The disability caused by a stroke is most consistently associated with muscle weakness and decreased co-ordination. But of these impairments, muscle weakness is the largest cause of disability after stroke (Canning et al 2004) because if you can’t produce enough force with your muscles you can’t move at all. People after stroke can have significant muscle weakness, often less than half of the strength of people without stroke (Dorsch et al 2016, Horstman et al 2008) so it is important to know what interventions can improve strength for these people. Generally, the most proven method of strengthening is progressive resistance training (PRT) which is training that involves lifting a load that can only be lifted 8 to 15 times before muscle fatigue. This has been shown to be effective in people without stroke but we didn’t know how effective it is in people with stroke. In this study we endeavored to find all the clinical trials that had used PRT in people with stroke and to pool the results to see the effects on muscle strength and activity outcomes.
We analysed data from 11 clinical trials that used PRT in people with stroke. The trials included study participants who were stroke survivors at any time after stroke, an intervention group that performed progressive resistance training and a control or placebo group that did not perform the training. We pooled the results for changes in muscle strength and activity in these studies. In general, the studies that involved training of leg muscles measured activity with walking speed and studies that involved training of arm muscles measured activity with functional tests of the arms.
We found that PRT is very effective in people with stroke with an average increase in strength of 50% in the muscles that were trained. However, while this is a very large increase in strength, surprisingly it did not have any impact at the level of activity i.e. no consistent improvements in walking or arm function.
So what is going on?
It is evident that PRT can effectively increase strength in weak muscles in stroke survivors but this doesn’t necessarily carry over to improvement at the level of activity. This suggests that if stroke survivors are strong enough to do PRT then strength wasn’t the main impairment affecting their task performance and coordination needs to be targeted to get an improvement at the level of activity. However, if you have very weak muscles, too weak to move against added resistance or against gravity then increasing strength is still the priority.