In running and swimming, economy of motion refers to movement efficiency achieved when what conditions are met?

• A. Economy Is Determined Solely by VO2 Max
• B. Stroke Rate Makes No Difference to Speed
• C. Movement Efficiency Where Optimal Stroke Rate and Stroke Length Maximize Speed; Excessive Rate Without Maintaining Length Reduces Efficiency
• D. Economy Of Motion Is Only About Endurance Capacity

Answer: (C)

Economy of motion is about how efficiently energy is turned into forward movement. In running and swimming, speed comes from both how often you move (cadence or stroke rate) and how far you move with each movement (stride or stroke length). There’s an optimal balance between rate and length that maximizes speed for a given energy cost. When you push the rate higher but can’t maintain length, each movement adds energy without a proportional gain in forward distance, so overall efficiency drops. So the best description is that maximum speed is achieved by an optimal combination of stroke rate and stroke length, and excessive rate without maintaining length reduces efficiency.