Sex-specific differences in people with spinal cord injury during high and moderate exercise intensities: A within-subject design

Research Objectives: To investigate sex-related differences in cardiorespiratory biomarkers during high-intensity interval (HIIT) and moderate-intensity continuous (MICT) training in people with spinal cord injury (PwSCI).

Design: Non-randomized within-subject design

Setting: Laboratory

Participants: 21 active community living PwSCI (10 females, 11 males; aged 23.56±4.69)

Interventions: Participants performed incremental test to exhaustion, 20-minute HIIT session (1-minute at 90% peak power output [PPO]: 1-minute at 10% PPO), and MICT session (45% PPO) while connected to open-circuit spirometry. Sessions occurred every 2-7 days with matched workloads.

Main Outcome Measures: Oxygen consumed, average and maximum oxygen uptake as percentage of peak capacity (%VO2peak), differences in %VO2peak between first and last minute of exercise, and respiratory exchange ratio (RER) during varied intensities (i.e., 10%, 45%, 90% PPO) were compared using independent t-test or non-parametric alternative across sexes.

Results: Total oxygen consumed was greater for males than females during HIIT (30.60±4.24 vs 19.18±1.74 liters) and MICT (28.48±4.93 vs 19.52±2.06 liters). No difference was found in average %VO2peak during HIIT. Females (57±8%) reached a greater average %VO2peak during MICT than males (51±4%). Both sexes reached elevated maximum %VO2peak during HIIT (M:90±9% vs F:92±14%); no difference was found in maximum %VO2peak across sexes in either exercise. Males experienced larger increases in %VO2peak from the first to last minute of HIIT (M:41±11% vs F:31±12%). No sex-related differences in %VO2peak changes from first to last minute of MICT were observed (p>.05). There were no sex-related differences in RER across exercise intensities (p>.05).

Conclusions: Results suggest males with SCI have greater ventilatory capacity than females. Females may more efficiently strain the cardiorespiratory system than males during MICT. Both sexes reached high %VO2peak during HIIT, supporting its clinical utility. No sex-related differences were observed in substrate utilization across intensities. This project provides insight into sex-specific responses to exercise in PwSCI.

Author(s) Disclosures: Authors have no financial disclosures to report.