossover trial

BackgroundAlthough softball players are often required to play in hot environments, scarce evidence is available regarding the effects of ice slurry ingestion on body temperature and pitching performance in softball pitchers in a hot environment. Thus, this study investigated the effects of ice slurry ingestion before and between innings on body temperature and softball pitching performance in a hot environment.MethodsIn a randomized crossover design, seven heat-acclimatized amateur softball pitchers (four males and three females) completed simulated softball games consisting of 15 best-effort pitches per inning for seven innings with between-pitch rest intervals of 20 s. Participants were assigned to either a control trial (CON: ingestion of 5.0 g·kg−1 of cool fluid [9.8 ± 2.2 °C] before simulated softball games and 1.25 g·kg−1 of cool fluid between inning intervals) or an ice trial (ICE: ingestion of ice slurry [− 1.2 ± 0.1 °C] based on the same timings and doses as the CON). Participants performed both trials in an outdoor ground during the summer season (30.8 ± 2.7 °C, 57.0 ± 7.9% relative humidity).ResultsIce slurry ingestion before the simulated softball game (pre-cooling) resulted in a greater reduction in rectal temperature compared with cool fluid ingestion (p = 0.021, d = 0.68). No significant differences were observed between the trials in rectal temperature changes during the simulated softball game (p > 0.05). Compared to the CON, heart rate during the game was significantly decreased (p < 0.001, d = 0.43), and handgrip strength during the game was significantly increased (p = 0.001, d = 1.16) in the ICE. Ratings of perceived exertion, thermal comfort, and thermal sensation were improved in the ICE compared to those in the CON (p < 0.05). Ball velocity and pitching accuracy were not affected by ICE.ConclusionsIce slurry ingestion before and between innings reduced thermal, cardiovascular, and perceptual strain. However, it did not affect softball pitching performance compared to cool fluid ingestion.

The effects of low and normal dose ice slurry ingestion on endurance capacity and intestinal epithelial injury in the heat.

Compare the effects of ice slurry ingestion at low and normal doses on endurance capacity and exertional heat stress-induced gastrointestinal perturbations. Randomised, cross-over design. Twelve physically active males completed four treadmill running trials, ingesting ice slurry (ICE) or ambient drink (AMB) at 2 g·kg-1 (Normal; N) or 1 g·kg-1 (Low; L) doses every 15-min during exercise and 8 g·kg-1 (N) or 4 g·kg-1 (L) pre- and post-exercise. Pre-, during and post-exercise serum intestinal fatty-acid binding protein ([I-FABP]) and lipopolysaccharide ([LPS]) concentrations were determined. Pre-exercise gastrointestinal temperature (Tgi) was lower in L + ICE than L + AMB (p < 0.05), N + ICE than N + AMB (p < 0.001) and N + ICE than L + ICE (p < 0.001). Higher rate of Tgi rise (p < 0.05) and lower estimated sweat rate (p < 0.001) were observed in N + ICE than N + AMB. Rate of Tgi rise was similar at low dose (p = 0.113) despite a lower estimated sweat rate in L + ICE than L+AMB (p < 0.01). Time-to-exhaustion was longer in L + ICE than L + AMB (p < 0.05), but similar between N + ICE and N + AMB (p = 0.142) and L + ICE and N + ICE (p = 0.766). [I-FABP] and [LPS] were similar (p > 0.05). L + ICE elicited a lower heat dissipation compensatory effect with similar endurance capacity as N + ICE. Ice slurry conferred no protection against exertional heat stress-induced gastrointestinal perturbations.

Effect of ice slurry ingestion on thermoregulatory responses during fixed-intensity cycling in humid and dry heat.

