Binary Sex Input Has No Effect on Metabolic or Pulmonary Variables: A Within-Subjects Observational Study.

Metabolic analysis systems require binary sex input, conflating biological sex with gender, limiting inclusivity. This study aimed to determine whether sex input altered metabolic or pulmonary variables during self-paced walking and running. Twenty adults completed two 5-min walking and running trials under both female (FC) and male (MC) input conditions in randomized order. Dependent t-tests determined differences between conditions; p-values < 0.05 were considered significant, and effect sizes were calculated. No significant within-participant differences were found between FC and MC for any variable. During walking, mean relative VO2 (mL/kg/min) was 11.13 ± 2.73 (FC) and 10.81 ± 2.39 (MC), p = 0.08, R2 = 0.93; mean energy expenditure (kcal) was 18.28 ± 4.74 (FC) and 17.86 ± 4.33 (MC), p = 0.12, R2 = 0.94. During running, mean relative VO2 was 28.80 ± 5.89 (FC) and 28.82 ± 6.06 (MC), p = 0.90, R2 = 0.98; mean energy expenditure was 45.79 ± 13.08 (FC) and 45.55 ± 12.26 (MC), p = 0.99, R2 = 0.98. Binary sex input in the TrueOne 2400 system did not affect variables, supporting inclusive sex and gender data collection to improve research ethics, accuracy, and representation of gender-diverse people without compromising integrity.