A recent review in Frontiers in Physiology suggests the familiar "burn" during resistance training may be more than discomfort — it could be a key trigger behind some of strength training's whole-body benefits. Writing in April 2025, Ivan Curovic (University of Central Lancashire) examines how local metabolic stress, that build-up of metabolites in working muscles during hard, fatiguing sets, may act like a biological "broadcast signal" that influences systems beyond the trained muscle.

Many people struggle to meet exercise guidelines, and high-intensity whole-body training can be difficult to sustain, especially for older adults and clinical populations. The review argues that smarter resistance-training formats that generate strong local metabolic stress (with lower overall systemic strain) might help widen access to effective training for health, not just aesthetics.

This narrative review synthesizes findings from multiple resistance-training approaches, including traditional training, condensed protocols (e.g., supersets and drop sets), and BFR, to map plausible mechanisms, highlight what seems consistent across studies, and identify where evidence is still thin.

· Light-to-moderate loads taken close to fatigue can still drive meaningful adaptations, including strength and hypertrophy, particularly when effort is high and rest is managed strategically.

· Metabolite-heavy sessions appear to be linked with the release of signalling molecules (e.g., myokines, cytokines, hormones and microRNAs) that are plausibly connected to cardiometabolic and immune-related outcomes.

· Techniques often labelled "time-saving", including supersets, drop sets, short rest periods, and blood-flow restriction (BFR), may be valuable not only for efficiency, but because they can intensify local metabolic stress.

· The review also discusses preliminary evidence for "spillover" effects, where metabolically demanding work in one region may support adaptations in muscles trained later in a session (a concept discussed as vertical strength transfer).

The review reframes "metabolic stress" as a potentially important mechanism linking resistance training to broader health and functional outcomes, while emphasising that more targeted research is needed to confirm the most effective protocols and who benefits most.

Editor: Bashir Mehvish

First-Round Review Editor: Guo Enkai

Second-Round Review Editor: Peng Xiyang