## 5 Impact of Exercise Training and Practical Recommendations
In aged people, the benefits of resistance exercise on muscle function were recently attributed to improvement of mitochondrial function, muscle hypertrophy, modulation of myonuclear domain, and newly formed myonuclei, increases of satellite cell-capillary interaction and content [49; 278; 279]. Of note, it appears that Nordic walking also improves lower limb strength, aerobic aptitude, body composition, life, and sleep quality in old people [280]. Finally, eccentric actions and hypoxic stress have emerged as promising strategies over the last few years. Eccentric actions may promote more robust mTOR1 pathway activation and increases of skeletal muscle mass and strength compared to concentric and isometric contractions [281; 282; 283]. Of note, normalization of the force-signal integral to a same magnitude effect leads to similar acute molecular anabolic responses [284; 285; 286; 287]. A recent study showed that combined maximal concentric and eccentric training does not produce greater gains in muscular isometric strength and hypertrophy than maximal concentric training alone in young males [288]. Low-intensity eccentric actions should be used in frail people, such as aged subjects, to minimize the occurrence of muscle damage and the risk of a traumatic injury. Furthermore, combination of resistance exercise with hypoxic stress promotes several advantages. Indeed, in the last decade, investigations have been conducted on supplementation of hypoxia during resistance training. Reduction of intramuscular oxygen partial pressure promotes greater cellular stress in skeletal muscle and may improve several aspects of performance, including aerobic capacity and sprint ability in athletes [289; 290; 291]. However, in older adults, hypoxic resistance training does not induce greater magnitude in gains of lean mass and muscle strength than normoxic resistance training [292]. Moreover, hypoxic training promotes similar changes in oxidative metabolism and insulin sensitivity than exercise in normoxia in older individuals [293]. However, cognitive performance may be improved with intermittent hypoxic training in aged people [294]. That said, the combination of eccentric endurance exercises with low hypoxia may present some advantages on muscle function during aging [295]. Importantly, among hypoxic methods, blood flow restriction (BFR, also called \"occlusion training\") is increasingly considered. BFR consists in the generation of local hypoxia in skeletal muscles or restricted venous return during exercise depending on the occlusive pressure level [296]. BFR promotes additional effects on both aerobic and resistance training adaptations. During resistance training, BFR can promote improvements in muscle size, strength, and athletic performance [296]. Resistance training with BFR also promotes proliferation of myogenic stem cells, myonuclei addition, as well as enhancement of angiogenic genes expression [297; 298]. Recently, it was found that BFR can limit skeletal muscle atrophy and MuRF1 expression during cast immobilization and muscular weakness induced by chronic unloading [299; 300]. In addition, there are some data about BFR during muscle wasting or aging and a case report has suggested that BFR should be considered to improve physical fitness, prevent muscle loss, and improve arterial compliance in frail aged subjects [301; 302]. In old women, resistance training at low intensity combined with BFR at 110 mmHg appears effective to induce hypertrophy and gains in muscle strength [303], and walking with BFR at higher pressure improves limb venous compliance [304]. However, a study reported that a six-week walking training with BFR did not improve peak oxygen uptake in old men and women, even if functional ability, muscle size, and strength were improved [305]. Finally, in postmenopausal women with osteopenia or osteoporosis, low intensity resistance training with BFR may also be an effective method to induce bone formation markers [306].