There is compelling evidence that similar whole muscle hypertrophy can be achieved across a broad spectrum of loading ranges—up to 30+ RM! However, it has been proposed that training load may differentially influence the growth of Type I and Type II muscle fibers. A new systematic review and meta-regression sought to determine whether the available evidence supports this hypothesis. What did they find? When fiber types were combined, there was no clear relationship between training load and muscle fiber hypertrophy. However, an interesting pattern emerged when fiber types were analyzed separately: --Lighter loads (20–30% 1RM) tended to favor Type I fiber growth --Moderate loads (40–50% 1RM) showed little difference between fiber types --As loads increased, the estimates progressively shifted toward greater Type II fiber growth It should be noted that the confidence intervals crossed zero for all comparisons, and the analysis included only 8 studies with 195 participants. Moreover, determination of fiber size has inherent challenges, with relatively large errors of the measurement. Thus, these findings should be considered preliminary rather than conclusive. Take-home: Muscle growth can be achieved across a broad range of training loads, but there may be a fiber-type-specific response, with lighter loads relatively favoring Type I fiber growth and heavier loads favoring Type II fibers. For the general public, these findings likely have little practical relevance—choose a rep range that best suits your preferences. However, for those seeking to maximize hypertrophy, combining different rep ranges could potentially provide complementary effects that enhance overall muscle mass. More research is needed to determine whether this pattern represents a true physiological effect. frontiersin.org/journals/phy…