Bareket Falk

Child-Adult Differences in the Recovery from High-Intensity Exercise

Children recover from physical exertion faster than adults, especially, from high-intensity exercise. It is argued that, qualitatively, this is due mainly to dimensional differences but that, predominantly, it is a quantitative difference, stemming from the lower relative power children can generate and from which they need to recover. Childrens lesser power capacity is, in turn, likely due to maturation-dependent neuromotor differences.

Exercise With and Without an Insulin Pump Among Children and Adolescents With Type 1 Diabetes Mellitus

Background. The use of insulin pumps is becoming a popular technique for insulin delivery among patients with type 1 diabetes mellitus (T1DM), but there is no consensus regarding the guidelines for proper pump use during exercise. Objective. To investigate the physiologic responses and risk of hypoglycemia among children and adolescents with T1DM when exercising with the pump on (PO) (50% of the basal rate) or pump off (PF). Methods. Ten subjects with T1DM (6 female subjects and 4 male subjects), 10 to 19 years of age, performed prolonged exercise (40–45 minutes) on a cycle ergometer ∼2 hours after a standard breakfast and an insulin (Lispro) bolus. Complex carbohydrates (20 g) were provided before and after the exercise. Each patient exercised once with PO and once with PF, in a randomized, crossover (single-blind) manner. During exercise and 45 minutes of recovery, subjects were monitored for cardiorespiratory, metabolic, and hormonal responses. Blood glucose concentrations were recorded for 24 hours after exercise, with a continuous glucose monitoring system, to document late hypoglycemic events. Results. During exercise, blood glucose concentrations decreased by 59 ± 58 mg/dL (mean ± SD: 29 ± 24%) with PF and by 74 ± 51 mg/dL (35.5 ± 18%) with PO (not significant). No significant differences were found in cortisol, growth hormone, or noradrenaline levels between PO and PF. There were no differences in cardiorespiratory parameters, blood lactate concentrations, or free fatty acids concentrations between pump modes. Hypoglycemic events during exercise were asymptomatic and occurred for 2 subjects with PO and 2 with PF. Nine subjects had late hypoglycemia after PO, compared with 6 after PF (not significant). Conclusions. We found no advantage for subjects with either PO or PF during exercise, and we noted that late hypoglycemia was more common than hypoglycemia during exercise. However, PO was associated with a trend of increased risk for late hypoglycemia. We recommend that the pump be removed or turned off during prolonged exercise and that blood glucose concentrations be monitored for several hours after exercise, regardless of the pump mode.

Measurement of talent in team handball: the questionable use of motor and physical tests.

Testing for selection is one of the most important fundamentals in any multistep sport program. In most ball games, coaches assess motor, physical, and technical skills on a regular basis in early stages of talent identification and development. However, selection processes are complex, are often unstructured, and lack clear-cut theory-based knowledge. For example, little is known about the relevance of the testing process to the final selection of the young prospects. The purpose of this study was to identify motor, physical, and skill variables that could provide coaches with relevant information in the selection process of young team handball players. In total, 405 players (12–13 years of age at the beginning of the testing period) were recommended by their coaches to undergo a battery of tests prior to selection to the Junior National Team. This number is the sum of all players participating in the different phases of the program. However, not all of them took part in each testing phase. The battery included physical measurements (height and weight), a 4 × 10-m running test, explosive power tests (medicine ball throw and standing long jump), speed tests (a 20-m sprint from a standing position and a 20-m sprint with a flying start), and a slalom dribbling test. Comparisons between those players eventually selected to the Junior National Team 2–3 years later with those not selected demonstrated that only the skill test served as a good indicator. In all other measurements, a wide overlap could be seen between the results of the selected and nonselected players. It is suggested that future studies investigate the usefulness of tests reflecting more specific physical ability and cognitive characteristics.

Reliability of peak-lactate, heart rate, and plasma volume following the Wingate test

