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

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 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   ∘ 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.

The Acute Physiological Responses of Eccentric Cycling During the Recovery Periods of a High Intensity Concentric Cycling Interval Session.

Eccentric and concentric exercise is associated with disparate acute and chronic responses. We uniquely interspersed workload equivalent eccentric cycling during each recovery period of a high intensity interval training (HIIT) cycling trial to determine acute cardiopulmonary, thermal and psycho-physiological responses. Twelve males [age 28 years (SD 6), peak oxygen consumption 48 mL ⋅ kg-1 ⋅ min-1 (SD 6)] completed two high intensity interval cycling trials [4 × 5 min, 60% peak power output (PPO)] separated by 7-10 days. The CONR trial required participants to cycle concentrically during each recovery period (5 min, 30% PPO). The ECC R trial modified the recovery to be eccentric cycling (5 min, 60% PPO). High intensity workload (CONR : 187 ± 17; ECC R: 187 ± 21 W), oxygen consumption (CONR : 2.55 ± 0.17; ECC R: 2.68 ± 0.20 L ⋅ min-1), heart rate (CONR : 165 ± 7; ECC R: 171 ± 10 beats ⋅ min-1) and RPE legs (CONR : 15 ± 3; ECC R: 15 ± 3) were equivalent between trials. Eccentric cycling recovery significantly increased external workload (CONR : 93 ± 18; ECC R: 196 ± 24 W, P < 0.01) yet lowered oxygen consumption (CONR : 1.51 ± 0.18; ECC R: 1.20 ± 0.20 L ⋅ min-1, P < 0.05) while heart rate (CONR : 132 ± 13; ECC R: 137 ± 12 beats ⋅ min-1) and RPE of the legs (CONR : 11 ± 7; ECC R: 12 ± 7) remained equivalent. There was no significant difference in the aural temperature between the trials (ECC R: 37.3 ± 0.1°C; CONR : 37.4 ± 0.1°C, P > 0.05), yet during recovery periods mean skin temperature was significantly elevated in the ECC R (ECC R: 33.9 ± 0.2°C; CONR : 33.3 ± 0.2°C, P < 0.05). Participants preferred ECC R (10/12) and rated the ECC R as more achievable (82.8 ± 11.4 mm) than CONR (79.4 ± 15.9 mm, P < 0.01). In conclusion, eccentric cycling during the recovery period of a HIIT training session, offers a novel approach to concurrent training methodology. The unique cardiopulmonary and skeletal muscle responses facilitate the achievement of both training stimuli within a single exercise bout.