How long does it take to build muscle?

You probably understand how important it is to build muscle and maintain strength, especially as muscle mass declines with age. If you’re starting a strength training program, you may wonder how long you’ll have to wait to feel improvements in strength. The quick answer is, “it takes eight to 12 weeks to build muscle, but you’ll notice gains within the first week or two,” says Timothy Aceto, a physical therapist with Harvard-affiliated Spaulding Rehabilitation.

How does muscle growth happen?

For muscles to grow, they must be challenged with increasing amounts of resistance, which is an opposing force that muscles must strain against. “Resistance training can be done with dumbbells, kettlebells, elasticized resistance bands, specialized machines, or your own body weight,” says Aceto.

To get started, choose a weight or other resistance level that allows you to complete three to four sets of eight to 12 repetitions of an exercise and feel that it’s relatively easy. “Then increase the weight so you feel like you’re one or two repetitions away from not being able to complete one more repetition,” says Aceto. “When you feel like you’re almost at your maximum, that’s a good weight that will build muscle.”

Once this becomes easy, it’s time to add more resistance. For example, if you’re using a five-pound dumbbell, try using a 10-pound dumbbell. You may need to adjust the repetitions. “If you can’t complete 12 repetitions, go down to eight,” says Aceto.

If you feel like you can’t safely add weight, then add repetitions. “Do an extra set or add extra repetitions to each set,” says Aceto.

To get a full-body workout, focus on the main muscle groups: chest, back, arms, shoulders, and legs. To save time, do exercises that engage multiple muscles at once. For example, squats work the quadriceps and hamstrings in your thighs and the gluteals in your buttocks. “You’re not focusing on your calves, but you’re also working the calf muscle,” says Aceto (see “How to make your squat more challenging”).

How to build muscle safely and consistently

Don’t be in hurry. You want to build muscle, but you also don’t want to damage the muscles you’re hoping to strengthen. “Some people start off lifting the heaviest weights possible too frequently, and they burn out,” says Aceto.

Start safely by fitting in two to three 20- to 30-minute workouts a week. Your muscles require time to rest and recover between exercise sessions. On recovery days, continue your aerobic activities such as walking, swimming, or bicycling.

If you do this consistently, you’ll get results. Over the first few weeks, you’ll notice that it becomes easier to lift heavier weights. But you haven’t built new muscles. Your nervous system has gotten better at recruiting the muscles you already have. Actual muscle growth usually takes about two to three months of consistent training.

People with certain health problems (such as arthritis or back pain) may be more prone to injury when starting a muscle-building exercise program. If you have any concerns about whether you can exercise safely, talk to your doctor before you begin and consider working with a physical therapist or experienced personal trainer.

The role of diet in building muscle

How fast you build and maintain muscle also depends on your diet. “You need to consume the right caloric building blocks for the body to build muscle,” says Aceto. This means consuming more calories than you burn and getting sufficient protein.

“Aim for about 0.8 grams per pound of body weight per day,” says Aceto.

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