Jim Minton, my youth ministry professor in seminary, used to say, "More physical changes take place in adolescence than at any other time in the life of a human, except in the first 18 months." The physical changes are the most widely acknowledged indicators of the transition from childhood to adulthood.

The more I observe adolescents, the more I agree with Dr. Minton. Although infants lack the self-awareness to reflect on their metamorphosis, adolescents are able to ponder their predicament with great anxiety (Stevens 1985, 53). Rapid development is taking place in almost every arena of the body. Skeletal growth is dramatic (just ask any jeans-buying mom). The respiratory and cardiovascular systems get caught up in the growth spurt, with dramatic increases in the heart and lungs. Recent research has shown that even the brain is still developing in adolescence. Skin is changing, body proportions are changing—and needless to say, minds are changing. It's safe to say that adolescents change their mind almost as often as adolescent girls change clothes (just kidding). For an overview of the physical changes that take place during early, middle, and late adolescence, see the Introduction.

Much of the change is because the hormones in the body which have to do with sexual maturation have reported for duty. Hormones are highly specialized substances secreted by one or more glands of the endocrine system. Glands are organs that stimulate parts of the body to respond in specific ways. It is probably more accurate to say that the brain inhibits puberty before adolescence than it is to say that it stimulates puberty at adolescence. The hormones kick in, causing massive growth spurts and the initiation of the sex drive, which causes all kinds of physical (and emotional) changes. A student's weight will fluctuate, and girls are especially conscious of this change. The rapid physical development may also bring on a kind of clumsy movement or overall awkwardness (Boshers 1997, 84).

An interesting sidebar to the discussion of puberty is the phenomenon known as the secular trend. The secular trend is the downward shift in age of puberty that has been occurring over the past hundred years or so, with the greatest changes taking place between the mid 1800s and the mid 1900s (Cobb 1998, 104). It represents a change in timing and effect of puberty, with the following noticeable traits:

• Puberty begins earlier—has been occurring earlier by 3 to 4 months per decade since the mid 1800s. In the mid 1800s, the average age for menarche was 15.5-16.5. Now the average age in the U.S. is 12.5.
  
  
• Adolescents grow faster (data from 19th century and earlier is slim). In 19th-century Britain, females reached adult height at about 21. Adolescent girls today stop growing by about 16-18. British males continued growing into their mid-twenties. Adolescent boys today reach adult height by 20-21.
  
  
• People grow larger. Males average an inch and 10 pounds heavier than their fathers. Females grow 1/2 inch to an inch more than their mothers and weigh about 2 pounds more on average
  
  
• Historical tidbits—The decks of the flagship of the United States navy, the USS Constitution (war of 1812) were only 5 feet 6 inches tall. Antique armor and clothing are likewise much smaller in scale. I like this one best: The seats at the La Scala opera house in Milan, Italy (circa 1776) are 13 inches wide. The average seat at a stadium in the United States today is 24 inches.

Puberty, as stated earlier, is that implosion of mischievous hormones which alters the human body with a pace second only to the first 18 months of life. Physically, several things are happening that may stimulate development in other areas, such as the emotional, cognitive and social. The endocrine system begins escalating its production, circulation, and regulation of the level of hormones in the body. Puberty is the term generally used to describe the beginning of the endocrine activity. See the discussion on the growth spurt that follows for more detail.

There is a gap between the onset of puberty for boys and girls. Roughly defined, puberty is the distinct event marked by the achievement of reproductive maturity, the completion of sexual development, when females can bear a child and males can impregnate a female. The beginning of menstruation signals puberty for females (menarche). Girls reach puberty on an average of two years before boys. The range for the onset of puberty for girls is 10-13 years of age as a norm, with extremes being from 9 to 18 (Rice 1999, 97). Some breast development usually precedes the first menstrual cycle which is generally accepted as the signal that puberty has begun.

Generally, the ejaculation of mobile sperm signals puberty for males (spermarche). For boys, the average age is 12-14, though the extreme range could be 10-16 years. The beginning of puberty in males is much harder to pinpoint; however, many writers use the initial growth of the testes and scrotum or the first nocturnal emission (wet dream).

For youth ministers the gender maturity gap has social implications. Boys do not "catch up" with girls in terms of physical maturity until about age 16. For cultural as well as physiological reasons, adolescent girls seem to be far ahead of their male peers in emotional maturity. They tend to be more expressive in their feelings and more responsive to the needs of others. The growth spurt, the change of body shape, the appearance of secondary sexual characteristics, and the development of the reproductive system (all of which are running slightly ahead in females) all demand great emotional resources and the ability to adjust. Whether the changes are sudden or drawn out over many years, the effects are deeply felt (Stevens 1985, 5).

