Author(s): GHIOTTO, L., AMINI, M., D’EMANUELE, S., VOLTOLINA, S., SCHENA, F., TARPERI, C. , Institution: UNIVERITY OF VERONA, Country: ITALY, Abstract-ID: 1496

INTRODUCTION:
Eccentric cycling (EC) is a novel approach for training and evaluating cardiometabolic and muscular function. Body position in cycling (recumbent, RC vs. upright, UP) may influence central and peripheral hemodynamic responses, due to differences in blood distribution, venous return, and muscle pump activity. Previous studies suggest cardiac output (CO) may be higher in RC at moderate intensities, with differences decreasing at higher intensities. Posture may affect central measures such as CO stroke volume (SV) and heart rate (HR), as well as peripheral factors (systemic vascular resistance (SVR) and left cardiac work index (LCWi)). However, limited evidence directly compares these responses between RC and UP positions during incremental EC. This study examined the effects of posture on CO, SV, SVR, and LCWi in healthy young adults.
METHODS:
After familiarisations, 49 participants (10F; 39M; 24±1 years; 70.9±11.1 kg; 1.76±0.09 m) completed two randomized incremental EC tests to voluntary exhaustion (starting from 100W for M and 50W for F + 25W·min⁻¹ at 65±5 rpm) in RC and UP position, separated by >14 days. CO, SV, HR, SVR and LCWi were continuously assessed using non-invasive impedance hemodynamic monitor. Data were analyzed using linear mixed-effects models with position and time as fixed factors and participant as a random effect.
RESULTS:
In both positions, comparing 20% to 80% of relative intensity, CO, SV, HR, and LCWi increased (CO: 41 and 44%; SV: 6 and 9%, HR: 32 and 31%, LCWi: 38 and 44%), while SVR decreased (28 and 24%) in RC and UP positions. Across all intensities, RC elicited higher CO (9-12-6-7%), SV (19-18-13-15%), and LCWi (8-11-7-4%) compared with UP, accompanied by lower HR (8-6-6-7%) and SVR (17-18-26-22%), at 20-40-60-80% of iso-relative load.
Linear mixed-effects analysis confirmed main effect of intensity for all parameters (all p <0.001). A significant main effect of position was also observed (p<0.001), with the UP position showing lower CO (β = −0.8±0.1), SV (β = −14.0±0.7), and LCWi (β = −0.59±0.10), but higher HR (β = +13.0±0.6) and SVR (β = +210±47) compared with RC.
CONCLUSION:
Riding position significantly modulates central and peripheral cardiovascular responses during incremental EC across iso-relative intensities. The RC consistently elicited higher CO and SV, alongside lower HR and SVR, compared with the UP. These differences were maintained across the entire intensity range, indicating a stable postural effect rather than an intensity-specific divergence. These results support the notion that body position influences the balance between cardiac preload and afterload, highlighting the importance of considering posture and hemodynamic responses in evaluating, training and rehabilitation programs. Training posture should be tailored to individual cardiovascular and functional needs.