Exploration of Gait Biomechanics and Muscle Pain of the Lower Extremity

Overview

This interventional study aims to test gait biomechanics in healthy individuals with and without experimental muscle pain in the lower extremities. The study aims to: A) Examine how experimental muscle pain in different types of muscles (ankle plantar-flexion, knee extension, and flexion muscles) affects kinematics, kinetics, and muscle activation Participants will receive six muscle injections: a) Hypertonic saline (painful condition) and b) Isotonic saline (control condition) in 1) m. gastrocnemius, 2) m. semitendinosus, and 3) m. biceps femoris.

The proposed study will be a randomized, crossover design in which experimental pain will be induced in healthy subjects using hypertonic saline injections to three muscles of the lower extremities: The gastrocnemius muscle, the vastus medialis muscle, and the semitendinosus muscle. Participants will be block-randomized to receive an injection in each of the three muscles and will receive either the painful or control condition first for each muscle. The participant will always be blinded to the type of injection received. Following the injection, there will typically be a 15-minute window of pain (45). Within this timeframe, motion capture will be carried out for both the control and painful conditions. During motion capture, the participants will perform multiple walking trials of approximately 10 meters. The participants will be equipped with electromyography (EMG) sensors on key muscles of the lower extremities. The participants will be asked for NRS ratings every 30 seconds throughout the 15 minutes with expected pain. There will be a 15-minute washout between the muscle injections.