Fundamentals of Biomechanics

LAB ACTIVITY 7A NAME _____________________________
ANGULAR KINETICS OF EXERCISE
LAB ACTIVITIES L-19
1. Where were the sites of most fatigue in the two squat tests? What muscle group feels more fatigue
in a nearly vertical trunk orientation? Why?
2. Kinematic measurements from film/video and anthropometric data are often combined to make angular
kinetic calculations. A static analysis can be done when the inertial forces and torques (dynamic
loading from high-speed movement) are small. Assume the figure below is an image of you captured
from video while performing bodyweight squats. Calculate a gravitational torque of your upper
body about the hip (M/L) axis. Assume your head, arms, and trunk (HAT) have mass equal to
0.679 of body mass. The center of gravity of your HAT acts at 62.6% up from the hip to the shoulder.
3. Calculate the gravitational torque about the hip if the bottom of your squat exercise has a trunk
lean of 40°. (Show free-body diagram and work.)
4. If the weight of the head, arms, and trunk do not change during the squat exercise, what does
change that increases gravitational torque as the person leans forward?
5. How different is the load on the back/hip extensors when you double your trunk lean? Is the size
of this difference what you expected? Why is it different?
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