This study examined the thermoregulatory response and ergogenic effects of ice slurry (ICE) ingestion in hot environments with high and low relative humidity (RH). Eight males completed four trials in a crossover manner in dry (DRY: 34.7 ± 0.2°C, 38 ± 2%RH) and humid heat (HUM: 34.8°C ± 0.2°C, 80 ± 1%RH). They ingested 8.0g·kg-1 of ICE (0.0°C) or 37.5°C water (CON) during 30min before exercise, and three aliquots (3.2g·kg-1) of ICE or CON during 45-min cycling at 50%[Formula: see text]O2peak, followed by cycling to exhaustion at 80%[Formula: see text]O2peak (TTE). Body core temperature (Tcore), mean skin temperature (Tsk), heart rate (HR), thermal comfort, thermal sensation and rating of perceived exertion (RPE) were measured. Relative to CON, ICE improved TTE by 76.5 ± 96.5% in HUM and 21.3 ± 44.9% in DRY (p = 0.044). End-exercise Tcore was lower in ICE versus CON in DRY (37.8 ± 0.4°C versus 38.1 ± 0.3°C, p = 0.005) and HUM (38.8 ± 0.4°C versus 39.3 ± 0.6°C, p = 0.004). ICE decreased HR, heat storage and heat strain index only in DRY (p < 0.001-0.018). ICE improved thermal sensation and comfort in DRY and HUM (p < 0.001-0.011), attenuated RPE in HUM (p = 0.012) but not in DRY (p = 0.065). ICE tended to benefit performance in humid heat more than in dry heat. This is likely due to the reduced extent of hyperthermia in dry heat and the relative importance of sensory inputs in mediating exercise capacity.

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

Background/ObjectivesThe 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 (Tint), psychomotor skills (reaction time, response time, movement time), and neuromuscular function (peak torque, average power, time to reach peak torque). MethodsUsing 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 Tint 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. ResultsICE led to a significantly lower Tint 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 Tint 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). ConclusionThe 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.

The Effects of Pre-Exercise Ice-Slurry Ingestion on Thermoregulation and Exercise Performance of Highly Trained Athletes: A Scoping Review

The Effects of Pre-Exercise Ice-Slurry Ingestion on Thermoregulation and Exercise Performance of Highly Trained Athletes: A Scoping Review

Ice Slurry Ingestion Lowers Thermoregulatory Strain in Wheelchair Tennis Players During Repeated Sprint Intervals in the Heat.

To examine the efficacy of per-cooling via ice slurry ingestion (ICE) in wheelchair tennis players exercising in the heat. Eight wheelchair tennis players undertook sprints (4 sets of 10 × 5s over 40min) in a hot environment (∼32 °C), interspersed by 3 boluses of 2.67g·kg (6.8g·kg total) ICE or drinking temperate water (control condition). Athletes performed an on-court test of repeated sprint ability (20 × 20m) in temperate conditions immediately before and 20minutes after the heat exposure, and time to complete each sprint as well as intermediate times were recorded. Gastrointestinal and weighted mean skin and forehead temperatures were collected throughout the heat exposure, as were thermal sensation, heart rate, and blood lactate concentration. Sweat rate was calculated from body mass changes and fluid/ice intakes. Compared with the control condition, ICE resulted in a significantly lower gastrointestinal temperature (95% CI, 0.11-0.17 °C; P < .001), forehead temperature (0.58-1.06 °C; P < .001), thermal sensation (0.07-0.50 units; P = .017), and sweat rate (0.06-0.46L·h-1; P = .017). Skin temperature, heart rate, and blood lactate concentration were not significantly different between conditions (P ≥ .598). There was no overall change preheating to postheating (P ≥ .114) or an effect of condition (P ≥ .251) on repeated sprint times. ICE is effective at lowering objective and subjective thermal strain when consumed between sets of repeated wheelchair sprints in the heat. However, ICE has no effect on on-court repeated 20-m sprint performance.

Effect of Ice Slurry Beverages on Voluntary Fluid Intake and Exercise Performance.

