Little evidence exists on which exercise modality is optimal for obese adolescents. Objective: To determine the effects of aerobic training, resistance training, and combined training on percentage body fat in overweight and obese adolescents.
Design, Setting, and Participants:
Randomized, parallel-group clinical trial at community-based exercise facilities in Ottawa (Ontario) and Gatineau (Quebec), Canada, among previously inactive postpubertal adolescents aged 14-18 years (Tanner stage IV or V) with body mass index at or above the 95th percentile for age and sex or at or above the 85th percentile plus an additional diabetes mellitus or cardiovascular risk factor. Interventions: After a 4-week run-in period, 304 participants were randomized to the following 4 groups for 22 weeks: aerobic training (n = 75), resistance training (n = 78), combined aerobic and resistance training (n = 75), or nonexercising control (n = 76). All participants received dietary counseling, with a daily energy deficit of 250 kcal.
Main Outcomes and Measures:
The primary outcome was percentage body fat measured by magnetic resonance imaging at baseline and 6 months. We hypothesized that aerobic training and resistance training would each yield greater decreases than the control and that combined training would cause greater decreases than aerobic or resistance training alone.
Decreases in percentage body fat were −0.3 (95% CI, −0.9 to 0.3) in the control group, −1.1 (95% CI, −1.7 to −0.5) in the aerobic training group (p = .06 vs. controls), and −1.6 (95% CI, −2.2 to −1.0) in the resistance training group (p = .002 vs controls). The −1.4 (95% CI, −2.0 to −0.8) decrease in the combined training group did not differ significantly from that in the aerobic or resistance training group. Waist circumference changes were −0.2 (95% CI, −1.7 to 1.2) cm in the control group, −3.0 (95% CI, −4.4 to −1.6) cm in the aerobic group (p = .006 vs controls), −2.2 (95% CI −3.7 to −0.8) cm in the resistance training group (p = .048 vs controls), and −4.1 (95% CI, −5.5 to −2.7) cm in the combined training group. In per-protocol analyses (> 70% adherence), the combined training group had greater changes in percentage body fat (-2.4, 95% CI, −3.2 to −1.6) vs the aerobic group (-1.2; 95% CI, −2.0 to −0.5; p = .04 vs the combined group) but not the resistance group (-1.6; 95% CI, −2.5 to −0.8).
Conclusions and Relevance:
Aerobic, resistance, and combined training reduced total body fat and waist circumference in obese adolescents. In more adherent participants, combined training may cause greater decreases than aerobic or resistance training alone.
As the incidence of childhood obesity increases, there is a need to promote leisure time physical activity. Traditional approaches to promote the population physical activity levels have shown at best moderate improvements. High percentage of children today carry a cell phone, thus the use of this portable device seems promising for enhancing physical activity.
Pokémon Go, is a smartphone game that uses augmented reality, where players are incentivized to get out and walk significant distances to catch the Pokémon. Initial reports suggested increases in the number of steps that players performed, yet this effect of the game was not sustained. Incorporating physical activity into modern technology seems promising, clearly there is need to explore creative ways to achieve a longer term effect.
Alon Eliakim and Dan Nemet
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.
Alon Eliakim and Dan Nemet
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.
Alon Eliakim, Dan M. Cooper, and Dan Nemet
The present study compares previous reports on the effect of “real-life” typical field individual (ie, cross-country running and wrestling—representing combat versus noncombat sports) and team sports (ie, 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 needed to better understand the effect of real-life typical training in prepubertal and adolescent athletes and their role in exercise adaptations.
Alon Eliakim, Ita Litmanovitz, and Dan Nemet
Premature infants have an increased risk of osteopenia due to limited bone mass accretion in utero and a greater need for bone nutrients. Until recently, most efforts to prevent osteopenia of prematurity focused on nutritional changes. Recent studies indicate that passive range-of-motion exercise of the extremities may lead to beneficial effects on body weight, increased bone mineralization, increased bone formation markers and leptin levels, and attenuation of the natural postnatal decline in bone speed of sound. These results suggest that exercise may play an important role in the prevention and treatment of osteopenia of prematurity. This review summarizes our current knowledge on the role of exercise in the prevention and treatment of osteopenia of prematurity.
Oren Tirosh, Guy Orland, Alon Eliakim, Dan Nemet, and Nili Steinberg
This study aimed to identify differences in ground impact shock attenuation between overweight and healthy-weight children during running. Twenty overweight children aged 8.4 (1.1) years and 12 healthy-weight children aged 10.7 (1.3) years ran on a treadmill (120% of baseline speed) while wearing 2 inertial sensors located on their distal tibia and lower back (L3). Peak acceleration attenuation coefficient at foot contact and transfer function of the acceleration were calculated. Peak positive acceleration values were not significantly different between the overweight children and healthy-weight children (3.98 [1.17] g and 3.71 [0.84] g, respectively, P = .49). Children with healthy weight demonstrated significant greater attenuation as evident by greater peak acceleration attenuation coefficient (35.4 [19.3] and 11.9 [27.3], respectively, P < .05) and lower transfer function of the acceleration values (−3.8 [1.9] and −1.2 [1.5], respectively, P < .05). Despite the nonsignificant differences between groups in tibia acceleration at foot–ground impact that was found in the current study, the shock absorption of overweight children was reduced compared with their healthy-weight counterparts.
Sigal Ben-Zaken, Yoav Meckel, Nitzan Dror, Dan Nemet, and Alon Eliakim
In recent years several genetic polymorphisms related to the GH-IGF-I axis were suggested to promote athletic excellence in endurance and power sports. We studied the presence of the C-1245T SNP (rs35767), a nucleotide substitution in the promoter region of the IGF-I gene, and the presence of the 275124A > C SNP (rs1464430), a common nucleotide substitution in the intron region of the IGF-I receptor (IGF-IR) gene in elite long and short-distance swimmers compared with nonphysically active controls. The rare T/T IGF-I polymorphism was found only in 5.3% of the long-distance swimmers, and was not found at all in the short-distance swimmers or among the control group participants. The prevalence of the IGF-I receptor AA genotype was significantly lower in the swimming group as a whole (35%) compared with the control group (46%), in particularly due to reduced frequency of the AA genotype among short-distance swimmers (26%). In contrast to previous reports in elite endurance and power track and field athletes, single nucleotide polymorphisms of the IGF-I and the IGF-IR were not frequent among elite Israeli short- and long-distance swimmers emphasizing the importance of other factors for excellence in swimming. The results also suggest that despite seemingly similar metabolic characteristics different sports disciplines may have different genetic polymorphisms. Thus, combining different disciplines for sports genetic research purposes should be done with extreme caution.