EFFECTS OF ISOKINETIC EXERCISES ON MUSCLE THICKNESS AND ULTRASOUND-MEASURED MUSCLE CONTRACTION RATIOS IN SACROILIAC JOINT DYSFUNCTION

Abstract

Background

Sacroiliac joint dysfunction (SIJD) remains a frequent source of lumbar and pelvic pain, directly linked to disrupted weight distribution, muscular imbalances, and compromised neuromuscular coordination. Standardized therapeutic protocols for its definitive conservative management are not yet universally established within rehabilitation pipelines.

Objective

To systematically assess the structural and functional effects of a manual isokinetic exercise protocol combined with conventional physiotherapy on the morphometric thickness and dynamic contraction ratios (CR) of key lumbopelvic stabilizing musculature (lumbar spine, abdomen, and gluteus) in individuals diagnosed with SIJD.

Methodology

A prospective, double-blinded randomized controlled trial (RCT) was conducted over six months at the Sundas Foundation, Lahore, Pakistan. Forty participants aged 18–35 years were randomly allocated into two identical cohorts (n=20 per group). Group A received a novel manual isokinetic strength training regimen alongside conventional physical therapy, while Group B received a standard conventional physical therapy protocol alone. Interventions were administered 4 days per week for 4 consecutive weeks. Right and left muscular resting thickness (mm) and active contraction ratios were tracked pre- and post-intervention via B-mode diagnostic rehabilitative ultrasound imaging (RUSI) of the lumbar multifidus (LM), gluteus maximus (GM), rectus abdominis (RA), and external oblique (EO). Primary data entries and subsequent processing were handled through IBM SPSS v27.0 using Wilcoxon signed-rank and Mann-Whitney U tests.

Results

Post-trial tracking revealed a distinct, muscle-specific pattern of morphological and functional adaptation. Group A demonstrated high statistical superiority in myofibrillar hypertrophy and neural activation over Group B. Specifically, Group A achieved a bilateral thickness increase of 0.68–0.72 mm (~3.7–3.8%) in the LM and 0.68–0.71 mm (~3.7%) in the GM, RA improved by 0.60-1.01%, E.O improved by 0.55- 0.74%. while Group B displayed complete structural stagnation (0.00–0.18% change, p  0.014). Neuromuscular recruitment profiles expanded profoundly in Group A, with contraction ratio improvements of 12.29–13.89% for the LM, 11.49–12.11% for the GM, 3.38–4.11% for the RA, and 3.49–3.51% for the EO. Group B displayed minor neural improvements in posterior metrics (LM CR: 6.10–6.59%; GM CR: 4.96–5.20%) with some improvement in anterolateral abdominal core. Large-to-massive inter-group effect magnitudes were validated across primary parameters, with Cohen's d values spanning from 0.80 to 5.14.

Conclusion

Manual isokinetic training paired with conventional physiotherapy effectively induces robust architectural hypertrophy and neuromuscular remodeling in primary lumbopelvic stabilizing muscles, while correcting latent structural asymmetries. This targeted protocol delivers superior evidence-based clinical efficacy compared to traditional passive physical modalities alone for patients with chronic sacroiliac joint dysfunction.