ECSS Paris 2023: OP-PN29
INTRODUCTION: Eccentric cycling allows for a greater mechanical power output at a lower oxygen consumption (V̇O2) than concentric cycling. Prior research on low-intensity eccentric cycling (<300W) reported higher cardiac output (Q̇c) and heart rate (HR) than concentric cycling at matched V̇O2 (~150 mL or 6%). However, physiological responses to higher-power eccentric cycling remain underexplored. This study expands on previous findings by investigating cardiopulmonary responses to high-intensity eccentric cycling (up to ~1000W) compared to isoenergetic concentric exercise. METHODS: Seven participants (2F, 5M; age: 31.4±7.7 years; VO2max: 56.8±4.6 mL·min-1·kg-1), who completed a 12-week progressive eccentric training protocol (1 session/week) completed incremental cycling tests in both eccentric and concentric modes. Each test comprised four 5-minute stages, with eccentric power at 25%, 50%, 75%, and 100% of maximal power (Pmax) attained at training’s end. Concentric power was adjusted to match eccentric V̇O2 assuming a net mechanical efficiency of 24%. When V̇O2 equivalence was not achieved, a fifth concentric exercise stage was added. Q̇c, HR (impedance cardiography) and V̇O2 (metabolic cart) were continuously recorded and averaged over the last 60 seconds of each stage, while blood pressure (BP) was measured after each stage. RESULTS: In the last stage, eccentric Pmax was 4.2 times higher than its concentric counterpart (756±110 vs. 181±50.2 W) despite a similar V̇O2 (2.38±0.67 vs. 2.50±0.65 L·min-1; 56.8±19.2 vs. 59.9±21.6% of concentric VO2max). Arteriovenous oxygen difference (a-v̄O2) was lower in eccentric mode (124±25.7 vs 159±36.8 mLO2·L-1, p<0.05), suggesting reduced peripheral oxygen uptake despite matched metabolic demand. Ventilatory responses also differed, with eccentric cycling eliciting higher breathing frequency (46.6±6.95 vs 32.9±5.18 cycles·min-1, p<0.05) and lower tidal volume (1.75±0.57 vs 2.02±0.48 L, p<0.05). Eccentric cycling resulted in a significantly higher cardiac output (19.5±5.9 vs 16.2±5.21 L·min-1, p<0.05) and heart rate (173±24.5 vs 148±22 bpm, p<0.05) despite lower systolic (142±14.8 vs 166±18.7 mmHg, p<0.05) and diastolic (69.1±4.49 vs 85.4±7.30 mmHg, p<0.05) blood pressures. Systemic vascular resistance decreased significantly during eccentric cycling (5.08±1.12 vs. 7.35±1.65 mmHg·L-1·min-1, p<0.05), indicating peripheral circulatory adjustments despite greater mechanical load. CONCLUSION: High-intensity eccentric cycling allows for >4x greater mechanical work at similar V̇O2, eliciting distinct cardiopulmonary responses characterized by higher Q̇c and HR, reduced peripheral oxygen uptake, and lower vascular resistance. These findings highlight its potential as a high-output yet metabolically efficient training modality, particularly for populations with reduced cardiovascular capacity.
Read CV Marc-Etienne VilleneuveECSS Paris 2023: OP-PN29
INTRODUCTION: Eccentric cycling (ECC) results in lower cardiorespiratory responses with lower heart rate (HR) and oxygen uptake (VO2) in comparison to conventional concentric cycling (CON) when they are performed at the same mechanical power output. However, higher HR has been documented in ECC vs CON when performed at the same VO2 [1,2]. Therefore, it remains unclear whether any difference in cardiorespiratory responses exists between ECC and CON performed at the same mode-specific relative intensity. Thus, the present study compares cardiorespiratory responses and exercise tolerance between ECC and CON conducted at the same mode-specific relative intensity. METHODS: Eleven healthy men (31 ± 7 yr, BMI 25.2 ± 3.2 kg/m2) participated in six sessions separated by at least 72 hours. The first two sessions were used to familiarize them with ECC. In the next two visits, the participants completed a CON and an ECC ramp incremental test until exhaustion (30W/min slope, starting from 100W at a pedal cadence of 50-60 rpm) to determine mode-specific maximal power output (Pmax) in each cycling mode. The fifth and sixth sessions consisted of CON or ECC constant-load trials performed at 100% of the mode-specific Pmax. The CON and ECC constant-load trials were performed until exhaustion and the total trial duration (i.e., tolerance) was recorded. Cardiorespiratory responses were continuously recorded during the trials by indirect