Abstract
Tarnopolsky et al. (1990) showed significantly higher fat oxidation (FOx) in women versus men during endurance exercise, likely due to their higher concentrations of estrogen and type I muscle fibers. Prior studies support this stance (Venables et al. 2000), yet Wallis et al. (2006) showed no effect of sex on the metabolic response to exercise. PURPOSE: To compare substrate metabolism between men and women during submaximal exercise prescribed using metabolic (percent ventilatory threshold, %VT) and relative (percent maximal heart rate, %HRmax) intensities. METHODS: Healthy, non-obese men (n = 23) and women (n = 13) (age, % fat, and VO2max = 24 ± 4 yr, 18 ± 4 %, and 47 ± 9 mL/kg FFM/min) underwent graded cycling to determine VO2max, HRmax, peak power output, and VT. Subsequently, participants completed 35 min of exercise at 30% below VT or at 62%HRmax that is attendant with maximal FOx (Venables et al. 2000). Participants replicated dietary intake in the 36 hr before each session. Intensity (in W) for the VT bout was fixed, while intensity was adjusted for the 62% HRmax bout to maintain the prescribed workload. Sessions were preceded by 36 hr abstinence from physical activity and a 12 hr fast. Blood glucose (BG) was measured pre- and post exercise and blood lactate concentration (BLa) was measured prior, 20 minutes in, and 3 min post-exercise. Gas exchange data were acquired during the bout. RESULTS: There was no difference in mean RER (0.88 ± 0.05 vs. 0.87 ± 0.05, p = 0.67), fat oxidation (4.5 ± 2.3 vs. 4.3 ± 1.8 mg/kg FFM/min, p = 0.72), or CHO oxidation (16.5 ± 4.8 vs. 14.8 ± 5.4, p = 0.35) between men and women for the 62%HRmax bout (mean PO = 93.3 ± 27.5 vs. 58.3 ± 22.0 W). Similarly, no differences in RER (0.92 ± 0.06 vs. 0.92 ± 0.05, p = 0.82), fat oxidation (3.8 ± 2.2 vs. 3.9 ±2.2 mg/kg FFM/min, p = 0.99), or CHO oxidation (27.6 ± 7.8 vs. 26.8 ± 10.3 mg/kg FFM/min, p = 0.80) existed for the VT bout (PO = 135.2 ± 33.2 vs. 98.2 ± 28.3 W). ANOVA with repeated measures exhibited no effect of sex on BG or BLa (p > 0.05), and no sexXtimeXbout interaction for FOx (p = 0.40). CONCLUSION: Results show no sex difference in metabolic responses to two unique intensities, challenging the belief that women oxidize more fat during exercise than men. These data may be due to their similar aerobic capacity as well as strict consideration of pre-exercise dietary and activity patterns.
Recommended Citation
MacDonald, Alexander J.; Anderson, Alexander M.; Lauritzen, Hanna; Pinter, Ryan; Mower, Madison; and Astorino, Todd Ph.D FACSM
(2024)
"No Sex Differences in Metabolic Responses to Submaximal Exercise,"
International Journal of Exercise Science: Conference Proceedings: Vol. 14:
Iss.
4, Article 17.
Available at:
https://digitalcommons.wku.edu/ijesab/vol14/iss4/17
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Health and Physical Education Commons, Medical Education Commons, Sports Sciences Commons