Exploring the Utility of Curvilinear Feedback Systems for Improving Muscle Strength via Surface Electromyography

Our knees play a crucial role in our everyday lives and mobility; however, their constant usage leads to life-changing injuries such as osteoarthritis and ligament tears. Recent advancements in knee-related interventions have focused on enhancing the recovery process, with a particular emphasis on the Vastus Medialis Oblique (VMO), a quadricep muscle pivotal for knee stability. The strengthening of this muscle can be beneficial for those recovering from knee-related injuries. Utilizing surface electromyography (sEMG) to measure muscle contractions, behavior analysts can provide feedback and establish contingencies for promoting stronger VMO contractions. While previous studies have worked with discrete schedules of reinforcement, this study utilizes conjugate schedules that mirror real-world contingencies. We compare two types of curvilinear relations in the conjugate schedule, influencing the relation between muscle response and feedback. In one condition, a negatively accelerating relation was created, where low to moderate muscle contractions produced the greatest amount of reinforcement. The other arrangement featured a positively accelerating relation, where highly intense contractions would be reinforced the most. Results showed that all eight participants had their strongest contractions under the positively accelerating relation. Six of them also demonstrated higher average amplitudes within that same condition, providing valuable insight into the efficacy of curvilinear relations in shaping VMO contractions.