Findings from our umbrella review including 14 meta-analyses suggest that RT is an effective means to improve proxies of physical fitness in healthy children and adolescents beyond a level achievable from growth and maturation. |
This umbrella review indicates that there are few consistent moderating effects of maturation, age, sex, expertise level, or RT type on muscle strength and muscle power across the included meta-analyses. |
This umbrella review identified current gaps in the literature and suggests that future RT research should consistently report data on participants’ maturational status. Pre-pubertal children as well as girls irrespective of their maturational status should be specifically targeted in future research. |
1 Introduction
2 Methods
2.1 Literature Search
Literature search | Search syntax | (“strength training“ OR “resistance training“ OR “weight training“ OR “power training“ OR “plyometric training“ OR “complex training“ OR “weight-bearing exercise“) AND (children OR adolescent* OR youth OR puberty OR kid* OR teen* OR girl* OR boy*) AND (“meta-analysis”) |
Selection criteria (PICOS) | Population | Healthy young children and adolescents (mean age ≤ 18 years) |
Intervention | RT = a specific method of physical conditioning that involves the progressive use of a wide range of resistive loads, different movement velocities, and a variety of training types (e.g., machine-based RT, free weight RT, elastic bands, plyometrics) [2] | |
Comparator | Age-matched control group to avoid bias due to growth and maturation [9], but no alternative RT type as only comparator/control group | |
Outcome | At least one measure of muscle strength, muscle power, linear sprint speed, change-of-direction speed/agility, throwing performance, or sport-specific performance | |
Study design | Meta-analysis | |
Potential moderator variables | Chronological age | Children Adolescents |
Maturation status | Prepubertal individuals Mid-/postpubertal individuals according to the maturity offset method (i.e., age at peak-height-velocity) from Mirwald et al. [10] or Tanner stages | |
Sex | Boys Girls | |
Expertise level | Trained individuals/young athletes Untrained young individuals | |
Overall RT types | Traditional RT = conditioning method which involves the use of a wide range of resistive loads and a variety of training types (e.g., machine-based RT, free weights RT) Plyometric training | |
Traditional RT types | Machine-based RT Free weights RT |
2.2 Selection Criteria
2.3 Data Extraction
2.4 Evaluation of the Methodological Quality
2.5 Quality of Evidence
2.6 Prediction Interval
2.7 Data Interpretation
