Physical exercise during childhood has been shown to enhance bone mineral density, thus reducing ... more Physical exercise during childhood has been shown to enhance bone mineral density, thus reducing the risk of osteoporosis. To examine bone properties, as measured by quantitative ultrasound, in prepubertal and early-pubertal female athletes engaged in impact and nonimpact sports. Survey. General community. Twenty-five acrobatic gymnasts, 21 swimmers, and 21 control subjects. Athletes had been training for at least 1(1/2) years. Bone speed of sound (bilateral) at the distal radius and the midtibia. Gymnasts were significantly shorter and lighter than swimmers and control girls (P<.001) but had a body mass index similar to that of swimmers. Adiposity was lower in athletes than in controls. Speed of sound did not correlate with measures of body size. Higher mean +/- SD radial speed of sound values (nondominant side) were observed in gymnasts (3764 +/- 104 m/s; P =.045) than in swimmers and control girls (3732 +/- 99 and 3721 +/- 83 m/s, respectively). Mean +/- SD tibial speed of sound values (nondominant side) were similar in gymnasts and swimmers (3629 +/- 87 and 3619 +/- 78 m/s, respectively) and higher in the athletic groups than in the control group (3516 +/- 127 m/s; P<.001). In all 3 groups, no differences were observed between dominant and nondominant sides in the radii or tibias. Physical exercise, impact and nonimpact, is related to enhanced bone properties, as measured by quantitative ultrasound. Longitudinal studies using various modes of bone evaluation are necessary to determine the long-term effect of various types of exercise on bone properties.
The purpose of this study was to examine the eVect of the Ramadan fast on performance capacities,... more The purpose of this study was to examine the eVect of the Ramadan fast on performance capacities, die- tary habits, and the daily behavioral patterns in adolescent (14-16-year-old) soccer players. Nineteen male players performed a series of Wtness tests before and at the end of Ramadan fast. Caloric intake, physical activity pattern and sleep habits were evaluated during the week
The myostatin (MSTN) Lys(K)-153Arg(R) polymorphism may influence skeletal muscle phenotypes. Carr... more The myostatin (MSTN) Lys(K)-153Arg(R) polymorphism may influence skeletal muscle phenotypes. Carrying the rare R allele was associated with greater muscle mass. The aim of the present study was to assess the frequency of the MSTN Lys(K)-153Arg(R) polymorphism among Israeli track and field athletes (n=185) and swimmers (n=80). Track and field athletes were divided into long distance runners (major event 5000m-marathon, n=113) and power athletes (major event 100200m sprints and long jump, n=72). Swimmers were divided into long-distance swimmers (major event: 800-1500m, n=38), and short-distance swimmers (major event: 50-100m, n=42). The control group included 118 non-athletes healthy participants. Twenty-seven track and field athletes (14.6%) and 7 swimmers (8.8%) were carriers of the rare MSTN R allele, and only two carried the 153RR genotype (0.8%). MSTN 153R allele frequency was significantly higher in top-compared to national-level among long-distance runners (26% versus 8%, p<0.05), short distance runners (16% versus 9%, p<0.05), and all runners combined (20% versus 8%, p<0.05), but not in top- compared to national-level swimmers. The frequency of arginine carriers was significantly greater among long compared to short-distance swimmers (16% versus 2%, p<0.03). In contrast to elite endurance and power track and field athletes, the MSTN 153RR genotype was not found in short distance-swimmers, and among the long distance-swimmers it was not associated with top level swimming performance. Whether evaluation of the MSTN K153R polymorphism can be used for sports selection in young athletes needs to be further studied.
Journal of pediatric endocrinology & metabolism : JPEM, 2007
Obesity is now the most common chronic pediatric disease. Early health education programs could s... more Obesity is now the most common chronic pediatric disease. Early health education programs could serve to prevent and treat childhood obesity and its numerous complications. To examine the effects of a randomized prospective school-based intervention on anthropometric measures, body composition, leisure time habits and fitness in preschool children. Fifty-four preschool children completed a 14-week combined dietary-behavioral-physical activity intervention and were compared to 47 age matched controls (age 5-6 yr). Daily physical activity was significantly greater in the intervention group compared to the controls (6,927 +/- 364 vs 5,489 +/- 284 steps/ day, respectively; p < 0.003). Favorable changes were observed in weight (0.35 +/- 0.08 vs 0.9 +/- 0.1 kg, p < 0.0005), BMI percentile (-3.8 +/- 1.3 vs 2.9 +/- 1.5 kg/m2, p < 0.001), fat percent (by skinfolds, -0.65 +/- 0.3 vs 1.64 +/- 0.3%, p < 0.028) and fitness (endurance time -3.55 +/- 1.85 vs 3.16 +/- 2.05%, p < 0.01...
