Facts by Age Groups


What’s Happening – Growth and Development

The preteen to teen years is a time of transition to puberty. However, chronological age is not a good indicator of the change to maturity. Not all children mature at the same rate. Growth patterns of boys and girls proceed differently. Typically, the growth spurt in girls occurs a year or two earlier than boys. The majority of girls start puberty between the ages of 10 to 12 and boys between 11 and 13 years.

Height accelerates at puberty fueled by the secretion of sex hormones. Growth of the trunk is more rapid than the long bones of the arms and legs. Long bone growth finishes once the growth plates at the end of the bones fuse while the spine may continue growing.

Although the growth rate in puberty is accelerated, the rate is not constant. Growth speed sharply increases and then falls. The peak height velocity occurs in girls at about age 11½ and the peak velocity of bone mass accumulation is about a year later. Your child is growing tall but his or her bone mass is not growing at a sufficient rate to fill in bone tissue.

Because the gain in bone mass lags behind that of height and bone size, bone strength is reduced. This mismatch results in transient bone fragility. As a consequence fractures particularly of the wrist and forearm are common in otherwise healthy youth. Also children with high body weight and obesity are at higher risk factors for fracture. Children who have experienced one fracture tend to have lower bone mass than their peers and be at risk of repeated fractures.

Bone Health Tips for Your Tweens

Prepuberty bone is more responsive to calcium, protein and exercise before the onset of puberty. Small increases in activity particularly high-impact exercises result in substantial gains in bone mass. While exercise is good for increasing bone mass, extreme forms of exercise may delay puberty and reduce height gain during the growth spurt.

Just as more calcium is needed for growth spurt, calcium intake plummets. According to a national survey, 85% of girls this age and 77% of boys do not take in enough calcium. The majority of preteens and teens are also low in vitamin D. Keep in mind that adequate vitamin D is essential for optimal calcium absorption.

Bone healthy measures for your tweens include:

1. Calcium

  • Recommended calcium intake increases to 1300 milligrams a day.
  • Four 8-ounce glasses of milk will cover the recommended amount.
  • If dairy is not the source of calcium, provide protein from other foods.

2. Vitamin D

  • Recommendations continue at 600 IU per day with no more than 4000 IU per day.
  • Diet may not supply sufficient vitamin D in the fall, winter, and spring; a supplement to diet may be needed.

3. Diet

  • Provide good nutrition that is a balanced diet of protein, vegetables, and fruits.
  • Limit soft drinks, juices, and fruit drinks.
  • Avoid stopping at fast foods for a quick meal.

4. Exercise

  • Encourage weight-bearing activities.
  • Add short periods of high-intensity exercise, such as jumping from boxes or jump rope, for 10 minutes 3 times per week.
  • Sign them up to participate in team sports.
  • Limit television, computer, and electronics time.

The increased bone mass acquired with early intensive activity persists into adult life. Bone mass is maintained in young adults even after training slows down or ceases completely. This is the critical time in forming the h3est bones possible.