Study | Population; N included participants | N included primary studies; study design; type of RT | Statistical model | Physical fitness outcome | Effect size (95% CI, p value); I2 (Chi2 p value) | Prediction interval |
---|---|---|---|---|---|---|
Meta-analyses reporting between-subject effect sizes | ||||||
Behringer et al. [18] | Healthy trained or untrained boys and girls (≤ 18 years) N = 1728 | N = 42 CT and RCT Traditional RT only (no plyometric training) | Between-subject SMDa,b (weighted) | Muscle strength | 1.12 (0.9–1.34, p < 0.001); 37% (p = n.a.) Sub-analyses Maturity (p ≤ 0.01) Prepubertalc: 0.81 (n.a., p = n.a.); n.a. Mid-/postpubertald: 1.91 (n.a., p = n.a.); n.a. Sex (p ≥ 0.05) Boys: 1.08 (n.a., p = n.a.); n.a. Girls: 1.42 (n.a., p = n.a.); n.a. Type of RT (p ≥ 0.05) Machine-based: 0.93 (n.a., p = n.a.); n.a. Free weights: 1.31 (n.a., p = n.a.); n.a. Mode of resistance (p ≥ 0.05) Isotonic: 1.17 (n.a., p = n.a.); n.a. Isokinetic: 1.00 (n.a., p = n.a.); n.a. Isometric: 1.03 (n.a., p = n.a.); n.a. | 1.12 (− 0.44 to 2.68) |
Behringer et al. [16] | Healthy trained or untrained boys and girls (≤ 18 years) N = 1432 | N = 34 CT and RCT Any type of RT | Between-subject SMDa,b (weighted) | Jump | 0.54 (0.34–0.74, p < 0.01); n.a. | n-c |
Linear speed | 0.53 (0.23–0.83, p < 0.01); n.a. | n-c | ||||
Throw | 0.99 (0.19–1.79, p < 0.01); n.a. | n-c | ||||
Combined motor performance | 0.52 (0.33–0.71, p < 0.05); 0% (n.a.) Sub-analyses Expertise (p ≥ 0.05) Trained: 0.40 (n.a., p = n.a.); n.a. Untrained: 0.64 (n.a., p = n.a.); n.a. Type of RT (p ≥ 0.05) Plyometric training: 0.51 (n.a., p = n.a.); n.a. RT but no plyometric training: 0.54 (n.a., p = n.a.); n.a. Mixed (any type of RT): 0.36 (n.a., p = n.a.); n.a. | n-c | ||||
Collins et al. [5] | Healthy trained or untrained boys and girls (5–18 years) N = 943 | N = 22 CT and RCT Traditional RT only (no plyometric training) | Between-subject SMDa,e | Vertical jump | 0.41 (0.25–0.56, p < 0.001); ≤ 35% (p = n.a.) | n-c |
Squat jump | 0.73 (0.37–1.09, p < 0.001); 59% (p = n.a.) Sub-analyses Sex (p ≤ 0.01) Boys: 0.84 (0.50–1.18, p = n.a.); n.a. Girls: 0.21 (− 0.11 to 0.52, p = n.a.); n.a. Expertise (p ≤ 0.01) Trained: 0.95 (0.59–1.76, p = n.a.); n.a. Untrained: 0.25 (− 0.03 to 0.53, p = n.a.); n.a. | n-c | ||||
Standing long jump | 0.30 (0.10–0.50, p < 0.01); ≤ 35% (p = n.a.) Sub-analysis Expertise (p ≤ 0.01) Trained: 1.66 (0.75–2.56, p = n.a.); n.a. Untrained: 0.23 (0.02–0.43, p = n.a.); n.a. | n-c | ||||
Linear speed | 0.29 (0.02–0.57, p < 0.05); ≤ 35% (p = n.a.) | n-c | ||||
Throw | 0.41 (0.09–0.72, p < 0.05); ≤ 35% (p = n.a.) | n-c | ||||
Falk et al. [19] | Healthy trained and untrained children (boys: < 13 years, girls: < 12 years) N = 635 + n.a. | N = 9 CT and RCT Any type of RT | Between-subject SMDa,b (weighted) | Muscle strength | 0.57 (0.34–0.80; p < 0.001); n.a. | n-c |
