Regular physical activity leads to which physiological adaptation?

• A. Increased resting heart rate
• B. Decreased heart rate
• C. Decreased blood flow
• D. Decreased endurance of slow twitch fibers

Answer: (B)

Regular aerobic activity makes the heart work more efficiently, and the main outward sign is a lower resting heart rate. When you train, the heart increases its stroke volume—the amount of blood ejected with each beat—so it can deliver the same amount of blood with fewer beats. That extra efficiency often shows up as a slower pulse when you’re at rest. Training also tends to boost parasympathetic (vagal) activity, further slowing the heart rate at rest.

The other ideas don’t fit with how the body adapts to regular activity. A higher resting heart rate would reflect poorer conditioning. Blood flow at rest doesn’t typically decrease with training; instead, the body becomes better at delivering blood via improved circulation and capillary density to support activity. Endurance of slow-twitch fibers actually increases with consistent aerobic training due to greater mitochondrial density and oxidative capacity, not decreases.