[Physical activity in children and adolescents in relation to growth and development]. / Fysisk aktivitet hos barn og unge i relasjon til vekst og utvikling.

BACKGROUND: Physical activity may influence the performance and health of children and adolescents. The purpose of this article is to give a review of present knowledge in this field. MATERIAL AND METHODS: Literature was searched using Medline and the Norwegian University of Sports library. RESULTS: Related to body mass, boys have an aerobic capacity like young adults. Girls show a reduction from prepuberty until adulthood. Their trainability seems to be lower than in adults. Anaerobic capacity and muscle strength are lower than in adults, but increase during puberty, especially in boys. The trainability is good at all ages. There are small differences in performance between boys and girls before puberty. Physical activity has favourable metabolic effects and influences the development of fat tissue, skeleton and probably tendons, ligaments and cartilage. INTERPRETATION: Physical activity is important for performance and health during the growing years and later. It is a factor in the prevention of artheriosclerotic disease, hypertension, obesity, diabetes type 2, some types of cancers, osteoporosis, and muscular problems. Specialisation in sports should normally be postponed until late puberty, even by those who aim at high performance.

Efficiency and costs of medical exercise therapy, conventional physiotherapy, and self-exercise in patients with chronic low back pain. A pragmatic, randomized, single-blinded, controlled trial with 1-year follow-up.

STUDY DESIGN: A multicenter, randomized, single-blinded controlled trial with 1-year follow-up. OBJECTIVES: To evaluate the efficiency of progressively graded medical exercise therapy, conventional physiotherapy, and self-exercise by walking in patients with chronic low back pain. SUMMARY AND BACKGROUND DATA: Varieties of medical exercise therapy and conventional physiotherapy are considered to reduce symptoms, improve function, and decrease sickness absence, but this opinion is controversial. METHODS: Patients with chronic low back pain or radicular pain sick-listed for more than 8 weeks and less than 52 weeks (Sickness Certificate II) were included. The treatment lasted 3 months (36 treatments). Pain intensity, functional ability, patient satisfaction, return to work, number of days on sick leave, and costs were recorded. RESULTS: Of the 208 patients included in this study, 71 were randomly assigned to medical exercise therapy, 67 to conventional physiotherapy, and 70 to self-exercise. Thirty-three (15.8%) patients dropped out during the treatment period. No difference was observed between the medical exercise therapy and conventional physiotherapy groups, but both were significantly better than self-exercise group. Patient satisfaction was highest for medical exercise therapy. Return to work rates were equal for all 3 intervention groups at assessment 15 months after therapy was started, with 123 patients were back to work. In terms of costs for days on sick leave, the medical exercise therapy group saved 906,732 Norwegian Kroner (NOK) ($122,531.00), and the conventional physiotherapy group saved NOK 1,882,560 ($254,200.00), compared with the self-exercise group. CONCLUSIONS: The efficiency of medical exercise therapy and conventional physiotherapy is shown. Leaving patients with chronic low back pain untampered poses a risk of worsening the disability, resulting in longer periods of sick leave.

The effect of medical exercise therapy on a patient with chronic supraspinatus tendinitis. Diagnostic ultrasound--tissue regeneration: a case study.

There is an increased focus on the importance of using active exercise regimes for treating dysfunction in the musculoskeletal system. However, we have little exact knowledge on how to dose and grade exercises or the effect of exercise on the regeneration of low metabolic tissue structures in vivo. This case study deals with both topics and emphasizes the use of exercise only when treating a 73-year-old patient with a 1-year history of shoulder pain. His evaluation indicated chronic supraspinatus syndrome. Different treatment methods had no effect, and medical exercise therapy was tried as a last resort. The patient recovered after 21/2 months with four treatments per week. Diagnostic ultrasound taken before treatment and after a 51/2-month period showed that the supraspinatus tendon had regenerated. These findings are encouraging, supporting the possibility of tendon repair with biomechanical stresses from exercise. To our knowledge, it has never been shown in vivo that it is possible for a low metabolic structure to regenerate using exercise only. Instead of having surgery with an uncertain outcome, today the patient is free of symptoms and living a normal life enjoying his sporting activities nearly 4 years after he finished the treatment.

Ambulatory electrocardiographic findings in top athletes, athletic students and control subjects.