Harries et al. [24] | Healthy trained boys and girls (13–18 years) N = 1070 | N = 14 CT and RCT Any type of RT | Between-subject mean difference (in cm)f (weighted) | Vertical jump | 3.08 cm (1.65–4.51 cm, p < 0.001); 68% (p < 0.001) Sub-analysis Type of RT (p ≥ 0.05) RT, but no plyometric/speed training: 2.09 cm (− 0.01 to 4.20 cm, p ≥ 0.05); 38% (p > 0.05) Plyometric training: 5.47 cm (1.95–9.00 cm, p < 0.01); 48% (p > 0.05) RT and plyometric/speed training: 3.03 cm (0.83–5.24 cm, p < 0.01); 80% (p < 0.001) | 3.08 cm (− 2.18 to 8.34 cm) |
Lesinski et al. [4] | Healthy trained boys and girls (6–18 years) N = 1558 | N = 43 CT and RCT Any type of RT | Between-subject SMDa,e (weighted) | Muscle strength | 1.09 (0.65–1.53, p < 0.001); 81% (p < 0.001) Sub-analyses Maturity Mid-/postpubertalg: 0.61 (0.26–0.96, p < 0.001); 18% (p > 0.05) Chronological age (p ≥ 0.05) Childrenh: 1.35 (0.37–2.33, p < 0.01); 68% (p < 0.05) Adolescentsi: 0.91 (0.45–1.37, p < 0.001); 78% (p < 0.001) Sex Boys: 1.21 (0.64–1.78, p < 0.001); 85% (p < 0.001) Sport (p ≥ 0.05) Team sport: 1.15 (0.64–1.66, p < 0.001); 83% (p < 0.001) Strength dominated sports: 0.58 (− 0.01 to 1.17, p ≥ 0.05); 0% (p > 0.05) Type of RT (p ≤ 0.001) Machine-based: 0.36 (− 0.44 to 1.16, p > 0.05); 62% (p > 0.05) Free weights: 2.97 (2.14–3.80, p < 0.001); 65% (p < 0.05) Machine-based and free weights: 1.16 (0.59–1.73, p < 0.001); 40% (p > 0.05) Functional training: 0.62 (0.13–1.11, p < 0.05); 0% (p > 0.05) Plyometric training: 0.39 (0.00–0.77, p ≥ 0.05); 0% (p > 0.05) | 1.09 (− 1.01 to 3.19) |
Vertical jump | 0.80 (0.60–1.00, p < 0.001); 67% (p < 0.001) Sub-analyses Maturity (p ≥ 0.05) Prepubertalj: 0.91 (0.13–1.69, p < 0.05); 80% (p < 0.001) Mid-/postpubertalg: 1.15 (0.67–1.64, p < 0.001); 82% (p < 0.001) Chronological age (p ≥ 0.05) Childrenh: 0.78 (0.46–1.10, p < 0.001); 63% (p < 0.001) Adolescentsi: 0.85 (0.57–1.13, p < 0.001); 70% (p < 0.001) Sex (p ≥ 0.05) Boys: 0.85 (0.62–1.07, p < 0.001); 69% (p < 0.001) Girls: 0.61 (− 0.14 to 1.35, p > 0.05); 51% (p > 0.05) Sport (p ≥ 0.05) Team sport: 0.79 (0.58–1.00, p < 0.001); 68% (p < 0.001) Strength dominated sports: 1.22 (0.60–1.83, p < 0.001); 0% (p > 0.05) Type of RT (p ≥ 0.05) Machine-based: 1.45 (− 0.33 to 3.22, p > 0.05); 90% (p < 0.001) Free weights: 0.90 (0.58–1.22, p < 0.001); 0% (p > 0.05) Machine-based and free weights: 0.77 (0.14–1.41, p < 0.05); 45% (p > 0.05) Functional training: 0.39 (− 0.09 to 0.88, p > 0.05); 26% (p > 0.05) Complex training: 1.66 (0.26–3.07, p < 0.05); 88% (p < 0.001) Plyometric training: 0.81 (0.57–1.06, p < 0.001); 60% (p < 0.001) | 0.80 (− 0.35 to 1.95) | ||||
