ABSTRACT
Claude Bouchard tremendous foresights allowed him to establish exercise systems genetics in humans three decades before systems genetics was recognized as a field. Bouchard began phenotyping exercise as early as 1976, when he correlated variables with skeletal maturity and chronological age in 8–18-year-old boys. Exercise is stress. Stress has numerous definitions. The operational definition for stress used is an increased blood cortisol concentration. As such, maximal exercise effort is one of the greatest stressors to the body. An underlying reason for intense exercise, and thus intense stress, was postulated by Charles Darwin. On a statistical basis, those who are physically unfit are more likely to be eliminated prior to their being able to reach reproductive age. The effect of exercise can be better elucidated by exercise in the absence of gravity. Weight-bearing exercise is necessary to prevent bone loss. Nongravity exercise such as cycling is associated with a seven times increased likelihood to have spine osteopenia than running.
