Relationship of Anaerobic Power to

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Pediatric Exercise Science, 1993,

5,

106-1 1 5

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1993 Human Kinetics Publishers, lnc.

Relationship of Anaerobic Power to Anthropometric Measures

The development of anaerobic power during the growing years has been evaluated principally with the Wingate test. An alternative methodology, the force-velocity test, has not been used in studies of growth of anaerobic function in children, but it has the advantage of employing incremental braking forces. Mercier et al. used the force-velocity test to assess the effects of age in relation to anthropometric measures upon maximal anaerobic power of the legs in 69 boys, ages 11-19 years. Four skinfold thickness measurements were used to estimate lean body mass, and leg volume and total muscular mass were determined by anthropometric methods. Maximal anaerobic power increased significantly between the ages of

11 and 19 years and was most highly correlated with lean body mass (r=.94).

Leg volume and total muscle mass were also closely associated with maximal anaerobic power

( r

=

.84 and .88, respectively). Maximal anaerobic power normal- ized for lean body mass rose significantly between ages 11 and 19 years. These results indicate that anaerobic function during growth is closely associated with changes in anthropometric characteristics, particularly lean body mass. In addi- tion, the observation that maximal anaerobic power increases with age when corrected for lean body mass suggests that factors other than muscle mass are responsibIe for the development of anaerobic function during the childhood years.

Mercier, B., J. Mercier, P. Granier, D. LeGallais, and C. Prefaut. Maximal anaerobic power: Relationship to anthropometric characteristics during growth.

Int. J. Sports Med.

13:21-26, 1992.

Influence of Pulmonary Regurgitation on Exercise Capacity

After Tetralogy of Fallot Repair

Diminished chronotropic response and decreased maximal oxygen uptake have been observed in patients following intracardiac repair of tetralogy of Fallot.

Residual pulmonary regurgitation has been suggested as a possible mechanism contributing to these findings. Carvalho et al. investigated the relationship be- tween pulmonary insufficiency (by analysis of right ventricular pressure-volume loops) and exercise capacity in 12 patients after tetralogy repair. Average age at surgery was 2.7 years, with mean follow-up of 8.7 years. Standard measurements of gas exchange parameters were made during exercise with a Bruce treadmill protocol. Pulmonary regurgitant fraction was estimated from pressure-volume loops constructed from angiographic right ventricular volumes and simultaneous micromanometer pressure tracings. Exercise data were compared with those of

12 healthy matched controls. Mean maximal heart rate was

180 bpm for the cardiac patients and 197 bpm in the controls. Average maximal oxygen uptake was 48 and 52 ml kg-' min-I, respectively. A significant negative correlation was observed between amount of pulmonary regurgitation and both total duration of

Research Digest

- exercise (r=-.43) and maximal heart rate (r=-.46). No relationship was observed between regurgitant fraction and either V0,max or ventilatory anaerobic thresh- old. These data indicate that residual pulmonary regurgitation is an important factor contributing to impaired exercise capacity following surgical repair of tetralogy of Fallot.

Carvalho, J.S., E.A. Shinebourne, C. Busst, M.L. Rigby, and A.N. Redington.

Exercise capacity after complete repair of tetralogy of Fallot: Deleterious effects of residual pulmonary regurgitation.

Br. Heart

J.

67:470-473, 1992.

Effects of Physical Activity and Training on Stress

Research in adults suggests that physical activity may ameliorate the psychologi- cal impact of stressful life events, but little information is available on exercise- psychological outcomes in adolescents. In a self-report questionnaire study of

147 adolescents, Norris et al. demonstrated that those reporting higher levels of regular physical activity had lower levels of stress and depression. In a second investigation, these authors examined the effects of exercise training on psycho- logical factors in

60 teenagers. Subjects were divided into high and moderate intensity aerobic training, flexibility training, and control groups. Training was conducted for 10 weeks, twice weekly for 25 to 30 minutes. Aerobic fitness levels, heart rate, blood pressure, and self-reports of stress and well-being were measured before and after the training period. The adolescents who underwent high intensity training reported significantly lower stress levels after training than did the remaining groups, and in these subjects the relationship between stress and exercise and exercise training can promote psychological well-being in adoles- cents by reducing stress, but training is likely to be effective only if the exercise program is of sufficient intensity.

Norris, R., D. Carroll, and R. Cochrane. The effects of physical activity and exercise training on psychological stress and well-being in an adolescent popula- tion. J.

Psychosom. Res.

36:55-65, 1992.

