OSMT (Ontario Society of Medical Technologists) Practice Exam

When a muscle contracts, it:

1. shortens and pushes a bone

2. lengthens and pulls a bone

3. shortens and pulls or pushes a bone

4. shortens and pulls a bone

The correct answer is: shortens and pulls a bone

When a muscle contracts, it undergoes a process known as contraction where the muscle fibers shorten. This shortening generates tension that primarily pulls on the bones to which the muscle is attached. Muscles cannot push; they can only pull. This is because when a muscle contracts, it exerts a force that is transmitted via tendons to the bone, causing the bone to move in the direction of the pull. The key aspect here is the biophysical mechanism of muscles, which work in pairs (agonists and antagonists) to achieve movement. For example, when the bicep muscle contracts, it pulls on the forearm bone and causes the arm to flex. This fundamental principle of muscle contraction plays a critical role in biomechanics and is essential in understanding the muscular-skeletal system. The other choices suggest actions that are not consistent with how muscles function. Some imply pushing, which is not possible with muscular contraction alone. Therefore, the correct understanding is that when a muscle contracts, it shortens and pulls a bone, allowing for movement around the joint.