The term "isotonic" refers to a solution that has the same concentration of solutes as another solution, typically in relation to cells. When cells are placed in an isotonic solution, there is no net movement of water into or out of the cells, allowing them to maintain their normal shape and function. This balance is crucial for cellular health. In exercise physiology, "isotonic" describes a type of muscle contraction where the muscle changes length while maintaining a constant tension. This is commonly seen in activities like lifting weights, where the muscle shortens during the lifting phase and lengthens while lowering the weight. Isotonic exercises are effective for building strength and endurance.