Journal of strength and conditioning research / National Strength & Conditioning Association, 2014
Exercise-associated effects on the growth hormone-insulin-like growth factor-I (GH-IGF-I) axis we... more Exercise-associated effects on the growth hormone-insulin-like growth factor-I (GH-IGF-I) axis were studied, mainly after aerobic exercise. We determined the gender effect on the GH-IGF-I axis response to a standard all-out Wingate anaerobic test (WAnT) in healthy active young adult men and women (men = 12 and women = 16; age range: 24-34 years). Blood samples for GH and IGF-I, key elements of the GH-IGF-I axis, were collected before and 20, 30, 40, and 60 minutes after the beginning of exercise. In addition, we collected postexercise blood lactate levels. Postexercise lactate levels were higher among men; however, this difference did not reach statistical significance (13.8 ± 1.3 vs. 11.1 ± 1.0 mmol·L, respectively; p = 0.1). The WAnT was associated with a significant increase in GH in both genders. However, GH peak was greater among women (10.8 ± 1.8 vs. 5.6 ± 1.4 ng·ml, in women and men, respectively; p < 0.01). In addition, postexercise GH peak occurred significantly earlier ...
The manuscript "Plasma Somatomedin-C in 8- to 10-Year-Old Swimmers" by Denison and Ben-... more The manuscript "Plasma Somatomedin-C in 8- to 10-Year-Old Swimmers" by Denison and Ben-Ezra published in the first issue of Pediatric Exercise Science in 1989 was among the first to address the relationship between growth, the growth hormone (GH)/Insulin like growth factor-1 (IGF-1) axis, and exercise. Since their pioneering article, this topic has become of great interest to pediatricians and pediatric exercise researchers, and today our understanding of the effects of exercise training on the growth axis during childhood and puberty, on differences between systemic and local (i.e., muscle) responses to exercise, and our ability to use these responses to assist the adolescent competitive athlete in the evaluation of the training load have markedly improved. The aim of the present review is to summarize our current knowledge on this topic.
International journal of pediatric obesity : IJPO : an official journal of the International Association for the Study of Obesity, Jan 3, 2010
To examine the immediate effect of three different types of popular exercise activities on food i... more To examine the immediate effect of three different types of popular exercise activities on food intake and preferences in normal weight and overweight children. Forty-four (22 overweight) age and gender matched, pre-pubertal children participated in four separate visits. All performed three typical, 45 min, aerobic, indoor resistance and swimming exercise sessions and a control visit (no exercise). A similar buffet lunch was served immediately after each visit to both groups. The total energy intake and relative consumption of carbohydrates, fat and protein were recorded. In the normal weight children, total energy intake was reduced following exercise. This difference reached statistical significance only following the resistance-type exercise (14.0 + or - 1.4 [58.6 + or - 5.9] versus 19.4 + or - 1.7 [81.2 + or - 7.1] kcal/kg [kJ/ kg], in resistance exercise and control, respectively; p<0.008). The different types of exercise were associated with increased relative consumption o...
The diagnosis of Growth Hormone (GH) deficiency in children with short stature is complex, and in... more The diagnosis of Growth Hormone (GH) deficiency in children with short stature is complex, and in certain cases, might be very difficult. Most of the provocative tests used to evaluate GH deficiency use pharmacological agents. The artificial nature of the pharmacological tests and the possibility that these tests might not always reflect GH secretion under normal physiological conditions provides the impetus for a more physiologic test. Exercise is one of the important GH releasing physiological stimuli. This review will summarize the current knowledge on the methods for performing laboratory exercise provocation test for GH secretion in children. In addition to recommendations of more standardized exercise protocols and environmental considerations, we will also focus on GH responses to exercise in unique populations such as obese children.
Ergogenic aids (from the Greek, ergon, meaning work) are ingested to enhance energy utilization i... more Ergogenic aids (from the Greek, ergon, meaning work) are ingested to enhance energy utilization in athletes. In recent years there has been an increase in youth participating in competitive sports and, as a consequence, a concomitant increase in the usage of performance enhancing substances. Ergogenic aid usage could influence, or its efficiency could be influenced, during this period of rapid growth and sexual maturation, and by the marked hormonal fluctuations. Ephedra alkaloids; pain relief medications, diuretics, anabolic steroids and protein hormones are among the ergogenic aids used by young athletes. While there is no scientific evidence to support the usage of these agents for enhancing performance in children and adolescents, using supra-physiological doses may be associated with undesired side effects.
