Overground running incurs a higher energetic cost than treadmill running at a 1% grade: A comparison of running economy, oxygen cost of transport, and energy cost in endurance athletes.

Shahidi, Seyed Houtan; Can, Rana; Paça, Furkan Murat; Zengin, Muhammed Doğukan · PLoS One · 2026

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Abstract

This study compared the physiological and metabolic demands of treadmill and overground running by examining running economy (RE), oxygen cost of transport (O2-COT), and energy cost (EC) across ventilatory threshold-scaled intensities in trained endurance athletes. Twelve male runners (21.3‍±‍2.4 years; 176.2‍±‍6.8 cm; 67.8‍±‍5.9 kg) completed a ramp test to determine V̇O2max, followed by identical stepwise protocols (8-15 km·h‍1‍¹; 3-min stages) performed indoors on a treadmill and outdoors on a 400 m track. Breath-by-breath gas exchange was averaged over the final 60-90 s of each stage to determine steady-state V̇O2. Within-subject comparisons were used to evaluate differences between field and treadmill running across exercise intensities. Two-way repeated-measures ANOVA revealed significant main effects of Condition and Intensity domain for all three primary outcomes (all p‍≤‍0.012). RE was significantly higher during overground running (51.3‍±‍2.2 vs. 49.6‍±‍3.1 mL·kg‍1‍¹·min‍1‍¹; p-FDR‍=‍0.01), with divergence occurring primarily at intensities between 70% and 100% of VT2. O2-COT was consistently greater during overground running across all intensity domains (204.2‍±‍11.3 vs. 197.1‍±‍12.3 mL·kg‍1‍¹·km‍1‍¹; p-FDR‍≤‍0.01), with no significant Condition‍×‍Intensity interaction, indicating a consistent between-condition difference across all intensity domains. Energy cost remained consistently higher during overground running (3.87‍±‍0.21 to 4.60‍±‍0.27 vs. 3.65‍±‍0.22 to 4.10‍±‍0.18 J·kg‍1‍¹·m‍1‍¹; p-FDR‍<‍0.001), with a significant Condition‍×‍Intensity interaction (p‍=‍0.045). Carbohydrate oxidation was significantly higher during overground running at intensities approaching VT2 (p-FDR‍=‍0.02). These findings suggest that the commonly used 1% treadmill grade correction does not fully replicate the energetic demands of overground running, with implications for laboratory-based performance evaluation.

Medical subject headings