Energy sources for muscular exercise.

The basic energy yielding mechanisms of muscle contraction are reviewed and the main structural and functional features of human muscle are compared with those of some common athletic animal species. Sex and age related muscle power (alactic) characteristics are examined in both sedentary and athletic subjects. Recent measurements of the kinetics of contraction of the O2 debt by NMR spectroscopy by the human plantar flexors are shown. The main features of anaerobic (lactic) exercise in untrained and trained subjects, as a function of sex, age and environmental conditions (high altitude), are described with particular emphasis on the so-called lactic anaerobic threshold. With regard to aerobic exercise, the main determinants of O2 transport to the tissues are reviewed and an update of the factors limiting human performance is made. The possible causes of arterial O2 desaturation in athletes, both at sea level and at altitude, are discussed. A comparative analysis between man and woman of the progress of the records of some typical competitions is made and possible implications are discussed. The potential role of some commonly used physiological and/or paraphysiological procedures for improving the performance is analyzed.