Linear speed | 0.58 (0.41, 0.75, p < 0.001); 41% (p < 0.01) Sub-analyses Maturity (p ≥ 0.05) Prepubertalj: 0.65 (0.22–1.08, p < 0.01); 42% (p > 0.05) Mid-/postpubertalg: 0.51 (0.30–0.72, p < 0.001); 0% (p > 0.05) Chronological age (p ≥ 0.05) Childrenh: 0.55 (0.32–0.79, p < 0.001); 20% (p > 0.05) Adolescentsi: 0.57 (0.32–0.82, p < 0.001); 48% (p < 0.05) Sex Boys: 0.63 (0.48–0.78, p < 0.001); 16% (p > 0.05) Sport Team sport: 0.58 (0.40–0.75, p < 0.001); 43% (p < 0.01) Type of RT (p ≥ 0.05) Free weights: 0.61 (0.30–0.92, p < 0.001); 0% (p > 0.05) Machine-based and free weights: 0.18 (− 0.34 to 0.69, p > 0.05); 0% (p > 0.05) Functional training: 0.19 (− 0.51 to 0.89, p > 0.05); 64% (p > 0.05) Complex training: 1.11 (0.55–1.66, p < 0.001); 12% (p > 0.05) Plyometric training: 0. (0.41–0.87, p < 0.001); 40% (p ≥ 0.05) | 0.58 (− 0.10 to 1.26) | ||||
Agility/change-of-direction speed | 0.68 (0.46–0.90, p < 0.001); 50% (p < 0.01) Sub-analyses Maturity (p ≥ 0.05) Prepubertalj: 0.58 (0.13–1.03, p < 0.05); 0% (p > 0.05) Mid-/postpubertalg: 0.57 (0.34–0.80, p < 0.001); 0% (p > 0.05) Chronological age (p ≥ 0.05) Childrenh: 0.52 (0.25–0.78, p < 0.001); 17% (p > 0.05) Adolescentsi: 0.71 (0.36–1.06, p < 0.001); 62% (p < 0.01) Sex Boys: 0.74 (0.52–0.95, p < 0.001); 42% (p < 0.05) Sport Team sport: 0.68 (0.46–0.90, p < 0.001); 50% (p < 0.01) Type of RT (p ≤ 0.05) Free weights: 1.31 (0.89–1.72, p < 0.001); 0% (p > 0.05) Functional training: 0.38 (− 0.83 to 1.59, p > 0.05); 88% (p < 0.001) Complex training: 0.66 (− 0.01 to 1.32, p ≥ 0.05); 42% (p > 0.05) Plyometric training: 0.62 (0.41–0.83, p < 0.001); 19% (p > 0.05) | 0.68 (− 0.17 to 1.53) | ||||
Sport-specific performance | 0.75 (0.48–1.02, p < 0.001); 62% (p = 0.001) Sub-analyses Maturity (p ≥ 0.05) Prepubertalj: 0.27 (− 0.17 to 0.72, p > 0.05); 0% (p > 0.05) Mid-/postpubertalg: 0.72 (0.26–1.18, p < 0.01.); 64% (p < 0.01) Age (p ≥ 0.05) Childrenh: 0.5 (0.27–0.72, p < 0.001); 0% (p > 0.05) Adolescentsi: 1.03 (0.55–1.51, p < 0.001); 73% (p < 0.001) Sex (p ≤ 0.05) Boys: 0.72 (0.44–1.01, p < 0.001); 58% (p < 0.001) Girls: 1.81 (0.82–2.80, p < 0.001); 33% (p > 0.05) Sport (p ≥ 0.05) Team sport: 0.80 (0.52–1.09, p < 0.001); 61% (p < 0.001) Strength dominated sports: 0.34 (− 0.60 to 1.28, p > 0.05); 71% (p < 0.05) Type of RT (p ≤ 0.05) Machine-based: 0.30 (− 0.36 to 0.97, p > 0.05); 43% (p > 0.05) Functional training: 0.79 (0.15–1.44, p < 0.05); 72% (p < 0.01) Complex training: 1.85 (1.12–2.58, p < 0.001); 0% (p > 0.05) Plyometric training: 0.74 (0.39–1.08, p < 0.001); 57% (p < 0.01) | 0.75 (− 0.46 to 1.96) | ||||
