Introduction: Isokinetic dynamometry is a gold standard for measuring the mechanical properties of voluntary muscle contraction. It is used to evaluate muscle performance. The isokinetic dynamometer provides data on muscle strength and the relationship between antagonistic muscles in the observed joint. An imbalance between the knee flexors and extensors can lead to a greater risk of injury to the joint. In addition to voluntary muscle contraction, we can also measure involuntary contraction. This is a muscle contraction that is triggered by a stretch reflex or external electrical stimulation. It is measured by different methods, including magnetic resonance, electromyography and mechanomyography. One of the mechanomyographic methods used to assess the contractile properties of muscles is tensiomyography. The validity of the relationships between antagonistic knee muscles measured with tensiomyography has not yet been investigated. Purpose: In a sample of young adults, conventional and functional isokinetic torque ratios between knee flexors and extensors measured with isokinetic dynamometry were compared with the ratios between time and amplitude parameters of tensiomyography. Methods: 30 healthy volunteers (15 women and 15 men) participated in the study. We measured the time (delay time, Td and contraction time, Tc) and amplitude parameters of the contractility of the knee flexors and extensors with tensiomyography (TMG) and thus calculated different ratios. We then measured the maximum isokinetic concentric and eccentric torques with a dynamometer at three different angular velocities (60°/s, 180°/s and 240°/s), calculated conventional and functional ratios and correlated them with the TMG ratios. Results: There is a moderate negative correlation between the functional isokinetic ratio of the knee muscles at 180°/s and TcFL/TcEKST (r=-0,465) and TcBF/TcEKST (r=-0,468). A weak negative correlation also exists between the functional isokinetic ratio of the knee muscles at 240°/s and TcFL/TcEKST (r=-0,366) and TcBF/TcEKST (r=-0,408). In addition, there is also a weak negative correlation (r=-0,397) between the conventional isokinetic ratio of the knee extensors and flexors at 60°/s and TdFL/TdEKST. Discussion and conclusion: The correlation coefficients between the observed knee muscle ratios were mostly non-significant and low; we detected only a few significant weak to moderate associations. We conclude that involuntary muscle contractility ratios calculated from TMG parameters are generally poor predictors of torque ratios achieved during voluntary movement. Further high quality studies on the validity of TMG parameter relationships of antagonistic knee muscle groups are needed.
|
