RESUMO
PURPOSE: Caffeine is a commonly used ergogenic aid for endurance events; however, its efficacy and safety have been questioned in hot environmental conditions. The aim of this study was to investigate the effects of acute caffeine supplementation on cycling time to exhaustion and thermoregulation in the heat. METHODS: In a double-blind, randomised, cross-over trial, 12 healthy caffeine-habituated and unacclimatised males cycled to exhaustion in the heat (35 °C, 40% RH) at an intensity associated with the thermoneutral gas exchange threshold, on two separate occasions, 60 min after ingesting caffeine (5 mg/kg) or placebo (5 mg/kg). RESULTS: There was no effect of caffeine supplementation on cycling time to exhaustion (TTE) (caffeine; 28.5 ± 8.3 min vs. placebo; 29.9 ± 8.8 min, P = 0.251). Caffeine increased pulmonary oxygen uptake by 7.4% (P = 0.003), heat production by 7.9% (P = 0.004), whole-body sweat rate (WBSR) by 21% (P = 0.008), evaporative heat transfer by 16.5% (P = 0.006) and decreased estimated skin blood flow by 14.1% (P < 0.001) compared to placebo. Core temperature was higher by 0.6% (P = 0.013) but thermal comfort decreased by - 18.3% (P = 0.040), in the caffeine condition, with no changes in rate of perceived exertion (P > 0.05). CONCLUSION: The greater heat production and storage, as indicated by a sustained increase in core temperature, corroborate previous research showing a thermogenic effect of caffeine ingestion. When exercising at the pre-determined gas exchange threshold in the heat, 5 mg/kg of caffeine did not provide a performance benefit and increased the thermal strain of participants.
RESUMO
The breasts are reported as the fourth largest barrier to participation in physical activity (PA). This scoping review provides a comprehensive understanding of experiences, knowledge and challenges relating to bra fit and sports participation. The search strategy was adopted by the Preferred Reporting Items for Scoping Reviews (PRISMA-ScR) guidelines and multiple databases were searched. All research was in English and within the last 20 years. Exclusion criteria excluded reviews, male participants and the inability to locate or access full-text articles. The JBI critical appraisal tool assessed methodological quality. Twenty-three studies were included. Key themes from the studies are breast motion during PA, sports bra design, perceived barriers to participation in PA and education/knowledge of breast support and bra fit. Increasing breast support reduces breast movement during PA yet breast motion and bra fit are still the most common breast concerns for females. This is likely influenced by poor breast knowledge, leading to poor breast support choices. Future research should explore to what extent breast motion, knowledge and bra fit influences sport participation, and this research should include a more diverse range of adult ages, cup sizes, ethnicities and PA levels to provide a wider understanding.
