Certified Personal Trainer (NSCA) Practice Exam 2025 – Complete Prep Guide

The response indicating that pH would decrease in person A and that there would be little change in person B accurately reflects the physiological responses to resistance training at different intensity levels.

When a lifter performs exercises with heavier weights, increased metabolic demand, and energy expenditure occurs. This leads to the production of lactic acid and other metabolites, which lower the pH in the muscles due to increased muscle fatigue and the body's efforts to generate energy anaerobically. Thus, in the scenario with person A, who is presumably lifting heavier weights, there's a significant increase in lactic acid production, resulting in a notable decrease in pH.

In contrast, for someone lifting lighter weights like person B, the muscular demand is lower, and the body is more likely to replicate aerobic energy production. This means there may be insufficient accumulation of lactic acid to cause a significant drop in pH, hence the idea that there's little change in this individual's muscle pH levels.

Therefore, the changes in pH are largely affected by the intensity of the weights lifted, with heavier resistance leading to a marked decrease in pH due to the by-products of high-intensity exercise, while lower resistance results in negligible changes in pH.