Ng, J and Wingo, JE. Effect of ice slurry beverages on voluntary fluid intake and exercise performance. J Strength Cond Res 37(6): e376-e383, 2023-Voluntary intake of cold fluid is greater than warm fluid as a result of more favorable palatability, resulting in better maintenance of hydration status and improved exercise performance. It remains unclear whether voluntary ingestion of ice slurry beverages compared with cold fluid during exercise yields superior results. Eight recreationally active subjects (mean ± SD ; age = 24 ± 4 years, height = 175.2 ± 7.8 cm, mass = 79.6 ± 11.2 kg, body fat = 13.0 ± 5.2%) completed a pretest in 22° C to determine maximal workload (W max ). Then, in 2, separate, counterbalanced trials, they cycled for 60 minutes at 50%W max in 35° C and 40% relative humidity with either ad libitum ice slurry (-1.3 ± 0.3° C) or cold fluid (11.1 ± 2.4° C) ingestion. This was immediately followed by a 15-minute cycling time trial. Subjects avoided 2% body mass loss in both conditions but ingested twice as much cold fluid as ice slurry (fluid: 1,074.7 ± 442.1 g, ice slurry: 526.9 ± 214.1 g; p = 0.001). Nonetheless, neither 15-minute performances (cold fluid: 119.5 ± 34.8 kJ, ice slurry: 114.6 ± 20.9 kJ; p = 0.59) nor whole-body sweat rates (fluid: 1,370 ± 311 ml·h -1 , ice slurry: 1,242 ± 191 ml·h -1 ; p = 0.20) were different between the conditions. Despite ingesting half as much ice slurry as cold fluid, subjects experienced similar physiological responses and thus had similar performances under heat stress while avoiding excessive hypohydration. Under the conditions of this study, ice slurry ingestion was an effective alternative form of exercise hydration.

Effect of Ice Slurry Ingestion on Post-Exercise Physiological Responses in Rugby Union Players

Delayed recovery of the core body temperature after exercise adversely affects physiological functions, and the effects of ingesting lower-temperature ice slurry on post-exercise recovery remain unclear. We investigated the effects of ingesting −2 °C ice slurry on physiological recovery after field-based rugby union training. Fifteen university rugby union players participated in our randomized controlled study. The players participated in the training for 60 min in a hot outdoor environment (wet-bulb globe temperature, 30.5 °C). Physiological responses were measured during a physical performance test performed after the players ingested either −2 °C-ice slurry (ICE, N = 7) at 5 g/kg body mass or a 30 °C-fluid (CON, N = 8) during the 15 min recovery period after the training. Tympanic temperatures and heart rates were measured as the physiological indices, as well as heat storage. The ICE group showed significantly decreased tympanic temperatures and heart rates (p &lt; 0.05) during the recovery period and increased heat storage (p &lt; 0.05) but did not show improvement of physiological indices during the performance test compared to the CON group. These results suggest that ingestion of −2 °C ice slurry in even lower amounts than those previously reported is useful for physiological recovery after training in hot outdoor environments.

Small Performance Effects of a Practical Mixed-Methods Cooling Strategy in Elite Team Sport Athletes

ABSTRACTPurpose: The ingestion of ice slurry and application of ice towels can elicit favorable physiological, perceptual, and performance benefits when used individually; however, the combined use and effectiveness of these practical cooling strategies have not been assessed using a sport-specific performance test, based on actual match demands, in an elite team sport context. Methods: Ten non-heat acclimated elite male rugby sevens athletes undertook two cycling heat response tests (HRT) designed to be specific to the demands of rugby sevens in hot conditions (35°C, 80% rH). In a crossover design, the HRTs were conducted with (COOLING) and without (HOT) the combined use of internal (ice slushy ingestion) and external (application of ice towels to the head, neck, and face) pre- and per-cooling strategies. Physiological, perceptual, and performance variables were monitored throughout each HRT. Results: COOLING resulted in reductions in mean tympanic temperature (−0.4 ± 0.2°C; d = 1.18); mean heart rate (−5 ± 8 bpm; d = 0.53); thermal discomfort (−0.5 ± 0.9 AU; d = 0.48); and thirst sensation (−1.0 ± 1.1 AU; d = 0.61) during the HRT. COOLING also resulted in a small increase in 4-min time trial power output (by 7 ± 33 W, ~3%; d = 0.35) compared to HOT. Discussion: A combination of internal and external pre- and per-cooling strategies can result in a range of small physiological, perceptual, and performance benefits during a rugby sevens specific HRT, compared to undertaking no cooling. Practitioners should include such strategies when performing in hot conditions.

