Define efficacy.

• A. time rate of adaptation
• B. physics of movements
• C. activity that improves nervous system
• D. tangible results from a program

Answer: (D)

Efficacy is about whether a program actually yields the intended, observable results. It focuses on the real outcomes you can measure or see after following the plan—things like stronger lifts, increased work capacity, or improved body composition. Those tangible results show the program is delivering what it aims to produce. The other ideas describe the mechanisms behind those changes (how fast adaptation happens, movement mechanics, neural contributions), but they’re not what efficacy itself measures. So, the best answer is the tangible results from a program.