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
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©Journal of Sports Science and Medicine (2010) 09, 326 - 331

Research article
Effects of Warm-Up on Vertical Jump Performance and Muscle Electrical Activity Using Half-Squats at Low and Moderate Intensity
Konstantinos Sotiropoulos1, Ilias Smilios, Marios Christou1,2, Karolina Barzouka3, Angelos Spaias1, Helen Douda1, Savvas p. Tokmakidis1,,1 
Author Information
1 Department of Physical Education and Sport Science, Democritus University of Thrace, Komotini, Greece
2 Department of Life & Health Sciences, University of Nicosia, Cyprus
3 Department of Physical Education and Sport Science, National and Kapodistrian University of Athens, Greece

Savvas p. Tokmakidis
✉ Democritus University of Thrace, Dept. of Physical Education & Sport Science, Komotini 691 00, Greece
Email: stokmaki@phyed.duth.gr
Publish Date
Received: 30-01-2010
Accepted: 20-04-2010
Published (online): 01-06-2010
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ABSTRACT

The purpose of this study was to determine the effects of a specific warm-up using half-squats at low and moderate intensity on vertical jump performance and electromyographic activity of the thigh muscles. The subjects were 26 men who were divided into a low intensity group (LIG; n = 13) and a moderate intensity group (MIG; n = 13). The LIG performed a specific warm-up protocol that included the explosive execution of half-squats with loads 25 and 35% of the one repetition maximum (1RM) and the MIG with loads 45 and 65% of the 1RM. The two groups performed a countermovement jump (CMJ) before and three minutes after the specific warm-up protocols. During the concentric phase of the CMJ a linear encoder connected to an A/D converter interfaced to a PC with a software for data acquisition and analysis allowed the calculation of average mechanical power. The electromyographic (EMG) activity of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) were recorded during the concentric phase of the jumps. The average quadriceps (Qc) activity (mean value of the VL, VM and RF) was also calculated. A two way ANOVA (protocols X time) with repeated measures on the second factor was used to analyze the data. Following the specific warm-up procedure both groups improved (p ≤ 0.05) CMJ performance and mechanical power by 3.5% and 6.3%, respectively, with no differences observed between the two groups. EMG activity of the Qc and VL increased (p ≤ 0.05) for both groups by 5.9% and 8.5%, respectively. It is concluded that the use of a specific warm-up that includes half-squats, performed explosively with low to moderate intensity, improves CMJ performance. This may be due to increased muscle activation as evaluated by the surface EMG.

Key words: EMG, contrast training, resistance exercise


           Key Points
  • The inclusion of two sets of explosively performed half squats with low to moderate loads in the warm up procedure elicited an acute performance en-hancement.
  • The performance was enhanced regardless of the load used in the warm-up.
  • The performance enhancement is accompanied by a greater electromyographic activity of the knee extensors muscles.
 
 
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