Plyometric training and performance

Introduction

The frequent use of plyometric training to improve performance is due to many systematic studies of its beneficial effects in recent years. As there are many studies available, it is important to have an overview of their conclusions. Rather than looking at each study individually, an umbrella review helps the reader summarize and interpret the evidence at a glance, taking into account potential shortcomings that have been identified. Plyometric training and performance are often mentioned in the same breath. This overarching umbrella review tried to summarize the current literature and examine the methodological aspects to ascertain that correct conclusions are taken. So, what can we say about plyometric training and performance?

Methods

An umbrella review, which forms the top of the evidence pyramid, was conducted. It includes the results of already published meta-analyses on a certain topic and provides the reader with an overarching conclusion. Rather than having to take a look at all different studies on the same object, the strength of an umbrella review is that it highlights findings with the interpretation of the current strengths and limitations.

The table hereunder summarizes the PICOS. Note that this umbrella review examined healthy people without relevant comorbidities or health issues.

Plyometric training and performance — From: Kons et al. (2022)

The effect size of an intervention was summarized by the standardized mean difference (SMD). Whenever necessary, the SMD was calculated by the provided data of the included meta-analyses. The effect sizes were interpreted as follows:

< 0.20 as trivial,
0.20 ≤ SMD < 0.50 as small,
0.50 ≤ SMD < 0.80 as moderate,
and SMD ≥ 0.80 as large effects.

The results were summarized and between-group differences (for example: plyometric training versus control) were separated from within-group differences (for example: pre- and post-plyometric intervention). The effect of plyometric training was examined separately on the outcomes: sprint or speed performance, change of direction, maximal strength, muscle power or explosive strength, vertical and horizontal jump performance, and additional outcomes.

Results

In total, 29 meta-analyses, published between 2007 and 2022 were included in the umbrella review. The included populations ranged from male and female youth athletes participating in sports such as volleyball, basketball, netball, and other jumping sports, youth athletes not participating in sports, healthy trained or untrained individuals with good, bad, and elite levels, individuals aged 50+, to individual sport athletes (runners, gymnasts, golfers, etc…).

5 meta-analyses compared the effects of plyometric training versus a control intervention (between-group differences) and 24 meta-analyses compared within-group effects (pre versus post intervention). The data came from 22 original studies in total. The ages of the participants ranged from 15-year-olds to individuals of 71 years of age.

The methodological quality of the included meta-analyses was rated using the AMSTAR-2, which has a maximum score of 16. Quality scores ranged from 2 out of 16 to 13 out of 16. In total, 75.9% of the studies were of moderate quality, 20.6% of studies were of low quality, and 1 study (3.4%) was rated as a high-quality study.

The effect of plyometric training on sprint or speed performance revealed that a general population had a small benefit for general sprint performance and short distance sprint performance (10-20m), but a large effect for 30m sprints. Young individuals had a small benefit from plyometric training. Athletes participating in individual sports had a small benefit, compared to a moderate effect that was seen in athletes from general sports. A moderate effect was observed for female soccer players, handball players, and volleyball players. Basketball players, on the other hand, benefitted largely from plyometric training to increase their performance in short (<10m) and longer sprints (>10m). There was an unclear effect in 5, 10, 15, 20, and 30-m sprint performance in male soccer players.

When looking at the outcome change of direction, it became clear that a large effect of plyometric training was observed in basketball players (for running distances shorter or longer than 40 m). A moderate effect was seen in female soccer players. For individual sports athletes and young athletes, the effects were uncertain.

Maximal strength after plyometric training was reported to increase largely in healthy individuals, moderately in basketball players, and individuals participating in individual sports. Athletes from general sports had only a minor benefit from plyometric training. Four studies reported unclear effects in healthy individuals, adolescents, and soccer players and on the hamstring/quadriceps ratio in basketball players.

Explosive strength improved with a large effect size in team sport athletes when participating in plyometric training. Muscular power was moderately influenced by plyometric training in older adults, while a small effect was seen in basketball players. It was unclear whether healthy individuals benefited from plyometric training to increase power.

A large proportion of studies investigated jump performance outcomes. These included performance during squat jumps, countermovement jumps (with arm swing or hands on the hip), drop jumps, Sargent jumps, and/or spike jump performance (i.e., jump height). In healthy people, the effects ranged from unclear to large, but athletes participating in team sports requiring explosivity (soccer, volleyball, handball, basketball) benefited mostly moderately to largely from the plyometric training. In trained and untrained individuals, a moderate effect size was observed. Two studies investigated the effects on horizontal jump performance. One study reported a large effect on horizontal jump performance after either horizontal (SMD = 1.05) or vertical plyometric training (SMD = 0.84). Another study reported unclear effects of plyometric training on horizontal jump distance in basketball players.

Last but not least, the effects of plyometric training on additional outcomes revealed that a small effect was seen on endurance performance for individual sport athletes, a moderate effect for endurance in female soccer players, and for high intermittent running performance in healthy people. Dynamic balance in basketball players largely improved after plyometric training, but the effect on static balance was unclear. Kicking performance in female soccer players improved with a large effect after performing plyometric training. Plyometric training is effective in improving the yo-yo intermittent recovery test.

Questions and thoughts

Plyometric training and performance are often attributed to athletes only. In doing so, plyometric training is often only used in rehabilitation in this group. This umbrella review found beneficial effects on physical performance outcomes in the general population as well. Therefore, in rehabilitation of non-athletes, plyometric training may be of benefit.

It has to be emphasized that this review examined healthy individuals and can therefore not be extrapolated to people with injuries or health concerns. Recently, the review of Hartley et al., which was summarized by Max in a synopsis video, indicated that plyometric interventions may be contraindicated in women with osteoporosis as they could result in stress reactions or structural failure due to excessive overload. I recommend watching Max’s synopsis to learn more about other exercise modes that may be used in osteoporosis by clicking on the following link:

Talk nerdy to me

I noticed that the studies showing no effects were not displayed in the figures. This may be misinterpreted when considering the figure alone. Most of the trials did not include control groups, therefore it is difficult to determine which factors have caused the effects and the influence of other variables that are not controlled for may have had a spell on the effects.

Keep in mind that an umbrella review is in fact a summary of summaries, and this may pose a problem to generalization. It can give a general idea but cannot be used as a simplification of research. To really understand the conclusions, the reader still needs to consider the details of the study showing these conclusions. This will help in determining the usefulness of the umbrella reviews’ conclusions to your general practice.

Take home messages

To summarize, large effects were seen in sprinting outcomes in the general population (30m sprint) and in basketball players, change of direction in sprints in basketball players, maximal strength in healthy individuals, explosive strength in team sport athletes, and horizontal jump performance in healthy trained/untrained individuals. Moderate to large effects were observed on jump performance in team sport athletes, and unclear to large effects were seen in jump performance in healthy people. Quality issues arise here, as most of the included reviews were low to moderate in quality. Therefore, this umbrella review should not be regarded as level 1 evidence on the evidence pyramid.