This study examined the physiological effects of crushed ice ingestion before steady state exercise in the heat. Ten healthy males with age (23 ± 3 y), height (176.9 ± 8.7 cm), body-mass (73.5 ± 8.0 kg), VO2peak (48.5 ± 3.6 mL∙kg∙min-1) participated in the study. Participants completed 60 min of cycling at 55% of their VO2peak preceded by 30 min of precooling whereby 7 g∙kg-1 of thermoneutral water (CON) or crushed ice (ICE) was ingested. The reduction in Tc at the conclusion of precooling was greater in ICE (-0.9 ± 0.3 °C) compared with CON (-0.2 ± 0.2 °C) (p ≤ .05). Heat storage capacity was greater in ICE compared with CON after precooling (ICE -29.3 ± 4.8 W∙m-2; CON -11.1 ± 7.3 W∙m-2, p < .05). Total heat storage was greater in ICE compared with CON at the end of the steady state cycle (ICE 62.0 ± 12.5 W∙m-2; CON 49.9 ± 13.4 W∙m-2, p < .05). Gross efficiency was higher in ICE compared with CON throughout the steady state cycle (ICE 21.4 ± 1.8%; CON 20.4 ± 1.9%, p < .05). Ice ingestion resulted in a lower thermal sensation at the end of precooling and a lower sweat rate during the initial stages of cycling (p < .05). Sweat loss, respiratory exchange ratio, heart rate and ratings of perceived exertion and thirst were similar between conditions (p > .05). Precooling with crushed ice led to improved gross efficiency while cycling due to an increased heat storage capacity, which was the result of a lower core temperature.
Matthew Zimmermann, Grant Landers, Karen E. Wallman and Jacinta Saldaris
Matt Brearley, Ian Norton, David Kingsbury and Simon Maas
Anecdotal reports suggest that elite road motorcyclists suffer from high core body temperatures and physiological and perceptual strain when competing in hot conditions.
Four male non-heat-acclimatized elite motorcyclists (3 Superbike, 1 Supersport) had their gastrointestinal temperature, heart rate, and respiratory rate measured and recorded throughout practice, qualifying, and race sessions of an Australian Superbike and Supersport Championship round contested in tropical conditions. Physiological strain was calculated during the sessions, and fluid-balance measures were taken during practice and qualifying. Rider thermal sensation was assessed immediately postsession.
Mean ambient temperature and relative humidity were 29.5–30.2°C and 64.5–68.7%, respectively, across the sessions. Gastrointestinal temperature rose from 37.6°C to 37.7°C presession at a median rate of 0.035°C, 0.037°C ,and 0.067°C/min during practice, qualifying, and race sessions to reach medians of 38.9°C, 38.8°C, and 39.1°C postsession, respectively. The peak postsession gastrointestinal temperature was 39.8°C. Median heart rates were ~164, 160, and 177 beats/min during the respective practice, qualifying, and race sessions, contributing to median physiological strain of 5.5, 5.6, and 6.2 across the sessions. Sweat rates were 1.01 and 0.90 L/h during practice and qualifying sessions, while rider thermal sensation was very hot after each session.
This investigation confirms that elite road motorcyclists endure moderate to high physiological strain during practice, qualifying, and race sessions, exhibiting more-rapid rates of body-heat storage, higher core body temperatures, and higher physiological and perceptual strain than their stock-car-racing counterparts when competing in tropical conditions.
