Research Review By Erin Haske ©

Date Posted:

October 2010

Study Title:

Does Plyometric Training Improve Strength Performance? A Meta-Analysis

Authors:

Sáez- Sáez de Villarreal E, Requena B, Newton RU

Author's Affiliations:

Laboratory of Human Performance, Department of Sports, University Pablo de Olavide, Spain, School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Australia

Publication Information:

Journal of Science and Medicine in Sport 2010; 13: 513-522.

Background Information:

Research evidence indicates that plyometric training improves muscular strength and power, coordination, and athletic performance (2), with greater improvements seen when plyometric exercise is employed in conjunction with other training modalities (i.e. weight-training, isometric training, etc.) (3).

However, the effects of plyometric training may differ according to subject variables such as age, gender, training or strength level, sporting history or familiarity with the exercise. Program duration and training volume also may influence the results of a plyometric training program.

The optimal combination of these factors for maximum performance enhancement remains unclear. As such, this meta-analysis examined the influence of various factors on the effectiveness of plyometric training based on the effect size (ES) of different independent variables.

Pertinent Results:

The effect of a large number of variables on the ES of plyometric interventions was considered. Overall, subject groups undertaking plyometric training had a significantly higher ES (r=0.97, n=24) compared to the ES of control groups (r=0.11, n=7).
  • Body mass was significantly correlated with ES (r=0.451)
  • No other subject physical characteristics including age (r=0.242) or height (r=0.396) had a significant effect on strength gains.
  • Gender did not significantly affect the ES (p=0.333), though this may be attributed to a large difference in sample size and a small number of effect sizes available. It should be noted that when strength is expressed relative to muscle cross-sectional area, no significant difference exists between genders (4).
  • No significant difference was found between ES with more or less experienced subjects (p=0.944), or with poor, good, or excellent fitness levels (p=0.304).
  • No significant difference (p>0.05) was found between ES with for sport level or sport activity.
With respect to program and training elements:
  • A positive relationship was found between weekly session frequency and ES (r=0.439).
  • There was no significant effect for program duration (r=-0.218), number of repetitions per session (r=-0.223) or number of exercises per session (r=-0.152), suggesting that shorter programs may be more beneficial.
  • High session intensity results in a greater improvement in strength performance, regardless of type of plyometric exercise (p=0.035).
  • Strength improvements were significantly higher (p=0.006) when plyometrics were combined with other types of exercises (i.e. weight training or electrostimulation).
  • The ES was not affected by the type of plyometric exercise used, or in programs with or without added resistance (p>0.05). Some studies included in this meta-analysis did show that training with additional resistance resulted in higher strength gains; however, the results of this meta-analysis show that superior results with additional load cannot be guaranteed.

Clinical Application & Conclusions:

This meta-analysis provides robust quantitative evidence that plyometric training is effective in improving strength performance, and outlines independent variables which may lead to enhanced results. Subjects performing plyometric exercises with excellent technique are likely to experience strength gains regardless of initial fitness level, and men and women are likely to achieve similar gains. A training program of less than 10 weeks, but including more than 15 sessions will maximize the likelihood of strength improvements; each session should contain a minimum of 40 repetitions performed at high intensity.

It is important to consider the maximum volume threshold, as increased training volume past this point will not elicit any additional gains. It is also suggested that greater gains are achieved when plyometric training is combined with weight-training.

It is also important to consider that despite the above results, the effects of plyometric training may vary due to a large number of variables including age, gender, training level and familiarity with plyometric training, as well as program design, duration, volume, and intensity.

The results presented in this meta-analysis may be considered when programming, however strength and conditioning or fitness professionals must consider the appropriate approach for prescribing plyometrics for any given athlete or client.

Study Methods:

  • Searches were applied in the following databases: ADONIS, ERIC, SPORTSDiscus, EBSCOhost, MedLine, and PubMed.
  • Searches were applied using the following keywords: jump training, drop jump, depth jump, stretch-shortening cycle, plyometric, plyometrics, training of power, plyometric training, pliometrique, and entrainement pliometricque.
  • Manual searches of relevant journals and reference lists obtained from articles were also conducted.
  • Criteria for inclusion in this meta-analysis included: A) use of plyometric training for the lower limbs, B) employment of true experimental design and valid and reliable measurements, and C) inclusion of sufficient data to calculate ES. Fifteen studies were identified for inclusion.
  • The effect of categorical study variables (i.e. fitness level, previous experience, exercise type) on the ES was examined using an analysis of variance (ANOVA), where p ? 0.05.
  • The effect of quantitative study variables (i.e. age, body mass, program duration, repetitions per session) on the ES was examined using a Pearson’s correlation (r) text where p ? 0.05.

Study Strengths / Weaknesses:

Strengths
  • The meta-analysis was performed on the results of a broad search of related keywords in several databases.
  • A large number of independent variables were considered in relation to ES.
Weaknesses
  • Studies investigating the effects of upper body plyometrics were not included.

Additional References:

  1. Kraemer WJ, Mazzetti SA, Nindl BC, et al. Effect of resistance training on women’s strength/power amd occupational performances. Med Sci Sports Exerc 2001; 33: 1011-25.
  2. Fatouros IG, Jamurtas AZ, Leontsini D, et al. Evaluation of plyometric exercise training, weight training, and their combination on vertical jumping performance and leg strength. J Strength Cond Res 2000; 14: 470-6.
  3. Bauer T, Thayer RE, Baras G. Comparison of training modalities for power development in the lower extremity. J Appl Sports Sci Res 1990; 4: 115-21.
  4. Miller AE, Macdougall JD, Tarnopolsky MA. Gender differences in strength and muscle fiber characteristics. Eur J Appl Physiol 1993; 66:254-62.