Moran et al. [26] | Healthy trained boys (10–18 years) N = 539 | N = 21; CT & RC; Plyometric training only | Between-subject SMDa,e (weighted) | Counter-movement jump | 0.73 (0.47–0.99; p < 0.001); 61% (p < 0.001) Sub-analyses Age - Children k: 0.91 (0.47–1.36, p > 0.001); 59% (p < 0.01) - Younger adolescents l: 0.47 (0.16–0.77, p < 0.01); 53% (p < 0.05) - Older adolescents m: 1.02 (0.52 –1.53, p < 0.001); 3% (p > 0.05) Sport - Soccer: 0.61 (0.36–0.86, p < 0.001); 45% (p < 0.05) - Other: 1.09 (0.38 –1.80, p < 0.01); 77% (p < 0.01) RT period < 7.5 weeks 0.38 (0.19–0.56, p < 0.001); 0% (p > 0.05) > 7.5 weeks: 1.21 (0.72–1.69, p < 0.001); 71% (p < 0.001) RT sessions < 14.5 sessions: 0.37 (0.19–0.56, p < 0.001); 0% (p > 0.05) > 14.5 sessions: 1.28 (0.78–1.78, p < 0.001); 71% (p > 0.05) | 0.73 (− 0.41 to 1.87) |
Moran et al. [22] | Healthy trained or untrained girls (8–18 years) N = 351 | N = 11 CT and RCT Any type of RT | Between-subject SMDa,e (weighted) | Muscle strength | 0.54 (0.23–0.85, p < 0.001); 42% (p < 0.05) Sub-analyses Age < 15 years: 0.38 (-0.02–0.79, p > 0.05); 41% (p > 0.05) > 15 years: 0.72 (0.23–1.21, p < 0.01); 42% (p > 0.05) Body height < 163 cm: 0.55 (0.08–1.02, p < 0.05); 57% (p < 0.05) > 163 cm: 0.67 (0.20–1.13, p < 0.01); 18% (p > 0.05) Body mass < 56 kg: 0.53 (0–1.06, p ≥ 0.05); 60% (p < 0.05) > 56 kg: 0.67 (0.30–1.03, p < 0.001); 3% (p > 0 05) RT period ≤ 8 weeks: 0.62 (0.17–1.07, p < 0.01); 56% (p < 0.05) > 8 weeks: 0.44 (-0.02–0.90, p > 0.05); 25% (p > 0.05) RT frequency ≤ 2 sessions/week: 0.72 (0.34–1.09, p < 0.001); 36% (p > 0.05) > 2 sessions/week: 0.18 (-0.26–0.61, p > 0.05); 21% (p > 0.05) RT sessions ≤ 16 sessions: 0.75 (0.33–1.17, p < 0.001); 35% (p > 0.05) > 16 sessions: 0.30 (-0.11–0.72, p > 0.05); 33% (p > 0.05) RT duration < 40 min per session: 0.34 (-0.38–1.06, p < 0.05); 53% (p > 0.05) > 40 min per session: 0.63 (0.11–1.16, p < 0.05); 4% (p > 0.05) | 0.54 (-0.41-1.49) |
Moran et al. [21] | Healthy trained or untrained girls (8-18 years); N = 452 | N = 14; CT & RCT; Plyometric training only | Between-subject SMD a,e (weighted) | Vertical jump | 0.57 (0.21–0.93; p < 0.01); 68% (p < 0.001) Sub-analyses Age < 15 years: 0.78 (0.25–1.30, p < 0.01); 71% (p < 0.01) > 15 years: 0.31 (-0.18–0.80, p > 0.05); 61% (p < 0.05) Body height < 163 cm: 1.03 (0.38–1.68, p < 0.01); 72% (p < 0.001) ≥ 163 cm: 0.25 (-0.20–0.70, p > 0.05); 63% (p < 0.05) Body mass < 54 kg: 1.14 (0.39–1.89, p < 0.01); 76% (p < 0.001) ≥ 54 kg: 0.26 (-0.15–0.67, p > 0.05); 56% (p < 0 05) RT period ≤ 8 weeks: 0.24 (-0.11–0.59, p > 0.05); 38% (p > 0.05) > 8 weeks: 1.04 (0.35–1.72, p < 0.01); 79% (p < 0.01) RT frequency ≤ 2 sessions/week: 0.37 (0.02–0.71, p < 0.05); 52% (p < 0.01) > 2 sessions/week: 1.22 (0.18–2.25, p < 0.05); 83% (p < 0.01) RT sessions < 16 sessions: 0.37 (-0.44–1.17, p > 0.05); 77% (p > 0.01) = 16 sessions: 0.46 (0.08–0.84, p < 0.05); 1% (p > 0.05) > 16 sessions: 0.85 (0.18–1.51, p < 0.05); 77% (p < 0.001) RT duration < 40 min per session: 0.33 (0.03–0.63, p < 0.05); 0% (p > 0.05) > 40 min per session: 1.16 (0.14–2.17, p < 0.05); 76% (p < 0.01) | 0.57 (-0.81-1.95) |
