How to Build Muscle at Age 15

Strength training with a balanced diet is best for teenagers.
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A skinny 15-year-old teen may want to put on lean muscle to look stronger, perform better at sports and prevent injury. To build muscle, teenagers must have gone through puberty — strength training before that can make them stronger but won't develop significant mass.



Strength training combined with a balanced diet can help teens maintain a healthy weight, improve overall fitness and start building lean mass. For best results, they should work out under the supervision of a personal trainer to learn proper form and avoid injuries.

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Benefits of Weight Training

Adults know that weight training offers numerous advantages to their health and physiques. The Cleveland Clinic explains that weight training and the subsequent muscle development may increase endurance, improve bone density, boost metabolism and balance blood sugar levels. It also promotes the development of lean body mass and muscle tone, leading to greater self-esteem.

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Weight training offers many of these same benefits to a skinny 15-year-old. Activities that build muscle can reduce fat levels and increase healthy lean tissue in teens. This more favorable body composition may help a teen burn calories at rest and maintain a normal weight.

Greater physical activity starting early in life, such as during adolescence, is a good way to achieve healthy bones and prevent osteoporosis later on, reports a review featured in the December 2016 issue of the Iranian Journal of Public Health. Efforts to build muscle certainly constitute physical activity.


Teens who work out with weights may reduce their risk of experiencing a sports injury, explains Stanford Children's Health. Weight training can also improve sports performance in a teen. By accruing more lean tissue, a teen may experience improved mental health and self-esteem, especially if they regularly say, "I'm skinny and I want to gain muscle."

A 15-year-old has likely passed through puberty and is able not only to build strength, but to develop muscle mass. This is because their hormones — specifically testosterone — have kicked in to support larger muscle size.


According to the British National Health Service, the average age for girls to begin puberty is 11, while boys' puberty usually comes a little later — on average, at age 12.

Of course, puberty onset and development are different for everyone, and it's normal for a child to experience puberty anywhere from age 8 to 14. Because the process can take up to four years, late bloomers may find it challenging to put on muscle at age 15.


Bodybuilding at Age 15

While weight training is a healthy activity for a 15-year-old, bodybuilding or powerlifting may not be appropriate. These, explains Stanford Children's Health, are competitive sports designed for adults.


Attempts to achieve a specific ideal or extremely muscle-bound look can be unhealthy for a teen too. A skinny 15-year-old understandably wants to fill out somewhat but should be aware of the perils of developing an obsession with looks. If a teen feels they aren't building muscle fast enough, they may fall into steroid usage, which can cause serious health effects.


If a 15-year-old wants to build muscle, it's also important to check with their doctor first. A thorough physical and sports exam ensures weight training is appropriate for their particular health needs and goals.

TeensHealth From Nemours emphasizes that 15-year-olds who are serious about putting on muscle should reach out to a certified strength-training coach or personal trainer. These professionals understand the specific hormonal, physiological and skeletal factors influencing teen weight training.


Teen Muscle Building Is Different

Teens need a specially designed program to match their individual training goals. Maybe a teen is looking to beef up or perhaps improve performance and stamina when playing a sport, such as football or volleyball. Every adolescent has a different starting weight, different abilities and different objectives.

Adult programs, says Stanford Children's Health, may be too strenuous and repetitive — putting an undue amount of wear-and-tear on developing joints.


When implementing a program for 15-year-old muscle building, the teen should be supervised. Program development and execution are particularly important because injuries are common, even in home gyms. If your teen reports feeling pain in the joints, it's a sign that the program is too aggressive, involving just too much weight or too many reps.

Read more: The Best Way to Gain Lean Muscle


Anyone just starting a weight-training program should do so gradually — and this is especially true for teens. Even though the goal is to build muscle, which usually means lifting weights, a 15-year-old needs to master proper form and techniques without any weight at first. Body-weight exercises, such as push-ups, squats and pull-ups, are a good place to start.

As explained by TeensHealth From Nemours, the best muscle-building programs for adolescents:

  • Include a five- to 10-minute warm-up and cool-down.
  • Focus on having the teen perform 8 to 12 repetitions of each exercise.
  • Leave rest days between muscle groups worked.
  • Emphasize proper technique.
  • Encourage just two or three sessions per week.

