The effect of trunk training on muscle thickness and muscle activity: a systematic review

Objective: A systematic review to examine the effect of static or dynamic trunk training compared to standard care or control therapy on muscle activity and muscle thickness of the trunk and lower limb muscles in stroke survivors. Materials and methods: This review was registered on PROSPERO (no: CRD42017063771) and was written according to the PRISMA guidelines. The search strategy included studies from the first indexed article until September 2017 and was performed in the electronical databases PubMed, Web of Science, Cochrane Library, Ovid Medline and PEDro. Two independent reviewers screened, assessed risk of bias by means of the PEDro scale and extracted data. Results: Eight studies were included of which three investigated the effects of trunk training on muscle thickness, the remaining five investigated muscle activity. The following muscles were investigated: erector spinae, multifidi, paravertebralis, transversus abdominis, internal and external oblique abdominis, rectus abdominis, quadriceps femoris, hamstrings, soleus and tibialis anterior. Trunk exercises significantly improved the muscle activity of the internal oblique abdominis and increased muscle thickness of transversus abdominis. Conclusions: Trunk training is effective in restoring symmetry in muscle thickness to improve muscle strength. The gain in muscle thickness is specific to the applied exercise program, suggesting that therapeutic goal setting is of great importance. However, no conclusion could be made concerning changes in muscle activity due to a high risk of bias. Implications for rehabilitation: Trunk training seems to be effective in restoring symmetry in trunk muscle thickness. Not all muscle groups benefit from specific trunk exercises. Patients suffering from chronic stroke are still capable of restoring muscle function.