# Non-Specific Strength Changes Between High- and Low-Load Isotonic Resistance Training: A Systematic Review and Meta-Analysis

## TL;DR

This study compares high- and low-load resistance training effects on non-specific strength, finding no conclusive difference despite a slight trend favoring high-load training.

## Contribution

A systematic review and meta-analysis quantitatively evaluates the differential effects of high- and low-load isotonic resistance training on non-specific strength.

## Key findings

- The overall effect size favored high-load training but was not statistically significant.
- Confidence intervals were wide and crossed zero, indicating inconclusive results.
- Ten studies with 245 participants were analyzed, showing no definitive advantage of one training method over the other.

## Abstract

In comparisons between high- and low-load isotonic resistance training, it has become common to include non-specific strength tests (e.g., isometric and isokinetic strength tests), presumably in attempt to minimize the influence of training specificity and better understand the efficacy of low-load training for developing maximal strength. Many have suggested that high- and low-load isotonic resistance training are similarly effective for increasing non-specific strength, provided exercise is performed to task failure. However, little work has been completed to examine the accuracy of such statements.

We aimed to quantitatively identify whether high-load isotonic resistance training results in differential changes in non-specific strength compared to low-load isotonic training.

A systematic search of the literature was conducted using PubMed, Scopus, and Embase from inception to 14 June, 2025. To be included in the present review, a study needed to: (a) be performed in healthy adult humans ≥ 18 years of age; (b) include isotonic high- and low-load isotonic resistance training protocols that were prescribed to task failure; (c) have measured non-specific strength at both pre- and post-intervention via an isometric or isokinetic maximum strength task; (d) matched the number of strength tests between the high- and low-load training groups; (e) be published in a peer-reviewed journal; and (f) published in the English language. A random-effect meta-analysis using robust estimation variation was then implemented on the changes (i.e., pre- to post-intervention) in non-specific strength between high- and low-load isotonic resistance training.

The literature search yielded 7885 unique articles, of which ten studies were selected for inclusion in the present analysis. Using effect size values calculated from the change score standard deviations resulted in 44 ES from ten studies (245 total participants; high load, n = 114; low load, n = 131). The overall effect size (Cohen’s d) was 0.322 with a standard error of 0.17, a 95% confidence interval of − 0.08 to 0.72 (p = 0.104), and 95% prediction intervals that ranged from − 0.45 to 1.1. A supplemental analysis using pre-standard deviations resulted in similar conclusions.

The results of the current analysis were inconclusive as to whether high- and low-load isotonic training induced differential changes in non-specific strength. The overall effect size appeared to be biased towards favoring high-load isotonic training; however, the confidence intervals were wide and crossed zero.

The online version contains supplementary material available at 10.1007/s40279-025-02370-8.