Onsiri, S., & Wilcox, A. (2013). Substrate utilization during exercise among males and females varying in age and training status. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 851.

This study compared fat and carbohydrate utilization during exercise among males and females varying in age and training status. Eight groups of 10 Ss for formed into: i) trained young males, ii) trained young females, iii) untrained young males, iv) untrained young females, v) trained older males, vi) trained older females, vii) untrained older males, and viii) untrained older females. All females were experiencing regular menstrual cycles, not using oral contraceptives, and were tested in the mid-follicular phase of their menstrual cycle. The young Ss averaged (~21.3 years) and older Ss (~40.1 years). Ss exercised for 35 minutes on a treadmill at an intensity just below the ventilatory threshold. Substrate utilization was indicated by the respiratory exchange ratio.

The average respiratory exchange ratio during exercise was lower for females than males, and lower in trained Ss compared to untrained Ss. While females used proportionately more fat during exercise than males as indicated by the respiratory exchange ratio, the difference between trained males and trained females was smaller than that between untrained males and untrained females. There was no difference in the average respiratory exchange ratio during exercise between the young and older groups.

Implication. Fat utilization during moderate exercise was significantly greater in females than males and the magnitude of that difference lessened between trained females and trained males. The 20-year age difference was insufficient for an age effect to be revealed.

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