PURPOSE The 30-s Wingate Anaerobic Test (WAnT) has been used to assess anaerobic performance capacity and to evaluate physiological responses to supramaximal exercise. Blood lactate concentration ([La]) following supramaximal exercise is often used in the field and in the laboratory to assess the glycolytic contribution to exercise. Although the reliability of the performance in the WAnT has been established, this has not been the case with the WAnTs [La] response. Thus, the main purpose of this research was to study the test-retest reliability of peak [La] following the WAnT. Additionally, the test-retest reliability of the heart rate (HR) and plasma volume changes (deltaPV) response was also evaluated. METHODS Twenty-nine subjects (15 male, 14 female) of diverse training levels as well as physical characteristics (mean +/- SD: 23.3+/-7.0 yr, 62.5+/-12.0 kg, 170.8+/-9.7 cm, and 16.3+/-6.2% fat) performed two WAnTs within 1 wk. Capillary blood was sampled from a prewarmed fingertip at rest, just before the WAnT and at 3, 5, 7, and 9 min following it. HR was also measured during these times. RESULTS Mean-power (MP) (+/-SE) in test 1 and test 2 was 8.4+/-0.2 and 8.3+/-0.2 W X kg(-1) body mass, respectively. Peak [La] was attained 5-7 min following the WAnTs and was not significantly different between test 1 and test 2 (9.7+/-0.3 vs 9.8+/-0.3 mM, respectively). Peak HR occurred within 5 s post-WAnT and was not different between tests (170.8+/-2.2 and 171.3+/-2.2 beats X min(-1), in test 1 and test 2, respectively). Peak deltaPV was not different between tests (-12.0+/-3.4 and -11.1+/-3.2%, in test 1 and test 2, respectively). The intraclass reliability coefficients for peak [La]. peak HR and deltaPV were 0.926, 0.941, and 0.878, respectively, whereas the corresponding value for MP was 0.982. CONCLUSIONS We conclude that peak [La], peak HR, and deltaPV following the WAnT are reliable measures.

Thermoregulatory responses of pre-, mid-, and late-pubertal boys to exercise in dry heat.

During exercise in a hot climate, children have been reported to have a less effective temperature regulation capability, compared with adults. It is likely that the transition from a child-like to an adult-like response occurs during puberty. To assess the association between the thermoregulatory response and physical maturation, three groups of circum-pubertal boys cycled at 50% VO2max (three 20-min bouts with 10-min rests), in a climatic chamber (42 degrees C, 20% relative humidity). Based on Tanner staging (pubic hair), 10 were classified as prepubertal (PP), 13 as midpubertal (MP), and eight as late pubertal (LP). Measurements included rectal and skin temperatures (Tre, Tsk), heart rate (HR), sweating rate (SR), oxygen consumption (VO2), and forearm blood flow (FBF). Tre, Tsk, and HR increased with time, with no significant difference among groups. Relative VO2 (ml O2.kg-1) was similar among groups. FBF was consistently higher in PP compared with LP. In spite of the higher SR (PP = 4.9 +/- 0.2, MP = 5.7 +/- 0.3, LP = 6.6 +/- 0.4 ml.min-1.m-2) (mean +/- SEM) among LP compared with PP, the rate of heat storage (PP = 5.5 +/- 0.4, MP = 5.3 +/- 0.4, LP = 6.8 +/- 0.3, kJ.h-1.kg-1) was also significantly higher among those in the LP group. Three of eight LP did not complete the session due to high Tre, while two of the 10 PP were unable to complete the session even though the physiologic heat strain was not high. The results suggest that the transition from a child-like to an adult-like thermoregulatory effectiveness in a hot, dry climate may occur at a somewhat later stage, but not during puberty.

Anaerobic power and muscle strength in young hemophilia patients.

PURPOSE The purpose of this study was to evaluate muscle strength and anaerobic power in young boys with hemophilia compared with healthy boys. METHODS Thirteen boys with severe hemophilia (H) (mean (+/- SD) age = 12.0 +/- 3.17 yr) and 16 control (C) boys (age = 11.9 +/- 2.8 yr) performed elbow and knee flexion and extension on the Biodex System II dynamometer at two angular velocities. They also performed a Wingate Anaerobic Test (WAnT) for the legs and for the arms. All H subjects received prophylactic factor VIII treatment in the 24 h pretesting, and no test was performed in the presence of hemorrhage. RESULTS C were consistently stronger than H in all dynamic strength measures (e.g., elbow flexors: 0.47 +/- 0.15 vs 0.36 +/- 0.08 N x m x kg(-1) for C and H, respectively, P < 0.05). Anaerobic mean power was also higher in C compared with H in both upper and lower extremities (arms: 3.08 +/- 0.99 vs 2.22 +/- 0.46 W x kg(-1) for C and H, respectively; legs: 6.94 +/- 1.62 vs 5.54 +/- 1.03 W x kg(-1) for C and H, respectively, P < 0.05). Upper and lower extremity strength, as well as anaerobic power, increased with age in C but not in H. By using the Godin Leisure-Time Exercise Questionnaire, H were found to be much less active, especially in intense activities, compared with C. CONCLUSION Children and adolescents with hemophilia are characterized by lower muscle strength and anaerobic power compared with age-matched controls. This may be related to their lower leisure-time activity.

