The effect of the menstrual cycle and hyperglycaemia on hormonal and metabolic responses during exercise

Purpose Variations in substrate metabolism have been identified in women during continuous steady-state aerobic exercise performed at the same relative intensity throughout discrete phases of the menstrual cycle, although some evidence exists that this is abolished when carbohydrate is ingested. This investigation examined the effects of a supraphysiologic exogenous glucose infusion protocol, administered during two phases of the menstrual cycle (follicular and luteal) in eumenorrheic women to identify differences between metabolic, hormonal and substrate oxidative responses. Methods During the experimental conditions, blood glucose was infused intravenously at rates to “clamp” blood glucose at 10 mM in seven healthy females (age 20 ± 1 y, mass 55.0 ± 4.1 kg, V̇O_2peak 40.0 ± 1.8 ml/kg/min). Following 30 min of seated rest, participants exercised on a cycle ergometer for 90 min at 60