166k views
0 votes
What happens to the muscle fibers as the arm flexes and extends?

User WinFXGuy
by
4.8k points

1 Answer

2 votes
When a muscle contracts, the contractile fibers shorten it to an even larger bulge. For example, extend and then flex your biceps brachii muscle; the large, middle section is the belly
User Alex Stewart
by
4.6k points