Purpose: Information on muscle fiber type composition is of great importance in muscle physiology and athletic performance. Because there are only a few techniques available that noninvasively and accurately provide an estimate of muscle fiber type composition, the development of additional and alternative approaches is required.
Methods: Twenty-seven participants (21 men, 6 women) with an average age of 43 ± 18 yr, height of 175 ± 7 cm, and mass of 74 ± 12 kg participated in the study. Delay, contraction, and half relaxation times were calculated from tensiomyographic radial twitch responses of the vastus lateralis muscle. Univariate and multiple linear regression analyses were used to correlate the proportion of myosin heavy chain I (%MHC-I) in a biopsy obtained from the same muscle with a single and all three radial twitch parameters.
Results: Delay, contraction, and half relaxation times all correlated with %MHC-I (r = 0.612, 0.878, and 0.669, respectively, at P ≤ 0.001). When all three parameters were included in a multiple linear regression, the correlation with the %MHC-I was even better (R = 0.933, P < 0.001).
Conclusions: These data suggest that time parameters of the skeletal muscle mechanical radial twitch response, measured with a contact linear displacement sensor, can be used as an accurate noninvasive predictor of the %MHC-I in a muscle.
1Institute for Kinesiology Research, Science and Research Centre Koper, University of Primorska, Koper, SLOVENIA; 2Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Manchester, UNITED KINGDOM; 3Institute of Aerospace Medicine, German Aerospace Center, Cologne, GERMANY; and 4Department of Automation, Biocybernetics, and Robotics, Jožef Stefan Institute, Ljubljana, SLOVENIA
Address for correspondence: Boštjan Šimunič, UP-ZRS, Garibaldijeva 1, 6000 Koper, Slovenia; E-mail: Bostjan.email@example.com.
Submitted for publication September 2010.
Accepted for publication February 2011.