Intramuscular electrical stimulation added to home exercise for myofascial shoulder pain: a randomized controlled trial

To determine whether intramuscular electrical stimulation (IMES) added to a standardized home-exercise program is more effective than home exercise alone for short-duration myofascial shoulder pain, and to assess effects on disability, pressure pain threshold, tissue perfusion, muscle mechanical properties, and shoulder abductor strength. In this single-centre, assessor-blinded, parallel-group randomized controlled trial, 50 adults with myofascial shoulder pain were allocated 1:1 to home exercise plus weekly IMES for 6 weeks or home exercise alone. Outcomes were assessed at baseline, post-treatment, and 4-week follow-up. The primary outcome was pain intensity (NRS). Secondary outcomes were DASH, pressure pain threshold, tissue perfusion, muscle tone, stiffness, and maximum voluntary contraction. IMES produced greater improvement in pain than exercise alone at post-treatment (ΔΔ -2.50 NRS points, 95% CI -3.05 to -1.94; p < 0.001; g=-3.25) and follow-up (ΔΔ -2.12, 95% CI -2.63 to -1.60; p < 0.001; g=-2.75). Disability also improved more with IMES (DASH: ΔΔ -16.28 and -21.97 points, both p < 0.001). IMES additionally improved pressure pain threshold, tissue perfusion, muscle tone, and stiffness (all p < 0.001), but not shoulder abductor strength (interaction p = 0.106). An exploratory pooled correlation was observed between increased perfusion and greater pain reduction (r=-0.87, p < 0.001), but this association should be interpreted cautiously. Minor adverse events occurred only in the IMES group. IMES was associated with short-term improvement in pain, disability, and physiological measures when added to home exercise in myofascial shoulder pain, but these findings require cautious interpretation and further confirmation because the study lacked a sham comparator, participant blinding was not feasible, and subjective outcomes may have been influenced by non-specific treatment effects.Trial registration: The study protocol was prospectively registered in the ISRCTN registry under trial number ISRCTN66866842 in 25/03/2025.