C H A P T E R 16

1. C H A P T E R 16 CHILDREN AND ADOLESCENTS IN SPORT AND EXERCISE

2. Maturation—process of taking on the adult form and function – measured or expressed in different ways: w Chronological age w Skeletal age w Stage of sexual maturation Terminology Growth—an increase in the size of the body or its parts Development—the functional changes that occur with growth

3. Phases of Growth and Development Infancy—first year of life Childhood—age 1 to puberty Puberty—development of secondary sex characteristics and capability of sexual reproduction; usually 8-12 years old Adolescence—puberty to completion of growth and development

4. RATE OF INCREASE IN HEIGHT AND WEIGHT

5. Bone Ossification: Transformation from Cartilage to Bone

6. Bone Growth w Is complete when cartilage cells stop growing and epiphyseal plates are replaced by bone (by early 20s; varies from pre-teens to mid-20s; 2-3 yrs earlier in girls) w Requires rich blood supply to deliver essential nutrients w Requires calcium to build and maintain strength; vitamin D promotes calcium absorption from the small intestine during digestion w Growth slows when blood calcium levels are too low; can lead later in life to osteoporosis w Is helped by gravity-resisting exercise, which loads the bone, affecting bone width, density, and strength (remember the problems with astronauts)

7. Fractures of the epiphyseal plate w Disrupts the blood supply w Disrupts growth, which can lead to limb length discrepancies Traumatic epiphysitis wInflammation of epiphyseal plate from overuse (pitchers) w Can lead to separation of epiphysis w If caught early it can be treated without permanent damage Bone Injuries and Growth

8. Muscle Growth wGrowth in diameter results primarily from hypertrophy of existing fibers due to increase in myofilaments and myofibrils caused by loading of the muscles wMuscle length increases with bone growth due to increase in the number of sarcomeres in series w Boys’ muscle mass peaks at about 50% of body weight at 18 to 25 years w Girls’ muscle mass peaks at about 40% of body weight at 16 to 20 years

9. Growth and Fat Storage w Fat (triglycerides) is stored starting at birth w Fat is stored by increasing the size and number of fat cells, but cells can only increase to a certain maximum volume and then new cells are formed w Fat storage depends on diet, exercise habits, and heredity w At maturity, fat content averages about 15% in males and about 25% in females

10. Skinfold Thickness: an Estimate of Fatness

11. CHANGES IN FAT AND FAT-FREE MASS

12. Key Points Tissue Growth and Development w Girls mature physiologically about 2 years earlier than boys w Balance, agility, and coordination improve as children’s nervous systems develop. wMyelination of neurons in the cerebral cortex—which speeds the transmission of impulses in those neurons—is necessary before fast reactions and skills are fully developed. This is usually not completed until during adolescence.

13. Physiological Responses to Exercise w Strength increases wGains in strength with growth also depend on neural maturation because neuromuscular control is limited until myelination is complete, usually around sexual maturity. w Blood volume, heart size (stroke volume), and blood pressure increase w Heart rate decreases w Aerobic and anaerobic capacities and running economy increase w Lung volume and peak flow increase

14. STRENGTH GAINS WITH AGE These data are for boys only.

15. Composite Strength Changes with Development PHV = peak height velocity

16. Blood pressure w Lower in children but progressively increases to adult levels in later teens w Larger body size results in higher blood pressure Cardiovascular function at a given oxygen uptake w Smaller heart size and total blood volume of children result in a lower stroke volume w Heart rate response is higher to compensate for the lower SV w Lower cardiac output than adults w Therefore, a higher a-vO2 diff than adults Submaximal Exercise and Growth

17. HR and SV as a Function of Oxygen Uptake

18. . Q and a-vO2 as a Function of Oxygen Uptake

19. . w Maximal stroke volume and Qmax are lower in children than in adults. Key Points Maximal Exercise and Growth w HRmax is higher in children but decreases linearly with age. w Lower oxygen delivery capacity (blood volume and pump capacity) limits performance at high absolute rates of work.