Aim of the present study was to evaluate 24 h electrocardiographic recording in 30 top athletes, 30 athletic students and 30 sedentary control subjects. Each group consisted of 15 males and 15 females and were matched for age (about 24 years). Training was not allowed during the recording. Top athletes had the lowest diurnal and nocturnal heart rate, but the difference between top athletes and athletic students was far less pronounced than between athletic students and controls. This may indicate that bradycardia reaches a lower limit with moderate degrees of training. Atrioventricular (AV) block II was found in 3 top athletes and 4 athletic students and in none of the subjects, the longest pause being 2.4 s in both athletic groups. Most episodes occurred during night and nearly all were Mobitz type I. In all cases of AV block II the QRS complexes were narrow and AV block III did not occur. SA block was found in 3 top athletes, 1 athletic student and 1 control subject, the longest pause being 3.1, 2.9 and 1.9 s, respectively. Ventricular premature beats were rare in all groups and complex ventricular arrhythmias were not found. Half of the subjects were in Lown class 0, the other half in Lown class 1. Supraventricular premature beats were also scarce and most frequent in top athletes, followed by athletic students and sedentary controls (2.0, 1.0, 0.7 beats/h, respectively).

Electrocardiographic findings of repolarization in athletic students and control subjects.

We have investigated resting electrocardiograms in 1,299 athletic students and 151 sedentary control subjects. ST elevations were more frequent and pronounced in athletes compared to controls, whereas there was no difference in ST depressions. Athletes with ST elevation above 2 mm were characterized by lower heart rate, increased PQ duration, increased indices of left, right and septal hypertrophy and T wave amplitude. Negative T waves in 3 of 6 precordial leads, V3-6, were found in 1.5% of athletes and 0.7% of controls, and in V5-6 in 0.4% of athletes and none of controls, the differences not being significant. Athletes had significantly more often a T wave axis between +30 and -180 degrees and less often a frontal T wave axis between +30 and +180 degrees. The mean QRS-T angle was significantly greater in athletes, and U waves were more prominent. Analyzing athletes with QTc below and above 0.430 s, we found an increased heart rate, QRS duration, ST depression and a more pronounced left QRS axis in the group with QTc above 0.430 s. There was a positive correlation between QTc and heart rate which indicates that the use of Bazett's formula leads to an underestimation of QTc at lower heart rates and to an overestimation at higher heart rates. Bazett's formula does not provide an adequate correction for heart rate and should be used with caution. Our finding of a prolonged QTc in athletes compared to control subjects in spite of lower heart rate in the athletic group demonstrates that a real QTc prolongation exists in athletes.

Electrocardiographic findings of left, right and septal hypertrophy in athletic students and sedentary controls.

We have previously demonstrated increased voltage of septal, right and left ventricular depolarization in 1,299 athletic students compared to 151 sedentary controls. In the present investigation we have studied the prevalence of hypertrophy and the correlation between hypertrophy and other ECG findings. An increase of Q waves of more than 0.2 mV was associated with increased indices of right and left ventricular hypertrophy. Right ventricular hypertrophy was associated with an increased prevalence of incomplete right bundle branch block and increased parameters of septal and left ventricular hypertrophy. Left ventricular hypertrophy was associated with increased indices of septal and right ventricular hypertrophy and with bradycardia. Furthermore, left ventricular hypertrophy was characterized by ST elevation and increased T wave amplitudes, but not by repolarization abnormalities. Thus, our data point to a harmonious hypertrophy. Based on our findings we suggest the following normal limits in young people (20-30 years) according to the 97.5 percentile regarding the Sokolow index: for athletic students 5.3 (males) and 3.6 mV (females), for sedentary controls 4.0 (males) and 3.6 mV (females). It remains to be clarified whether these values are also valid in top athletes.

Electrocardiographic and echocardiographic findings in top athletes, athletic students and sedentary controls.

Thirty top level athletes, 30 athletic students and 30 sedentary controls underwent electrocardiographic and echocardiographic investigation. Resting ECG in athletes showed increased indices of hypertrophy compared to controls. The echocardiographic examination demonstrated an increase in left ventricular mass (LVM) of 47% in top athletes and 23% in athletic students compared to controls. The relationship between wall thickness and diameter was similar in all groups, as were parameters of systolic and diastolic left ventricular function at rest. There was no correlation between LVM assessed by echocardiography and ventricular ectopic activity assessed by Holter monitoring in this normotensive population. Highly significant correlations between ECG and echocardiographic parameters of hypertrophy were demonstrated.