Perceptions of Heat Stress, Heat Strain and Mitigation Practices in Wildfire Suppression across Southern Europe and Latin America.

This study aimed to assess current perceptions of heat stress, heat strain, acclimatisation and recovery practices in wildland fire suppression. A total of 1459 wildfire and structural firefighters, all involved in wildland fire suppression, completed an 18-question survey. Most participants (81.3%) reported heat strain as one of the main risks faced during wildland firefighting. Thermal strain is considered an important risk for health and safety in wildland firefighting. The best-valued heat strain mitigation strategies were those traditionally recommended in wildland fire suppression: (i) an adequate work/rest ratio (79.0%), (ii) acclimatisation (71.6%), (iii) enhancing body ventilation by opening protective clothing or removing helmets or gloves (63.5%), and (iv) drinking water and food supplementation (52.1%). Despite these results, only 22% of the participants reported carrying out acclimatisation in the workplace. The vast majority of the respondents (87.4%) consider active cooling strategies (i.e., ice slurry ingestion, ice vests, etc.) impractical in combating heat strain during wildfire suppression. We identified a gap between knowledge about heat strain, its mitigation strategies and the level of actual implementation of these practices in the workplace. Our results highlight the need to improve heat strain management and implement operational directives for acclimatisation and active cooling interventions.

Ice slurry ingestion improves physical performance during high-intensity intermittent exercise in a hot environment.

Ice slurry ingestion enhances exercise performance by lowering the core body temperature. However, an operational issue related to this ingestion is the requirement for a high intake of 7.5 g·kg-1 to produce the desired effects. We investigated the effects of the intake of low amounts of ice slurry at −2°C on the tympanic temperature and exercise performance during repeated high-intensity intermittent exercises in a hot environment. This study was a randomized, crossover study, with a 6-day washout period. Twelve university rugby union players performed two 30-min sessions of high-intensity intermittent exercises separated by a 15-min half-time break on a cycle ergometer in a hot environment (28.8°C ± 0.1°C, 49.5% ± 0.6% relative humidity). The participants ingested 450 g of −2°C-ice slurry (ICE), or a 30°C-beverage (CON) having the same composition as ICE, or 30°C-water (WAT) during the half-time break. The tympanic temperature and skin temperature were measured as the physiological data, and the peak power and mean power as the exercise performance data. The tympanic temperature at the half-time break and beginning of the 2nd session was significantly lower in the ICE group as compared with the CON and WAT groups. The skin temperature at the half-time break was significantly lower in the ICE group as compared with the WAT group. While the peak power and mean power during the 2nd session were significantly greater in the ICE group as compared with the CON and WAT groups. Our findings suggest that even the intake of lower amounts, as compared with those used in previous studies, of low-temperature ice slurry can reduce the body temperature and improve the peak power. These results suggest that intake of low-temperature ice slurry as a strategy for internal body cooling is useful for improving endurance exercise performance in hot environments.

Effects of mixed-method cooling between exercise bouts on thermoregulation and cycling time-trial performance in the heat

