You are carrying a case of 24 bottles of water up the stairs to your third-story apartment. What type of contraction are the muscles in your arms experiencing

Concentric contraction.

Explanation:

Concentric contraction is a type of contraction that the muscles in arms experiencing when an individual lifting 24 bottles of water up the stairs. A concentric contraction is a type of muscle activation that creates tension on your muscle as it shortens. As your muscle shortens, it produces enough force to move an object in the upward direction. In weight training we can easily see concentric movement.

the answer is: the „power stroke“ step.

muscle contraction can be divided into a few steps:

1. the release of ach (acetylcholine) in the synaptic cleft, binding of ach for its receptor and consequently opening of the ca channels.

2. the release of ca, binding of ca for the troponin

3. troponin shifting the tropomyosin, which was blocking the active site on the actin

4. myosin heads attaching to actin by breaking down atp to adp+ pi

5.   formation of the ‘cross-bridge’ on the active site of the actin filament by myosin head

6. “power stroke” -the cross bridge pulls actin, which slides over the myosin

9.     7. the release of adp completes the cross-bridge movement and atp attaches to myosin, breaking the actin-myosin cross bridge.