The Effect of a Stretch-Shortening Cycle on Muscle Activation and Muscle Oxygen Consumption: A Study of History-Dependence

Exploring the Influence of Cognitive and Ecological Dynamics Approaches on Countermovement Jumping Enhancement: A Comparative Training Study

Countermovement jumping (CMJ) and free-arm countermovement jumping (CMJFA) express the explosive-elastic force of the lower limbs. Strategies to enhance performance in both types of jumping can be categorized into cognitive and ecological-dynamic approaches. However, the effectiveness of these approaches in improving CMJ and CMJFA remains incompletely understood. This study aims to investigate the impact of training protocols based on the two approaches to improving CMJ. Thirty-six subjects with an average age of 26 years were selected and divided into two groups: the ecological-dynamic group (EDG) and the cognitive group (CG). For 12 weeks, both groups followed separate protocols of three weekly one-hour sessions. EDG group followed a protocol focused on circle time. The CG group followed an instructor-led training protocol. Incoming and outgoing flight heights were measured. Pre and post-intervention differences within and between groups were assessed using t-tests for dependent and independent samples, respectively (p ≤ 0.05). CG demonstrated a 12.2% increase in CMJ and a 7.8% improvement in CMJFA, while EDG showed a 10.2% increase in CMJ and 19.5% progress in CMJFA. No statistically significant differences (p > 0.05) were observed between the groups in the improvement of CMJ; statistically significant differences (p < 0.05) were found in the improvement of CMJFA in favor of EDG.

Effectiveness of Vertical versus Horizontal Plyometric Training on Stretch-Shortening Cycle Performance Enhancement in Adolescent Soccer Players

Plyometric exercise is a major tool for improving explosive actions. This study aimed to compare the efficacy of a vertical and horizontal plyometric training program on stretch-shortening performance variables in adolescent soccer players. Thirty-two male soccer players (aged 12.09 ± 0.89 years, with soccer experience 5.37 ± 1.58 years) were divided into horizontal plyometric, vertical plyometric, or control groups. The horizontal and vertical plyometric groups participated in a 6-week training program that was performed twice per week, with a 48-h interval, in conjunction with regular soccer training. The control group participated only in regular soccer training. Vertical jump height, reactive strength index, leg stiffness, ground contact time, standing long jump distance, agility, and 10 and 20 m sprint performances were tested as stretch-shortening performance variables of the participants. Stretch-shortening performance variables were assessed before and after completion of the training program. The results showed that either horizontal or vertical plyometric training had no effect on VJH, RSI, GCT, or Kleg performance (F = 2.14, 1.32, 0.66, 1.03; p > 0.05). Furthermore, there was no effect on SLJ, 10 m sprint, 20 m sprint, or agility performance (F = 2.06, 0.14, 0.06, 0.27; p > 0.05). A 6-week horizontal or vertical plyometric intervention was found to be insufficient to elicit stretch-shortening performance enhancement in adolescent male soccer players. Although there was no performance change in any group, it was observed that the players enjoyed plyometric training. Therefore, coaches could safely use plyometric exercises to design enjoyable training programs.

Effects of Plyometric Training on Physical Performance: An Umbrella Review

BACKGROUND

Plyometric training can be performed through many types of exercises involving the stretch-shortening cycle in lower limbs. In the last decades, a high number of studies have investigated the effects of plyometric training on several outcomes in different populations.

OBJECTIVES

To systematically review, summarize the findings, and access the quality of published meta-analyses investigating the effects of plyometric training on physical performance.

DESIGN

Systematic umbrella review of meta-analyses.

DATA SOURCES

Meta-analyses were identified using a systematic literature search in the databases PubMed/MEDLINE, Scopus, SPORTDiscus, Web of Science, Cochrane Library and Scielo.

ELIGIBILITY CRITERIA FOR SELECTING META-ANALYSES

Meta-analyses that examined the effects of plyometric training on physical fitness in different populations, age groups, and sex.

RESULTS

Twenty-nine meta-analyses with moderate-to-high methodological quality were included in this umbrella review. We identified a relevant weakness in the current literature, in which five meta-analyses included control group comparisons, while 24 included pre-to-post-effect sizes. Trivial-to-large effects were found considering the effects of plyometric training on physical performance for healthy individuals, medium-trivial effects for the sports athletes' groups and medium effects for different sports athletes' groups, age groups, and physical performance.

CONCLUSION

The available evidence indicates that plyometric training improves most related physical fitness parameters and sports performance. However, it is important to outline that most meta-analyses included papers lacking a control condition. As such, the results should be interpreted with caution. PROSPERO number: CRD42020217918.