Muscle Growth in Girls

Mother and daughter exercising together

Though strength training exercises are traditionally regarded as movements that bulk-up the male physique, muscle growth in girls is also a critical component to overall health. Girls' muscle growth is distinct from boys, and differences between the sexes in terms of musculature appear in early puberty. A successful strength training program for girls should consider the unique female growth pattern, as well as the gender-specific goals of the strength training program.

Muscle Growth and Development

Throughout childhood and adolescence, muscle mass increases along with other growth factors such as height and weight. The onset of puberty occurs anywhere from ages 9 to 14 in girls, and with it comes a rapid period of muscle growth. Muscles not only increase in size, but the individual muscle fibers also thicken, which generally leads to an increased strength capacity. Before muscles have had a chance to mature and increase their bulk, strength training exercises are minimally effective, at best, or even dangerous, at worst. Incorporating simple strength training exercises to increase or facilitate muscle growth is best delayed until cues of puberty indicate muscle fiber density has increased, typically not before age 9 in most girls.

Key Distinctions

Until puberty, the muscle development of boys and girls is nearly identical, but development through puberty and into adulthood is vastly different according to gender. Both boys and girls see an increase in the amount of body fat and muscle tissue, but boys see a more rapid and pronounced increase in muscular tissue than girls do. Boys also develop muscle tissue for a longer period of times than girls; girls see a decrease in the rate of muscle development around age 16, but boys continue to see rapid growth much later in adolescence. Muscle distribution is also different; boys tend to see a more dramatic broadening of the shoulder and back than girls do, and girls tend to develop more adipose tissue around their hips and stomachs. Knowing the difference in musculature between boys and girls is essential for developing a targeted routine tailored to girls.

Developing a Strength Program

The right type of strength training program is specifically suited to the current and target strength goals of the athlete. For adolescent girls or women just starting out with a strength training program, beginning with a low level of weight or resistance but a higher number of repetitions is a safe way to introduce strength training for muscle growth. Determine the appropriate level of weight or resistance by starting off with a low weight, like two to five pounds. If the athlete can easily perform more than 15 repetitions at that weight, add additional resistance. If the athlete cannot perform at least eight repetitions of the exercise at that weight, the resistance is too high. Once the athlete is advanced, a higher lever of weight and less than 15 repetitions can be introduced to add more muscle bulk.

Considerations for Training

Young women may not be interested in increasing muscle bulk so much as they may be in toning muscles. Instead of free weight exercises, consider strength training classes such as Pilates that focus on muscle toning as well as elongation, flexibility and balance. Limit a free weight workout to six to eight different exercises that each target a different muscle group. For example, a circuit might include 15 repetitions of pushups for back strength, squats for thigh strength and crunches for core strength, as well as five other exercises that target smaller muscle groups. Another option is to target one major muscle group each training day, allow a day of rest, and then target another muscle group. Resting is important for preventing injury.