Gregg Afman, Richard M. Garside, Neal Dinan, Nicholas Gant, James A. Betts and Clyde Williams
Current recommendations for nutritional interventions in basketball are largely extrapolated from laboratory-based studies that are not sport-specific. We therefore adapted and validated a basketball simulation test relative to competitive basketball games using well-trained basketball players (n = 10), then employed this test to evaluate the effects of two common preexercise nutritional interventions on basketball-specific physical and skilled performance. Specifically, in a randomized and counterbalanced order, participants ingested solutions providing either 75 g carbohydrate (sucrose) 45 min before exercise (Study A; n = 10) or 2 × 0.2 g·kg−1 sodium bicarbonate (NaHCO3) 90 and 20 min before exercise (Study B; n = 7), each relative to appropriate placebos (H2O and 2 × 0.14 g·kg−1 NaCl, respectively). Heart rate, sweat rate, pedometer count, and perceived exertion did not systematically differ between the 60-min basketball simulation test and competitive basketball, with a strong positive correlation in heart rate response (r = .9, p < .001). Preexercise carbohydrate ingestion resulted in marked hypoglycemia (< 3.5 mmol·l−1) throughout the first quarter, coincident with impaired sprinting (+0.08 ± 0.05 second; p = .01) and layup shooting performance (8.5/11 versus 10.3/11 baskets; p < .01). However, ingestion of either carbohydrate or sodium bicarbonate before exercise offset fatigue such that sprinting performance was maintained into the final quarter relative to placebo (Study A: –0.07 ± 0.04 second; p < .01 and Study B: -0.08 ± 0.05 second; p = .02), although neither translated into improved skilled (layup shooting) performance. This basketball simulation test provides a valid reflection of physiological demands in competitive basketball and is sufficiently sensitive to detect meaningful changes in physical and skilled performance. While there are benefits of preexercise carbohydrate or sodium bicarbonate ingestion, these should be balanced against potential negative side effects.
Michael J. Zurawlew, Jessica A. Mee and Neil P. Walsh
sweating rate, a reduction in cardiovascular strain, and improved thermal comfort. 2 – 4 Despite practical limitations, heat acclimation recommendations state that individuals should exercise in the heat on 5 to 14 occasions, maintaining a specific degree of hyperthermia (rectal temperature: T re ≥ 38
Douglas J. Casa, Samuel N. Cheuvront, Stuart D. Galloway and Susan M. Shirreffs
, 1972 ). The primary factors that influence total sweat loss (L; Sweating Rate × Time) include body size, exercise intensity, exercise duration, the environment, and choice of clothing. These factors explain more than 90% of the widely different sweat losses expected among athletes ( Gagnon et al., 2013
Matthew Zimmermann, Grant Landers, Karen Wallman and Georgina Kent
of an earlier sweat onset and increase in sweat rate in male athletes, which in turn enhances cooling. 9 , 10 Because of this, long-term heat acclimation has resulted in greater endurance-performance benefits than short-term heat acclimation. 9 Precooling involves lowering body temperature, and
Alan J. McCubbin, Bethanie A. Allanson, Joanne N. Caldwell Odgers, Michelle M. Cort, Ricardo J.S. Costa, Gregory R. Cox, Siobhan T. Crawshay, Ben Desbrow, Eliza G. Freney, Stephanie K. Gaskell, David Hughes, Chris Irwin, Ollie Jay, Benita J. Lalor, Megan L.R. Ross, Gregory Shaw, Julien D. Périard and Louise M. Burke
ratings of perceived exertion, begin to emerge in 3–5 days of acclimation ( Gisolfi & Cohen, 1979 ; Patterson et al., 2004 ). Reductions in resting core temperature, increased sweat rate, and decreased sweat sodium ([Na + ] sweat ) and chloride ([Cl − ] sweat ) concentrations develop over a longer time
Thomas Reeve, Ralph Gordon, Paul B. Laursen, Jason K.W. Lee and Christopher J. Tyler
nude body mass was recorded once the participant had left the environmental chamber to estimate sweat loss and sweat rate. Heat Acclimation Heat acclimation participants sat in the chamber for 10 minutes to establish baseline values before cycling (Monark 874E; Monark) for 30 minutes in the heat (35°C
Rachel Lohman, Amelia Carr and Dominique Condo
). It has, however, been established that athletes’ sweat rates increase when they exercise in the heat, possibility increasing overall sodium loss and sweat sodium concentrations ( Holmes et al., 2011 ), which has been observed in football players ( Duffield et al., 2012 ; Maughan et al., 2004 ). Thus
Joseph A. McQuillan, Julia R. Casadio, Deborah K. Dulson, Paul B. Laursen and Andrew E. Kilding
, after 10-min T re stabilization, and before and after the time trial). Participants then exited the chamber and toweled dry before reweighing nude body mass, with subsequent data used to establish the effect of NO 3 − supplementation on sweat rate. Heart rate was measured using a heart-rate monitor