Girls tend to outgrow boys in early adolescence, reaching their mature height at approximately 16 years old. But while girls have stopped growing in their mid- to late teens, boys keep growing until age 18 or beyond. Both genders continue to mature physically after reaching optimum height, attaining physical peak in their 20s or 30s.
The ability to perform physical work and to reproduce without difficulty generally peaks during the early 20s, according to Robert V. Kail and John C. Cavanaugh in “Human Development: A Life-Span View.” Although environment, lifestyle factors and genetics play a role in how fast your body declines, all men and women lose a degree of dexterity and coordination by the time they reach their late 30s. This loss of physical acuity leads to early retirement of athletes who compete in strenuous sports such as basketball, football and tennis.
Muscle and Bone Mass
Bones are in a constant state of building until men and women are in their early to mid-30s, according to the American College of Sports Medicine. Men maintain peak bone development longer than women, due to women’s decreasing estrogen levels at midlife, which causes women to lose bone mass more quickly. Peak muscle strength occurs earlier, before age 30, and continues throughout midlife, for approximately 20 years. After age 50, muscle strength declines at the rate of 5 percent per decade, according to ACSM. Weight-bearing exercises can help offset these losses when practiced at least twice a week for 45- to 60-minute sessions.
Your metabolic rate – the rate at which your body consumes calories – peaks in your mid-20s, coinciding with other peak factors, such as bone mass and muscle development. After the mid-20s, men’s and women’s metabolic rate declines at the rate of approximately 2 percent per decade, according to Gabriella Boston in “Basal Metabolic Rate Changes as You Age.” Slowing the rate of muscle mass loss through exercise and a well-balanced diet can keep your metabolism rate up and slow the rate of decline.
Heart and Lung Capacity
Heart and lung function peak at an early age, according to “Exercise Standards” by Fletcher et al. published in the journal “Circulation.” Muscles require oxygen to fuel exercise. VO2max, the measure of your body’s maximum ability to use oxygen during exercise, peaks between the ages of 15 and 30 years, with males peaking at a later age than females. During childhood, both boys and girls have similar VO2max, but as boys outgrow girls in height, they also increase in muscle mass, hemoglobin and blood volume, and heart stroke strength, according to these researchers.
- Human Development: A Life-Span View; Robert V. Kail and John C. Cavanaugh
- American College of Sports Medicine: Strength Training for Bone, Muscle and Hormones
- The Washington Post: Basal Metabolic Rate Changes as You Age
- Circulation: Exercise Standards
- USDA/ARS Children's Nutrition Research Center at Baylor College of Medicine
- Photo Credit Kraig Scarbinsky/Digital Vision/Getty Images