There was little evidence of deterioration in the older athletes’ musculature, however. The athletes in their 70s and 80s had almost as much thigh muscle mass as the athletes in their 40s, with minor if any fat infiltration. The athletes also remained strong. There was, as scientists noted, a drop-off in leg muscle strength around age 60 in both men and women. They weren’t as strong as the 50-year-olds, but the differential was not huge, and little additional decline followed. The 70- and 80-year-old athletes were about as strong as those in their 60s.
“Several studies have indicated that the maintenance of training intensity during periods of reduced training and taper (...) is of paramount importance in order to keep training-induced physiological and performance adaptations. [59,64,68-74] On the other hand, training volume can be reduced to a great extent without falling into detraining. This reduction can reach 60 to 90% of previous weekly volume, depending on the duration of the reduced training period, both in highly trained athletes and recently trained individuals. [28,29,57-60,63,69-8]”
Early in your fast, your brain relies on glycogen to meet its functional needs. When glycogen stores become depleted, you may experience a headache or even feelings of anxiety. But after three to five days of fasting, your brain function is fueled primarily by ketone bodies produced in your liver. In a 2009 study published in "Advances in Experimental Medicine and Biology," researchers hypothesized that ketones serve to suppress glucose consumption and the break down of amino acids derived from muscle protein, thereby minimizing muscle wasting while continuing to sustain brain function.