Strength and skeletal muscle adaptations in heavy-resistance-trained women after detraining and retraining

Abstract

Six women who had participated in a previous 20-wk strength training study for the lower limb detrained for 30-32 wk and subsequently retrained for 6 wk. Seven untrained women also participated in the 6-wk "retraining" phase. In addition, four women from each group volunteered to continue training an additional 7 wk. The initial 20-wk training program caused an increase in maximal dynamic strength, hypertrophy of all three major fiber types, and a decrease in the percentage of type IIb fibers. Detraining had relatively little effect on fiber cross-sectional area but resulted in an increased percentage of type IIb fibers with a concomitant decrease in IIa fibers. Maximal dynamic strength decreased but not to pretraining levels. Retraining for 6 wk resulted in significant increases in the cross-sectional areas of both fast fiber types (IIa and IIab + IIb) compared with detraining values and a decrease in the percentage of type IIb fibers. The 7-wk extension accentuated these trends such that cross-sectional areas continued to increase (nonsignificant) and no IIb fibers could be found. Similar results were found for the nonpreviously trained women. These data suggest that rapid muscular adaptations occur as a result of strength training in previously trained as well as non-previously trained women. Some adaptations (fiber area and maximal dynamic strength) may be retained for long periods during detraining and may contribute to a rapid return to "competitive" form.

Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining

“…muscle memory | muscle nuclei | muscle atrophy | muscle hypertrophy | apoptosis I ndividuals with a history of previous training acquire force quickly on retraining (1,2), and this commonly observed phenomenon has been dubbed "muscle memory." There is no known mechanism for memory in muscle cells, and, to date, the longlasting effects of previous training have been attributed to motor learning in the central nervous system (3).…”

“…There is no known mechanism for memory in muscle cells, and, to date, the longlasting effects of previous training have been attributed to motor learning in the central nervous system (3). However, it has been reported that muscles can remain hypertrophic after several months of detraining (1,(4)(5)(6)(7)(8). In one study on elderly individuals who had strength-trained, force was still 9-14% higher even after 2 y of detraining (7).…”

“…In one study on elderly individuals who had strength-trained, force was still 9-14% higher even after 2 y of detraining (7). During 30-32 wk of detraining, a group of women lost a considerable part of the extra strength obtained by 20 wk of previous training but regained the strength after only 6 wk of retraining (1). This suggests the possible presence of a local memory mechanism in the muscle.…”

mTOR signaling response to resistance exercise is altered by chronic resistance training and detraining in skeletal muscle

“…In humans, resistance training-induced muscle anabolism and subsequent hypertrophy occur most rapidly during the early phases of training, becoming progressively slower with time (33,40). On the other hand, following a detraining period, muscle adaptation responses may return to their initial levels, and the effects of retraining on muscle growth are similar to those observed during the initial phase of resistance training (33,37). However, the mechanisms underlying such changes in the sensitivity of muscles to training stimuli are unclear.…”

Skeletal Muscles Do not Undergo Apoptosis During Either Atrophy or Programmed Cell Death

“…In fact, the retention of "surplus" nuclei during atrophy confers a distinct advantage for the individual since skeletal muscle frequently undergoes cycles of atrophy and hypertrophy in response to environmental conditions. The ability to recover quickly by utilizing pre-existing nuclei may serve an important role in muscle adaptation and may explain the phenomenon of "muscle memory" [54]. It is well documented in the field of exercise physiology that it is far easier to reacquire a certain level of muscle fitness through exercise then it was to achieve it the first place, even if there has been a long intervening period of detraining.…”