International journal of pediatric obesity : IJPO : an official journal of the International Association for the Study of Obesity, 2006
To examine the prevalence of abnormal thyroid function tests among obese children and adolescents... more To examine the prevalence of abnormal thyroid function tests among obese children and adolescents, and to study the effect of thyroid hormone supplementation on body weight, linear growth and lipid profiles in these children. Thyroid function tests and lipid profiles were measured in 196 obese children and adolescents. Thyroid auto-antibodies were measured in children with hyperthyrotropinemia (elevated thyroid stimulating hormone (TSH) and normal free thyroxine-FT4). All children with hyperthyrotropinemia participated in a combined dietary-behavioral-physical activity weight management intervention. Fifteen of the obese children with hyperthyrotropinemia were also treated with thyroid hormone substitution for 6 months and were compared to non-treated subjects (n = 26). Forty-one obese children had hyperthyrotropinemia (20.9%). Positive thyroid auto-antibodies were only found in 19.5% of these children. Treatment had no significant effect on body weight, linear growth and lipid prof...
The aim of the present study was to determine physical activity and nutritional knowledge and pre... more The aim of the present study was to determine physical activity and nutritional knowledge and preferences in kindergarten children. Following height and weight measurement, and age and gender adjusted BMI percentile calculation, 202 kindergarten children (4 - 6.5 yr) completed twice in a random order, a photo-pair food and exercise questionnaire. Knowledge was determined by asking the child to choose food/activity that would make a selected doll healthier, while preferences where determined by the child's own choise. Nutritional knowledge score was higher than the physical activity knowledge score (73.4 +/- 1.5 vs. 67.5 +/- 1.9 %, p < 0.006), while the nutrition preference score was lower than the physical activity preference score (42.2 +/- 1. 8 vs. 66.5 +/- 1.6 %, p < 0.0001). There was a difference between nutrition knowledge and preferences (73.4 +/- 1.5 vs. 42.2 +/- 1.8 %, p < 0.0001). No differences were found between physical activity knowledge and preferences. N...
Weight-bearing, high-impact exercise, as opposed to nonimpact exercise, has been demonstrated to ... more Weight-bearing, high-impact exercise, as opposed to nonimpact exercise, has been demonstrated to increase bone mineral density. This was traditionally demonstrated with dual energy X-ray absorptiometry. Our objective was to assess the differences in bone properties, using quantitative ultrasound (QUS, Sunlight Omnisense, Sunlight Medical, Ltd., Tel Aviv, Israel), in male athletes involved in a weight-bearing, impact sport (soccer, SC) or a nonimpact sport (swimming and water polo, AQ), compared with nonathletic control (C) males. A total of 266 boys and men, aged 8 - 23 years, were divided into children (11.1 +/- 1.0 years; 34 SC, 34 AQ, 25 C), adolescents (14.7 +/- 1.2 years; 32 SC, 31 AQ, 31 C), and young adults (19.8 +/- 1.1 years; 31 SC, 24 AQ, 24 C) . Training experience varied between 1.5 years in the children to 15 years in the adults. Bone speed of sound (SOS) was measured bilaterally at the distal radius and the mid-tibia. Body fat was significantly lower in athletes compar...
The evaluation of training load and effectiveness in elite athletes is difficult. We determined t... more The evaluation of training load and effectiveness in elite athletes is difficult. We determined the effect of a four-week training camp on changes in self-assessment physical conditioning scores, fitness and circulating IGF-I in elite Israeli handball players during their preparation for the 1999 World Junior Handball Championship. Training consisted of two weeks of intense training followed by two weeks of relative tapering. Fitness was assessed by field test measurements of 1000-m run, 4 x 10-m shuttle run and vertical jump. Serum IGF-I levels were measured by immunoradiometric assay. Measurements were performed before, after two weeks, and at the end of training. Training resulted in a significant (p &lt; 0.05) improvement in the results of the 4 x 10-m run, 1000-m run and vertical jump. Changes in the self-assessment physical conditioning score showed a bi-directional pattern. After two weeks of training the players reported decreased physical conditioning scores, with return to basal levels after four weeks. Similarly, circulating IGF-I decreased significantly after two weeks, and returned to basal levels after four weeks of training. We found a significant correlation between changes in circulating IGF-I, and self-assessments of physical conditioning scores (r = 0.71, p &lt; 0.001). Intensive training resulted in a decrease, while tapering was associated with an increase in IGF-I levels. These changes were accompanied by parallel changes in subjective physical conditioning self-assessments.
Ballet dancers tend to restrict caloric intake and/or to use inappropriate compensatory behavior ... more Ballet dancers tend to restrict caloric intake and/or to use inappropriate compensatory behavior (e.g. self-induced vomiting, use of laxatives) in order to maintain a low body weight. Therefore careful assessment of body composition and determination of minimal body weight for maintenance of a desirable percent fat may reduce unnecessary weight loss and decrease the use of a potentially dangerous weight-control behavior. The purpose of this study was to determine body fat in a homogenous group of 59 adolescent, female ballet dancers (age range 14-17 y). Body composition was assessed using three different techniques: skinfold thickness measurements, bio-electrical impedance analysis (BIA), and dual energy X-ray absorptiometry (DXA). Percent body fat and the sum of skinfold thickness were calculated from measurements of four sites (i.e. triceps, biceps, subscapular, and suprailiac). All eumenorrheic dancers were examined in the early follicular phase of the menstrual cycle whereas ame...
