Endocrine response to physical efforts with equivalent total work loads but different intensities in man

The purpose of this study was to determine relationships between some exercise-induced neurohormonal changes and either exercise intensity, or its duration, or the total work output. Plasma catecholamine, cortisol, growth hormone and insulin concentrations were measured in healthy male subjects having performed three bicycle-ergometer exercise tests of the same total work output (2160 J kg-1) but differing in intensity and duration. The results showed that during the relatively short exercise plasma noradrenaline, adrenaline and cortisol responses depend more on work intensity than on the total work output. No relationship was demonstrated between the exercise-induced increases in plasma growth hormone concentration and work intensity or its duration, while the plasma insulin concentration was more decreased during the effort of lower intensity, but longer duration than during a short exercise of high intensity.