Carbohydrate and caffeine are known to independently improve certain aspects of athletic performance. However, less is understood about physiological and performance outcomes when these compounds are coingested in a rehydration and carbohydrate-replacement strategy. The aim of this study was to examine the influence of adding a moderate dose of caffeine to a carbohydrate solution during prolonged soccer activity. Fifteen male soccer players performed two 90-min intermittent shuttle-running trials. They ingested a carbohydrate-electrolyte solution (CON) providing a total of 1.8 g/kg body mass (BM) of carbohydrate or a similar solution with added caffeine (CAF; 3.7 mg/kg BM). Solutions were ingested 1 hr before exercise and every 15 min during the protocol. Soccer passing skill and countermovement-jump height (CMJ) were quantified before exercise and regularly during exercise. Sprinting performance, heart rate, blood lactate concentration (La) and the subjective experiences of participants were measured routinely. Mean 15-m sprint time was faster during CAF (p = .04); over the final 15 min of exercise mean sprint times were CAF 2.48 ± 0.15 s vs. CON 2.59 ± 0.2 s. Explosive leg power (CMJ) was improved during CAF (52.9 ± 5.8 vs. CON 51.7 ± 5.7 cm, p = .03). Heart rate was elevated throughout CAF, and ratings of pleasure were significantly enhanced. There were no significant differences in passing skill, rating of perceived exertion, La, or body-mass losses between trials. The addition of caffeine to the carbohydrate-electrolyte solution improved sprinting performance, countermovement jumping, and the subjective experiences of players. Caffeine appeared to offset the fatigue-induced decline in self-selected components of performance.
Nicholas Gant, Ajmol Ali and Andrew Foskett
Stephen A. Mears and Susan M. Shirreffs
Water intake occurs following a period of high-intensity intermittent exercise (HIIE) due to sensations of thirst yet this does not always appear to be caused by body water losses. Thus, the aim was to assess voluntary water intake following HIIE. Ten healthy males (22 ± 2 y, 75.6 ± 6.9 kg, VO2peak 57.3 ± 11.4 m·kg−1·min−1; mean± SD) completed two trials (7–14 d apart). Subjects sat for 30 min then completed an exercise period involving 2 min of rest followed by 1 min at 100% VO2peak repeated for 60 min (HIIE) or 60 min continuously at 33% VO2peak (LO). Subjects then sat for 60 min and were allowed ad libitum water intake. Body mass was measured at start and end of trials. Serum osmolality, blood lactate, and sodium concentrations, sensations of thirst and mouth dryness were measured at baseline, postexercise and after 5, 15, 30, and 60 min of recovery. Vasopressin concentration was measured at baseline, postexercise, 5 min, and 30 min. Body mass loss over the whole trial was similar (HIIE: 0.77 ± 0.50; LO: 0.85 ± 0.55%; p = .124). Sweat lost during exercise (0.78 ± 0.22 vs. 0.66 ± 0.26 L) and voluntary water intake during recovery (0.416 ± 0.299 vs. 0.294 ± 0.295 L; p < .05) were greater in HIIE. Serum osmolality (297 ± 3 vs. 288 ± 4mOsmol·kg−1), blood lactate (8.5 ± 2.7 vs. 0.7 ± 0.4 mmol·L−1), serum sodium (146 ± 1 vs. 143 ± 1 mmol·L−1) and vasopressin (9.91 ± 3.36 vs. 4.43 ± 0.86 pg·ml−1) concentrations were higher after HIIE (p < .05) and thirst (84 ± 7 vs. 60 ± 21) and mouth dryness (87 ± 7 vs. 64 ± 23) also tended to be higher (p = .060). Greater voluntary water intake after HIIE was mainly caused by increased sweat loss and the consequences of increased serum osmolality mainly resulting from higher blood lactate concentrations.
