You probably have a favorite group fitness class and a solid (if repetitive) workout routine. But guess what? Getting used to your workout—and your weight level—is a recipe for plateauing. After all, in order to get stronger, gain more endurance, and see those muscles really pop, you have to really challenge them. But how do you know when you’ve maxed out and are ready to move onto something bigger, better, and heavier? Here are four signs.
1. You Can Do 18 Reps
Get to the end of a set of 18 and feel A-Okay? It’s time to increase your weight, says Michele Olson, Ph.D., an adjunct professor of Sports Science at Huntingdon College in Montgomery, AL. “Research clearly shows that you need to exhaust the muscles by about 15 reps in order for them to become stronger.”
The right weight should fatigue your muscles in about 12 to 15 reps. And if you’re gassed by rep five? Shave off the amount of pounds hindering you from getting there.
Related: The Hard-Gainer’s Guide To Building Muscle
2. Your Body Weight Indicates You Should
“A general rule of thumb is to use upper body weights that are about 15 percent of your total body weight,” says Olson. So, if you weigh 140 pounds, that’s 21 pounds—or about a 10-pound weight in each hand, she notes. “This is still considered a moderately light weight, so you won’t bulk up, but you will burn calories and develop strength.”
As for your lower body? Consider a weight of about 20 percent your total body weight—that’s about 12-15 pounds for a 140-pound person who’s doing exercises like lunges or squats. If it doesn’t feel like a solid challenge, add more weight until it does.
3. You’re Spending Forever At The Gym
“Serious strength-training enthusiasts know that lifting heavy for five repetitions or less, while extremely challenging, is the quickest way to increase muscle strength,” says Pete McCall, C.S.C.S., a San Diego-based trainer.
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If you’re using a light weight for ‘toning,’ the only way to improve your muscle definition is to do as many reps as possible until the muscle fatigues, he adds. “That can take too long; using a heavier weight for fewer reps to fatigue is easier.”
4. You’re Never Sore
Can’t remember the last time you actually, truly felt that day-after burn? Might be time to up the ante. You don’t want to be so sore you can’t even walk, but sometimes, soreness is a sign that you’re improving and making real strides in your muscular fitness, says Olson. That’s important because the stronger you are, the less likely you are to get injured, fall, or lose lean body tissue, she says.
Related: Shop protein to give your muscles the strength and power they need.