Figure 12.

Time course of muscle growth and loss (starting after 600 days of hypertrophy) in response to a regular resistance training program (every 3 days) with three sets of 10 repetitions at 20 pN per titin (our estimate of ∼70% 1RM), followed by detraining. The diffusive feedback depends on the degree of sarcoplasmic titin degradation, which in turn increases with myonuclear domain size and lysosomal activity. Slow detraining may combine with an initial fast loss due to atrophic conditions (see below). In this case, a 5–10% ribosome degradation en route to the titin synthesis sites (0.05 < αn_titin < 0.1) appears to support training and detraining at the correct rates; see (8,49,75,76). To see this figure in color, go online.