Physical activity during childhood and adolescence may influence the development of childhood obe... more Physical activity during childhood and adolescence may influence the development of childhood obesity and cardiovascular disease later in life. Research focused prospectively on the effects of training on lipid levels in nonobese subjects, and studies using noninvasive measurements of subcutaneous and intraabdominal fat are lacking. It was hypothesized in nonobese sedentary adolescent males that a brief endurance-type exercise training intervention would reduce body fat and improve lipid profiles. Thirty-eight healthy, nonobese sedentary adolescent males (mean age 16 +/- 0.7 years old; 18 controls, 20 trained) completed a 5-week prospective, randomized, controlled study. Adiposity was measured using magnetic resonance images of the thigh and abdomen (subcutaneous abdominal adipose tissue [SAAT] and intraabdominal adipose tissue [IAAT]). Lipid measurements included serum triglycerides (TG), total cholesterol (TC), HDL and LDL cholesterol. There was no change in body weight in either ...
International journal of obesity and related metabolic disorders : journal of the International Association for the Study of Obesity, 1998
In healthy, nonobese, adolescent males and females to: (1) Determine the relationship between fit... more In healthy, nonobese, adolescent males and females to: (1) Determine the relationship between fitness and energy intake; (2) assess the effect of five-weeks endurance training on energy intake and food choice and (3) compare food record assessments of energy intake with doubly-labeled water (DLW) measurement of total energy expenditure (TEE). (1) Cross sectional analysis of fitness and food intake and (2) Prospective, randomized, controlled interventional study of endurance-type exercise training in 44 females and 44 males (age range, 15-17 y). Pre and end interventional three day food records were successfully collected from 32 females (15 controls, 17 trained) and 39 males (19 controls, 20 trained). Fitness was assessed from cycle ergometry as peak oxygen uptake normalized both to thigh muscle mass and body weight. Thigh muscle mass was measured by magnetic resonance imaging. TEE using the DLW technique was measured in 12 females (6 controls, 6 trained) and 20 males (10 controls, ...
Recent studies reported reduced immunity in athletes following exercise. Physical activity affect... more Recent studies reported reduced immunity in athletes following exercise. Physical activity affects both cellular and humoral immune functions. Scant information exists on exercise-induced changes in the immune system among children. The purpose of the present study was to investigate the effect of aerobic exercise on several aspects of cellular and humoral functions among 10-12 year-old highly trained female gymnasts (n = 7) and untrained girls (n = 6). All girls were pre-pubertal. Venous blood samples were drawn before, immediately after and 24 h following 20 min of treadmill running (heart rate 170-180 beats.min-1). White blood cells' number rose significantly following exercise and remained elevated for 24 h. The increase in leukocyte number was due to an increase in granulocytes as well as an increase in lymphocytes and monocytes. While neutrophil count returned to basal values after 24 h, lymphocytes and monocytes number remained elevated 24 h following exercise. Exercise r...
The purpose of this study was to determine indices of swimming repeated sprint ability (RSA) in 1... more The purpose of this study was to determine indices of swimming repeated sprint ability (RSA) in 19 elite water polo players compared to 16 elite swimmers during a repeated sprint swimming test (RST), and to examine the relationships between these indices and aerobic and anaerobic performance capabilities in both groups. Indices of RSA were determined by the ideal sprint time (IS), the total sprint time (TS), and the performance decrement (PD) recorded during an 8 x 15-m swimming RST. Single long - (800-m) and short-(25-m) distance swim tests were used to determined indices of aerobic and anaerobic swimming capabilities, respectively. The water polo players exhibited lower RSA swimming indices, as well as lower scores in the single short and long swim distances, compared to the swimmers. Significant relationships were found between the 25- m swim results and the IS and the TS, but not the PD of both the swimmers and the water polo players. No significant relationships were found betw...
The present study compares previous reports on the effect of "real-life" typical field ... more The present study compares previous reports on the effect of "real-life" typical field individual (i.e., cross-country running and wrestling--representing combat versus noncombat sports) and team sports (i.e., volleyball and water polo-representing water and land team sports) training on GH and IGF-1, the main growth factors of the GH→IGF axis, in male and female late pubertal athletes. Cross-country running practice and volleyball practice in both males and females were associated with significant increases of circulating GH levels, while none of the practices led to a significant increase in IGF-I levels. The magnitude (percent change) of the GH response to the different practices was determined mainly by preexercise GH levels. There was no difference in the training-associated GH response between individual and team sports practices. The GH response to the different typical practices was not influenced by the practice-associated lactate change. Further studies are neede...