Comparison of changes in testosterone concentrations after strength and endurance exercise in well trained men.

Changes in the testosterone concentrations after single sessions of endurance and strength training were measured in seven well trained men, experienced in both forms of training. Both training sessions were rated as hard to very hard on the Borg scale. Blood samples for testosterone measurements were taken before, immediately after, and 2, 4 and 6 h after the training sessions as well as the next morning. The mean testosterone concentration increased 27% (P less than 0.02) and 37% (P less than 0.02) during the strength and endurance training session, respectively. Two hours after the training sessions the mean testosterone concentration had returned to the pre-training level and remained at that level for the length of the observation period. There were no significant differences in the changes in testosterone concentration after strength and endurance training but there were large differences in the testosterone response at the level of the individual. A high correlation (r = 0.98; P less than 0.001) for individuals was found between increases in testosterone concentration after strength and after endurance training. It was concluded that the changes in mean testosterone values followed the same timecourse after single sessions of strength and endurance training of the same duration and perceived exertion. The interindividual differences in testosterone response may be of importance for individual adaptation to training.

Electrocardiographic findings in athletic students and sedentary controls.

We have investigated resting electrocardiograms from 1,299 athletic students taken in the same laboratory during the years 1973-1982 and compared them with electrocardiograms recorded in 151 age- and sex-matched sedentary controls. Fifty-two parameters were recorded for each electrocardiogram and computerized. We found that athletic students had a significant lower heart rate, longer PQ time and a prolonged QTc compared to control subjects. Athletes had higher maximal Q amplitudes in precordial leads, higher R in V1, and higher indices of right ventricular hypertrophy (RV1 + SV5) and left ventricular hypertrophy (Sokolow-Lyon and Grant indices). Furthermore, the athletes had higher maximal ST elevation and higher maximal T wave amplitudes in precordial leads. Sinus bradycardia was more frequent in athletes. All control subjects were in sinus rhythm whereas 0.9% of the athletes had other rhythms (nodal, coronary sinus or wandering pacemaker). Athletes and control subjects did not differ significantly with regard to premature beats, atrioventricular block, bundle branch block or the Wolff-Parkinson-White pattern. We conclude that training induces significant changes in heart rate, conduction times, ST elevation. QRS and T voltage, slow rhythm disturbances and atrioventricular and sinoatrial block were infrequent in the resting electrocardiogram taken in the supine position and disappeared immediately on sitting and during exercise. Training-induced electrocardiographic changes may partly be due to alterations in autonomic tone and partly to structural changes in the myocardium. Different normal criteria for left ventricular hypertrophy may be warranted in athletes.

Electrocardiographic findings according to sex in athletes and controls.

We have previously compared the electrocardiogram of 1,299 male and female students of physical education and sports with 151 age- and sex-matched sedentary controls and found that the former had lower heart rate, longer conduction times and increased voltages. The same material of 1,450 young adult subjects was split according to sex into 617 females and 833 males in order to analyze the influence of gender on the resting 12-lead electrocardiogram. We found that females had a significant higher heart rate, shortened conduction times (PQ, Q, ventricular activation time and QRS) and a prolonged repolarization time (QTc), decreased P, Q and T amplitudes as well as indices of right, septal and left hypertrophy, and ST elevation in precordial leads were lower in females than in males. These differences were highly significant with p values less than 0.0001 for almost all parameters. Sinus bradycardia was more common in men and sinus tachycardia in women. The prevalence of other rhythms and supraventricular and ventricular premature beats was low in both sexes. AV block grade I was found in 1% of females and 3% of males (p less than 0.02). Notching of R/S in V1-V2 and incomplete right bundle branch block were less common in females (p less than 0.0001). The differences in ECG parameters between the two sexes in the total material persisted also when the athletic and control groups were investigated separately. Gender seems to be highly important for most ECG parameters in the resting ECG. This points to the necessity of discussing different upper normal limits for ECG parameters according to gender.

Diabetes mellitus and physical activity.

