A comparative analysis of muscle activation profiles of elastic and weight resistance exercise

The use of elastic materials in implemented as a resistance method for exercise in both rehabilitation and performance contexts. Despite the increasing popularity of this material, there is paucity of research on muscular responses that occur as a result of using it as a resistance method for exercise. The specific muscular activation patterns that occur throughout the range of motion (ROM) of an exercise can have a crucial impact on strength adaptations and their identification is imperative to the applicability of elastic training in different exercise settings. This project, therefore, aimed to provide an understanding of muscular responses elicited by elastic resistance during exercise. The project consisted of five studies, of which four analytical and one intervention. The first study compared the patterns in muscular activation produced in response to exercising with elastic and weight resistance. Electromyographic responses of the agonist, antagonist and synergist muscles portrayed opposing muscular activation patterns with either method and higher activation of auxiliary muscles with elastic resistance. It was proposed that, due to the opposing activation patterns, the two methods may result in differing architectural adaptations of the skeletal muscles involved, indicating that they could be effectively used as complementary resistance methods. The higher engagement of auxiliary muscles further indicates that elastic resistance may be more effective at improving proprioception and joint stability than weight resistance. The second study analysed the effect of movement velocity on muscular activation patterns with elastic and weight resistance. Peak muscular activation increased at higher velocities with both methods. However, the previously observed activation patterns (Study 1) became more pronounced at higher velocities, where peak activation occurred at earlier stages of movement with weight resistance, but remained at final stages of movement with elastic resistance. These results further indicate that architectural adaptations of the muscles involved may differ substantially with the long term implementation of either method, and that the combined use of elastic and weight resistance may prove beneficial in high speed resistance training in order to maximise muscle overload throughout the ROM. The third study analysed the effects of combining half elastic and half weight resistance on muscular activation patterns. The combined condition portrayed a plateau in muscular activation for most of the concentric phase, as opposed to the peaks exhibited by the two methods on their own, and both the elastic and combined condition exhibited a greater engagement of secondary muscles than weight resistance, indicating that combining the two resistances does effectively maximise muscle overload throughout the concentric phase, offering the added benefit of engaging auxiliary muscles more than weight resistance alone. The fourth study analysed the effect of multiple repetitions with either resistance method on electromyographic indicators of fatigue. Results indicated that elastic and weight resistances induce fatigue of the agonist muscle at similar rates, while synergist and antagonist muscles may fatigue at higher rates under elastic resistance. The final study examined isokinetic and isometric strength adaptations at specific joint angles in response to eight weeks of bicep curl training with elastic resistance, weight resistance or a combination of the two. The opposing patterns in muscular activation elicited by the two methods, observed through the analytical studies, were reflected in angle-specific strength adaptations in the intervention study, where elastic training demonstrated a tendency to produce greater strength gains at stretched muscle lengths and the combination of the two resistances offered mixed responses. The findings indicate an effect of muscular activation pattern on angle specific strength adaptations, emphasizing the importance of understanding the specificity of muscular adaptations for the effective implementation of different resistance methods. In conclusion, elastic and weight resistance produce opposing muscular activation patterns that are enhanced at high movement velocities and effectively complement each other when combined. The activation patterns were reflected in angle-specific strength adaptations through training, suggesting that they may produce different effects on changes in muscle architecture. Finally, auxiliary muscles were more active with elastic resistance, regardless of movement velocity or whether it was combined with weight resistance, indicating that the implementation of elastic resistance is more effective in improving proprioception and joint stability.