Payne et al. [17] | Healthy trained or untrained boys and girls (11–18 years) N = 252 | N = 28 CT and RCT n.a. | Between-subject SMDn (not weighted) | Muscle strength and endurance | 0.75 (n.a., p < 0.05); 63% (p = n.a.) Sub-analyses Age Childreno: 0.75 (n.a., p < 0.05); 55% (p = n.a.) Adolescentsp: 0.69 (n.a., p < 0.05); 79% (p = n.a.) Sex Boys: 0.72 (n.a., p < 0.05); 57% (p = n.a.) Girls: 0.81 (n.a., p < 0.05); 69% (p = n.a.) Mode of resistance Isokinetic: 0.20 (n.a., p < 0.05); 59% (p = n.a.) Isometric: 0.71 (n.a., p < 0.05); 70% (p = n.a.) Isotonic: 0.90 (n.a., p < 0.05); 72% (p = n.a.) Body segment Arm: 0.74 (n.a., p < 0.05); 59% (p = n.a.) Back: 0.83 (n.a., p < 0.05); 79% (p = n.a.) Leg: 0.71 (n.a., p < 0.05); 65% (p = n.a.) | n-c |
Slimani et al. [23] | Healthy trained boys and girls (6–18 years) N = 428 | N = 15 CT and RCT No plyometric or power training | Between-subject SMDe (weighted) | Counter-movement jump | 0.65 (0.34–0.96, p < 0.001); 53% (p = n.a.) Sub-analyses Age (p ≥ 0.05) Childrenq: 0.41 (− 0.07 to 0.89, p > 0.05); 22% (p = n.a.) Adolescentsr: 0.69 (0.29–1.08, p < 0.001); 56% (p = n.a.) Sex (p ≤ 0.05) Boys: 0.79 (0.43–1.15, p < 0.001); 55% (p = n.a.) Boys and girls: 0.18 (− 0.24 to 0.60, p < 0.05); 0% (p = n.a.) Expertise level (p ≥ 0.05) Trained: 0.81 (0.38–1.25, p < 0.001); 60% (p = n.a.) Recreationally trained: 0.36 (0.01–0.72, p < 0.05); 0% (p = n.a) | n-c |
Squat jump | 0.80 (0.23–1.37, p < 0.05); 71% (p = n.a.) Sub-analyses Age (p ≤ 0.05) Childrenq: − 0.54 (− 1.44 to 0.35, p > 0.05); 0% (p = n.a.) Adolescentsr: 0.95 (0.40–1.50, p < 0.001); 65% (p = n.a.) Sex (p ≥ 0.05) Boys: 0.89 (0.27–1.51, p < 0.01); 72% (p = n.a.) Boys and girls: 0.07 (− 0.72 to 0.86, p > 0.05); 0% (p = n.a.) | n-c | ||||
Meta-analyses reporting within-subject effect sizes | ||||||
Asadi et al. [27] | Healthy trained or untrained boys (10–18 years) N = 669 | N = 16 CT and RCT Plyometric training only | Within-subject SMDa,s | Change-of-direction speed | 0.86 (n.a., p ≤ 0.05); n.a. Sub-analysis Age Childrenk: 0.68 (n.a., p ≤ 0.05); n.a. Younger adolescentsl: 0.95 (n.a., p ≤ 0.05); n.a. Older adolescentsm: 0.99 (n.a., p ≤ 0.05); n.a. | n-c |
Behm et al. [20] | Healthy trained or untrained boys and girls (< 18 years) N = 1351 | N = 107 CT and RCT Any type of RT | Within-subject SMDa,s (weighted) | Muscle strength | RT 1.14 (0.89–1.39, p < 0.05); 77% (p < 0.001) Sub-analyses Expertise (p ≥ 0.05) Trained: 1.23 (0.80–1.67, p < 0.001); 81% (p < 0.001) Untrained: 1.08 (0.78–1.38, p < 0.001); 77% (p < 0.001) Age (p ≥ 0.05) Children: 1.39 (0.89–1.90, p < 0.001); 80% (p < 0.001) Adolescents: 0.88 (0.61–1.14, p < 0.001); 67% (p < 0.001) | 1.14 (− 0.35 to 2.63) |