Fat and carbohydrate metabolism in diabetic patients during exercise is described and compared with the metabolism of healthy individuals. In well-regulated insulin-treated diabetics, fat and carbohydrate metabolism does not differ greatly from that of healthy individuals. It is therefore concluded that well-regulated diabetics can actively participate in all degrees of exercise, including highly competitive sports, when diet and insulin dosages are adequately adjusted. The effect of exercise on diabetes control is discussed, and it is concluded that there is not existing evidence that exercise delays or prevents the development of diabetic angiopathy.

Physical activity in children and adolescents in relation to growth and development.

Physical activity during the growth period appears to be necessary for normal growth and development of the skeleton, musculature and oxygen-carrying organs. Compared with the adult, the child (in relation to body size) has poor maximal strength and low anaerobic capacity. Muscular endurance and aerobic performance are more comparable to what is found in adults, but even as regards these qualities the child is immature and not on the same level as the adult. The growth period appears to be particularly favourable for learning new movement patterns. In arranging training and competitive sport for children or growing adolescents, attention must be paid to their special physical qualifications and also to the need for versatility in the choice of exercise.

Changes in 2,3-Diphosphoglycerate (2,3-DPG) after exercise.

Previous studies of the influence of physical exercise on erythrocyte 2,3-DPG have shown conflicting results, including that exercise induces increase, decrease or no changes in 2,3-DPG. Assuming that the interplay between the factors governing 2,3-DPG metabolism may change considerably during the early phase of recovery after exercise, the level of erythrocyte 2,3-DPG was examined over a prolonged period of time after heavy exercise in five healthy men, on 3 separate days, the duration of exercise being 6 min, 6 min + 6 min with 1 h of rest between, and 60 min, respectively. The short exercise periods were accompanied by a substantial lactate acidosis, whereas the 60 min work was essentially aerobic. With the 6 min work, the erythrocyte 2,3-DPG was unchanged or slightly reduced immediately after and 15 min after the end of exercise, then rose to a new level, 8% above the initial level, 30 min after the exercise (P less than 0.001). With the 6 + 6 min work, the pattern of change followed both bouts of exercise, resulting in a two-step increase of 2,3-DPG, to a new level 12% above its initial value (P less than 0.001). With the 60 min work, 2,3-DPG was increased after a new level, 10% above initial value, 45 min after the exercise (P less than 0.001). With all three types of exercise 2,3-DPG remained unchanged during the following 4 h. Thus, heavy exercise is followed by a definite, slowly developing increase in erythrocyte 2,3-DPG, reaching a new level 30-45 min after exercise.

The effect of exercise on diabetic control and hemoglobin A1 (HbA1) in children.

14 children with juvenile diabetes mellitus (mean age 11 years, mean diabetes duration 5 years) were enrolled in a one-hour twice weekly supervised exercise program for 5 months. A group of 8 diabetic children of same age and diabetic duration served as control group. Maximum oxygen uptake was within normal range for all children. With this exercise program the maximum oxygen uptake of the training group did not change significantly compared with the control group. The physicians rating of degree of the metabolic control based on blood-glucose measurements and urinary glucose excretion did not change in any of the groups. The insulin dosage per kilo body weight remained unchanged in both groups. In the training group the HbA1 values decreased during the exercise period from 15.1 +/- 2.2 (mean HbA1 % +/- 1 S.D.) to 13.8 +/- 1.9 (2p less than 0.001). In the control group the HbA1 values did not change significantly (13.4 +/- 1.9 to 12.9 +/- 1.6; 2p = 0.20). In a co-study the effect of freezing and storage of hemolysates, resulting in increased levels of HbA1, was demonstrated.

Assessment of maximal aerobic power in specifically trained athletes.

Maximal aerobic power of 37 athletes (14 females and ten male cross-country skiers, eight male rowers and five male cyclists) was determined during uphill running on the treadmill and during maximal performance of their specific sport activity. For the skiers a significantly (P less than 0.005) higher VO2max was found during uphill skiing than during running, the differences being 2.9 and 3.1% for the females and males, respectively. The rowers and cyclists obtained a difference of 4.2 and 5.6%, respectively (P less than 0.01). The largest individual differences between the two test procedures were 12.2, 5.4, 14.3, and 7.9% for female and male cross-country skiers, rowers, and cyclists, respectively. It is concluded that in evaluation of maximal aerobic power of atheletes, it becomes important to select a work situation which allows optimal use of the specifically trained muscle fibres. This means that the test preferably should be identical with the subjects' specific sport activity, under the assumption that a reasonably large muscle mass is engaged during the performance.