Besides the two year "gender gap," another consideration for youth workers is the "early-on time-later maturing" phenomenon. Though it has been said, many times, many ways (sorry), in adolescent development, a principle worth repeating and remembering is, timing of development may vary, but sequence is relatively unchanging. Some teenagers mature early in the expected chronological range, while others are "on time" or late. When you combine the gender gap with maturity gaps, the potential ministry opportunities become apparent. Here are some bullet points you may use as discussion starters with either youth or parents.

Early Maturing Boys (Advantages)

• Appear more adult—adults sometimes give preference in opportunities for leadership
• More attractive to peers and adults
• More popular
• Achieve more recognition

Early Maturing Boys (Disadvantages)

• May feel pressure to commit to life goals and choices prematurely
• Sometimes adults place unrealistic expectations, especially regarding athletics
• Tend to be somber, less spontaneous, more submissive, and less flexible
• Occasionally awkward with their size

Early Maturing Girls (Advantages)

• More popular with girls and boys
• Enjoy prestige once they are comfortable with body changes
• Eventually develop more social competence (deal with more situations earlier)
• Develop more self-confidence

Early Maturing Girls (Disadvantages)

• More likely to get "hit on" by older boys or men
• May be introverted and experience more emotional conflict as a young adult
• Are more likely to smoke, drink, be depressed, have an eating disorder, and request earlier independence from parents (Santrock 1998, 96)

Late Maturing Boys (Advantages)

• Have more opportunity to explore roles
• Continue to focus on development of "other than physical" abilities
• Have more stable identity in young adulthood
• Less pressure to live up to expectations of others

Late Maturing Boys (Disadvantages)

• Might have lasting impressions of ridicule
• Social skills may not come naturally
• More pronounced difference in prestige among working class
• May feel "invisible"

Late Maturing Girls (Advantages)

• Prepubescent body is more likely to be tall and thin, the "American fashion ideal"
• Possible advantage in early teen years
• More likely to receive adequate information on menarche from parents and peers
• Less likely to be self-conscious about their bodies

Late Maturing Girls (Disadvantages)

• May try to compensate for physical immaturity through promiscuity
• Sometimes slower to develop social competency and confidence
• Parents may be slow to recognize them as "emerging adults"

Be careful not to make more of the timing of maturity than is necessary. Because parents can be obsessive about making sure that their adolescent is "normal," the preceding chart may provide a resource for advising parents concerning their teenager.

Other factors can affect the rate at which growth begins or proceeds—diet, exercise, psychological stress, and even altitude. Females who are under stress generally begin to menstruate earlier while athletes usually begin later. It is believed that body fat percentage is the trigger for the menstrual cycle. Some researchers have discovered that menarche cannot start until the body weight is about 105 pounds or until body fat is about 17 percent; this has implications for runners and anorexics.

The growth spurt takes place somewhere near the beginning of puberty. Easily recognizable but hardly predictable, the dramatic changes in stature and body dimension sneak up on parents and youth workers. At the onset of puberty the person still looks much like a child. By the end, just six or seven years later, that same person looks much like an adult. Boys can grow an average of about 4.1 inches a year, while girls average about 3.5 (Steinberg 1996, 24ff). Beginning at about 11 for girls and 13 for boys, a summary of the events of the growth spurt is as follows:

• Lengthening of trunk; legs are already adult length
• Lungs double in capacity
• Heart doubles in size
• Increase in muscle to fat ratio

During the growth spurt, males develop larger heart and lungs, higher systolic blood pressure, thicker muscles, and more red blood cells as compared to their female counterparts. These differences may increase activity level in males and decrease that of females during adolescence (Cobb 1998, 95).

When the feedback loop is fully active, the visible changes which differentiate men from women begin to appear. The emergence of the characteristics which indicate that boys are becoming men and girls are becoming women is called sexual dimorphism. The best way to explain the concept of sexual dimorphism is that it is the fork in the road between childhood and adulthood. Prior to the growth spurt, preteens are somewhat asexual; the differences between the external physical appearance of boys and girls are relatively few. The visible gender differences that accompany the growth spurt are the result of the emergence of secondary sex characteristics, primarily initiated by the endocrine system. The primary sex characteristics are the differences in the reproductive system itself (ovaries and testes). The secondary sex characteristics and the approximate age of emergence are listed in the table below.

