Differences and Changes in Lower Limb Muscle Activation and Ankle Stability in Different Blackboard Configurations

The goal of this observational study is to analyze the differences in muscle activation of six muscles of the lower leg (soleus, gastrocnemius medialis, gastrocnemius lateralis, tibialis anterior, peroneus longus, peroneus brevis) in seven possible configurations of a specific instability device, the Blackboard (BB), as well as on the floor, among healthy active subjects. The main questions it aims to answer are: 1. Which configuration of the BB produces the highest activation for each studied muscle? 2. Which muscle is the most activated in each configuration of the BB? 3. What is the muscle activation pattern obtained in each configuration of the BB? A single group of participants will be analyzed. Both the studied leg and the order of configurations of the instability device and ground condition will be randomly assigned. Participants will first undergo a 2-minute continuous walking warm-up, followed by a performance of a maximum voluntary isometric contraction (MVIC) for each muscle, during which the maximum activation produced will be recorded. Each participant will be allowed a 30-second familiarization period on the most unstable configuration of the BB. Three repetitions of 20 seconds will be recorded on both the ground and each configuration, with a 30-second rest between repetitions. The central 10 seconds of each trial will be used for subsequent analysis. The mean of the three repetitions for each muscle will be calculated and subsequently processed and normalized by the maximum activation value during the MIVC. Finally, a statistical analysis of the differences in muscle activation in each configuration will be conducted with the intention of addressing the mentioned questions.