Substrate Utilization During Exercise in Girls and Women

Children characteristically demonstrate poorer running economy (higher weight- relative oxygen uptake at a given work rate) than adults. The observation in some studies that children have a lower respiratory exchange ratio (RER) during exercise than adults has prompted the suggestion that variations in substrate utilization may contribute to maturity related differences in running economy.

Martinez and Haymes compared markers of substrate utilization during moderate- intensity treadmill running in 10 prepubertal girls and 10 young women (mean ages 9.1 and 24.4 years, respectively). Oxygen uptake and respiratory exchange ratio (RER) were measured during 30-min runs at the same relative (70%

V0,max) and absolute (7.2 km h-') intensities. Blood samples for glucose, lactate, free fatty acids, and glycerol were obtained before and immediately after exercise.

RER

was significantly lower in the girls at the same work intensity, and RER

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Research Digest

- athletics or swimming, and 8 untrained boys ran to exhaustion on a progressive treadmill protocol. Blood samples for lactate and ammonia were drawn just before exercise and 3 minutes afterward. Plasma ammonia increased with exercise in all subjects, but the rise was smaller than that previously reported in adults.

Postexercise ammonia correlated with blood lactate (r=.56 and .81 in the girls and boys, respectively). Ammonia levels in response to treadmill testing were negative related to field test times in the boys (r=-.67 and -64 for the 30- and

60-m runs, respectively), but no such correlations were observed in the girls.

These results suggest that ammonia reflects anaerobic metabolism during maximal treadmill testing but is of little value in predicting field test capabilities.

Nazar,

K., B. Dobrzynski, and

R. Lewicki. Relationship between plasma ammonia and blood lactate concentrations after maximal treadmill exercise in circumpuber- tal girls and boys. Eur. J.

Appl.

Physiol.

65:246-250, 1992.

Effects of Training Regimen on Hockey Performance

Controversy surrounds the most optimal summer training regimen for developing the performance of young hockey players. Traditionally these programs have consisted of participation in two or three games a week over a 4- to 6-week period. It has been suggested that on-ice and off-ice training specific to hockey would be more effective in improving performance than playing games alone.

Greer et al. investigated the effects of a 7-week hockey-specific training program on performance scores of 14- to 15-year-old players. Sixteen players participated in 1- to 2-hour sessions 3 days a week consisting of skating drills and resistance training, while 12 subjects served as controls, playing 10 to 20 league games during the same time period. Skating performance was measured by skating acceleration, speed, and cornering. Other evaluation included determination of percent body fat, center of gravity location, 40-yard dash, and vertical jump. The training group showed significant improvements in all on-ice tests (top speed, acceleration, and cornering) and also reduced body fat. The only improvement observed in the controls was in diminished body fat. These findings suggest that regular summer league play alone cannot be expected to improve skating skills and that hockey-specific training regimens are more appropriate for summer training of developing players.

Greer, N., R. Serfass, W. Picconatto, and J. Blatherwick. The effects of a hockey- specific training program on performance of bantam players. Can. J. Spt. Sci.

17:65-69, 1992.

Exercise Testing as a Prognostic Indicator for Cystic Fibrosis

Numerous factors are associated with an unfavorable prognosis in patients with cystic fibrosis, including fat malabsorption, female sex, and poor nutritional status. Nixon et al. evaluated the role of pulmonary function values and aerobic fitness during exercise testing as indicators of clinical outcome in patients with this disease. A total of 109 patients (ages 7 to 35 years) were evaluated initially

in the late 1970s with gas exchange parameters during maximal cycle exercise as well as measures of resting lung function. After 8 years of follow-up these variables were analyzed to determine their value as prognostic indicators of patient mortality. When adjustments were made for otherrisk factors, patients who originally had low aerobic power ( 4 8 % predicted) had three times the risk of dying during the follow-up period than those with V0,max over 82% predicted.

The 8-year survival rate was 28% in the former group but 83% in the latter. No significant independent correlations with mortality were observed, for age, sex, body mass index, forced expiratory volume in 1 minute, and end-tidal PCO, at peak exercise. These findings support the role of exercise testing as a prognostic indicator in patients with cystic fibrosis. Specifically, lower levels of aerobic capacity appear to be linked to greater mortality rates. The authors comment that further research is indicated to determine whether improvement in aerobic capac- ity through physical training will help improve the outlook for these patients.

Nixon, P.A., D.M. Orenstein, S.F. Kelsey, and C.F. Doershuk. The prognostic value of exercise testing in patients with cystic fibrosis. N.

Engl.

J. Med.

327: 1785-

1788, 1992.

Resistance Training and Muscle Size in Children

A

growing body of research data indicates that prepubertal children are capable of improving muscle strength after a period of resistance training. In adults, increases in strength with training are accompanied by muscle hypertrophy.

