organization, but it is considered by many to be a performance-enhancing drug. 4 With upcoming events such as the Tokyo Olympics, it is imperative that athletes are safely using caffeine for performance benefits. If the combination of heat and moderate dosages of caffeine can increase core temperature (C T
Search Results
Increased Rate of Heat Storage, and No Performance Benefits, With Caffeine Ingestion Before a 10-km Run in Hot, Humid Conditions
Nicholas J. Hanson, Sarah C. Martinez, Erik N. Byl, Rachel M. Maceri, and Michael G. Miller
Heat Adaptation and Nutrition Practices: Athlete and Practitioner Knowledge and Use
Salma Alabdulwahed, Natalia Galán-López, Tom Hill, Lewis J. James, Bryna Catherine Rose Chrismas, Sebastien Racinais, Trent Stellingwerff, Diogo V. Leal, Matheus Hausen, Karim Chamari, Hugh H.K. Fullagar, Christopher Esh, and Lee Taylor
.000, r = .22, small ES) (Figure 3 ). Figure 3 —Median and individual responses for perceived maximum safest T c during training and competition. *Statistically significant difference between ROLEs; •“small” effect size. Practitioners n = 99, and athletes n = 55. T c indicates core temperature
High-Resolution Dynamics of Hemodilution After Exercise-Related Hemoconcentration
Zsolt Komka, Brigitta Szilágyi, Dóra Molnár, Bence Sipos, Miklós Tóth, János Elek, and Máté Szász
. Samples and data were collected at the following points: at rest before exercise; at a maximum load; and at first, second, third, fourth, fifth, seventh, 10th, and 30th minutes of the recovery. Sample collection included HR, noninvasive blood pressure (upper left arm cuff), core temperature measured on
Exploring the Efficacy of a Safe Cryotherapy Alternative: Physiological Temperature Changes From Cold-Water Immersion Versus Prolonged Cooling of Phase-Change Material
Susan Y. Kwiecien, Malachy P. McHugh, Stuart Goodall, Kirsty M. Hicks, Angus M. Hunter, and Glyn Howatson
inside compression shorts and maintained a constant temperature of 15°C for at least 3 hours before melting. Cold-water immersion has been shown to reduce muscle temperature, 9 – 12 core temperature, 6 , 13 , 14 and increase heart-rate variability (HRV). 15 – 17 It is purported to enhance recovery
Does Precooling With Whole-Body Immersion Affect Thermal Sensation or Perceived Exertion? A Critically Appraised Topic
Timothy M. Wohlfert and Kevin C. Miller
Abbreviations: BSA, body surface area; CON, control; ht = height; N/A, not available; PC, precooling; RH, relative humidity; RPE, rating of perceived exertion; T core , body core temperature; T skin , skin temperature; TS, thermal sensation. Note: All data are reported as mean (SD); data were rounded to the
Night Games and Sleep: Physiological, Neuroendocrine, and Psychometric Mechanisms
Laura E. Juliff, Jeremiah J. Peiffer, and Shona L. Halson
, adrenaline, noradrenaline, core temperature, and psychometric measures) following a night game and a time-matched control day in elite netballers. Methods Participants Twelve Australian netball athletes (mean [SD]: age = 19.2 [0.9] y, height = 184.1 [6.9] cm, and body mass = 72.8 [5.2] kg) volunteered to
Impaired Heat Adaptation From Combined Heat Training and “Live High, Train Low” Hypoxia
Erin L. McCleave, Katie M. Slattery, Rob Duffield, Philo U. Saunders, Avish P. Sharma, Stephen Crowcroft, and Aaron J. Coutts
acclimation reduces thermal and cardiovascular strain during exercise, predominantly by reduced core temperature, increased plasma volume (PV), increased sweat rate, and earlier sweat onset. 3 The benefits of both heat and hypoxia can last for several weeks following exposure. 5 , 6 As heat and hypoxia have
Beneficial Effects of Ice Ingestion as a Precooling Strategy on 40-km Cycling Time-Trial Performance
Mohammed Ihsan, Grant Landers, Matthew Brearley, and Peter Peeling
Purpose:
The effect of crushed ice ingestion as a precooling method on 40-km cycling time trial (CTT) performance was investigated.
