The effects of 10,000 voluntary contractions over 8 weeks on the strength of very weak muscles in people with spinal cord injury: a randomised controlled trial

Lydia W Chen,Lovely Chaudhary,Punam D Costa,Lisa A Harvey,Marsha Ben,Sophie Denis,Yuan Xiong,Jun Wang,Joanne V Glinsky,Md Abu Khayer Hasnat,Chitra Kataria,Jayne Yeomans,Jason Redhead,Claire L Boswell-Ruys,Emilie Gollan,Md Shofiqul Islam,Muzaffor Hossain,Simon C Gandevia

doi:10.1038/s41393-020-0439-1

Abstract

Study designA multi-centred, single-blinded randomised controlled trial.ObjectivesTo determine the effect of 10,000 voluntary contractions over 8 weeks on the strength of very weak muscles in people with spinal cord injury (SCI).SettingsSeven hospitals in Australia and Asia.MethodsOne hundred and twenty people with recent SCI undergoing inpatient rehabilitation were randomised to either a Treatment or Control Group. One major muscle group from an upper or lower limb was selected if the muscle had grade 1 or grade 2 strength on a standard six-point manual muscle test. Participants allocated to the Treatment Group performed 10,000 isolated contractions of the selected muscle group, as well as usual care in 48 sessions over 8 weeks. Participants allocated to the Control Group received usual care alone. Participants were assessed at baseline and 8 weeks by a blinded assessor. The primary outcome was voluntary muscle strength on a 13-point manual muscle test. There were three secondary outcomes capturing therapists’ and participants’ perceptions of strength and function.ResultsThe mean between-group difference of voluntary strength at 8 weeks was 0.4/13 points (95% confidence interval −0.5 to 1.4) in favour of the Treatment Group. There were no notable between-group differences on any secondary outcome.ConclusionTen thousand isolated contractions of very weak muscles in people with SCI over 8 weeks has either no or a very small effect on voluntary strength.

Highlights

While progressive resistance training appears to be effective for stronger muscles (i.e., those muscles able to actively move through full range of motion (ROM) against gravity), our work suggests that it may not be effective for weaker muscles where strength is directly affected by spinal cord injury (SCI) [11, 19]
Three participants dropped out of the trial. Two of these participants self-discharged from their facilities after less than a week of training and were unavailable for the 8-week assessments, and one participant died due to respiratory complications
The data collected for these three participants were not included in the analyses