Fukunga et a]. studied the effects of resistance training in children to determine whether strength improvements are accompanied by increased upper arm muscle mass in the prepubertal age group. Fifty boys and girls, ages 6.9 to 10.9 years, underwent a 12-week strength training program. Cross-sectional area of tissues of the upper arm was measured by ultrasound, and a Cybex dynamometer was used to evaluate maximum isometric and isokinetic strength of flexion and extension at the elbow. Results were compared to those of

47 nontraining control subjects.

Upper arm cross-sectional area was greater for both training and control groups at the end of the study, but the increase was due to muscle and bone area in the former and adipose tissue in the latter. The increment in muscle area from training was closely related to skeletal age. Significant improvements in isometric strength were observed in the training group, but there was no increase in strength per cross-sectional area. The training children increased muscle mass 50% and iso- metric strength 40% compared to improvements observed in adult subjects pre- viously trained by the authors. These results suggest that prepubertal children are capable of increasing both muscle strength and size with resistance training, but the magnitude of the responses is less than in adults.

Fukunga, T., K. Funato, and S. Ikegawa. The effects of resistance training on muscle area and strength in prepubescent age.

Ann. Physiol. Anthrop.

11:357-

364, 1992.

Research

Digest

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Longitudinal Relationship of Oxygen Uptake to Body Mass

During Exercise

Theoretical dimensional considerations have suggested that maximal and submax- imal oxygen uptake should be proportional to body mass raised to the 314 power.

Sjodin and Svedenhag tested 8 young training runners and 4 untrained control subjects every 6 months for 8 years, beginning at the age of 12, to determine longitudinal changes in the relationship of oxygen uptake and body mass during the circumpubertal years. Maximal oxygen uptake relative to body weight de- creased with growth in the untrained group, with a body mass scaling factor of

.78. The scaling factor in the training subjects was 1.01; that is, V0,max per kg remained stable during the study period. Running economy at a treadmill speed of 15 km h-' improved in both groups as they grew, with a steady decline in

V0, per kg at this speed. The body mass scaling factor for submaximal oxygen uptake was .75 for both the trained and untrained subjects. Thus, when oxygen uptake values were expressed relative to weight7', V0,max remained stable in the untrained but increased in the trained subjects, while submaximal V0, (running economy) was unchanged with growth in both groups. Blood lactate levels at peak exercise remained the same in both trained and untrained subjects, but the running speed at 4 mmol L-I of lactate rose only in the training group. This study supports the concept that oxygen uptake obtained during treadmill running is

Sjodin, B., and J. Svedenhag. Oxygen uptake during running as related to body mass in circumpubertal boys:

A

longitudinal study.

Eur. J. Appl. Physiol.

65:150-

157, 1992.

Therapeutic Value of Exercise for Emotionally Ill Adolescents

The ability of exercise to improve emotional well-being has been documented, but information on the therapeutic value of physical activity in the management of psychiatric illness is limited. Brown et al. reported the influence of a 9-week aerobic exercise program on psychologic factors in a group of institutionalized adolescents with dysthymia and conduct disorders. Eleven of 27 subjects who began the program completed the full study, the high level of dropout mainly due to discharge from the facility. Variables determined at the initiation, midpoint, and end of the program, as well as at 4-week follow-up, included (a) 1-mile run time, (b) resting, exercise, and recovery heart rates, (c) body mass index, (d) the

Beck Depression Inventory, (e) the Profile of Mood States, and

(f)

a self-report measure of self-efficacy. Approximately half of the subjects participated in a program of runninglaerobic exercise three times a week plus regularly scheduled physical activities. The remainder, who served as controls, exercised only in the regularly scheduled program. By 4-112 weeks the training subjects showed decreased depression and anger as well as increased self-efficacy that persisted at the end of the training period. Similar changes were not observed in the

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- controls. For most measures, changes occurred prior to improvements in aerobic fitness and were more prominent in females. All alterations occumng with training disappeared at the 4-week follow-up assessment. These findings support the role of physical exercise in the management of psychiatric disorders in adolescents.

Brown, S.W., M.C. Welsh, E.E. Labbe, W.F. Vitulli, and P. Kulkarni. Aerobic exercise in the psychological treatment of adolescents.

Percept. Mot.

Skills

74555-560, 1992.