This study investigated the effects of mixed-method cooling during a short break between exercise bouts on thermoregulation and cycling time-trial (TT) performance in the heat. In a randomized crossover design, nine physically active men performed two 30-min cycling bouts that consisted of 25-min constant-paced cycling at 55% of maximal oxygen uptake followed by a 5-min TT in the heat (35 °C, 50% relative humidity). The two bouts were separated by a 15-min break. During the break, participants were assigned to a control trial (CON; 5 g kg−1 fluid ingestion at room temperature) or a mixed-method cooling trial (COOL; 5 g kg−1 ice slurry ingestion and cooling vest to cool the neck and torso). Physiological (rectal [Tre], forehead deep-tissue [Tdeep-head], mean skin [T‾sk], forehead skin [Thead], and neck skin [Tneck] temperatures, heart rate [HR], and skin blood flow [SkBF]) and perceptual data (ratings of perceived exertion [RPE], thermal comfort [TC], and thermal sensation [TS]) were measured. At the end of the 15-min break, Tdeep-head (−0.5 ± 0.2 °C, p < 0.001), T‾sk (−5.6 ± 3.1 °C, p = 0.001), Thead (−0.8 ± 0.4 °C, p = 0.001), Tneck (−9.8 ± 6.0 °C, p = 0.002), HR (−17 ± 6 bpm, p < 0.001), SkBF (−27.7 ± 13.9%, p = 0.002), TC (+2.6 ± 2.5, p = 0.024), and TS (−4.7 ± 2.5, p = 0.011) improved in COOL compared to CON. Reductions in T‾sk and Tneck were quickly lost (5 min) during the second exercise bout but Tdeep-head, Thead, and TS remained lower in COOL until the commencement of the second TT. Compared to CON, Tre (−0.2 ± 0.2 °C, p = 0.002) and RPE (−1.3 ± 0.9, p = 0.010) were lower in COOL during the second exercise bout. The reduction in mean power output at the second TT was attenuated in COOL (−13.9 ± 26.9 W) compared to CON (−29.3 ± 29.4 W; p = 0.015). In conclusion, the mixed-method cooling during a short break reduced physiological and perceptual strain and improved cycling TT performance.

Effect of Ingestion of Ice Slurry on the Sleep Quality of Rugby Union Players in the Summer Season

The aim of this study was to investigate the effect of ingestion of ice slurry before bedtime on the sleep quality of rugby union players in the summer season. Thirteen healthy male university rugby union players volunteered for this study. The participants ingested either ice slurry or a room-temperature beverage (control) 30 min before bedtime. A wearable activity-based sleep monitor was used to analyze objective sleep parameters, and the subjective sleep scores were assessed using the Oguri–Shirakawa–Azumi Sleep Inventory, middle-aged and aged version (OSA-MA). No differences in the amount or efficiency of sleep were observed between the ice slurry/control beverage conditions. Significant shortening of the sleep latency was observed in the ice slurry condition as compared with the control beverage condition. Moreover, significant improvement of the subjective sleep score for “feeling refreshed” on the OSA-MA was observed in the ice slurry condition. There were no significant differences in the other subjective sleep scores between the two conditions. The results suggest that ice slurry ingestion before bedtime may improve the latency of sleep onset, accelerate recovery from fatigue, and be useful as a sleep improvement strategy in rugby union players engaging in exercises during the summer season.

Heat Strain and Use of Heat Mitigation Strategies among COVID-19 Healthcare Workers Wearing Personal Protective Equipment-A Retrospective Study.

The combination of an exacerbated workload and impermeable nature of the personal protective equipment (PPE) worn by COVID-19 healthcare workers increases heat strain. We aimed to compare the prevalence of heat strain symptoms before (routine care without PPE) versus during the COVID-19 pandemic (COVID-19 care with PPE), identify risk factors associated with experiencing heat strain, and evaluate the access to and use of heat mitigation strategies. Dutch healthcare workers (n = 791) working at COVID-19 wards for ≥1 week, completed an online questionnaire to assess personal characteristics, heat strain symptoms before and during the COVID-19 pandemic, and the access to and use of heat mitigation strategies. Healthcare workers experienced ~25× more often heat strain symptoms during medical duties with PPE (93% of healthcare workers) compared to without PPE (30% of healthcare workers; OR = 25.57 (95% CI = 18.17–35.98)). Female healthcare workers and those with an age <40 years were most affected by heat strain, whereas exposure time and sports activity level were not significantly associated with heat strain prevalence. Cold drinks and ice slurry ingestion were the most frequently used heat mitigation strategies and were available in 63.5% and 30.1% of participants, respectively. Our findings indicate that heat strain is a major challenge for COVID-19 healthcare workers, and heat mitigations strategies are often used to counteract heat strain.