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   ∘ 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   ∘ C during ECC. Mean skin (8-sites) and body temperature (weighting of 8020 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   ∘ 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.