The effects of single versus repeated plyometrics on landing biomechanics and jumping performance in men

The aim of this study was to examine the chronic effects of single and repeated jumps training on vertical landing force (VGRF) and jump height in untrained men. The VGRF and jump height were compared after a six-week plyometric training programme containing single and repeated jumps, together with two additional parameters: landing time (LT) and range of the knee flexion during landing (KF). Thirty-six untrained physical education students with a plyometric training background were randomly assigned to a single jump group (SJG, n =12), repeated jumps group (RJG, n =12), and control group (CON, n =12). The SJG performed only single jumps, the RJG executed repeated (consecutive) jumps, whereas the CON did not perform any exercises at all. A countermovement jump (CMJ), repeated countermovement jumps (RCMJ), and a drop jump (DJ) were tested before and after the training. Only the RJG showed a significantly reduced VGRF (p < 0.05) in all tests. Both plyometric groups significantly improved (p < 0.05) their jump height in all tests. The LT was significantly greater in the RJG, compared to the SJG, in all tests. The KF was also significantly (p < 0.05) greater in the RJG than in the SJG for CMJ and RCMJ. The results suggest that repeated jumps are beneficial for simultaneous landing force reduction and jumping performance enhancement.

The role of attentional focus in plyometric training

AIM

The purpose of this study was to examine how focusing attention during nine weeks of plyometric training influence jumping performance. It was hypothesized that participants utilizing an external focus of attention during practice would produce greater improvements in jumping behavior compared to participants practicing in the internal and control conditions.

METHODS

Thirty-six untrained but physically active male college students were randomly assigned to 1 of 3 plyometric groups with a different focus of attention: external (EXF; N.=12), internal (INF; N.=12), and control (CON; N.=12). All participants subsequently participated in the same an 9-week periodized training program. Standing long jump (SLJ), countermovement jump (CMJ) and drop jump (DJ) were tested pre- and posttraining intervention.

RESULTS

The EXF group exhibited greater improvement (P<0.05) in jumping distance for SLJ and height for CMJ than both the INF and CON groups, while the enhancement in jumping height for DJ was not superior (P<0.05) in the EXF group in comparison with the INF and CON groups. However, the CON group showed a greater increase (P<0.05) in jumping height for DJ than the INF group. The EXF group increased the range of knee flexion (KF), whereas both the INF and CON groups decreased the KF during the CMJ. Additionally, only the CON group reduced KF during the execution of the DJ. The EXF group (P<0.05) increased contact time, whereas both the INF and CON groups decreased (P<0.05) contact time in DJ. The EXF group had significantly (P<0.05) greater vertical ground reaction force in CMJ and DJ when compared with the INF and CON groups.

CONCLUSION

These results suggest that the external focus of attention during plyometric training may provide a greater stimulus to jump performance in slow stretch shortening cycle (SSC) tasks by producing greater force than adopting the internal and no specific focus.