This study explored differences in running economy between well-conditioned young male and female (tested within the early follicular phase of their menstrual cycle) participants, matched for age and percent difference between predicted and actual maximum oxygen uptake (V̇o2max). Twenty-five recreational runners (13 men and 12 women), aged 19-27 yr, performed graded treadmill exercise to assess V̇o2max. Participants also performed three bouts of submaximal continuous treadmill running at 8, 10, and 12 km/h. Sex comparisons revealed lower maximal aerobic speed (MAS) and V̇o2max in women relative to men (P < 0.05). However, the percent difference from predicted V̇o2max was similar between men and women (men: 149.6 ± 18.7%, women: 150.8 ± 16.4%; P > 0.05). Absolute running economy (mL·kg-0.75·km-1) improved in transition between treadmill speeds, and this occurred similarly in both sexes. Despite this, women showed overall lower oxygen cost of running than men during treadmill locomotion at predetermined absolute and relative intensities (P < 0.05). Finally, in a small subset of participants (n = 6, 3 male and 3 female participants) with similar MAS (16 km/h), men still exhibited higher V̇o2max and gross oxygen cost of running than women (difference of ~6%, statistics not computed). The present results indicate that, in men and women with similar percent of predicted V̇o2max, running economy follows a sexually dimorphic pattern throughout a broad spectrum of treadmill speeds. Ultimately, from a motor performance perspective, our data strongly suggest that lower V̇o2max values in female recreational runners are partially compensated by lower gross oxygen cost of locomotion during submaximal running.NEW & NOTEWORTHY Our data demonstrate that, compared with that seen in men with similar percent difference from predicted maximum oxygen uptake (V̇o2max), scaled gross oxygen cost of running (in absolute and relative terms) is lower in women throughout a broad spectrum of treadmill speeds. Importantly, these findings were obtained after controlling for the effects of the menstrual cycle on running economy, and this is novel.
Keywords: metabolism; oxygen cost; physical performance; physiology; sex.