Changes in the isometric knee flexion torque and hamstrings EMGs under different muscle length conditions

• Published in: Japan Journal of Test and Measurement in Health and Physical Education Vol. 18; pp. 47 - 58
• Main Authors: YAMAZAKI, Yukina, KASHIWAGI, Yu, YAMAGISHI, Michio, FUNATO, Kazuo
• Format: Journal Article
• Language: Japanese
• Published: Japanese Society of Test and Measurement in Health and Physical Education 31.03.2019
• Subjects: hamstring muscles; knee flexion torque; muscle length; surface electromyography
• ISSN: 1347-1309
• DOI: 10.14859/jjtehpe.18.47

Objective: The present study aimed to clarify the influence of different lengths of the muscle tendon complex (LMTC) by investigating the relationship of the amplitude of the surface electromyogram (EMG) of the biceps femoris long head (BF), semitendinosus (ST), and semimembranosus muscles (SM). Methods: Thirteen healthy young men (age, 21.1 ± 1.0 years; height, 173.1 ± 4.4 cm; weight, 71.1 ± 8.7 kg) performed the maximum isometric knee flexion (MVC) using a dynamometer (CON-TREX). Knee flexion torque data were collected from ten combinations of knee flexion angles (K) at 5, 30, 60, 90, and 105 degrees at both the sitting (S) and the prone position (P). The EMGs were acquired by attaching electrodes to the middle, proximal, and distal parts of each muscle. The LMTCs were estimated using the regression equation of Hawkins and Hull (1990). Results: The LMTC was the shortest at P-K105 and the longest at S-K5. High MVC torque was indicated with extended LMTC. However, different EMG amplitude patterns were present in the BF, ST, and SM during MVC torque production in different LMTCs. Conclusion: The influence of different lengths of the LMTC on the EMG of BF, ST, and SM was attributed to different morphological and structural features among the muscles and can be interpreted as being indicative of the angle–force relationship due to the length–tension curve of each muscle.