Secondary Sex Characteristics (and Related Occurrences)

Male

11.5-13

• Height spurt begins
• Beginning growth of reproductive organs, some pubic hair
• Eruption of second molars

13-16

• Growth of pubic hair
• Growth of hair under arms
• Facial hair

15-17

• Heavy growth hair on body
• Considerable growth of larynx
• Change of voice by octave
• Considerable thickening of muscles
• Widening of shoulders        
• Increase in perspiration                              
• Oil- and sweat-producing glands, acne

8-13

• Growth of breasts
• Growth of pubic hair
• Rapid height growth
• Eruption of second molars

10-16

• Menarche
• Growth of hair underarms
• Light growth of hair face
• Light growth hair on body
• Slight growth of larynx
• Moderate lowering of voice
• Slight thickening of muscles
• Widening of hips
• Increase in perspiration
• Oil- and sweat-producing glands, acne

In addition to the visible signs of emerging adulthood, other systems are at work as well. The circulatory system is growing, with the weight of the heart nearly doubling. Arteries don't grow nearly as much as the heart, as the arteries were more closely the size of an adult (which is why blood pressure for children is low). The respiratory system is growing also. Lungs grow rapidly during adolescence, coming close to doubling in capacity. Testosterone (an androgen) gives greater muscular structure, which is partly responsible for girls being bypassed by boys athletically; estrogen encourages fat production. Also, the lungs in females do not develop as fast or end up as large due to the smaller size of the rib cage.

It is no surprise to any grocery-buying parent that the digestive system is now raging out of control. The stomach grows, the appetite increases, and metabolism (the body's ability to process food) is at an all-time high. Metabolic rate peaks at around age 20. There are implications here for the benefits of proper exercise and nutrition. The proper amount of exercise for adolescents:

• Builds physical fitness
• Helps with weight control
• Promotes psychological and mental health
• Improves intellectual performance

Five common nutrition deficiencies in adolescents are:

• Insufficient calcium
• Insufficient iron
• Insufficient protein
• Insufficient vitamins (esp. A & C)
• Insufficient thiamin and riboflavin

As adulthood looms for the adolescent and poor exercise and nutrition catch up, the body mass gets more difficult to change when the rapid metabolism of adolescence shuts off!

The nervous system is also becoming more refined. The discussion of the brain will be taken up in the section on cognitive development, but new research is interesting. Remember that physical development is controlled by the central nervous system and regulated by the endocrine system. The hypothalamus gland could be considered to be a nervous system agent as it keeps the endocrine system in check. Otherwise the central nervous system has little growth in adolescence. Nerve endings may become more refined, but relatively no new growth.

Before this article becomes an amateur biology lesson, let's move our focus to the ministry application of all the information you have just read. Aleshire said, "Fortunately, youth do not need to know about these hormones for them to be effective, nor do youth leaders need to be able to pronounce their names in order to be competent guides and helpers for youth!" (Aleshire 1982, 39). Youth workers and parents need to keep in mind that the physical changes are the centerpiece of the adolescent experience and ministry opportunities abound.

Maybe a little information about sweat glands and an introduction to a can of deodorant would help the confidence and social skills of an eighth-grade boy. Perhaps an understanding of the incessant need of an adolescent to have a body image that is acceptable to peers will help youth ministers as they consider biblical topics to discuss. Body characteristics considered as important are the media-driven images of what is beautiful or handsome. It could even be that the youth ministry would help remind parents that adequate information about the changes taking place can make all the difference in the world to a teenager. The adolescent who faces the violent changes of puberty armed with information as to what is about to happen with his or her body is much more likely to transition smoothly to adulthood (Rice 1999, 102).

As a part of ministry to parents, it may prove helpful to stress that timing may vary, but sequence of development is reasonably constant. Parents may be grateful for resources and information as to how to help their teenager navigate the rapid physical changes that are inevitable with the onset of puberty. An awareness of the tremendous emotional swings that can result from the influx of hormones could also be beneficial in ministry. Finally, I quote Dr. Aleshire whose words in 1982 are still appropriate:

Physical changes make some youth feel unlovable. . . . [They] make the world seem less predictable and dependable than it once was. The call to faith, the love of Christ, and the integrity of scriptural truth are predictable and dependable. Youth need to be encouraged to continue to believe these long-term truths in the midst of constantly changing short-term feelings. . . . Youth leaders can help youth with each of these feelings, and acquaint them with the resources of the Christian faith for dealing with human fears, anxieties, and frustrations (Aleshire 1982, 43).

YQ: Consider your teenagers and their physical development. Which ones are early maturing? Which ones are late maturing? Are any of your teenagers experiencing problems with their self-image related to their maturing bodies? Identify ways parents and teachers can partner to help teenagers physically mature to adulthood.