HORMONAL AND METABOLIC RESPONSES TO EXERCISE IN SUBJECTS OF HIGH AND LOW WORK CAPACITIES

  • 1 January 1978
    • journal article
    • research article
    • Vol. 10  (1) , 1-6
Abstract
Hormonal and metabolic responses to submaximal exercise were studied in 8 normal subjects. Four subjects had high maximal O2 uptakes [VO2 max] (4.55 .+-. 0.49 l/min) and were classified as fit and 4 had low VO2 max (2.13 .+-. 0.32 l/min) and were classified as unfit. All subjects exercised for 20 min at 750 kpm/min on a cycle ergometer, which represented 35% and 85% of the VO2 max for the fit and the unfit subjects respectively. The unfit subjects had a higher heart rate and CO2 output at the same O2 uptake when compared with the fit group. There was a high blood lactate in the unfit subjects and also a greater rise in blood glucose, plasma cortisol and serum growth hormone during exercise in these subjects. Free fatty acids increased in the fit subjects, but not in the unfit and serum insulin was depressed in both groups. The cardiorespiratory fitness is an important determinant of the hormonal and metabolic response to submaximal exercise, which differed considerably when fit and unfit subjects exercised at identical absolute levels of power output. These differences have implications for the control of energy substrates used during exercise.