What physical quality is effectively increased by training at ≤67% of one-repetition maximum (1RM) for ≥12 repetitions?

Training at a load of ≤67% of one-repetition maximum (1RM) for a duration of 12 or more repetitions is primarily aimed at enhancing muscular endurance. This training modality encourages the muscle fibers to develop improved resistance to fatigue, allowing them to sustain prolonged efforts over an extended period.

When performing high-repetition sets at lower percentages of 1RM, the body adapts by improving its capacity to utilize energy efficiently and maintain activity without requiring significant rest. The focus on endurance rather than maximal strength or hypertrophy stems from both the repetition volume and the lower intensity, which allows for more sustained physical activity and less reliance on maximal force outputs.

In contrast, higher percentages of 1RM emphasize strength and power, typically requiring fewer repetitions, while hypertrophy training often targets moderate to high repetitions at slightly higher percentages, generally in the range of 67%-85% 1RM. Thus, the physiological adaptations from training at ≤67% of 1RM with ≥12 repetitions specifically target enhancements in muscular endurance.