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Adulthood: Physical Development
Young Adulthood (20 to 40 years)
Young adulthood covers roughly the age between 20 to 40 years. Young adults are at the peak of their physical, sexual, and perceptual functioning. Maximum muscle strength is reached at age 25 to 30, while vision, hearing, reaction time, and coordination are at peak levels in the early to mid-twenties. While many physical capacities decline in the mid-thirties, the changes are not noticeable until years later.
Middle Adulthood (40 to 60 years)
Physical status typically declines at midlife. Visual acuity often decreases, and muscles become stiffer and weaker. After age 40, basal metabolic rate, the rate at which the resting body converts food into energy, slows and produces a tendency to gain weight. The efficiency of oxygen consumption decreases and it is harder for middle-aged adults to maintain the physical endurance they need for sustained exercise. At around age 50, womenâs ovaries stop producing estrogen, and women experience menopause, the end of menstruation. Men remain fertile, but this gradually declines in middle age.
Middle-aged adults are still in excellent health and are very active. Growing experience in job and recreational skills can offset many age-related declines.
Late Adulthood (60 years and older)
The physical changes of middle adulthood become more pronounced in late adulthood. With young adults, about 80% of their body consists of lean body mass (muscles, organs, and bone), while 20% consists of fatty tissue. By age 70, the balance between lean and fat body mass may be 50-50. Bones lose calcium and become brittle and slower to heal, while hardened ligaments make movements stiffer and slower. By age 90, the brain of a healthy adult has lost 5 to 10 percent of its early adult weight, due to a normal loss of neurons that occurs as we grow older. However, with good nutrition, regular exercise, and a good attitude â barring major disease â many adults maintain physical vigor and an active lifestyle well into old age.