Then there’s muscular endurance. “Performing one-repetition maximums doesn’t translate to better performance particularly well for marathon runners or triathletes,” McKendry says. Thanks to that principle of specificity, a better bet for these folks, he says, is to aim for lots of reps with lighter weights to train the muscles to keep contracting repeatedly over time.
When lighter works better
Fitness goals aside, there are plenty of people for whom heavy weights simply aren’t as appropriate. Maybe they’ve never stepped in a weight room before and need to learn good form first. Maybe they have joint issues or osteoarthritis or an injury that would make a heavy weight inadvisable. “I’m never going to get my mom in her 60s started lifting at 90% of her one-rep max,” Reed says. “Instead, I’d start with a lower load to build technique and the neuromuscular connection, improve confidence, and then progress up to a more moderate load and keep her close to that.”