calorimetry and telemetry, with mean values used for analysis. Paired Student’s t-tests compared variables between cycling modes (mean ± SD, significance at p<0.05). RESULTS: Mean power output was higher (p<0.001) during ECC (386 ± 55 W) than CON (287 ± 49 W) without difference (p=0.381) in pedal cadence (56 ± 5 rpm). Tolerance was greater (p<0.01) for ECC (7.9 ± 5.1 min) than CON (2.1 ± 0.5 min). Mean VO2 (1.74 ± 0.31 vs 2.13 ± 0.39 L/min), pulmonary ventilation (42.22 ± 9.94 vs 53.14 ± 13.72 L/min) and tidal volume (1.67 ± 0.40 vs 2.23 ± 0.37 L) were lower (p<0.05) during ECC than CON, but respiratory frequency was not different (p=0.071) between ECC (31 ± 9 cycles/min) and CON (27 ± 7 cycles/min). However, no significant differences (p=0.290) in mean HR were evident between ECC (139 ± 15 bpm) and CON (134 ± 16 bpm). CONCLUSION: The results show unique characteristics of ECC enabling higher mechanical power output with lower pulmonary ventilation and VO2 responses but similar HR to CON despite similar mode-specific relative intensity. Therefore, prescribing ECC at the same mode-specific relative intensity to CON increases mechanical load to lower limb muscles while reducing breathing load and metabolic demand, without imposing additional cardiac burden. This could be a useful strategy for exercise interventions to improve health and fitness.
Read CV Renan BarretoECSS Paris 2023: OP-PN29
INTRODUCTION: Ramp incremental (RI) exercise tests have been proposed to determine critical power (CP) and the work capacity above CP (W´), as a more feasible alternative to the traditional methodology, which requires multiple exhaustive constant work rate (CWR) tests. W´ estimated from a RI test is defined as the total work done above CP during such test (W´R). This study assessed the influence of ramp slope on the magnitude of the estimated W´, and the agreement between W´ derived from the traditional method and W´R. METHODS: 13 healthy men (23 ± 3 yr, 56.2 ± 7.5 mL·min-1·kg-1) performed a maximal RI test with a standard slope (30 W·min-1) on an electromagnetically braked cycle ergometer, followed by a series of CWR trials to determine CP and W´. Subsequently, they performed two maximal RI tests with slow and fast slopes (10 and 50 W·min-1). Each RI test was immediately succeeded by a CWR bout above CP to compute the additional amount of work that could be delivered above CP (W´extra). CP and W´ were estimated using the two-parameter model equations, selecting the model with the lowest total error on an individual basis. Total work done above CP during the different RI tests (W´R10, W´R30 and W´R50) were compared with the conventionally determined W´. Pulmonary gas exchange was measured during all tests on a breath-by-breath basis to ensure the attainment of maximal oxygen consumption (V̇O2max) at task failure. Differences in performance parameters and W´ estimates across the different tests were assessed using Repeated Measures ANOVA with pairwise comparisons (LSD adjustment). RESULTS: Time to exhaustion (TTE) became longer with decreasing ramp slope (1615 ± 262 s > 661 ± 91 s > 430 ± 26 s, p < 0.001). Conversely, POpeak was the lowest in the slow and the highest in the fast protocol (319 ± 44 W < 378 ± 48 W < 405 ± 52 W, p < 0.001). V̇O2max did not differ across the three RI tests (p = 0.15). CP and W´ were respectively 251 ± 44 W and 19.1 ± 3.4 kJ. We found significantly lower values for W´R10 (14.4 ± 6.2 kJ, Δ = 4.7 ± 5.1 kJ, p = 0.006), W´R30 (16.4 ± 2.5 kJ, Δ = 2.7 ± 3.6 kJ, p = 0.018) and W´R50 (14.6 ± 3.5 kJ, Δ = 4.5 ± 3.3 kJ, p < 0.001) compared to the conventionally determined W´. W´extra was the highest in the fast protocol (3.1 ± 1.5 kJ) compared to the normal (1.6 ± 1.5 kJ, p = 0.013) and slow protocol (1.7 ± 1.4 kJ, p = 0.007), whereas there was no difference between the normal and slow test in W´extra (p = 0.899). For all three RI protocols, the sum of W´R and W´extra did not differ from each other, nor from W´ (p = 0.098). CONCLUSION: A standard ramp slope of 30 W·min-1 showed the lowest underestimation of W´, indicating that a full depletion of W´ is obstructed during particularly slow or fast ramp protocols. However, performing an additional work bout above CP, immediately after the RI test, led to higher estimates of W´ that were closer to the conventionally determined W´.
Read CV Lena StuerECSS Paris 2023: OP-PN29