Cardiorespiratory Responses to Exercise

Following Kawasaki Disease

Kawasaki disease is an inflammatory condition of unknown etiology that com- monly disturbs normal myocardial function in its acute phase and is associated with the subsequent development of coronary artery aneurysms. Allen et al. examined the effects of Kawasaki disease on exercise tolerance and cardiopulmo- nary function among 47 patients (mean age 10 years) followed for an average of 5 years after their illness. Coronary artery aneurysms were detected by echocar- diography in 18 (37%) patients, but in only 2 patients were these considered significant (5-7 mm). On cycle exercise testing with the James protocol, maximal work capacity and V 0 2 did not differ from those of normal healthy control subjects. Chronotropic responses to exercise were unremarkable. Oxygen uptake at the ventilatory threshold was within the normal range as well. Exercise electro- cardiograms were normal in all subjects except the two with large coronary artery aneurysms, who demonstrated ST-T wave abnormalities on serial testing. These results indicate that in the absence of serious coronary artery involvement, patients who have had Kawasaki disease can be expected to demonstrate normal exercise capacity and cardiopulmonary reserve as assessed by maximal heart rate, work rate, and oxygen uptake. Consequently, Allen et al. support the recommendation that restrictions of physical exercise are not warranted in this group of patients.

Allen, S.W., E.M. Shaffer, L.A. Harrigan, R.R. Wolfe, M.P. Glode, and J.W.

Wiggins. Maximal voluntary work and cardiorespiratory fitness in patients who have had Kawasaki syndrome.

J. Pediatr.

121:221-225, 1992.

Metabolic Responses to Prolonged Exercise

Children appear to demonstrate lower levels of catecholamine responses to exer- cise than do adults. These hormones play an important role in regulating substrate utilization during exercise. Delamarche et al. investigated the sympatho- adrenergic and metabolic responses of prepubertal boys during prolonged sub- maximal cycle exercise. Ten boys, ages 8.5 to 11.0 years, volunteered to perform

60 minutes of cycling at 60% of their previously measured maximal oxygen uptake (average 48.5 ml kg-' m i d ) . Packed red cell volume, plasma glucose, free fatty acids, glycerol, and catecholamines were measured at 15, 30, and 60 minutes of exercise and again at 30 minutes of recovery. Mean heart rate rose from 157 bpm at 5 minutes to 165 bpm at the end of the exercise testing.

A

6.6% increase in packed red cell volume occurred during the first 15 minutes of

Research Digest

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cycling, but with no further subsequent rise. After an initial small drop, blood glucose remained constant during the test. Free fatty acids rose slowly, while glycerol concentration increased more abruptly; both rose linearly with increases in adrenaline. Compared to previous studies of adults, the children showed a greater free fatty acid uptake, while increases of both adrenaline and noradrenaline were lower than those described in adult subjects. A rapid initial rise in noradrena- line noted in the children may have been important in preventing hypoglycemia.

Delamarche, P., M. Monnier, A. Gratas-Delamarche, H.E. Koubi, M.H. Mayet, and R. Favier. Glucose and free fatty acid utilization during prolonged exercise in prepubertal boys in relation to catecholamine responses. Eur. J. Appl. Physiol.

65:66-72, 1992.

Parental Influences on Children's Physical Activity

Multiple biological, psychosocial, and environmental factors affect habitual phys- ical exercise in children. An understanding of these influences is important, as efforts are made to increase the level of health related activity during the pediatric years. Parents may serve as important modifiers of their children's activity through role modeling, encouragement, and time management. Sallis et al. investigated the relationships of these factors within families on the extent of children's physical activity and fitness. A total of 148 girls and 149 boys in the fourth grade in a suburban California city comprised the study group. Level of physical activity was assessed by self-report questionnaire, accelerometer, and field fitness testing. Parents' activities and support of their child's activity were estimated by questionnaire. No relationship was observed between the parents' physical activity levels and the activity or fitness of their children. This contradicts the findings of most other reports, which have indicated a close connection between the two.

Likewise, the role of verbal encouragement was not significant in increasing children's activity. Those parents who played more often with their children had more active boys. In this study, the ability of parents to provide transportation to exercise activities was the single most significant influence related to the activity of the children. It was concluded that interventions to improve the level of physical activity in children should involve improving parental support.

Sallis, J.F., J.E. Alcaraz, T.L. McKenzie, M.F. Hovell, B. Kolody, and P.R.

Nader. Parental behavior in relation to physical activity and fitness in 9-year- old children. AJDC 146: 1383-1388, 1992.