Methods:
Seven trained male subjects underwent a familiarization trial and two experimental CTT which were preceded by 30 min of either crushed ice ingestion (ICE) or tap water (CON) consumption amounting to 6.8 g⋅kg-1 body mass. The CTT required athletes to complete 1200 kJ of work on a wind-braked cycle ergometer. During the CTT, gastrointestinal (Tgi) and skin (Tsk) temperatures, cycling time, power output, heart rate (HR), blood lactate (BLa), ratings of perceived exertion (RPE) and thermal sensation (RPTS) were measured at set intervals of work.
Results:
Precooling lowered the Tgi after ICE significantly more than CON (36.74 ± 0.67°C vs 37.27 ± 0.24°C, P < .05). This difference remained evident until 200 kJ of work was completed on the bike (37.43 ± 0.42°C vs 37.64 ± 0.21°C). No significant differences existed between conditions at any time point for Tsk, RPE or HR (P > .05). The CTT completion time was 6.5% faster in ICE when compared with CON (ICE: 5011 ± 810 s, CON: 5359 ± 820 s, P < .05).
Conclusions:
Crushed ice ingestion was effective in lowering Tgi and improving subsequent 40-km cycling time trial performance. The mechanisms for this enhanced exercise performance remain to be clarified.
Partial Heat Acclimation in Cricketers Using a 4-Day High Intensity Cycling Protocol
Carl J. Petersen, Marc R. Portus, David B. Pyne, Brian T. Dawson, Matthew N. Cramer, and Aaron D. Kellett
Cricketers are often required to play in hot/humid environments with little time for heat adaptation.
Purpose:
We examined the effect of a short 4-d hot/humid acclimation program on classical physiological indicators of heat acclimation.
Methods:
Male club cricketers were randomly assigned into heat acclimation (ACC, n = 6) or control (CON, n = 6) groups, and 30 min treadmill trials (10 km/h, approx. 30 ± 1.0°C, approx. 65 ± 6% RH) were conducted at baseline and postacclimation. The ACC group completed four high intensity (30–45 min) acclimation sessions on consecutive days at approx. 30°C and approx. 60% RH using a cycle ergometer. The CON group completed matched cycle training in moderate conditions (approx. 20°C, approx. 60% RH). Physiological measures during each treadmill trial included heart rate; core and skin temperatures; sweat Na+, K+ and Cl– electrolyte concentrations; and sweat rate.
Results:
After the 4-d intervention, the ACC group had a moderate decrease of -11 (3 to -24 beats/min; mean and 90% CI) in the 30 min heart rate, and moderate to large reductions in electrolyte concentrations: Na+ -18% (–4 to -31%), K+ -15% (0 to -27%), Cl– -22% (-9 to -33%). Both ACC and CON groups had only trivial changes in core and skin temperatures and sweat rate. After the intervention, both groups perceived they were more comfortable exercising in the heat. The 4-d heat intervention had no detrimental effect on performance.
Conclusions:
Four 30–45 min high intensity cycle sessions in hot/humid conditions elicited partial heat acclimation. For full heat acclimation a more intensive and extensive (and modality-specific) acclimation intervention is needed for cricket players.
Hydration during Exercise in Warm, Humid Conditions: Effect of a Caffeinated Sports Drink
Mindy L. Millard-Stafford, Kirk J. Cureton, Jonathan E. Wingo, Jennifer Trilk, Gordon L. Warren, and Maxime Buyckx
Caffeine is regarded as a diuretic despite evidence that hydration is not impaired with habitual ingestion. The purpose of this study was to determine whether a caffeinated sports drink impairs fluid delivery and hydration during exercise in warm, humid conditions (28.5 °C, 60% relative humidity). Sixteen cyclists completed 3 trials: placebo (P), carbohydrate-electrolyte (CE), and caffeinated (195 mg/L) sports drink (CAF+CE). Subjects cycled for 120 min at 60–75%VO2max followed by 15 min of maximal-effort cycling. Heart rate and rectal temperature were similar until the final 15 min, when these responses and exercise intensity were higher with CAF+CE than with CE and P. Sweat rate, urine output, plasma-volume losses, serum electrolytes, and blood deuterium-oxide accumulation were not different. Serum osmolality was higher with CAF+CE vs. P but not CE. The authors conclude that CAF+CE appears as rapidly in blood as CE and maintains hydration and sustains cardiovascular and thermoregulatory function as well as CE during exercise in a warm, humid environment.
