Plyometric training programmes improve motor performance in prepubertal children
- 1Children's Hospital Institute of Sports Medicine, Sydney Children's Hospitals Network, Sydney, New South Wales, Australia
- 2Musculoskeletal Division, The George Institute for Global Health, The University of Sydney, Sydney, New South Wales, Australia
- Correspondence to Dr Damien McKay, Children's Hospital Institute of Sports Medicine, Locked bag 4001, Westmead, Sydney, New South Wales 2145, Australia;
Contributors DM and NH contributed to the design and selected the systematic review. DM drafted this manuscript and both authors accepted the final version.
- Received 30 May 2012
- Accepted 1 June 2012
▸ Johnson BA, Salzberg CL, Stevenson DA. A systematic review: plyometric training programs for young children. J Strength Cond Res 2011;25:2623–33.
Children with low motor competence have lower levels of physical fitness, perform less physical activity and participate in fewer organised recreational and play activities.1 Plyometric exercise can potentially enhance a child's speed of movement, running speed, power production and jumping ability. However, it is unclear whether plyometric training can be a safe and effective way to progress exercise load in young children.
To evaluate the efficacy and safety of plyometric training for improving motor performance in young children and to determine whether plyometric training could be used to improve the strength, running speed, agility and jumping ability of children with low motor competence.
Searches and inclusion criteria
Four electronic databases (CINAHL, HealthSource, MEDLINE and SportDisc) were searched up to March 2010 for articles describing plyometrics training programmes for children. An initial search for literature using plyometric training in children with low motor proficiency, low motor competence or for children with developmental coordination disorder resulted in no eligible articles. A new search was undertaken to identify articles describing plyometric training programmes for children. Studies were included if they reported on the outcomes of a plyometric training intervention; included measures of strength, balance, running speed, jumping ability or agility; included children 5–14 years of age; and used a randomised or quasi-randomised design. The Physiotherapy Evidence Database (PEDro) scale was used to assess the methodological quality of the included studies.
Plyometric training programmes were defined as programmes including specific exercises, that begin with a rapid stretch of a muscle followed by a rapid shortening. All studies described plyometric programmes consisting of jumping, hopping, skipping, bounding and jumping over hurdles. Additional elements included in some studies included resistive exercises, footwork and sprint drills, sprints and throws, or strengthening and balance.
Main outcome measures
The main outcome measures used were jumping ability (eg, squat jumps, long jumps and vertical jumps), strength (eg, isokinetic dynamometry), running speed (eg, over distances from 10 metres to half a mile), agility, balance and kicking distance.
Effect sizes (ESs) were calculated for included studies that reported means and standard deviations. Cohen's description was used to classify ESs as small, medium or large.2 The GRADE method3 was used to rate the quality of the evidence in terms of consistency of results (ie, the homogeneity of the ES across studies), and directness of the intervention (ie, the extent to which the people, interventions and outcome measures are similar to those of interest). Descriptive results were presented for exercise dosage (ie, frequency, duration, intensity, number of repetitions), effect on motor skill improvement and safety of the interventions.
After applying the inclusion criteria to the results of the search, eight articles evaluating a total of 275 participants were considered eligible for the review. Seven of the eight included studies found statistically significant effects for improving motor performance. The study that did not demonstrate an improvement in motor performance was excluded because the control group had greater preintervention strength, power and levels of sports participation than the intervention group. Five studies measured jumping ability, of which three studies found statistically significant improvements with large ESs (ES=1.41–2.20). One study had a small ES (ES=0.24) and one study did not find a statistically significant change in vertical jump. Four studies measured running velocity, three of which demonstrated statistically significant improvements with variable ESs. Two studies measured strength outcomes and both demonstrated statistically significant improvements with small to moderate ESs. Outcomes for agility, balance and kicking were measured in one study each.
The frequency of the training programmes varied across studies from one to three times a week. The duration of the intervention (range 8 weeks–9 months), number of jumps (range 16–200) and the method for progressing exercise load also varied widely across studies.
Five studies described safety precautions including a warm-up and cool-down period, emphasis of correct technique and use of appropriate location for exercise. Only two studies documented that there were no injuries during the intervention.
The eight included studies were judged to be of low quality, fulfilling between 3 and 6 of the 10 items on the PEDro scale. Across all studies there was a lack of blinding of evaluators, subjects and coaches, and no study reported a concealed allocation procedure. Only three studies performed an intention-to-treat analysis, and only one study reported CIs around the estimate of the effect.
The participants in the included studies had average or above-average motor competence (healthy, typically developing children or athletes). All participants ranged in age from 8 to 14 years (mean age of 13). Four studies all studied participants of the same sex and age (12- to 13-year-old boys), which introduces the potential for age/sex bias.
Only one study performed a follow-up evaluation 12 weeks after the intervention. A decline of strength was observed at this follow-up, indicating a need to continue the exercise training to maintain strength gains.
Future research is necessary to determine whether children with low motor competence including those with comorbidities associated with low motor proficiency (such as developmental coordination disorder) can participate in and benefit from plyometric training.
Moderate quality evidence suggests that plyometric training has a large effect on improving the ability to run and jump in prepubescent children. Low-quality evidence is available that plyometric training also has an effect on increasing kicking distance, balance and agility. The current evidence suggests that plyometric training programmes with appropriate safety guidelines incorporated into the intervention are safe for children with average or above-average motor competence.
Competing interests None.
Provenance and peer review Not commissioned; internally peer reviewed.