Final answer:
Heat cramps are the muscle injury associated with working or exercising in high temperatures without proper hydration, characterized by painful and involuntary spasms.
Step-by-step explanation:
The muscle injury that can be caused by working or exercising in hot conditions and not hydrating properly is referred to as heat cramps. Heat cramps are painful and involuntary muscle spasms that typically occur in individuals who sweat a lot during strenuous activity, leading to dehydration and a loss of electrolytes. Unlike muscle strains which involve tearing of muscle fibers often due to overstretching, or sprains which affect ligaments, or a rupture which is a severe tear of muscle tissue, heat cramps are specifically related to the conditions of heat and inadequate hydration. The best response to heat cramps includes resting in a cool place, drinking electrolyte-rich fluids, and gently stretching and massaging the affected muscles.