**Question:** The kinetic energy of the body is least in one of the following phases of the walking cycle:

A. Swing phase
B. Initial contact and push-off phases
C. Mid-stance phase
D. Double support phase

**Core Concept:** Kinetic energy is a measure of an object's motion and is directly proportional to mass and velocity squared. In human movement, kinetic energy refers to the motion of body segments during walking. Kinetic energy is least when an individual's body is stationary or has very low velocity.

**Why the Correct Answer is Right:** The correct answer, D. Double support phase, is chosen because it represents the least kinetic energy due to the body being stationary or moving with the slowest velocity during this phase.

During the double support phase, both feet are in contact with the ground, allowing the body to maintain a stationary position. As a result, the kinetic energy of the body segments is at its lowest point compared to the other phases of the walking cycle.

**Why Each Wrong Option is Incorrect:**

A. Swing phase: Kinetic energy is not at its highest during this phase because the body is moving with a moderate velocity.

B. Initial contact and push-off phases: While kinetic energy is not at its least during these phases, it is higher than the double support phase due to increased body segment motion.

C. Mid-stance phase: Kinetic energy is not at its least during this phase because the body is still moving, albeit with moderate velocity.

**Clinical Pearl:** The double support phase helps minimize energy expenditure during walking by maintaining balance and reducing the workload on the musculoskeletal system. This concept is particularly relevant when considering energy conservation strategies in various clinical scenarios, such as when patients are recovering from injuries or dealing with muscle weakness.

**Correct Answer:** D. Double support phase

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