Elevated body temperature contributes to the increased heart rate response during eccentric compared to concentric cycling when matched for oxygen consumption

ABSTRACT

A cardiovascular requirement to facilitate thermal homeostasis may partly contribute to the elevated heart rate during eccentric cycling. This study compared the body temperature response to a bout of eccentric (ECC) and concentric (CON) cycling to account for the difference in heart rate. Eight (N = 8) aerobically trained males (age 35 y [SD 8], peak oxygen consumption 3.82 L.min⁻¹ [SD 0.79]) completed an ECC cycling trial (60% PPO) followed by an oxygen consumption/duration matched CON trial (30${ }^{\circ }C$, 35% RH) on a separate day. Trial termination was determined as an elevation in aural temperature, a surrogate of deep body temperature, by +0.5${ }^{\circ }C$ during ECC. Mean skin (8-sites) and body temperature (weighting of 80:20 for auditory canal and mean skin temperature) were calculated. Matching the oxygen consumption between the trials increased external work during ECC cycling (CON: 71 [SD 14] ECC: 194 [SD 38] W, p < 0.05) and elevated aural temperature (+0.5${ }^{\circ }C$) by 20 min 32 s [SD 9 min 19 s] in that trial. The peak rate of rise in aural temperature was significantly greater in ECC (CON: 0.012 [SD 0.007] ECC: 0.031 [SD 0.002] ^oC.s⁻¹, p < 0.05). Aural, mean skin and body temperature were significantly higher during the ECC trial (p < 0.05) and this was accompanied by elevated mean heart rate (CON: 103 [SD 14] ECC: 118 [SD 12] b.min⁻¹, p < 0.05) and thermal discomfort (p < 0.05). Moderate load eccentric cycling imposes an elevated thermal strain when compared to concentric cycling. This requirement for dissipating heat, in part, explains the elevated heart rate during eccentric cycling.

KEYWORDS:

• Eccentric cycling
• muscle lengthening
• thermal response
• body temperature
• heart rate

Acknowledgments

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author contribution

GP, HG, and CB conceived and designed research. TE, GP, AH, and CB conducted experiments and data analysis. All authors and wrote the manuscript. All authors read and approved the manuscript.

Disclosure statement

There are no personal, professional, or financial conflicts of interest for any of the authors of this submitted work.