20. . w VEmax increases with age until physical maturity at which point it begins to decrease with age. Key Points Lung Function and Growth w As body size increases, lung size and lung function increase. w Lung volumes and peak flow rates increase until growth is complete. w Boys' absolute lung volumes and peak flow rate values are higher than girls' absolute values due to girls’ smaller body size.

21. . w VO2max (L/min) peaks around age 17 to 21 in males and then decreases linearly with age. . w VO2max (L/min) has been shown to peak around age 12 to 15 in females, though the decrease after age 15 may be due to females tending to reduce physical activity. . w Absolute VO2max (L/min) is lower in children than adults at similar training levels. . w When VO2max is expressed relative to body weight, there is little difference in aerobic capacity between adults and children, thus, additional muscle mass increases maximal oxygen consumption. Aerobic Capacity in Children w Relative to body weight, running economy is lower inchildren compared to adults.

22. . CHANGES IN VO2MAX WITH AGE Absolute (i.e., l/min) Relative to body weight (i.e., ml/kg/min)

23. Anaerobic Capacity in Children w Ability to perform anaerobic activities is lower than in adults w Glycolytic capacity (i.e., glycolytic enzyme levels) is lower w Produce less lactate and cannot attain as high RER values during maximal exercise as adults • Anaerobic mean and peak power outputs are lower than in adults, even when scaled for body mass

24. Resistance Training in Preadolescents w May protect against injury and help build bones w Improves motor skill coordination w Increases strength largely through increased neural activation of motor units w Causes little change in muscle size (i.e., little hypertrophy) and is considered safe if not overdone

25. w Aerobic training improves cardiorespiratory endurance performance in children, but the changes in VO2max are less than expected. . (continued) Key Points Training the Young Athlete w Training programs for children should be conservative to reduce the risk of injury, overtraining, and loss of interest in the sport. w An appropriate resistance training program is relatively safe for children.

26. Key Points Training the Young Athlete w Anaerobic capacity increases with anaerobic training. w Regular training typically results in decreased total body fat, increased fat-free mass, and increased total body mass. w Generally, training does not appear to significantly alter growth and maturation rates.

27. Changes in Motor Ability with Age

28. C H A P T E R 17 AGING IN SPORT AND EXERCISE

29. “Of Mice and Men” – Voluntary Wheel Running in Rats One of the most difficult things to determine is whether physiological deterioration with age is due to aging per se or to the dramatic decrease in daily activity levels. It is undoubtedly a combination of the two.

30. Relative body fat increases after maturity due to w Increased dietary intake of calories and/or w Decreased physical activity w Reduced ability to mobilize fat After age 30, fat-free mass decreases due to w Decreased muscle mass (decreasing testosterone levels) w Increased bone mineral loss w Decreased physical activity Body Composition and Aging: A Double Whammy

31. CHANGES IN BODY HEIGHT AND WEIGHT

32. Body Composition and Training One of the important things about physical training as one ages is that it can help offset age-related loss of fat-free mass and gains in fat mass, i.e., the double whammy.

33. Strength Changes With Aging w Maximal strength decreases w Muscle mass decreases w Percentage of ST muscle fibers increases because of death of fast twitch alpha-motoneurons followed by reinnervation of the denervated fast muscle fibers by slow motoneurons, which converts the muscle fibers to ST w Total number and size of muscle fibers decreases w Nervous system response slows w Little change in oxidative enzyme capacity or number of capillaries

34. CHANGES IN STRENGTH WITH AGING

35. Effects of Training on Strength While endurance training does not prevent the aging loss in muscle mass, resistance training can maintain or increase the muscle fiber cross-sectional area in older men and women.

