Question

During which phase of the gait cycle does the ground reaction force (GRF) occur?

1) Initial swing phase
2) Terminal stance phase
3) Midstance phase
4) Pre-swing phase

Answer 1

GRF occurs during the terminal stance, midstance, and pre-swing phases of the gait cycle, not during the initial swing phase. In the context of a pendulum, it possesses both potential and kinetic energy at the ends of its swing and a combination of both as it swings through the middle.

Step-by-step explanation:

The ground reaction force (GRF) occurs during all phases of the gait cycle where the foot is in contact with the ground. GRF is not present during the initial swing phase, as this is when the foot is off the ground and moving forward. The phases in which GRF plays a role include: the terminal stance phase, when the heel starts to lift off the ground; the midstance phase, when the body weight is directly over the supporting foot; and the pre-swing phase, which prepares the foot for the coming swing. In addressing the question regarding the pendulum, at the moment it completes one cycle, just before it begins to fall back towards the other end (i), it has both potential and kinetic energy. At the middle between the two ends (ii), it also has both potential and kinetic energy. Finally, just before it reaches the end of one cycle (iii), it has primarily kinetic energy.