Physical exercise during childhood has been shown to enhance bone mineral density, thus reducing ... more Physical exercise during childhood has been shown to enhance bone mineral density, thus reducing the risk of osteoporosis. To examine bone properties, as measured by quantitative ultrasound, in prepubertal and early-pubertal female athletes engaged in impact and nonimpact sports. Survey. General community. Twenty-five acrobatic gymnasts, 21 swimmers, and 21 control subjects. Athletes had been training for at least 1(1/2) years. Bone speed of sound (bilateral) at the distal radius and the midtibia. Gymnasts were significantly shorter and lighter than swimmers and control girls (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;.001) but had a body mass index similar to that of swimmers. Adiposity was lower in athletes than in controls. Speed of sound did not correlate with measures of body size. Higher mean +/- SD radial speed of sound values (nondominant side) were observed in gymnasts (3764 +/- 104 m/s; P =.045) than in swimmers and control girls (3732 +/- 99 and 3721 +/- 83 m/s, respectively). Mean +/- SD tibial speed of sound values (nondominant side) were similar in gymnasts and swimmers (3629 +/- 87 and 3619 +/- 78 m/s, respectively) and higher in the athletic groups than in the control group (3516 +/- 127 m/s; P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;.001). In all 3 groups, no differences were observed between dominant and nondominant sides in the radii or tibias. Physical exercise, impact and nonimpact, is related to enhanced bone properties, as measured by quantitative ultrasound. Longitudinal studies using various modes of bone evaluation are necessary to determine the long-term effect of various types of exercise on bone properties.
The purpose of this study was to examine the eVect of the Ramadan fast on performance capacities,... more The purpose of this study was to examine the eVect of the Ramadan fast on performance capacities, die- tary habits, and the daily behavioral patterns in adolescent (14-16-year-old) soccer players. Nineteen male players performed a series of Wtness tests before and at the end of Ramadan fast. Caloric intake, physical activity pattern and sleep habits were evaluated during the week
The myostatin (MSTN) Lys(K)-153Arg(R) polymorphism may influence skeletal muscle phenotypes. Carr... more The myostatin (MSTN) Lys(K)-153Arg(R) polymorphism may influence skeletal muscle phenotypes. Carrying the rare R allele was associated with greater muscle mass. The aim of the present study was to assess the frequency of the MSTN Lys(K)-153Arg(R) polymorphism among Israeli track and field athletes (n=185) and swimmers (n=80). Track and field athletes were divided into long distance runners (major event 5000m-marathon, n=113) and power athletes (major event 100200m sprints and long jump, n=72). Swimmers were divided into long-distance swimmers (major event: 800-1500m, n=38), and short-distance swimmers (major event: 50-100m, n=42). The control group included 118 non-athletes healthy participants. Twenty-seven track and field athletes (14.6%) and 7 swimmers (8.8%) were carriers of the rare MSTN R allele, and only two carried the 153RR genotype (0.8%). MSTN 153R allele frequency was significantly higher in top-compared to national-level among long-distance runners (26% versus 8%, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05), short distance runners (16% versus 9%, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05), and all runners combined (20% versus 8%, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05), but not in top- compared to national-level swimmers. The frequency of arginine carriers was significantly greater among long compared to short-distance swimmers (16% versus 2%, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.03). In contrast to elite endurance and power track and field athletes, the MSTN 153RR genotype was not found in short distance-swimmers, and among the long distance-swimmers it was not associated with top level swimming performance. Whether evaluation of the MSTN K153R polymorphism can be used for sports selection in young athletes needs to be further studied.
Journal of pediatric endocrinology & metabolism : JPEM, 2007
Obesity is now the most common chronic pediatric disease. Early health education programs could s... more Obesity is now the most common chronic pediatric disease. Early health education programs could serve to prevent and treat childhood obesity and its numerous complications. To examine the effects of a randomized prospective school-based intervention on anthropometric measures, body composition, leisure time habits and fitness in preschool children. Fifty-four preschool children completed a 14-week combined dietary-behavioral-physical activity intervention and were compared to 47 age matched controls (age 5-6 yr). Daily physical activity was significantly greater in the intervention group compared to the controls (6,927 +/- 364 vs 5,489 +/- 284 steps/ day, respectively; p < 0.003). Favorable changes were observed in weight (0.35 +/- 0.08 vs 0.9 +/- 0.1 kg, p < 0.0005), BMI percentile (-3.8 +/- 1.3 vs 2.9 +/- 1.5 kg/m2, p < 0.001), fat percent (by skinfolds, -0.65 +/- 0.3 vs 1.64 +/- 0.3%, p < 0.028) and fitness (endurance time -3.55 +/- 1.85 vs 3.16 +/- 2.05%, p < 0.01...
