Effects of Added Mass on Muscle Activity and Joint Movement During Walking

Added mass provided irregular interference towards human movement and shifted the force generated by lower limb muscles. However, the association between mass and muscle activities is not well recognized. Our study aims at investigating the influence of added mass on lower limbs. In our study, five young, healthy walkers performed walking trials under three load conditions (unload; C1: 0.25 pounds on feet, 1 pound on calves, and 2 pounds on thighs; C2: 1 pound on feet, 2 pounds on calves, and 4 pounds on thighs). During walking, three-dimensional kinematics, sEMG signals, and oxygen consumption were collected which allowed us to understand the effects of added mass on muscles. We also generated OpenSim simulation, designed to comprehend the relationship between added mass and muscles. With the increase of added mass, maximum sEMG signal and peak joint torque increased; whereas, the horizontal stride time reduced (unload: 1.697 & PLUSMN; 0.02 s, C1: 1.651 & PLUSMN; 0.02 s, C2: 1.622 & PLUSMN; 0.02 s). Energy expenditure raised correspondingly (C1: 6.53%, C2: 24.85%). Moreover, joint moment increased, while same change occurred in muscle force. Overall, our results show that participants responded positively to additional mass by adjusting muscle activities, joint movement, and stride frequency, which demonstrates the relationship between energy consumption and added mass.

Automated summary

Adding mass affects human movement and alters lower limb muscle activities. This study investigated the influence of added mass on lower limbs by analyzing kinematics, muscle activities, and energy consumption. The results showed that with increased mass, muscle activation and joint torque increased, stride time decreased, and energy expenditure raised correspondingly. Overall, participants adjusted their muscle activities and movement patterns in response to added mass, indicating a relationship between energy consumption and added mass.