When doing slow, gentle weight training for your whole body, your muscles get just as tired and produce the same chemical buildup as fast, hard training—even though you're not lifting as heavy. This...

A lighter workout style called LST can make your muscles produce as much lactic acid as a harder workout called HN, which might help build muscle size just as well, even though it's less intense.

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 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 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.

A certain type of weight training keeps your muscles working non-stop, making them use more oxygen and possibly grow bigger because of changes inside your body.