Journal of strength and conditioning research / National Strength & Conditioning Association, 2014
Exercise-associated effects on the growth hormone-insulin-like growth factor-I (GH-IGF-I) axis we... more Exercise-associated effects on the growth hormone-insulin-like growth factor-I (GH-IGF-I) axis were studied, mainly after aerobic exercise. We determined the gender effect on the GH-IGF-I axis response to a standard all-out Wingate anaerobic test (WAnT) in healthy active young adult men and women (men = 12 and women = 16; age range: 24-34 years). Blood samples for GH and IGF-I, key elements of the GH-IGF-I axis, were collected before and 20, 30, 40, and 60 minutes after the beginning of exercise. In addition, we collected postexercise blood lactate levels. Postexercise lactate levels were higher among men; however, this difference did not reach statistical significance (13.8 ± 1.3 vs. 11.1 ± 1.0 mmol·L, respectively; p = 0.1). The WAnT was associated with a significant increase in GH in both genders. However, GH peak was greater among women (10.8 ± 1.8 vs. 5.6 ± 1.4 ng·ml, in women and men, respectively; p < 0.01). In addition, postexercise GH peak occurred significantly earlier ...
The manuscript "Plasma Somatomedin-C in 8- to 10-Year-Old Swimmers" by Denison and Ben-... more The manuscript "Plasma Somatomedin-C in 8- to 10-Year-Old Swimmers" by Denison and Ben-Ezra published in the first issue of Pediatric Exercise Science in 1989 was among the first to address the relationship between growth, the growth hormone (GH)/Insulin like growth factor-1 (IGF-1) axis, and exercise. Since their pioneering article, this topic has become of great interest to pediatricians and pediatric exercise researchers, and today our understanding of the effects of exercise training on the growth axis during childhood and puberty, on differences between systemic and local (i.e., muscle) responses to exercise, and our ability to use these responses to assist the adolescent competitive athlete in the evaluation of the training load have markedly improved. The aim of the present review is to summarize our current knowledge on this topic.
International journal of pediatric obesity : IJPO : an official journal of the International Association for the Study of Obesity, Jan 3, 2010
To examine the immediate effect of three different types of popular exercise activities on food i... more To examine the immediate effect of three different types of popular exercise activities on food intake and preferences in normal weight and overweight children. Forty-four (22 overweight) age and gender matched, pre-pubertal children participated in four separate visits. All performed three typical, 45 min, aerobic, indoor resistance and swimming exercise sessions and a control visit (no exercise). A similar buffet lunch was served immediately after each visit to both groups. The total energy intake and relative consumption of carbohydrates, fat and protein were recorded. In the normal weight children, total energy intake was reduced following exercise. This difference reached statistical significance only following the resistance-type exercise (14.0 + or - 1.4 [58.6 + or - 5.9] versus 19.4 + or - 1.7 [81.2 + or - 7.1] kcal/kg [kJ/ kg], in resistance exercise and control, respectively; p<0.008). The different types of exercise were associated with increased relative consumption o...
The diagnosis of Growth Hormone (GH) deficiency in children with short stature is complex, and in... more The diagnosis of Growth Hormone (GH) deficiency in children with short stature is complex, and in certain cases, might be very difficult. Most of the provocative tests used to evaluate GH deficiency use pharmacological agents. The artificial nature of the pharmacological tests and the possibility that these tests might not always reflect GH secretion under normal physiological conditions provides the impetus for a more physiologic test. Exercise is one of the important GH releasing physiological stimuli. This review will summarize the current knowledge on the methods for performing laboratory exercise provocation test for GH secretion in children. In addition to recommendations of more standardized exercise protocols and environmental considerations, we will also focus on GH responses to exercise in unique populations such as obese children.
Ergogenic aids (from the Greek, ergon, meaning work) are ingested to enhance energy utilization i... more Ergogenic aids (from the Greek, ergon, meaning work) are ingested to enhance energy utilization in athletes. In recent years there has been an increase in youth participating in competitive sports and, as a consequence, a concomitant increase in the usage of performance enhancing substances. Ergogenic aid usage could influence, or its efficiency could be influenced, during this period of rapid growth and sexual maturation, and by the marked hormonal fluctuations. Ephedra alkaloids; pain relief medications, diuretics, anabolic steroids and protein hormones are among the ergogenic aids used by young athletes. While there is no scientific evidence to support the usage of these agents for enhancing performance in children and adolescents, using supra-physiological doses may be associated with undesired side effects.
