Mechanical Running Power and Energy Expenditure in Uphill and Downhill Running

Trail running involves constant changes in terrain and slope, complicating the accu-rate assessment of energy expenditure during performance. This study aimed to ex-amine the relationship between running power output (RPO), oxygen consumption (VO₂), carbon dioxide production (VCO₂) and energy expenditure per minute (EEmin) across positive and negative slopes in trained trail runners under standardized labor-atory conditions. Fifteen male trail runners performed five randomized 5-minute treadmill runs at 70% of VO₂ maximal speed on −7%, −5%, 0%, +5%, and +7% slopes. VO₂, VCO₂, EEmin, respiratory exchange ratio (RQ), heart rate (HR), and RPO were rec-orded. Statistical analysis included Shapiro-Wilk tests for normality, repeat-ed-measures ANOVA to compare variables across slopes and Spearman or Pearson correlations between RPO and physiological variables. Moderate to strong positive correlations were found between RPO and VO₂ (Rho = 0.67–0.75, p < 0.01) and between RPO and EEmin (Rho= 0.69–0.84, p < 0.001) across all conditions. These findings suggest that RPO measured via a wearable device may reflect changes in energy expenditure and supports the integration of wearable power metrics into training and nutritional strategies for trail running. However, further studies in female athletes, outdoor set-tings, extreme slopes and altitude conditions are needed to confirm the generalizability of these results.