Janaka P. Gamage, Angela P. De Silva, Arjan K. Nalliah and Stuart D.R. Galloway
The aim of the current study was to assess the effects of dehydration on cricket specific motor skill performance among fast-bowlers, fielders, and batsmen playing in a hot and humid environment. 10 fast-bowlers, 12 fielders and 8 batsmen participated in two field trials conducted 7 days apart: a fluid provision trial (FP) and a fluid restriction trial (FR). Each trial consisted of a 2-hr standardized training session and pretraining and posttraining skill performance assessments. Bowling speed and accuracy (line and length), throwing speed and accuracy (overarm, sidearm and underarm) and timed running between wickets (1, 2, and 3 runs) was assessed pre to posttraining in each trial. Mass loss was 0.6 ± 0.3 kg (0.9 ± 0.5%) in FP, and 2.6 ± 0.5kg (3.7 ± 0.8%) in FR trials. Maintaining mass within 1% of initial values did not cause any significant skill performance decline. However, the dehydration on the FR trial induced a significant time and trial effect for bowling speed by 1.0 ± 0.8% reduction (0.3 ± 0.8% reduction in FP trial; p < .01) and 19.8 ± 17.3% reduction in bowling accuracy for line (3.6 ± 14.2% reduction in FP trial; p < .01), but no effect on bowling length. A significant decline was noted in the FR trial for throwing speed for overarm (6.6 ± 4.1%; p < .01; 1.6 ± 3.4% reduction in FP trial) and sidearm (4.1 ± 2.3%; p < .01; 0.6 ± 4.7% increase in FP trial) techniques, and for throwing accuracy for overarm (14.2 ± 16.3%; p < .01; 0.8 ± 24.2% increase in FP trial) and sidearm (22.3 ± 13.3%; p < .05; 3.2 ± 34.9% reduction in FP trial) techniques. Batsmen demonstrated significant performance drop in making three runs (0.8 ± 1.2% increase in time in FP trial and 2.2 ± 1.7% increase in time in FR trial; p < .01). Moderate-severe dehydration of 3.7% body mass loss significantly impairs motor skill performance among cricketers, particularly bowlers and fielders, playing in hot and humid conditions. Fluid ingestion strategies maintaining mass loss within 1% prevented a decline in skill performance.
Paola Rodriguez-Giustiniani and Stuart D.R. Galloway
evening in order to begin the dehydration process. After overnight dehydration and fasting, participants arrived at the laboratory at 08:00 a.m. They were first asked to empty their bladder and provide a urine sample. Nude body mass was measured, and the body mass loss required to attain a 2% loss, in
Emily C. Borden, William J. Kraemer, Bryant J. Walrod, Emily M. Post, Lydia K. Caldwell, Matthew K. Beeler, William H. DuPont, John Paul Anders, Emily R. Martini, Jeff S. Volek and Carl M. Maresh
For over 20 years, there have been concerns about the potential negative physiological effects of repeated body-mass losses over a wrestling season to “make weight” through a variety of methods including starvation, fluid restriction, and exercise. 1 – 3 In 1998, a study by Yankanich et al 1 was
Alexander S.D. Gamble, Jessica L. Bigg, Tyler F. Vermeulen, Stephanie M. Boville, Greg S. Eskedjian, Sebastian Jannas-Vela, Jamie Whitfield, Matthew S. Palmer and Lawrence L. Spriet
Fluid Intake, Sweat Loss, and Body Mass Loss of JR, AHL, and NHL Players During On-Ice Practices JR ( n = 77) AHL ( n = 60) NHL ( n = 77) Urine specific gravity All players 1.018 ± 0.007 1.019 ± 0.007 1.018 ± 0.008 Goalies 1.021 ± 0.006 1.019 ± 0.002 1.025 ± 0.006 Defensemen 1.015 ± 0.007 1
Douglas J. Casa, Samuel N. Cheuvront, Stuart D. Galloway and Susan M. Shirreffs
between 1% and 4% dehydration ( Cheuvront et al., 2010 ; Gutiérrez et al., 2003 ; Hoffman et al., 1995 ; Watson et al., 2005 ) although a 6% body mass loss has been investigated when energy restriction has been combined with dehydration ( Kraemer et al., 2001 ; Viitasalo et al., 1987 ). Yet the
Julian A. Owen, Matthew B. Fortes, Saeed Ur Rahman, Mahdi Jibani, Neil P. Walsh and Samuel J. Oliver
body mass loss during the 48-hr trials was the reference standard in this study, we standardized energy intake and physical activity 24 hr before and during trials. Energy intake was calculated as the product of resting metabolic rate and an estimated physical activity factor. Resting metabolic rate
Paola Rodriguez-Giustiniani, Ian Rollo, Oliver C. Witard and Stuart D. R. Galloway
), we set out to control for many of these additional factors, that is, maintain body mass loss within 1%, adopt prematch feeding guidelines prior to an afternoon kickoff, assess outcomes in professional youth players, and distinguish between potential effects in dominant and nondominant feet. Therefore
Jason D. Vescovi and Greig Watson
prevalence of players in various categories of relative body mass change following matches. These data show that a wide range of players experienced 1–2% reduction in body mass (up to 12), and an additional two to eight players experienced body mass loss of >−2%. Table 1 Variability of Usg and Body Mass