Abstract
The aim of this study was to investigate the effects of two training protocols on the isokinetic performance of athletes. The study was conducted in 38 athletes, (age 23.3 ± 3.6 years) participating in national level leagues of different sports, whose initial concentric hamstrings-to-quadriceps (conH/Q) torque ratio was lower than 0.5. During seasonal testing, an isokinetic measurement of knee extensors and flexors was performed at 60°/s. The athletes were divided into two groups. Nineteen athletes performed the isokinetic training protocol (IT) while the second group of 19 athletes followed the isotonic training protocol (RT). Both protocols lasted 4 weeks. After completing the training protocols, both groups underwent a final isokinetic testing. The isokinetic data revealed significant increases after training in measures of peak torque in both extensor and flexor muscle groups, in both the IT and RT study groups (p < 0.05). There were significant increases (p< 0.05) in conH/Q ratio in both groups after the implemented protocols, but greater in IT group. Consequently, applied IT protocol induced changes in working muscles, thereby restoring detected asymmetry to an acceptable balance more efficiently compared to RT protocol.
Highlights
In isokinetic testing the term of asymmetry does not refer only to unequal bilateral torque values, and to the balance between the torque ratios of agonistic and antagonistic ipsilateral muscle groups
Among these 38, bilateral differences between the strength of muscles were found in 5% for knee extensors and in 8% for the knee flexors for the tested angular velocity of 60°/s
Two specific training protocols were introduced in order to restore desired values of the concentric ratio and muscle strength and to evaluate the effects they induced in the trained muscle groups
Summary
In isokinetic testing the term of asymmetry does not refer only to unequal bilateral torque values, and to the balance between the torque ratios of agonistic and antagonistic ipsilateral muscle groups. Many papers report that bilateral differences are an important predictor of injury occurrence (Dauty et al, 2003; Yeung et al, 2009; Fousekis et al, 2010). Poor flexibility is assumed to be associated with a higher risk of hamstrings muscle injury (Brockett et al, 2004). In his recent study, Schlumberger et al (2006) found that muscle imbalance could increase injury rate in top-level athletes. It appears difficult to define imbalance as a deviation from an assumed normative value because the margins of acceptable deviation are unclear (Schlumberger et al, 2006). Impellizzeri et al (2008) pointed out
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