A study comparing gait and lower limb muscle activity during aquatic treadmill running with different water depth and land treadmill running

Aquatic treadmill running is a partial weight-bearing exercise for rehabilitation. The purpose of this study was to investigate the surface electromyography activities of the rectus femoris, tibialis anterior, biceps femoris and medial head of gastrocnemius, and gait kinematics during aquatic treadmill running in water levels at waist, mid-thigh and mid-shin and on land. Seventeen healthy subjects (9 males and 8 females) were recruited by convenience sampling. Participants performed 2-min aquatic treadmill running at a specific speed for each water depth. The test speed was selected based upon the speed that elicited 110 steps per min. The surface electromyography data of lower limb muscles and the joint angles at three different water depths and on land were collected to evaluate the muscle activity and gait kinematics using a waterproofed surface electromyography system and inertial measurement unit for each muscle. Results showed that rectus femoris electromyography was different between depths during the swing and stance phases. Likewise, biceps femoris and tibialis anterior electromyography were different between depths for the swing phase. However, it was not the case for gastrocnemius electromyography. Peak flexion angles in both left and right hips were different between depths. A significant increase in a stance/swing ratio was observed with rising water depths. Water depth influenced muscle activity as well as kinematics. Aquatic treadmill running in the mid-thigh level should be further evaluated for its effectiveness, training value and applicability.