A smart ramp-up of intensity will help prevent injury and provide better long-term success.

Choosing Weight Types and Sizes

Always choose weights — whether that's free weights, barbells or bands — that are appropriate for the teen's size and capabilities. Some 15-year-olds don't fit into the gym machines designed for full-grown adults.

Before picking up any equipment, the teen should start with body weight only and then add weights once those exercises can easily be done for about 12 repetitions with good form. When weights are added, make sure your teen can safely complete 8 to 12 repetitions with a given load. Every teen is different, so there's no one-size-fits-all weight to use.

TeensHealth From Nemours notes that maximum lifts aren't appropriate for teens. Max lifts involve lifting a weight that's so heavy that a person can only complete one repetition.

If you're concerned that doing a higher number of reps with moderate weight will hold your teen back from gaining muscle as a 15-year-old, consider a small study published in August 2016 in PLOS One.


Forty-five teens of both sexes underwent either a high-load, low-repetition program or a moderate-load, high-repetition training program. Both groups who performed each routine two times a week for nine weeks experienced improvements in muscular fitness.

Read more: How Many Sets and Reps Build Big Muscles?

Another small study, which was published in the Scandinavian Journal of Medicine & Science in Sports in March 2015, showed that muscle failure is not critical for creating neural and structural changes in muscle tissue. This means a teen doesn't have to perform maximum lifts or reach muscular failure to make gains.

Muscle Building Is Fun

Any 15-year-old muscle-building plan should be fun and noncompetitive. If a workout routine feels forced or becomes a chore, commitment to the program wanes. Or if a teen starts to compete to "be the best" or "lift the most," injury becomes more likely, warns Stanford Children's Health.

A muscle-building routine should be something a teen looks forward to doing as part of a comprehensive wellness routine. Weight training and the goal to gain muscle shouldn't take the place of other physical activity that brings pleasure, joy and muscle balance. Weight training complements fun recreational activities, such as riding a bike, swimming or playing a casual game of touch football.

The Centers for Disease Control and Prevention recommends that adolescents participate in 60 minutes or more of moderate- or vigorous-intensity aerobic physical activity daily. Three times per week at least, teens should make it a point to do vigorous-intensity aerobic activity, such as running.

Three days a week, those 60 minutes should consist of muscle-strengthening and/or bone-strengthening exercise. Weight training to build muscle is in that muscle- and bone-strengthening category.


Nutrition for Muscle Building

Protein plays a big role in the body's ability to put on muscle, but only when combined with a smart training routine. As explained by the Academy of Nutrition and Dietetics, dietary protein helps repair the muscle cells that break down during weight training. When a person consumes adequate amounts of protein, the body can also build up more muscle in response to training.

A teen shouldn't just go out and binge on protein, however, in an effort to gain muscle mass. Yes, the right amount of protein is important, but overdosing on it only means it will be used for energy or stored in the form of fat. Protein isn't a super-efficient energy source, either — carbohydrates are superior.

Teenagers seeking to gain muscle need between 0.45 and 0.60 grams of protein for every pound of body weight. Even if your child weighs just 130 pounds, that's approximately 59 to 78 grams per day. Going above the recommended levels doesn't boost the ability to build mass. Examples of muscle-building, protein-filled foods include:

  • 4 oz chicken breast: 33 g protein.
  • 4 oz ground beef: 26 g protein.
  • 2 tbsp peanut butter or other nut butter: 7 to 8 g protein.
  • 1 c milk: 8 g protein.
  • 1/2 c tofu: 11 g protein.

When teens include these or other protein-rich foods at each meal, they can reach their protein requirements pretty readily.

When the goal is to build muscle, it can be tempting to use protein supplements. But getting all the needed protein for muscle gain is pretty easily achievable and preferable with whole foods.

Protein powders and drinks are highly processed and can lead to excessive consumption of protein, which may tax the kidneys and promote dehydration. Plus, these products can be contaminated with hormones, chemicals and heavy metals.

Read more: Your Ultimate Guide to Gaining Lean Muscle

Remember, teens also need to eat adequate calories to support their energy needs. Teens should aim for balanced nutrition in the form of carbohydrates and fat along with protein to get all the macro- and micronutrients needed to support optimal performance, continued growth and steady energy.