Abstract
This study aimed to evaluate the quadriceps femoris neural adaptations during isometric contractions using force and electromyogram (EMG) signals as visual biofeedback. Forty-two participants were randomly assigned to three groups: EMG group, tested with EMG biofeedback; Force group, tested with force biofeedback; and Control group, tested without biofeedback. Evaluations were performed pre (baseline) and post-tests to determine the maximum force and EMG amplitude during maximal voluntary isometric contraction (MVIC). The tests consisted of series of MVICs in which the participants were encouraged to surpass the force or EMG thresholds determined at baseline. The vastus lateralis EMG amplitude and knee extensor force increased significantly in all groups when compared the baseline and post-test evaluations values (p < .05). EMG percentage gain was significantly different between Force and Control groups (p < .01), while force percentage gain was not different between groups. Force biofeedback was more effective in producing neural adaptations.
Highlights
In sports and physical rehabilitation, athletes and health professionals are constantly looking for innovative ways to improve physical function
The results of this study show three important aspects: 1. The electromyographic activity of the vastus lateralis muscle and knee extensor force increased significantly within the same session of isometric tests; 2
Biofeedback that used the force signal showed a significant difference in percentage gain in EMG amplitude when compared to the Control group; 3
Summary
In sports and physical rehabilitation, athletes and health professionals are constantly looking for innovative ways to improve physical function. Among these resources, biofeedback techniques are frequently used to maximize physical performance (Campenella, Mattacola, & Kimura, 2000). Biofeedback techniques are frequently used to maximize physical performance (Campenella, Mattacola, & Kimura, 2000) Some instruments, such as electromyography and force transducers, have been used to directly or indirectly evaluate muscle internal and external forces in research. Those instruments are based on non-invasive, painless procedures that allow easy measurement reproducibility (Dvir, 2004). Its utilization provides the individual the ability to have multiple stimuli (such as visual and auditory) that add up to facilitate and enhance learning and motor response (Huang, Wolf, & He, 2006)
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