What is the required intensity level (as a percentage of maximum) to improve muscular strength?

To improve muscular strength effectively, the required intensity level is typically around 75% to 90% of one’s maximum effort. When engaging in resistance training, lifting weights or performing exercises at this intensity level stimulates the body to adapt and grow stronger by recruiting a greater number of muscle fibers and increasing the overall capacity of the muscles being trained.

By lifting at 90% of your maximum, you engage in a high level of effort that's essential for maximizing strength gains. At this intensity, you are challenging the muscles sufficiently to elicit adaptations such as increased muscle size and improved neuromuscular connections, which are vital for strength enhancement.

The lower intensity levels like 40% or 60% generally focus more on endurance or light strengthening, which do not provide the same stimulus necessary for maximizing strength gains as high-intensity lifting does. Thus, the 90% effort level is crucial for those specifically aiming to improve muscular strength.