Child–adult differences in muscle strength and activation pattern during isometric elbow flexion and extension

Muscle strength and activation were compared in boys and men during maximal voluntary elbow flexion and extension contractions. Peak torque, peak rate of torque development (d/dmax), rate of muscle activation, and electromechanical delay (EMD) were measured in 15 boys (aged 9.7 +/- 1.6 years) and 16 men (aged 22.1 +/- 2.8 years). During flexion, peak torque was significantly lower in boys than in men (19.5 +/- 5.8 vs. 68.5 +/- 11.0 Nm, respectively; p < 0.05), even when controlling for upper-arm cross-sectional area (CSA), and peak electromyography activity. Boys also exhibited a lower normalized d/dmax (7.2 +/- 1.7 vs. 9.5 +/- 1.6 (Nm.s-1).(Nm-1), respectively; p < 0.05) and a significantly longer EMD (75.5 +/- 28.4 vs. 47.6 +/- 17.5 ms, respectively). The pattern was similar for extension, except that group differences in peak torque were no longer significant when normalized for CSA. These results suggest that children may be less able to recruit or fully utilize their higher-threshold motor units, resulting in lower dimensionally normalized maximal torque and rate of torque development.

Sweat gland response to exercise in the heat among pre-, mid-, and late-pubertal boys

Sweating rate (SR) of boys is lower than that of men. To assess the association between the response of individual sweat glands and physical growth and maturation, three groups of circumpubertal boys cycled at 50% VO2max in a climatic chamber (42 degrees C, 20% relative humidity). Based on Tanner staging (pubic hair), 16 were classified as prepubertal (PP, Tanner 1), 15 as midpubertal (MP, Tanner 2-4), and five as late-pubertal (LP, Tanner 5). Population density (PD) of the heat-activated sweat glands, the mean area of sweat drops (DA), and the proportion of skin covered by sweat (%A) were measured by skin photography and computer-assisted imaging analysis. Other measurements included rectal and skin temperatures (Tre, Tsk, respectively), heart rate (HR), and total body SR. The rise in HR, Tre and Tsk did not differ among groups. Whole body SR was significantly higher in the LP group compared with PP (PP = 4.95 +/- 0.23, MP = 5.79 +/- 0.20, LP = 6.70 +/- 0.42 ml.min-1.m-2) (mean +/- SEM). PD was significantly higher in the PP group (PP = 128 +/- 8, MP = 97 +/- 9, LP = 74 +/- 9 glands.cm-2), while DA was higher in the LP group (PP = 5.47 +/- 0.59, MP = 6.92 +/- 0.47, LP = 12.83 +/- 1.41 microns2.10(4)). %A did not differ among groups. The calculated SR per gland was higher among the LP groups compared with the less mature ones (PP = 4.6 +/- 0.3, MP = 7.2 +/- 0.8, LP = 9.6 +/- 1.0 nl.min-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Bone properties and muscle strength of young haemophilia patients.

Summary.  Purpose:  To evaluate bone properties, muscle strength and the relationship between the two, in young (7.0–17.7 years) haemophilia patients (h) and healthy boys (c).

Neutrophil function response to aerobic and anaerobic exercise in female judoka and untrained subjects

Objectives—Recent studies have indicated reduced immunity in trained athletes. Aim—To assess the effects of aerobic and anaerobic exercise on the phagocytic process in 18–26 year old trained female judoka (n = 8) and untrained controls (n = 7). Methods—Each subject participated randomly in two different testing sessions (aerobic, 20 minutes of treadmill running at 70–80% of maximal heart rate; anaerobic, Wingate anaerobic test). Venous blood samples were drawn before, immediately after, and 24 hours after each session. Results—There were no significant differences in basal values of net chemotaxis (chemotaxis − random migration), bactericidal activity, and superoxide anion release between the judoka and the untrained women. There was a significant decrease in net chemotaxis 24 hours after the aerobic exercise in both the judoka (from 64 (19) to 39 (13) cells/field, p<0.02) and the untrained controls (from 60 (7) to 47 (12) cells/field, p<0.05). Bactericidal activity and superoxide anion release did not change significantly after aerobic exercise in either group. There were no significant changes in net chemotaxis, bactericidal activity, and superoxide anion release after anaerobic exercise in either the judoka or untrained women. Conclusions—The decrease in net chemotaxis after aerobic, but not after anaerobic, exercise, suggests that net chemotaxis is affected by the combination of exercise intensity and duration, and not by the exercise intensity itself. Similar effects of both exercise sessions in the judoka and the untrained women suggest that training had no effect on neutrophil function response to aerobic and anaerobic exercises.