What training variable should be increased to improve strength?

To improve strength, the training variable that should be increased is the resistance or load. This approach is grounded in the principle of progressive overload, which states that in order to enhance strength, the muscles must be subjected to greater-than-normal levels of stress. By increasing the resistance, whether by adding weight to an exercise or using more challenging implements (like resistance bands or heavier kettlebells), the muscles are forced to adapt to the increased demands, leading to increased muscle fibers' recruitment and overall strength gains.

This method ensures that the muscles deal with higher loads, stimulating the body to develop greater force production capabilities. It is vital for training programs designed to target strength improvements to incorporate progressively heavier weights over time, allowing the body to continually adapt and grow stronger.

In contrast, the other variables—duration of exercise, frequency of workouts, and rest time—play different roles in a training program. Increasing the duration might improve endurance rather than strength, while frequency affects workout volume and recovery rather than directly increasing strength. Lastly, rest time can influence the quality of strength training sessions but is not the main factor for increasing strength itself. Thus, focusing on increasing the resistance or load is the most effective strategy for enhancing strength.