HEAT ACCUMULATION DIFFERS BETWEEN INTERMITTENT AND CONTINUOUS EXERCISE
Mora-Rodríguez, R., Del Coso, J., Estevez, E., & Aguado-Jiménez, R. (2006). Intermittent exercise reduces skin blood flow and increases heat storage in the heat. Medicine and Science in Sports and Exercise, 38(5), Supplement abstract 2057.
"Short bouts of intermittent exercise (30 s exercise; 30 s rest) in a thermoneutral environment resulted in higher rectal temperature and lower sweat rate in comparison to another trial where the same amount of work was performed continuously. However, it is unclear if in a hot environment variations in exercise intensity (above and below anaerobic threshold as takes place in many sports) would increase heat storage in comparison to continuous exercise for the same amount of work performed". This study investigated if intermittent exercise, in comparison to continuous exercise, resulted in higher heat storage and exaggerations in the response mechanism. Endurance-trained and heat acclimated Ss (N = 7) pedaled for 90 minutes in a hot-dry environment (35ºC; 29 % RH; 2.5 m/s wind speed). On one occasion the workload was maintained constantly (63% VO2max) while in the other the workload was increased alternatively to 90% VO2max for 1.5 minutes and then reduced to 50% VO2max for 4.5 minutes until completion of the 90 min. These constituted the continuous and intermittent exercise protocols.
Heat production was similar in both protocols. The intermittent exercise condition produced a higher final rectal temperature and more stored heat than was recorded for the continuous exercise condition. Intermittent exercise increased sweat rate, blood lactate concentration, and heart rate significantly more than in the continuous condition.
Implication. Intermittent exercise induces to higher heat storage than continuous exercise despite similar heat production. Thus, heat dissipation is partially impaired during intermittent exercise.
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