Detraining: Loss of training-induced physiological and performance adaptations. Part II Long term insufficient training stimulus

This part II discusses detraining following an insufficient training stimul us period longer than 4 weeks, as well as several strategies that may be us eful to avoid its negative impact. The maximal oxygen uptake (VO2max) of at hletes declines markedly but remains above control values during long term detraining, whereas recently acquired VO2max gains are completely lost. Thi s is partly due to reduced blood volume, cardiac dimensions and ventilatory efficiency, resulting in lower stroke volume and cardiac output, despite i ncreased heart rates. Endurance performance it accordingly impaired. Restin g muscle glycogen levels return levels return to baseline, carbohydrate uti lisation increases and the lactate threshold is lowered, although it remain s above untrained values in the highly trained. At the muscle level, capill arisation, arterial-venous oxygen difference and oxidative enzyme activitie s decline in athletes and are completely reversed in recently trained indiv iduals, contributing significantly to the long term loss in VO2max. Oxidati ve fibre proportion is decreased in endurance athletes, whereas it increase s in strength athletes, whose fibre areas are significantly reduced. Force production declines slowly, and usually remains above control values for ve ry long periods. All these negative effects can be avoided or limited by re duced training strategies, as long as training intensity is maintained and frequency reduced only moderately. On the other hand, training volume can b e markedly reduced. Cross-training may also be effective in maintaining tra ining-induced adaptations. Athletes should use similar-mode exercise, but m oderately trained individuals could also benefit from dissimilar-mode cross -training. Finally, the existence of a cross-transfer effect between ipsila teral and contralateral limbs should be considered in order to limit detrai ning during periods of unilateral immobilisation.