Author(s): LEMIRE, M., FARICIER, R., MEYER, F., TRIGUERA, R., MAUVIEUX, B., FAVRET, F., MILLET, G., DUFOUR, P.S., Institution: UNIVERSITY OF STRASBOURG, Country: FRANCE, Abstract-ID: 1897

INTRODUCTION:
Understanding the interplay between biomechanical and physiological responses during graded running is essential for optimizing endurance performance, especially in sports involving varied terrains. This study aimed to investigate the relationships between ventilatory (V̇E) and cardiac (HR) responses with biomechanical, neuromuscular, and muscle oxygenation parameters during downhill (DR), level (LR), and uphill running (UR), all performed at equivalent submaximal oxygen uptake (V̇O2) levels.
METHODS:
Fifteen trained male runners (mean V̇O2max: 62.0±6.2 ml·kg-1·min-1 - Training: 3-5 sessions per week) completed five incremental treadmill tests at different slopes: level (0%), moderate (±7.5%), and steep (±15%) inclines/declines. At equivalent V̇O2 across conditions, V̇E, HR, ground reaction forces, spatiotemporal parameters, and near infrared spectroscopy-derived muscle oxygenation were collected. For each slope condition, the strength and direction of the associations between HR and V̇E with the selected biomechanical, spatiotemporal, and muscle oxygenation variables were analyzed using Pearson correlation coefficients.
RESULTS:
At equivalent V̇O2 across all slope conditions, DR elicited elevated V̇E and HR compared to LR, whereas UR induced increased HR without a corresponding rise in V̇E. Heart rate was negatively correlated with muscle oxygenation indices, particularly during steep slopes DR and UR. Conversely, V̇E was more strongly associated with biomechanical variables, especially ground reaction forces and running velocity, across all gradients.
CONCLUSION:
These findings reveal divergent couplings between ventilatory and cardiac regulation during graded running: HR primarily reflects internal metabolic strain linked to muscle oxygenation, while V̇E aligns more closely with external mechanical demands. Monitoring both variables provides a more comprehensive understanding of physiological stress in varied running conditions.