Impact of Warm-Up on Muscle Temperature and Athletic Performance.

Purpose: We performed two studies to investigate: the minute-by-minute changes in muscle temperature following a 20-min warm-up routine (Study-1) and the impact of the typical post-warm-up period of inactivity on the performance of basketball athletes (Study-2). Method: In Study-1, 26 males (age: 23.6 ± 6.2 yr; BMI: 24.1 ± 3.1 kg/m2) performed a 20-min cycling warm-up and then rested for 20 min. Tibialis anterior muscle temperature was assessed throughout. In Study-2, six male professional basketball players (age: 24.9 ± 4.6 yr; BMI: 25.5 ± 1.8 kg/m2) performed a series of basketball performance tests after a 20-min warm-up, as well as 9-min and 23-min into a post-warm-up period of inactivity. Results: On average, muscle temperature increased by 0.1°C every minute during warm-up and dropped by the same amount every minute during inactivity. The increase during warm-up and the decrease during inactivity were higher at the start of each period. A 9-min inactivity period is accompanied by 3.8 ± 0.6% reduction in countermovement jump (p = .046). A 23-min inactivity period is accompanied by 7.3 ± 0.7% reduction in lay-up points (p = .027). Conclusion: These two studies show that a 20-min warm-up routine increases muscle temperature but this benefit is lost after a typical post-warm-up inactivity period in high-level basketball, leading to reductions in certain aspects of athletic performance.

Warm-up increases muscle temperature and benefits performance, but it is not clear how long these benefits are active for.In sports, such as basketball, athletes may stay on the bench for a considerable amount of time post warm-up, and then are required to enter the game and perform at maximum intensity despite that they may have cooled down, posing an important knowledge gap for athletes, coaches, and event organizers.We found that muscle temperature increases, on average, by 0.1°C every minute during a 20-min warm-up routine and drops by the same amount every minute during a 20-min post-warm-up inactivity period.In total, the two studies presented in this article show that a warm-up routine increases muscle temperature, but this benefit is lost after a typical post-warm-up period of inactivity in high-level basketball, leading to reductions in certain aspects of athletic performance.

Occupational Heat Stress: Multi-Country Observations and Interventions.

BACKGROUND: Occupational heat exposure can provoke health problems that increase the risk of certain diseases and affect workers' ability to maintain healthy and productive lives. This study investigates the effects of occupational heat stress on workers' physiological strain and labor productivity, as well as examining multiple interventions to mitigate the problem. METHODS: We monitored 518 full work-shifts obtained from 238 experienced and acclimatized individuals who work in key industrial sectors located in Cyprus, Greece, Qatar, and Spain. Continuous core body temperature, mean skin temperature, heart rate, and labor productivity were collected from the beginning to the end of all work-shifts. RESULTS: In workplaces where self-pacing is not feasible or very limited, we found that occupational heat stress is associated with the heat strain experienced by workers. Strategies focusing on hydration, work-rest cycles, and ventilated clothing were able to mitigate the physiological heat strain experienced by workers. Increasing mechanization enhanced labor productivity without increasing workers' physiological strain. CONCLUSIONS: Empowering laborers to self-pace is the basis of heat mitigation, while tailored strategies focusing on hydration, work-rest cycles, ventilated garments, and mechanization can further reduce the physiological heat strain experienced by workers under certain conditions.

High prevalence of hypohydration in occupations with heat stress-Perspectives for performance in combined cognitive and motor tasks.

PURPOSE: To evaluate the prevalence of dehydration in occupational settings and contextualize findings to effects on performance in cognitively dominated tasks, simple and complex motor tasks during moderate and high heat stress. METHODS: The study included an occupational part with hydration assessed in five industries across Europe with urine samples collected from 139 workers and analyzed for urine specific gravity. In addition, laboratory experiments included eight male participants completing mild-intensity exercise once with full fluid replacement to maintain euhydration, and once with restricted water intake until the dehydration level corresponded to 2% bodyweight deficit. Following familiarization, euhydration and dehydration sessions were completed on separate days in random order (cross-over design) with assessment of simple motor (target pinch), complex motor (visuo-motor tracking), cognitive (math addition) and combined motor-cognitive (math and pinch) performance at baseline, at 1°C (MOD) and 2°C (HYPER) delta increase in body core temperature. RESULTS: The field studies revealed that 70% of all workers had urine specific gravity values ≥1.020 corresponding to the urine specific gravity (1.020±0.001) at the end of the laboratory dehydration session. At this hydration level, HYPER was associated with reductions in simple motor task performance by 4±1%, math task by 4±1%, math and pinch by 9±3% and visuo-motor tracking by 16±4% (all P<0.05 compared to baseline), whereas no significant changes were observed when the heat stress was MOD (P>0.05). In the euhydration session, HYPER reduced complex (tracking) motor performance by 10±3% and simple pinch by 3±1% (both P<0.05, compared to baseline), while performance in the two cognitively dominated tasks were unaffected when dehydration was prevented (P>0.05). CONCLUSION: Dehydration at levels commonly observed across a range of occupational settings with environmental heat stress aggravates the impact of hyperthermia on performance in tasks relying on combinations of cognitive function and motor response accuracy.