International journal of pediatric obesity : IJPO : an official journal of the International Association for the Study of Obesity, 2006
To examine the prevalence of abnormal thyroid function tests among obese children and adolescents... more To examine the prevalence of abnormal thyroid function tests among obese children and adolescents, and to study the effect of thyroid hormone supplementation on body weight, linear growth and lipid profiles in these children. Thyroid function tests and lipid profiles were measured in 196 obese children and adolescents. Thyroid auto-antibodies were measured in children with hyperthyrotropinemia (elevated thyroid stimulating hormone (TSH) and normal free thyroxine-FT4). All children with hyperthyrotropinemia participated in a combined dietary-behavioral-physical activity weight management intervention. Fifteen of the obese children with hyperthyrotropinemia were also treated with thyroid hormone substitution for 6 months and were compared to non-treated subjects (n = 26). Forty-one obese children had hyperthyrotropinemia (20.9%). Positive thyroid auto-antibodies were only found in 19.5% of these children. Treatment had no significant effect on body weight, linear growth and lipid prof...
The aim of the present study was to determine physical activity and nutritional knowledge and pre... more The aim of the present study was to determine physical activity and nutritional knowledge and preferences in kindergarten children. Following height and weight measurement, and age and gender adjusted BMI percentile calculation, 202 kindergarten children (4 - 6.5 yr) completed twice in a random order, a photo-pair food and exercise questionnaire. Knowledge was determined by asking the child to choose food/activity that would make a selected doll healthier, while preferences where determined by the child's own choise. Nutritional knowledge score was higher than the physical activity knowledge score (73.4 +/- 1.5 vs. 67.5 +/- 1.9 %, p < 0.006), while the nutrition preference score was lower than the physical activity preference score (42.2 +/- 1. 8 vs. 66.5 +/- 1.6 %, p < 0.0001). There was a difference between nutrition knowledge and preferences (73.4 +/- 1.5 vs. 42.2 +/- 1.8 %, p < 0.0001). No differences were found between physical activity knowledge and preferences. N...
Weight-bearing, high-impact exercise, as opposed to nonimpact exercise, has been demonstrated to ... more Weight-bearing, high-impact exercise, as opposed to nonimpact exercise, has been demonstrated to increase bone mineral density. This was traditionally demonstrated with dual energy X-ray absorptiometry. Our objective was to assess the differences in bone properties, using quantitative ultrasound (QUS, Sunlight Omnisense, Sunlight Medical, Ltd., Tel Aviv, Israel), in male athletes involved in a weight-bearing, impact sport (soccer, SC) or a nonimpact sport (swimming and water polo, AQ), compared with nonathletic control (C) males. A total of 266 boys and men, aged 8 - 23 years, were divided into children (11.1 +/- 1.0 years; 34 SC, 34 AQ, 25 C), adolescents (14.7 +/- 1.2 years; 32 SC, 31 AQ, 31 C), and young adults (19.8 +/- 1.1 years; 31 SC, 24 AQ, 24 C) . Training experience varied between 1.5 years in the children to 15 years in the adults. Bone speed of sound (SOS) was measured bilaterally at the distal radius and the mid-tibia. Body fat was significantly lower in athletes compar...
The evaluation of training load and effectiveness in elite athletes is difficult. We determined t... more The evaluation of training load and effectiveness in elite athletes is difficult. We determined the effect of a four-week training camp on changes in self-assessment physical conditioning scores, fitness and circulating IGF-I in elite Israeli handball players during their preparation for the 1999 World Junior Handball Championship. Training consisted of two weeks of intense training followed by two weeks of relative tapering. Fitness was assessed by field test measurements of 1000-m run, 4 x 10-m shuttle run and vertical jump. Serum IGF-I levels were measured by immunoradiometric assay. Measurements were performed before, after two weeks, and at the end of training. Training resulted in a significant (p &lt; 0.05) improvement in the results of the 4 x 10-m run, 1000-m run and vertical jump. Changes in the self-assessment physical conditioning score showed a bi-directional pattern. After two weeks of training the players reported decreased physical conditioning scores, with return to basal levels after four weeks. Similarly, circulating IGF-I decreased significantly after two weeks, and returned to basal levels after four weeks of training. We found a significant correlation between changes in circulating IGF-I, and self-assessments of physical conditioning scores (r = 0.71, p &lt; 0.001). Intensive training resulted in a decrease, while tapering was associated with an increase in IGF-I levels. These changes were accompanied by parallel changes in subjective physical conditioning self-assessments.
Ballet dancers tend to restrict caloric intake and/or to use inappropriate compensatory behavior ... more Ballet dancers tend to restrict caloric intake and/or to use inappropriate compensatory behavior (e.g. self-induced vomiting, use of laxatives) in order to maintain a low body weight. Therefore careful assessment of body composition and determination of minimal body weight for maintenance of a desirable percent fat may reduce unnecessary weight loss and decrease the use of a potentially dangerous weight-control behavior. The purpose of this study was to determine body fat in a homogenous group of 59 adolescent, female ballet dancers (age range 14-17 y). Body composition was assessed using three different techniques: skinfold thickness measurements, bio-electrical impedance analysis (BIA), and dual energy X-ray absorptiometry (DXA). Percent body fat and the sum of skinfold thickness were calculated from measurements of four sites (i.e. triceps, biceps, subscapular, and suprailiac). All eumenorrheic dancers were examined in the early follicular phase of the menstrual cycle whereas ame...