Power training 0.16 (− 0.26 to 0.58, p > 0.05); 0% (p > 0.05) | 0.16 (− 2.56 to 2.88) | |||||
Muscle power | RT 0.52 (0.39–0.64, p < 0.05); 29% (p < 0.05) Sub-analyses Expertise (p ≥ 0.05) Trained: 0.48 (0.33–0.63, p < 0.001); 13% (p > 0.05) Untrained: 0.61 (0.37–0.85, p < 0.05); 49% (p < 0.001) Age (p ≥ 0.05) Children: 0.68 (0.45–0.91, p < 0.05); 44% (p < 0.05) Adolescents: 0.42 (0.28–0.56, p < 0.05); 9% (p > 0.05) | 0.52 (0.05–0.99) | ||||
Power training 0.69 (0.53–0.84, p < 0.001); 51% (p < 0.001) Sub-analyses Expertise (p ≥ 0.05) Trained: 0.67 (0.52–0.82, p < 0.001); 39% (p < 0.05) Untrained: 0.80 (0.24–1.35, p < 0.01); 80% (p < 0.001) Age (p ≥ 0.05) Children: 0.74 (0.53–0.94, p < 0.001); 62% (p < 0.001) Adolescents: 0.57 (0.37–0.77, p < 0.001); 14% (p > 0.05) | 0.69 (− 0.11 to 1.49) | |||||
Linear speed | RT 0.48 (0.25–0.71, p < 0.001); 30% (p > 0.05) Sub-analyses Expertise (p ≥ 0.05) Trained: 0.45 (0.19–0.70, p < 0.001); 28% (p > 0.05) Untrained: 0.57 (− 0.02 to 1.16, p > 0.05); 45% (p > 0.05) Age (p ≥ 0.05) Children: 0.73 (0.35–1.12, p < 0.001); 17% (p > 0.05) Adolescents: 0.36 (0.10–0.62, p > 0.05); 19% (p > 0.05) | 0.48 (− 0.15 to 1.11) | ||||
Power training 0.38 (0.23–0.53, p < 0.001); 12% (p > 0.05) Sub-analyses Expertise (p ≥ 0.05) Trained: 0.32 (0.18–0.46, p < 0.001); 0% (p > 0.05) Untrained: 1.19 (− 0.32 to 2.69, p < 0.001); 87% (p < 0.001) Age (p ≥ 0.05) Children: 0.47 (0.28–0.67, p < 0.001); 31% (p > 0.05) Adolescents: 0.13 (− 0.17 to 0.44, p > 0.05); 0% (p > 0.05) | 0.38 (0.04–0.72) | |||||
Moran et al. [25] | Healthy, trained boys (10–18 years) N = 496 | N = 19 n.a. Any type of RT | Within-subject SMDa,s (weighted) | Muscle strength | 0.98 (0.70–1.27, p < 0.001); 75% (p < 0.001) Sub-analysis Age Childrenk: 0.50 (− 0.06 to 1.07, p > 0.05); 54% (p > 0.05) Younger adolescentsl: 1.11 (0.67–1.54, p < 0.001); 80% (p < 0.001) Older adolescentsm: 1.01 (0.56 − 1.46, p < 0.001); 71% (p < 0.001) | 0.98 (− 0.51 to 2.47) |
3 Results
3.1 Search Results
3.2 Characteristics of the Meta-analyses
3.3 Effectiveness of Resistance Training in Healthy Youth
3.4 Maturation-, Age-, Sex-, Expertise Level- and Type-Specific Effects of Resistance Training on Muscle Strength and Muscle Power
Outcomes | Study | Chronological age | Maturational status | Sex | Expertise level | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Children | Adolescents | p | Prepubertal | Mid-/postpubertal | p | Boys | Girls | p | Trained (athletes) | Untrained | p | ||
Muscle strength | Behringer et al. [18]a | 0.21 | > 0.05 | 0.81 (n = n.a./16) | 1.91 (n = n.a./11) | < 0.05 | 1.08 (n = 29/43) | 1.42 (n = 8/10) | > 0.05 | – | |||
