Calorimetric Measurement of Postexercise Net Heat Loss and Residual Body Heat Storage

• Autores: Glenn P. Kenny, Paul Webb, Michel B. Ducharme, Francis d. Reardon, Ollie Jay
• Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 40, Nº. 9, 2008, págs. 1629-1636
• Idioma: inglés
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• Resumen

  • Purpose: Previous studies have shown a rapid reduction in postexercise local sweating and blood flow despite elevated core temperatures. However, local heat loss responses do not illustrate how much whole-body heat dissipation is reduced, and core temperature measurements do not accurately represent the magnitude of residual body heat storage. Whole-body evaporative (H[spacing dot above]E) and dry (H[spacing dot above]D) heat loss as well as changes in body heat content ([DELTA]Hb) were measured using simultaneous direct whole-body and indirect calorimetry.

    Methods: Eight participants cycled for 60 min at an external work rate of 70 W followed by 60 min of recovery in a calorimeter at 30[degrees]C and 30% relative humidity. Core temperature was measured in the esophagus (Tes), rectum (Tre), and aural canal (Tau). Regional muscle temperature was measured in the vastus lateralis (Tvl), triceps brachii (Ttb), and upper trapezius (Tut).

    Results: After 60 min of exercise, average [DELTA]Hb was +273 +/- 57 kJ, paralleled by increases in Tes, Tre, and Tau of 0.84 +/- 0.49, 0.67 +/- 0.36, and 0.83 +/- 0.53[degrees]C, respectively, and increases in Tvl, Ttb, and Tut of 2.43 +/- 0.60, 2.20 +/- 0.64, and 0.80 +/- 0.20[degrees]C, respectively. After a 10-min recovery, metabolic heat production returned to pre-exercise levels, and H[spacing dot above]E was only 22.9 +/- 6.9% of the end-exercise value despite elevations in all core temperatures. After a 60-min recovery, [DELTA]Hb was +129 +/- 58 kJ paralleled by elevations of Tes = 0.19 +/- 0.13[degrees]C, Tre = 0.20 +/- 0.03[degrees]C, Tau = 0.18 +/- 0.04[degrees]C, Tvl = 1.00 +/- 0.43[degrees]C, Ttb = 0.92 +/- 0.46[degrees]C, and Tut = 0.31 +/- 0.27[degrees]C. Despite this, H[spacing dot above]E returned to preexercise levels. Only minimal changes in H[spacing dot above]D occurred throughout.

    Conclusion: We confirm a rapid reduction in postexercise whole-body heat dissipation by evaporation despite elevated core temperatures. Consequently, only 53% of the heat stored during 60 min of exercise was dissipated after 60 min of recovery, with the majority of residual heat stored in muscle tissue.