When trained men do certain types of weightlifting workouts, their bodies produce more lactic acid compared to other workout styles, which means their muscles are working harder and under more stress.

When trained men do different types of strength exercises, their muscles produce more lactate (a sign of effort), and it peaks at similar high levels after ten sets, showing their bodies respond the same way to all the workouts.

When lifting weights at 30% or more of your maximum strength, your blood lactate levels and heart rate rise more than when lifting at 10% of your maximum, showing greater metabolic demand.

When men who already lift weights do lots of reps with lighter weights, their muscles produce more lactic acid buildup than when they lift heavy weights for fewer reps, both right away and after two months of training.

Doing a special kind of weight training that builds up lactic acid gives pro bodybuilders a bigger metabolic boost than regular weightlifting — their muscles show more stress signs like lactic acid and ammonia after just one workout.

Even though one method uses lighter weights with pauses and more reps, and the other uses heavier weights with fewer reps, both make the muscles equally tired in terms of lactic acid buildup.