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Short-term heat acclimation training does not improve kinetics of lactate removal following maximal exercise.

DiLeo T; Powell J; Roberge R; Coca A; Kim J-H
Med Sci Sports Exerc 2014 May; 46(5)(Suppl 1):657
Heat acclimation training (HA) evokes numerous physiological adaptations, as well as improves heat tolerance and endurance performance. Moreover, HA has been shown to affect lactate responses, similar to those seen with endurance training. To our knowledge, no study has investigated how HA alters lactate kinetic parameters during exercise recovery. PURPOSE: To examine whether HA (5 days) improves the body's ability to remove lactate during recovery from maximal exercise. METHODS: Eight recreationally active males (21+/-1 years, 79.9+/-10.7 kg, 180+/-10cm) completed two trials of maximal treadmill exercise (Pre and Post-GXT) separated by five consecutive days of HA: two 45 min periods of cycling at approximately 50% VO2max with 15 min of rest between periods in an environmental chamber (33 degrees C WBGT; Tdb 46 degrees C, RH 20%). During the GXTs, blood was collected from the antecubital vein at rest, after exercise (0min), and during one hour of recovery (blood sampling at 1-5,7,9,11,13,15,2 0,25,30,45,60min). Blood draws were used to measure lactate concentrations (La) over time, and to determine the Amplitude (A2) and corresponding Velocity Constant (Y2) of lactate kinetics using bi-exponential curve fitting. RESULTS: Physiological adaptations to HA significantly developed over the course of five days. This is evidenced by a final core body temperature (Day 1-5: 39.0+/-0.5 - 38.6+/-0.5 degrees C; p=.039), final heart rate (173+/-11 - 160+/-18 beats/min; p=.045), and whole body sweat rate (1.3+/-0.2 - 1.5+/-0.2 kg/h; p=.005). However, the subject's VO2max did not differ from Pre to Post-GXT (61.8+/-5.3 and 61.1+/-4.6 ml/kg/min, respectively). There was no significant difference from Pre to Post-GXT La (Larest: 1.55+/-0.26 and 1.53+/-3.0 mmol/L, La0min: 8.28+/-0.87 and 9.13+/-1.17 mmol/L, Lapeak: 9.99+/-1.38 and 10.12+/-1.20 mmol/L, and La60min: 2.61+/-0.65 and 2.72+/-.0.62 mmol/L). Also, the parameters of lactate kinetics were not significantly different from Pre to Post-GXT (A2: -17.23+/-14.54 and -18.22+/-18.57 mmol/L, Y2: 0.051+/-0.03 and 0.053+/-0.03 min-1). CONCLUSION: These data suggest that while effective in inducing thermophysiological adaptations to heat-stress, short-term HA does not improve the body's ability to remove lactate following maximal exercise. Therefore, individuals training for faster exercise recovery may not benefit from HA.
Heat; Heat-exposure; Heat-regulation; Heat-tolerance; Training; Physiological-effects; Physiological-function; Physiology; Physical-reactions; Humans; Men; Age-groups; Physical-exercise; Blood-sampling
7782-44-7; 630-08-0
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Medicine and Science in Sports and Exercise
Page last reviewed: July 1, 2022
Content source: National Institute for Occupational Safety and Health Education and Information Division