Why some muscles tire much faster?


For example, when I workout my chest, and I use the max weight I can lift 10 times, I can do it 10 times only in the first set. The next set I can do 7 reps at the most.
On the other hand, when I workout my tricep, I can do at least 5 sets with 10 reps everytime.

In: Biology

Muscles can contain “fast” twitch fibers, and “slow” twitch fibers. Fast fibers give you more power at the cost of using a lot of energy very fast. On the other hand slow fibers can maintain their contraction for prolonged periods of time.

So for example the bicep muscle typically contain a lot of fast twitch fibers, while the muscles of the back in charge of your posture contain more slow fibers. There are other reasons why a certain muscle might require more energy but I want to keep it eli5.

Endurance training typically results in increased slow fibers while muscle building results in more fast fibers.