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Relationship between knee joint angle and fine-wire EMG activity of the four quadriceps femoris muscles
Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
2015 (English)Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The purpose of the present study was to investigate the electromyography (EMG)-knee joint angle relationship and the differences in activity among the four quadriceps femoris (QF) muscles during maximal voluntary isometric knee extensions. Ten well-trained healthy male volunteers (mean ± 1 standard deviation (SD) age 33 ± 11 years, height 1.83 ± 0.07 m, body mass 79 ± 4.7 kg) performed maximal isometric knee extensions in a seated position at four different knee joint angles (90º, 65º, 40º, and 15º of knee flexion). Myoelectric activity was simultaneously recorded from rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), and vastus intermedius (VI) using fine-wire EMG. Root-mean-square (RMS) was calculated during a sustained phase of one second at each of the different knee joint angles tested. Results showed that the RMS value of the VM was significantly higher at 90º compared to 40º (P < 0.05). When comparing 90º-normalized RMS values among the four QF muscles collapsed across the three most extended positions (65º, 40º, and 15º of knee flexion), significantly lower normalized RMS value was observed for the VM compared to that of the RF (P < 0.01) and VL (P < 0.05), respectively. No significant differences in RMS values between knee joint angles were observed for any of the other QF muscles (RF, VL, and VI). These results suggest that VM muscle activity is highest at more flexed knee joint angles during a seated knee extension task. Further, as the knee gets more extended, muscle activity of the VM decreases and VM becomes less active than the VL and RF, respectively.

Abstract [sv]

Syftet med denna studie var att undersöka sambandet mellan elektromyografisk aktivitet (EMG) och vinkel i knäled, samt att jämföra skillnaden i aktiveringsgrad mellan quadriceps femoris (QF) fyra delmuskler vid maximala viljemässiga isometriska knäextensioner. Tio vältränade friska män (medelvärde ± 1 standardavvikelse, ålder 33 ± 11 år, kroppslängd 1,83 ± 0,07 m, kroppsvikt 79 ± 4,7 kg) deltog frivilligt i studien. Samtliga deltagare genomförde maximala isometriska knäextensioner i sittande position vid fyra olika vinklar i knäled (90º, 65º, 40º och 15º knäflexion). Myoelektrisk aktivitet registrerades samtidigt från rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM) och vastus intermedius (VI) med hjälp av intramuskulär EMG (trådelektroder). Det kvadratiska medelvärdet (engelska root-mean-square, RMS) beräknades under en en-sekundersperiod vid respektive ledvinkel. Resultaten visade att RMS-värdet för VM var signifikant högre vid 90º jämfört med 40º (P < 0,05). Vid en jämförelse av 90º-normaliserade RMS-värden mellan QF olika delmuskler för de tre mest extenderade positionerna (65º, 40º och 15º knäflexion) observerades signifikant lägre normaliserade RMS-värden för VM jämfört med RF (P < 0,01) respektive VL (P < 0,05). Inga signifikanta skillnader i RMS-värde mellan de olika ledvinklarna sågs för någon av de övriga delmusklerna (RF, VL och VI). Dessa resultat tyder på att VM är som mest aktiv vid mer flekterade knäledsvinklar under sittande knäextensioner. Vidare kommer aktiviteten i VM att minska allteftersom knäet blir mer extenderat, och dess aktivitet blir då lägre jämfört med VL respektive RF.

Place, publisher, year, edition, pages
2015.
Series
Examensarbete, 2015:36
National Category
Sport and Fitness Sciences
Identifiers
URN: urn:nbn:se:gih:diva-4120OAI: oai:DiVA.org:gih-4120DiVA: diva2:850769
Educational program
Master programme
Supervisors
Examiners
Available from: 2015-09-02 Created: 2015-09-02 Last updated: 2015-09-02Bibliographically approved

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