With Resistance Training, Load is Only Half the Story
A study published in Medicine & Science in Sports & Exercise® has analyzed how load and fatigue interact to influence muscle adaptations during resistance training. The research, conducted with 158 trained men, aimed to compare different loads while objectively controlling fatigue, using speed loss as an indicator.
The Interaction Between Load and Fatigue in Resistance Training
For decades, research on resistance training has focused on determining the optimal weight to maximize strength and muscle hypertrophy. However, these studies have based their comparisons on the premise that load would be the only changing variable, while the fatigue generated by that load remained uncontrolled.
This means that many studies have actually compared different combinations of load and fatigue. Therefore, the effects attributed solely to load could be influenced by differences in accumulated fatigue during training.
Objective Measurement of Fatigue Through Speed Loss
To address this limitation, the study employed speed loss during execution as an objective and continuous measure of accumulated fatigue. Movement speed progressively decreases in a set, reflecting the level of fatigue in real-time.
This method allows for quantifying and controlling fatigue during each repetition, rather than estimating it retrospectively based on the number of completed repetitions or proximity to muscular failure. Thus, it is possible to compare different loads while keeping the level of fatigue constant, something that had not been achieved in previous research.
Experimental Design and Key Findings
The study randomly assigned 158 trained men to 12 groups that performed eight weeks of bench press with three relative intensity ranges (40–55%, 55–70%, and 70–85% of one-repetition maximum) combined with four speed loss thresholds (0%, 15%, 25%, and 50%).
For a given speed loss threshold, the highest relative loads produced the greatest improvements in maximum strength. Additionally, for a given load, strength adaptations followed an inverted U-shaped relationship with fatigue, where moderate levels of speed loss produced greater gains than minimal or near-maximal levels.
On the other hand, for an equal load, greater fatigue promoted more pronounced hypertrophic adaptations.
Implications and Limitations of the Study
These findings do not contradict previous evidence but rather provide a framework for interpreting the variability observed in earlier studies. The apparent inconsistency could be due to the different combinations of load and fatigue used, rather than disagreements about the mechanisms driving adaptation.
The study introduces a methodology for investigating resistance training by considering load and fatigue as independent yet interrelated dimensions of the stimulus.
It does not allow for a conclusion on the optimal combination of load and fatigue for all goals, but it confirms that fatigue is a relevant factor alongside load in strength and muscle mass adaptations.
More details can be found in the original source.
Published: 12/08/2026. Content reviewed using experience, authority and trustworthiness criteria (E-E-A-T).
This article may have used artificial intelligence tools to support structure, editing, translation or review. Editorial responsibility and final review remain with Toni Berraquero. View AI policy
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