There is certainly “resensitization” of muscle fibers to damage, if we wait longer than about 28 days between workouts (i.e. detraining). This is approximately how long the repeated bout effect lasts. Therefore, we might expect to see greater signaling responses for muscle fiber repair in a muscle fiber that has not been trained for a few weeks (as can occur during deloads if they involve submaximal levels of motor unit recruitment) in the same way. But we should not confuse the tendency of a muscle fiber to be damaged with its ability to increase in size.

In that respect, bear in mind that muscle fibers reduce in size quite dramatically over a period of about 4 weeks, if they are not being loaded (during detraining and potentially also during longer deloads). Therefore, they will appear to grow faster during that retraining period, simply because they are regaining lost size, rather than gaining new size. Indeed, there are studies showing more rapid muscle growth during retraining after an initial period of training followed by detraining. This is likely caused by the greater levels of voluntary activation that can be achieved after training, which allow us to train more motor units (and therefore more muscle fibers), since voluntary activation gains are not lost during detraining and can remain for months after stopping working out.