Question

Which of the following statements are true about the effect of endurance training or detraining on mitochondria volume in human skeletal muscle?

Five weeks of endurance training can increase skeletal muscle mitochondrial volume by two times about normal.
Seven days of detraining can reduce mitochondrial volume by 50% below the trained level.
After a period of detraining, approximately 4 weeks of retraining is required to regain the lost mitochondrial volume.

Answer 1

Endurance training doubles mitochondrial volume in muscle cells after five weeks, but seven days of detraining can reduce this volume by half from the trained level. Approximately four weeks of retraining is required to regain the lost mitochondrial volume.

Step-by-step explanation:

Effects of Endurance Training and Detraining on Mitochondria Volume

Endurance training leads to several cellular changes in human skeletal muscle. One significant change is the increase in mitochondrial volume, which is vital for enhancing aerobic metabolism in muscle fibers, especially in slow-twitch (Type I) fibers used for endurance activities. Five weeks of endurance training can double the skeletal muscle mitochondrial volume relative to the untrained state. This adaptation allows for more efficient ATP production for sustained muscle contractions during endurance exercises.

Detraining or a cessation of training can have a rapid effect on the muscle's cellular makeup, including a decrease in mitochondrial volume. Within seven days of detraining, mitochondrial volume can decrease by 50% from the trained level, signifying a quick regression in endurance capacity if training is not maintained.

To recover the lost mitochondrial volume after a period of inactivity, it is generally necessary to undergo approximately four weeks of retraining. This period allows for the re-adaptation of the muscle cells and restoration of the mitochondrial volume to support endurance once again.