Effects of Rate of Force Development on EMG Amplitude and Frequency

M. D. Ricard; C. Ugrinowitsch; A. C. Parcell; S. Hilton; M. D. Rubley; R. Sawyer; C. R. Poole

doi:10.1055/s-2004-817856

International Journal of Sports Medicine, Table of Contents

Int J Sports Med 2005; 26(1/02): 66-70
DOI: 10.1055/s-2004-817856

Training & Testing

Effects of Rate of Force Development on EMG Amplitude and Frequency

M. D. Ricard¹ , C. Ugrinowitsch² ^, ³ , A. C. Parcell² , S. Hilton⁴ , M. D. Rubley⁵ , R. Sawyer² , C. R. Poole²

¹Biomechanics Laboratory, Western Michigan University, Kalamazoo, MI, USA
²Human Performance Research Center, Brigham Young University, Provo, UT, USA
³Universidade de Sao Paulo, Coordenadoria de Aperfeicoamento de Pessoal de Ensino Superior (Capes), Brazil
⁴Department of Statistics, Brigham Young University, Provo, UT, USA
⁵Kinesiology Department, University of Nevada Las Vegas, Las Vegas, NV, USA

Abstract

The purpose of this study was to compare the amplitude and frequency of the gastrocnemius EMG during ramp and ballistic contractions in highly trained sprint athletes. Sixteen female sprinters performed ramp and ballistic isometric contractions on a Biodex dynamometer. RMS and median frequency of the gastrocnemius EMG signals were obtained at the following torque levels: 25 ± 5 %, 50 ± 5 %, 75 ± 5 %, 100 % MVC. The average rate of force development (RFD), was 610.2 ± 123.1 N · m/s and 212.3 ± 155.6 N · m/s for the ballistic and ramp contractions, respectively. In the ramp contractions the EMG amplitude increased as a function of torque. In the ballistic contractions the EMG amplitude decreased from 25 % to 100 % MVC. The highest RFD of 889.45 N · m/s was generated in ballistic contractions by a muscular activation pattern with high EMG amplitude (475.7 μV) and low frequency (116.7 Hz) at 25 % MVC. The findings suggest that the CNS utilizes different muscular activation patterns to modulate RFD in ramp and ballistic contractions. In ramp contractions the EMG amplitude increased linearly with force. In ballistic contractions a high RFD is generated with a muscular activation pattern consisting of high amplitude and low frequency at the start of the contraction.

Key words

EMG - ballistic contraction - ramp contraction - isometric - isokinetic exercise

Full Text

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M. D. Ricard

Biomechanics Laboratory 1060 SRC · Western Michigan University

1903 West Michigan Avenue

Kalamazoo, MI 49008

USA

Phone: + 2693872546

Fax: + 26 93 87 27 04

Email: Mark.Ricard@wmich.edu