We just don’t know yet if light or heavy weights make muscles grow better — the results could swing either way in future studies, so we need more research.

Scientific Claim

The available evidence on muscle fiber hypertrophy from low-load and high-load resistance training is highly uncertain, with 95% prediction intervals ranging from -0.71 to 1.28 for type I fibers and -0.28 to 0.88 for type II fibers, indicating that future studies may find large beneficial or harmful effects in either direction.

Original Statement

“The 95% confidence and prediction intervals were very wide, suggesting that the true effect in the population and the effect reported in a future study conducted on this topic could be in different directions and anywhere from trivial to very large.”

From study:The Effects of Low-Load Vs. High-Load Resistance Training on Muscle Fiber Hypertrophy: A Meta-Analysis

Evidence Quality Assessment

Claim Status

appropriately stated

Study Design Support

Design supports claim

Appropriate Language Strength

association

Can only show association/correlation

Assessment Explanation

The claim directly reflects the authors’ own interpretation of prediction intervals, which are a valid statistical tool for expressing uncertainty. No overstatement is present.

Evidence from Studies

Supporting (1)

The Effects of Low-Load Vs. High-Load Resistance Training on Muscle Fiber Hypertrophy: A Meta-Analysis

Systematic Review With Meta-Analysis

Human

2020 Aug

This study found that lifting light weights and heavy weights might both make muscles grow similarly, but we can't be sure — future studies could show one is much better, much worse, or the same. The numbers show a big range of possible outcomes.

Contradicting (0)

No contradicting evidence found

Source Study

The Effects of Low-Load Vs. High-Load Resistance Training on Muscle Fiber Hypertrophy: A Meta-Analysis

Score: 46

DOI: 10.2478/hukin-2020-0013

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