Response to Exercise After Heart Transplant

There is little information concerning the hemodynamic responses to exercise in adolescents after heart transplantation. Christos et al. studied 7 adolescents, ages

15 to 17 years, who had undergone transplantation more than a year previously for dilated cardiomyopathy or univentricular heart. Subjects were tested with an upright discontinuous cycle protocol to volitional exhaustion with standard measures of gas exchange variables. Cardiac output was estimated using the

1

14 Research Digest

acetylene-helium rebreathing technique. Results were compared to those of

7 control subjects matched for age, gender, body mass, percent body fat, and body surface area. Work capacity and mean maximal oxygen uptake were lower in the transplant group (V02max 22 vs. 32 ml kg-' min-I), corresponding to lower average peak heart rate (154 vs. 177 bpm). Maximal cardiac output did not differ significantly between transplant subjects and controls, indicating a greater stroke volume in the former group. These higher stroke volumes were felt to be possibly related to a greater decrease in systemic resistance during exercise in transplant subjects. Peak venous lactate and catecholamine concentrations were similar in the transplant and control subjects. The authors suggested these findings indicate that the decreased aerobic fitness and work capacity in adolescent transplant patients may be due to peripheral muscle deconditioning rather than to cardiac dysfunction.

Christos, S.C., V. Katch, D.C. Crowley, B.L. Eakin, A.L. Lindauer, and R.H.

Beekman. Hemodynamic responses to upright exercise of adolescent cardiac transplant recipients. J.

Pediatr.

12 1 :3 12-3 15, 1992.

Physiologic Responses to Submaximal Exercise

With Chronotropic Incompetence

In normal individuals, absolute oxygen uptake values at submaximal work are similar, although resting, submaximal, and maximal heart rates vary appreciably according to age, body size, and state of physical fitness. Schulze-Neick et al. investigated physiologic responses to exercise in children with heart disease to determine submaximal heart rates and oxygen uptake values in those with low peak exercise heart rate. Seventy-eight subjects, all with peak heart rates <I50 bpm, were compared to 201 controls of similar body size and peak exercise heart rates >I80 bpm on a maximal cycle exercise test. Those with low peak heart rates showed significantly lower rates at submaximal levels as well, but oxygen uptake at comparable submaximal levels was not different from controls. Those with low peak heart rates thus had a higher V02 pulse at all submaximal levels of exercise. Differences between males and females were observed only in the control subjects: greater V02 and lower heart rates at the same exercise level were observed in the male subjects. These findings indicate that cardiac patients with low submaximal and maximal heart rates may have a normal oxygen uptake during exercise. The authors felt that such findings could not be entirely explained by an increase in arteriovenous oxygen uptake and suggested that these children with heart disease were able to successfully augment cardiac stroke volume.

Schulze-Neick, I.M., H.U. Wessel, and M.H. Paul. Heart rate and oxygen uptake response to exercise in children with low peak exercise heart rate. Eur.

J.

Pediatr.

151:160-166, 1992.

Strength Training and Wheelchair Propulsion

Effective use of wheelchairs is often dependent upon upper body muscular strength or endurance. The ability of resistance training to improve muscular

Research Digest

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endurance and wheelchair propulsion, however, has received little research atten- tion. O'Connell et al. examined the effects of strength conditioning on the relation- ships between muscular endurance, six-repetition maximum (6-RM) strength, and short (anaerobic) and long (aerobic) distance wheelchair propulsion tasks in six children with cerebral palsy or myelomeningocele. Distance traveled in 12 minutes and the 50-meter dash were used as wheelchair performance variables.

Six-repetition maximum tests with eight joint motions were performed with hand- held weights. Performance variables were measured and correlated before and after an

&week circuit training program. On the pretest, results of only one of the eight 6-RM tests correlated significantly with the 12-min test, and none were related to the 50-meter dash. Following training, a relationship was observed between both the 12-min test and the 50-meter dash and all eight of the 6-RM tests. Significant improvements were seen in all 6-RM tests following training.

The training resulted in an increased distance in the 12-min test but not in the 50- meter time. These findings indicate that training improves strength and increases correlation of upper body 6-RM endurance with both aerobic and anaerobic exercise tests.

O'Connell,

D.G.,

R. Barnhart, and

L.

Parks. Muscular endurance and wheelchair propulsion in children with cerebral palsy or myelomeningocele.

Arch. Phys.

Med. Rehabil.

73:709-711, 1992.

"Children and Youth in 2001: Realizing Dreams"

October 21-24, 1993, California State Polytechnic University

The conference will be held by the Institute for the Study of Children

and

Youth at California State Polytechnic University, Pomona.

Themes:

-Children and the legal system

-The place of children in the world

Contact Sonia Blackman, PhD

Director, Institute for the Study of Children and Youth

California State Polytechnic University

3801 W. Temple Ave.

Pomona, CA 91768

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