Final answer:
Gait speed requires more power from the lower extremities than the upper extremities because they generate the force to propel the body forward. An example includes a woman who uses more energy climbing stairs (lower extremity activity) than to merely accelerate her movement.
Step-by-step explanation:
The question pertains to whether gait speed requires more power from the upper extremities (UE) or the lower extremities (LE's). Power in the context of human movement is often associated with the energy exerted to perform a task over a certain period. When it comes to gait speed, which is the speed at which a person walks or runs, it primarily involves the lower extremities as they are responsible for generating the force needed to propel the body forward.
As an example, consider a woman who does 1764 J of work to move up the stairs compared to only 120 J to increase her kinetic energy. This indicates that most of her power output is required for climbing—effectively an exercise engaging the lower extremities—rather than accelerating, which involves more kinetic movement. Similarly, a runner moving at a constant speed of 3 m/s would require more energy to run uphill because the lower extremities have to work against gravity, whereas running downhill would require less energy as gravity aids the descent.