Objectives: To assess the immediate effect of a suboccipital muscle inhibition (SMI) technique on: (a) neck pain, (b) elbow extension range of motion during the upper limb neurodynamic test of the median nerve (ULNT-1), and (c) grip strength in subjects with cervical whiplash; and determine the relationships between key variables.

Design: Randomised, single-blind, controlled clinical trial.

Setting: Faculty of Nursing, Physiotherapy and Podiatry, University of Seville, Spain.

Participants: Forty subjects {mean age 34 years [standard deviation (SD) 3.6]} with Grade I or II cervical whiplash and a positive response to the ULNT-1 were recruited and distributed into two study groups: intervention group (IG) (n=20) and control group (CG) (n=20).

Interventions: The IG underwent the SMI technique for 4minutes and the CG received a sham (placebo) intervention. Measures were collected immediately after the intervention.

Main outcome measures: The primary outcome was elbow range of motion during the ULNT-1, measured with a goniometer. The secondary outcomes were self-perceived neck pain (visual analogue scale) and free-pain grip strength, measured with a digital dynamometer.

Results: The mean baseline elbow range of motion was 116.0° (SD 10.2) for the CG and 130.1° (SD 7.8) for the IG. The within-group comparison found a significant difference in elbow range of motion for the IG [mean difference -15.4°, 95% confidence interval (CI) -20.1 to -10.6; P=0.01], but not for the CG (mean difference -4.9°, 95% CI -11.8 to 2.0; P=0.15). In the between-group comparison, the difference in elbow range of motion was significant (mean difference -10.5°, 95% CI -18.6 to -2.3; P=0.013), but the differences in grip strength (P=0.06) and neck pain (P=0.38) were not significant.

Conclusion: The SMI technique has an immediate positive effect on elbow extension in the ULNT-1. No immediate effects on self-perceived cervical pain or grip strength were observed.