36. Computed Tomography Scans of Arms of Three 57-Year-Old Men of Similar Body Weights Biceps Brachii M. Humerus Triceps Brachii M. Untrained Swim-Trained Strength-Trained

37. MUSCLE FIBER CHANGES WITH AGING

38. w Muscle blood flow decreases are offset in trained individuals by an increased submaximal a-vO2 difference – Cardiovascular Function and Aging w Aerobic capacity decreases about 1% per year after age 25 w Maximum heart rate decreases about 1 beat per year w Maximum stroke volume decreases, though it can be well maintained with training w Maximum cardiac output decreases

39. . w Qmax decreases due to decreased HRmax and SVmax. . w VO2max decreases due to reduced blood flow to active tissues because of reduced Qmax. . Key Points Cardiovascular Changes With Aging w HRmax decreases due to decreased sympathetic nervous system activity and changes in cardiac conduction. w SVmax decreases primarily due to increased total peripheral resistance (increased afterload).

40. . w VEmax decreases after maturity Respiratory Changes With Aging w Vital capacity (VC) and forced expiratory volume in 1 s (FEV1.0) decrease linearly with age w Residual volume (RV) increases w Total lung capacity (TLC) remains unchanged w RV:TLC increases (less air can be exchanged) w Elasticity in lung tissue and chest walls decreases, which is the primary mechanism for the above listed changes; there may also be a decreased function of the respiratory muscles

41. w Limitations in oxygen transport to the muscles (i.e., muscle blood flow)and a decreased a-vO2 difference are the main causes for reduced VO2max. – . Key Points Respiratory Aging and Performance w Endurance training in middle and older age reduces the loss of elasticity from the lungs. w The pulmonary ventilation capabilities of endurance-trained athletes are only slightly decreased with aging. w Arterial oxygen saturation does not decrease during strenuous exercise for normally active older adults.

42. . w Aging alone may not necessarily decrease VO2max; decreased daily activity levels also contribute. w When you keep intensity and volume of training high, your rate of decrease in SV and VO2max with aging slows, especially between ages 30 and 50 and less so after age 50. . Studies of Older Athletes w There are individual differences in the rate of decline with aging. w Prior training offers little advantage to endurance capacity later in life unless you stay active.

43. . CHANGES IN VO2MAX WITH AGE

44. Aging alone might decrease cardiorespiratory fitness less than the deconditioning that occurs with inactivity, decreased activity, or decreased intensity of training. If body composition and physical activity are kept constant, VO2max decreases only 2% to 5% per decade, rather than the 10% per decade normally attributed to aging. . Aging versus Inactivity

45. C H A P T E R 18 SEX DIFFERENCES IN SPORT AND EXERCISE

46. Biological versus Social Differences Performance differences between men and women likely result from biological differences as well as social and cultural restrictions placed on females during their development and the fact that, historically, fewer women have competed in athletic events than men.

47. Body Size and Composition w Major differences between boys and girls do not occur until puberty w Puberty in girls—estrogen causes pelvis broadening, breast development, fat deposition in hips and thighs, increased bone growth, and faster closure of growth plates w Puberty in boys—testosterone causes increased bone formation and muscle mass w After puberty, girls’ average relative body fat is about 10% greater than boys w Men not only have a greater muscle mass, but they carry a higher percentage of their muscle mass in the upper body compared to women

48. SEX DIFFERENCES IN FAT-FREE MASS

49. Effects of Estrogen on Fat Storage 1. Estrogen increases activity of lipoprotein lipase (LPL—produced by fat cells), particularly in the hips and thighs. 2. LPL is bound to walls of capillaries. 3. Chylomicrons—major transporters of triglycerides—pass by in the blood. 4. LPL removes FFA from triglycerides in chylomicrons and they are taken up by fat cells where most of the fat is stored. 5. There is a decrease in lipolytic activity in the sites of fat storage in the hip and thigh areas making it difficult to lose fat in these areas.

50. Strength Differences—Women and Men w Innate qualities of muscle and motor control are similar w For the same amount of muscle, strength is similar w Muscle fiber cross-sectional areas are smaller and muscle mass is less in women w More muscle mass is proportionately distributed below the waist in women w Upper-body strength expressed relative to body weight or fat-free mass is less in women