Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
©Journal of Sports Science and Medicine (2023) 22, 769 - 777   DOI:

Research article
Comparing the Effects of Static Stretching Alone and in Combination with Post-Activation Performance Enhancement on Squat Jump Performance at Different Knee Starting Angles
Ming Li, Xiangwei Meng, Lihao Guan, Youngsuk Kim, Sukwon Kim 
Author Information
Department of Physical Education, Jeonbuk National University, Republic of Korea
These authors contributed equally to this work and share first authorship

Sukwon Kim
✉ Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
Publish Date
Received: 21-09-2023
Accepted: 06-11-2023
Published (online): 01-12-2023

We aimed to investigate the impact of isolated static stretching (4 sets of 30 seconds) and its combined form with 10 repetitive drop jumps on lower limb performance during squat jumps at different knee joint starting angles (60°, 90°, and 120°). Thirteen participants completed three randomly ordered experimental visits, each including a standardized warm-up and squat jumps at three angles, apart from the intervention or control. Information was gathered through a three-dimensional movement tracking system, electromyography system, and force platform. The electromyography data underwent wavelet analysis to compute the energy values across the four wavelet frequency bands. The average power (Pavg), peak power (Ppeak), peak ground reaction force (GRFpeak), peak center of mass velocity (Vpeak), and force-velocity relationship at peak power (SFv) were extracted from the force and velocity-time data. The results revealed no significant influence of isolated static stretching, or its combined form with drop jumps, on the energy values across the frequency bands of the gastrocnemius, biceps femoris and rectus femoris, or the Pavg or Ppeak (P > 0.05). However, at 120°, static stretching reduced the GRFpeak (P = 0.001, d = 0.86) and SFv (P < 0.001, d = 1.12), and increased the Vpeak (P = 0.001, d = 0.5). The GRFpeak, Pavg, Ppeak, and SFv increased with an increase in the joint angle (P < 0.05), whereas the Vpeak decreased (P < 0.05). These findings suggest that static stretching does not diminish power output during squat jumps at the three angles; however, it alters GRFpeak, Vpeak, and the relative contributions of force and velocity to peak power at 120°, which can be eliminated by post-activation performance enhancement. Moreover, compared to 60° and 90°, 120° was more favorable for power and peak force output.

Key words: Electromyography, wavelet analysis, peak power, average power, peak ground reaction force, peak center of mass velocity

           Key Points
  • We investigated and compared the effects of acute static stretching (StS) alone, and in combination with, 10 repetitive drop jumps (S-D) on squat jump performance at different knee joint starting angles (60°, 90°, 120°).
  • We designed three experimental groups to explore the efficacy of different intervention methods: a control group, a group solely performing static stretching, and a group combining static stretching with repetitive drop jumps.
  • Key performance indicators included energy values across various wavelet frequency bands for the gastrocnemius, biceps femoris, and rectus femoris muscles, as well as average power, peak power, peak ground reaction force, maximum velocity, and the force-velocity ratio corresponding to peak power.
  • We recommend incorporating StS as part of warm-up when the goal is to increase range of motion (ROM) while maintaining power output. However, for activities emphasizing pure power or speed output, we suggest combining StS with ten repetitive drop jumps or avoiding StS altogether.
  • We advise selecting an appropriate takeoff angle based on the specific requirements of the sport, such as an emphasis on power or speed.
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