Which biomechanical adaptation indicates a more efficient energy cost during physical activity?

Choosing "improved economy" is correct because it specifically refers to how efficiently an individual can perform physical activities, particularly in terms of energy expenditure. Improved economy means that with the same amount of physical activity, a person can use less energy, resulting in better performance and endurance. This adaptation is crucial for athletes and individuals engaged in regular physical activity, as it allows them to perform longer and with less fatigue.

In contrast, increased stroke volume relates to the heart's efficiency in pumping blood, but it doesn’t directly address energy efficiency in movement. While it’s important for overall cardiovascular fitness, it doesn’t solely indicate improved energy economy in physical performance.

Improved proprioception is the body's ability to perceive its position and movement in space. While this is important for balance and coordination, it doesn’t directly correlate with how efficiently energy is used during physical activity.

Increased heart rate reflects the body's response to physical exertion rather than the energy cost of the activity itself. While a higher heart rate can indicate a higher level of exertion, it doesn’t directly signify an efficient energy expenditure during physical activity.

Overall, "improved economy" is the best indicator of a more efficient energy cost during physical activity, highlighting the importance of how well the body utilizes energy