It's relatively taxing. You are still offering your muscles a lot of stimulation, but providing a substantial break before completing the second half.
Get developments in medicine, nutrition and fitness delivered to your inbox with our The Health Report newsletter. Sign up »
We have a difference of opinion on this question from two strength-training experts.
Breaking up the same exercise into two separate workouts isn't the best idea, says Justin Price, owner of the BioMechanics, a personal-training and wellness coaching facility in San Diego. The goal in weight lifting is putting enough stress on the muscles so that micro-tears appear. During a period of rest, the muscles repair themselves and, in the process, grow stronger.
"If you're tearing them down and they don't have a chance to recover," he says, "you're never going to get the gains you want." A few hours, he adds, isn't enough time for the muscles to repair.
A better idea, Price says, is to split sessions by muscle groups. For example, you could do bench presses, which incorporate triceps muscles, with your tri extensions, then pair similar exercises later on. Or, you could work larger muscle groups such as quadriceps in the morning, when you have more energy, and save smaller muscle groups, such as calves, for the afternoon.
Scott Lucett, director of education for the National Academy of Sports Medicine, has a different opinion. He thinks your muscles should still reap benefits if you separate your reps by a couple of hours.
A gap won't really matter in terms of repairing and rebuilding them: You just need to leave enough time after your last session for the muscles to repair, he says.
In fact, Lucett says, breaking up a single exercise might give you more energy when tackling it later on: "Maybe you'll be able to lift more later on in the day," he says. That could actually translate to better results.
The decision is ultimately yours — but why not become your own guinea pig? Work certain body parts — your left leg for example — using one method. Then work the right leg using the other method. See which one ends up stronger.
Of course, it's only a suggestion. We remain blameless if you end up looking lopsided.
— Jeannine Stein