Effects of Resistance and Endurance Training Alone or Combined on Hormonal Adaptations and Cytokines in Healthy Children and Adolescents: A Systematic Review and Meta-analysis

Abstract

Background No previous systematic review has quantitatively compared the effects of resistance training, endurance training, or concurrent training on hormonal adaptations in children and adolescents. Objective was to examine the effects of exercise training and training type on hormonal adaptations in children and adolescents. Methods A systematic literature search was conducted in the following databases: PubMed, Web of Science, and EBSCO. Eligibility criteria were: population: healthy youth population sample (mean age < 18 years); intervention: resistance training, endurance training, or concurrent training (> 4 weeks duration); comparison: control group; outcome: pre- and post-levels of hormones and cytokines; and study design: randomized and non-randomized controlled trials. We used a random-effect model for the meta-analysis. The raw mean difference in hormones from baseline to post-intervention was presented alongside 95% confidence intervals (CI). Further, the certainty of evidence quality and the risk of bias were assessed. Results A total of 3689 records were identified, of which 14 studies were eligible for inclusion. Most studies examined adolescents with fewer studies on children (age < 12 years, N = 5 studies) and females (N = 2 studies). Nine exercise training programs used endurance training, five studies used resistance training, and no eligible study used concurrent training. The meta-analysis showed no significant effect of exercise training on testosterone (MD = 0.84 nmol/L), cortisol (MD = − 17.4 nmol/L), or SHBG (MD = − 5.58 nmol/L). Subgroup analysis showed that resistance training significantly increased testosterone levels after training (MD = 3.42 nmol/L) which was not observed after endurance training (MD = − 0.01 nmol/L). No other outcome differed between training types. Exercise training resulted in small and non-significant changes in GH (MD = 0.48 ng/mL, p = 0.06) and IGF-I (MD = − 22.90 ng/mL, p = 0.07). GH response to endurance training may be age-dependent and evident in adolescents (MD = 0.59 ng/mL, p = 0.04) but not when children and adolescents are pooled (MD = 0.48 ng/mL, p = 0.06). Limited evidence exists to conclude on IL-6 and TNF-α effects of exercise training. Assessments of GRADE domains (risk of bias, consistency, directness, or precision of the findings) revealed serious weaknesses with most of the included outcomes (hormones and cytokines). Conclusions This systematic review suggests that exercise training has small effects on hormonal concentrations in children and adolescents. Changes in testosterone concentrations with training are evident after resistance training but not endurance training. GH's response to training may be affected by maturation and evident in adolescents but not children. Further high-quality, robust training studies on the effect of resistance training, endurance training, and concurrent training are warranted to compare their training-specific effects. Registration: PROSPERO: CRD42021241130.

Effects of Eight-Week Strength Training on Basal Hormone Levels, Oxidative Stress Markers and IL-6 Levels in Adolescent Athletes

“…It appears that strength training can boost growth and maturation in adolescents. Sex hormone-binding globulins (SHBGs), normally stable during childhood, were noted to decrease after puberty [12,29]. Given the part strength training plays in growth and maturation, it is conceivable that it contributed to the decrease in SHBGs in the strength training (ST) group.…”

“…However, prior to the competition periods, IL-6 levels were basal between the pre-season and the preparation season[L1] [11]. It has been suggested that limited evidence exists to conclude IL-6 in healthy adolescent players doing long-term resistance training [12].…”

“…Adolescence brings physical and physiological changes and increases some hormones related to the adolescent phase [18]; also, during this phase is thought that the effects of resistance training on anabolic hormones and catabolic mediators are thought to be essential [12]. Resistance exercise has been shown to initiate several acute and chronic responses in human skeletal muscle.…”

“…Resistance exercise has been shown to initiate several acute and chronic responses in human skeletal muscle. One potentially bene cial long and short-term responses are that resistance exercise affects circulating anabolic and catabolic hormone levels [12,18]. Long-term resistance training has not changed serum Cortisol and Growth hormone concentration, while total testosterone basal concentration has been increased in junior athletes [19].…”

Körperliches Training und Frakturprävention. Trainingsinhaltliche Empfehlungen zur Verbesserung der Knochenfestigkeit

“… Kurze, intensive Reize scheinen dabei besonders geeignet die Serumkonzentration anabol wirkender Hormone und Substanzen zu erhöhen 13 . …”