Physical activity during childhood and adolescence may influence the development of childhood obe... more Physical activity during childhood and adolescence may influence the development of childhood obesity and cardiovascular disease later in life. Research focused prospectively on the effects of training on lipid levels in nonobese subjects, and studies using noninvasive measurements of subcutaneous and intraabdominal fat are lacking. It was hypothesized in nonobese sedentary adolescent males that a brief endurance-type exercise training intervention would reduce body fat and improve lipid profiles. Thirty-eight healthy, nonobese sedentary adolescent males (mean age 16 +/- 0.7 years old; 18 controls, 20 trained) completed a 5-week prospective, randomized, controlled study. Adiposity was measured using magnetic resonance images of the thigh and abdomen (subcutaneous abdominal adipose tissue [SAAT] and intraabdominal adipose tissue [IAAT]). Lipid measurements included serum triglycerides (TG), total cholesterol (TC), HDL and LDL cholesterol. There was no change in body weight in either ...
International journal of obesity and related metabolic disorders : journal of the International Association for the Study of Obesity, 1998
In healthy, nonobese, adolescent males and females to: (1) Determine the relationship between fit... more In healthy, nonobese, adolescent males and females to: (1) Determine the relationship between fitness and energy intake; (2) assess the effect of five-weeks endurance training on energy intake and food choice and (3) compare food record assessments of energy intake with doubly-labeled water (DLW) measurement of total energy expenditure (TEE). (1) Cross sectional analysis of fitness and food intake and (2) Prospective, randomized, controlled interventional study of endurance-type exercise training in 44 females and 44 males (age range, 15-17 y). Pre and end interventional three day food records were successfully collected from 32 females (15 controls, 17 trained) and 39 males (19 controls, 20 trained). Fitness was assessed from cycle ergometry as peak oxygen uptake normalized both to thigh muscle mass and body weight. Thigh muscle mass was measured by magnetic resonance imaging. TEE using the DLW technique was measured in 12 females (6 controls, 6 trained) and 20 males (10 controls, ...
Recent studies reported reduced immunity in athletes following exercise. Physical activity affect... more Recent studies reported reduced immunity in athletes following exercise. Physical activity affects both cellular and humoral immune functions. Scant information exists on exercise-induced changes in the immune system among children. The purpose of the present study was to investigate the effect of aerobic exercise on several aspects of cellular and humoral functions among 10-12 year-old highly trained female gymnasts (n = 7) and untrained girls (n = 6). All girls were pre-pubertal. Venous blood samples were drawn before, immediately after and 24 h following 20 min of treadmill running (heart rate 170-180 beats.min-1). White blood cells' number rose significantly following exercise and remained elevated for 24 h. The increase in leukocyte number was due to an increase in granulocytes as well as an increase in lymphocytes and monocytes. While neutrophil count returned to basal values after 24 h, lymphocytes and monocytes number remained elevated 24 h following exercise. Exercise r...
The purpose of this study was to determine indices of swimming repeated sprint ability (RSA) in 1... more The purpose of this study was to determine indices of swimming repeated sprint ability (RSA) in 19 elite water polo players compared to 16 elite swimmers during a repeated sprint swimming test (RST), and to examine the relationships between these indices and aerobic and anaerobic performance capabilities in both groups. Indices of RSA were determined by the ideal sprint time (IS), the total sprint time (TS), and the performance decrement (PD) recorded during an 8 x 15-m swimming RST. Single long - (800-m) and short-(25-m) distance swim tests were used to determined indices of aerobic and anaerobic swimming capabilities, respectively. The water polo players exhibited lower RSA swimming indices, as well as lower scores in the single short and long swim distances, compared to the swimmers. Significant relationships were found between the 25- m swim results and the IS and the TS, but not the PD of both the swimmers and the water polo players. No significant relationships were found betw...
The present study compares previous reports on the effect of "real-life" typical field ... more The present study compares previous reports on the effect of "real-life" typical field individual (i.e., cross-country running and wrestling--representing combat versus noncombat sports) and team sports (i.e., volleyball and water polo-representing water and land team sports) training on GH and IGF-1, the main growth factors of the GH→IGF axis, in male and female late pubertal athletes. Cross-country running practice and volleyball practice in both males and females were associated with significant increases of circulating GH levels, while none of the practices led to a significant increase in IGF-I levels. The magnitude (percent change) of the GH response to the different practices was determined mainly by preexercise GH levels. There was no difference in the training-associated GH response between individual and team sports practices. The GH response to the different typical practices was not influenced by the practice-associated lactate change. Further studies are neede...
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Papers by Alon Eliakim