Behm et al. [20]b,c | 1.39 (n = 13/14) | 0.88 (n = 22/27) | > 0.05 | – | – | 1.23 (n = 19/22) | 1.08 (n = 18/22) | > 0.05 | |||||
Falk et al. [19]a | 0.57 (n = 9/n.a.) | – | – | – | |||||||||
Lesinski et al. [4]a | 1.35 (n = 3/4) | 0.91 (n = 13/17) | > 0.05 | 0.61 (n = 6/8) | 1.21 (n = 12/18) | 1.09 (n = 16/23) | |||||||
Moran et al. [22]a | – | – | 0.54 (n = 11/16) | – | |||||||||
Moran et al. [25]b | 0.50 (n = 3/4) | 1.11 (n = 11/17) and 1.01* (n = 7/11) | > 0.05* | – | 0.98 (n = 19/32) | 0.98 (n = 19/32) | |||||||
Payne et al. [17]a | 0.75 (n = n.a.) | 0.69 (n = n.a.) | n.a. | – | 0.72 (n = n.a.) | 0.81 (n = n.a.) | n.a. | – | |||||
Muscle power | Behm et al. [20]b,c | 0.68 (n = 16/17) | 0.42 (n = 23/30) | > 0.05* | – | – | 0.48 (n = 23/30) | 0.61 (n = 14/16) | > 0.05 | ||||
Behm et al. [20]b,d | 0.74 (n = 25/34) | 0.57 (n = 16/20) | > 0.05* | – | – | 0.67 (n = 33/46) | 0.80 (n = 6/8) | > 0.05 | |||||
Collins et al. [5]a vertical jump | n.a. | n.a. | > 0.05 | n.a. | n.a. | > 0.05 | – | – | |||||
Collins et al. [5]a SJ | n.a. | n.a. | > 0.05 | n.a. | n.a. | > 0.05 | 0.84 (n = 9/14) | 0.21 (n = 1/1) | < 0.01 | 0.95 (n = 7/n.a.) | 0.25 (n = 3/n.a.) | < 0.01 | |
Lesinski et al. [4]a | 0.78 (n = 10/17) | 0.85 (n = 22/28) | > 0.05 | 0.91 (n = 3/5) | 1.15 (n = 11/13) | > 0.05 | 0.85 (n = 27/40) | 0.61 (n = 3/3) | > 0.05 | 0.80 (n = 47) | |||
Moran et al. [26]a | 0.91 (n = 7/13) | 0.47 (n = 11/12) and 1.02 (n = 4/5) | > 0.05 | – | 0.73 (n = 22/30) | 0.73 (n = 22/30) | |||||||
Moran et al. [21]a | – | – | 0.57 (n = 14/17) | ||||||||||
Slimani et al. [23]a CMJ | 0.41 (n = 2/2) | 0.69 (n = 13/15) | > 0.05 | – | 0.79 (n = 12/14) | 0.65 (n = 13/16) | |||||||
Slimani et al. [23]a SJ | − 0.54 (n = 1/1) | 0.95 (n = 9/9) | < 0.05 | – | 0.89 (n = 10/10) | 0.80 (n = 8/10) |
Outcome | Study | Resistance training type | Traditional resistance training type | ||||
---|---|---|---|---|---|---|---|
Traditional resistance training | Plyometric training | p | Machine-based training | Free weights training | p | ||
Muscle strength | Behm et al. [20]a | 1.14 (n = 37/44) | 0.16 (n = 3/4) | n.a. | – | ||
Behringer et al. [18]b | 1.12 (n = 42/69) | 0.93 (n = 31) | 1.31 (n = 13) | > 0.05 | |||
Lesinski et al. [4]b | 0.39 (n = 4/5) | 0.36 (n = 3/3) | 2.97 (n = 2/4) | < 0.001 | |||
Muscle power | Behm et al. [20]b | 0.52 (n = 39/47) | 0.69 (n = 41/54) | n.a. | – | ||
Collins et al. [5]b vertical jump | 0.41 (n = 17/25) | – | |||||
Collins et al. [5]b SJ | 0.73 (n = 9/10) | – | |||||
Lesinski et al. [4]b | 0.81 (n = 16/25) | 1.45 (n = 3/3) | 0.90 (n = 3/5) | > 0.05 | |||
Moran et al. [26]b | 0.73 (n = 22/30) | – | |||||
Moran et al. [21]b | 0.57 (n = 14/17) | – | |||||
Slimani et al. [23]b CMJ | 0.65 (n = 14/17) | – | |||||
Slimani et al. [23]b SJ | 0.80 (n = 9/10) | – |