A dose-response meta-analysis of 20 randomised trials and 791 patients examined isotonic lower-limb resistance training in knee osteoarthritis, modelling volume with restricted cubic splines rather than treating exercise as present or absent.
The relationships were non-linear, with identifiable peaks: greatest estimated pain reduction at around 6,000 total repetitions (mean difference -3.52), best functional improvement at around 2,600 repetitions of moderate intensity (-16.66), and maximal strength gains at around 1,600 (standardised mean difference 0.12). Very light to moderate intensity produced the greatest pain reduction; moderate intensity the best function; moderate to vigorous, similar strength gains. Both home and centre-based programmes helped, with centre-based more pronounced.
The striking implication is that pain, function and strength peak at different doses — so a prescription optimised for one is not optimised for the others, and asking what the patient wants most is a clinically meaningful question rather than a courtesy.
Certainty of evidence was rated low to very low, and 791 patients across 20 trials is thin for spline modelling. Treat the peaks as approximate landmarks rather than prescriptions, and note that the strength effect size of 0.12 is small whatever the dose.
- Pain, function and strength peak at different training volumes
- Very light to moderate intensity was best for pain, not vigorous
- Centre-based programmes outperformed home-based
- Certainty rated low to very low by the authors
- 791 patients across 20 trials is a thin base for dose-response modelling
The statistics, in plain English
Restricted cubic splines fit a flexible curve rather than assuming more is better, which is why peaks appear. The cost is that they demand more data than a linear model, and with 791 patients the curves are estimated loosely — the precise repetition counts should be read as regions rather than targets. Low to very low GRADE certainty is the authors' own summary of that.
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