When does injury or failure of a tissue generally occur?

Tissue injury or failure typically occurs when the load applied to the tissue surpasses its failure tolerance. Each type of tissue in the body—muscle, tendon, ligament, bone—has a specific capacity to withstand forces. When the external force exceeds this inherent capacity, the tissue cannot maintain its structural integrity, which leads to injury.

Understanding the mechanics of load and tissue tolerance is crucial in kinesiology. Humans can tolerate certain amounts of stress, but excessive loads—whether from acute injury, overuse, or improper technique—can cause damage to the tissue. This principle is foundational for preventing injuries in both clinical and athletic environments, emphasizing the importance of carefully monitoring load during training and rehabilitation programs.

The other options do not accurately reflect the conditions under which injury occurs. Load application does not necessarily lead to injury unless it exceeds the tissue's tolerance. Periods of rest can aid in recovery rather than contribute to tissue failure. Finally, if the failure tolerance of the tissue exceeds the applied load, the tissue remains unharmed.