James, Carl A.

Maxwell, Neil

Richardson, Alan

Watt, Peter

English

Aim: Precooling techniques are acute interventions that ameliorate exertional heat stress and mediate a decline in endurance running performance in the heat. This study compared two prominent approaches to precooling on the determinants of endurance performance under heat stress. Methods: Twelve males (age 38.6±11.1 years, body mass 77.3±7.1 kg) completed three incremental, discontinuous treadmill tests in the heat (31.9±1°C, 61.9±8.9% relative humidity) to determine speed at lactate threshold at two fixed blood lactate concentrations (2 &amp; 3.5 mmol. L-1), running economy and VO2max. Trials involved 20 minutes of either internal cooling (INT, 7.5 g.kg-1 ice slurry ingestion) or mixed-methods external cooling (EXT, cold towels, forearm immersion, ice vest and cooling shorts), alongside no intervention (CON). Results: An effect on running speed was observed at fixed lactate concentrations (F=3.78, p=0.04, partial η2 = 0.27). Mean values at 2 mmol.L-1 were INT 12.3±1.1 km.h-1, EXT 12.3±1.1 km.h-1, CON 12±1.1 km.h-1 and at 3.5 mmol.L-1 INT 13.8±1 km.h-1, EXT 13.8±1 km.h-1, CON 13.6±1 km.h-1. Bonferroni pairwise comparisons identified a difference between INT and CON (p=0.03), but not for EXT (p=0.12). There was no effect of cooling on running economy across six exercise stages (INT 269.5±36.5 ml.km-1.min-1, EXT 269.7±37.9 ml.km-1.min-1, CON 266.5±35.2 ml.km-1.min-1, p=0.82), nor on VO2max (INT 57.5±5.6 ml.kg-1.min-1, EXT 58.4±4.7 ml.kg-1.min-1, CON 57.3±4.9 ml.kg-1.min-1, p=0.69). An effect for cooling on physiological strain index was observed (F=4.85, p=0.02, partial η2 = 0.38), with differences between EXT and CON (CON 4.8±1.6 vs. EXT 4.3±1.5, p=0.02), but not for INT (4.2±1.8, p=0.15). Precooling reduced thermal sensation (F=20.98, p&lt;0.01, partial η2 = 0.66) with differences in both cooling methods (INT 5.7±0.9, EXT 5.4±0.8, CON 6.2±0.8, p&lt;0.01). Conclusions: Beneficial effects of precooling on endurance performance have been widely evidenced during free-paced and open-ended trials. Results from this study may indicate that modest changes in lactate threshold or physiological strain, alongside a diminished perceptual strain, could help explain the better maintenance of endurance running performance in the heat from precooling

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Comparison of internal and external precooling on the determinants of endurance running performance in hot and humid conditions  James CA, Richardson AJ, Watt PW, Maxwell NS Environmental Extremes Laboratory, Centre for Sport and Exercise Science and Medicine, University of Brighton, Welkin Laboratories, Denton Road, Eastbourne, UK.  Aim: Precooling techniques are acute interventions that ameliorate exertional heat stress and mediate a decline in endurance running performance in the heat. This study compared two prominent approaches to precooling on the determinants of endurance performance under heat stress. Methods: Twelve males (age 38.6±11.1 years, body mass 77.3±7.1 kg) completed three incremental, discontinuous treadmill tests in the heat (31.9±1°C, 61.9±8.9% relative humidity) to determine speed at lactate threshold at two fixed blood lactate concentrations (2 & 3.5 mmol. L-1), running economy and VO2max. Trials involved 20 minutes of either internal cooling (INT, 7.5 g.kg-1 ice slurry ingestion) or mixed-methods external cooling (EXT, cold towels, forearm immersion, ice vest and cooling shorts), alongside no intervention (CON). Results: An effect on running speed was observed at fixed lactate concentrations (F=3.78, p=0.04, partial η2 = 0.27). Mean values at 2 mmol.L-1 were INT 12.3±1.1 km.h-1, EXT 12.3±1.1 km.h-1, CON 12±1.1 km.h-1 and at 3.5 mmol.L-1 INT 13.8±1 km.h-1, EXT 13.8±1 km.h-1, CON 13.6±1 km.h-1. Bonferroni pairwise comparisons identified a difference between INT and CON (p=0.03), but not for EXT (p=0.12). There was no effect of cooling on running economy across six exercise stages (INT 269.5±36.5 ml.km-1.min-1, EXT 269.7±37.9 ml.km-1.min-1, CON 266.5±35.2 ml.km-1.min-1, p=0.82), nor on VO2max (INT 57.5±5.6 ml.kg-1.min-1, EXT 58.4±4.7 ml.kg-1.min-1, CON 57.3±4.9 ml.kg-1.min-1, p=0.69). An effect for cooling on physiological strain index was observed (F=4.85, p=0.02, partial η2 = 0.38), with differences between EXT and CON (CON 4.8±1.6 vs. EXT 4.3±1.5, p=0.02), but not for INT (4.2±1.8, p=0.15). Precooling reduced thermal sensation (F=20.98, p<0.01, partial η2 = 0.66) with differences in both cooling methods (INT 5.7±0.9, EXT 5.4±0.8, CON 6.2±0.8, p<0.01). Conclusions: Beneficial effects of precooling on endurance performance have been widely evidenced during free-paced and open-ended trials. Results from this study may indicate that modest changes in lactate threshold or physiological strain, alongside a diminished perceptual strain, could help explain the better maintenance of endurance running performance in the heat from precooling.   

Comparison of internal and external precooling on the determinants of endurance running performance in hot and humid conditions:Training and Competing in the Heat Conference, Aspetar, Doha

https://cris.brighton.ac.uk/ws/files/24240770/James_et_al_2014_.pdf

Comparison of internal and external precooling on the determinants of endurance running performance in hot and humid conditions:Training and Competing in the Heat Conference, Aspetar, Doha

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