Whiplash injury results in sustained impairments of cervical muscle function: A one-year prospective, controlled study

OBJECTIVE: To investigate the temporal development of neck muscle function following whiplash injuries. DESIGN: A 1-year prospective, controlled observational study. SUBJECTS: A total of 141 individuals exposed to whiplash injury due to rear-end vehicle collisions and 40 age- and sex-matched controls with acute ankle distortion. METHODS: Neck muscle strength and endurance during cervical flexion and extension were measured at 1 week, 1 month, 3 months, 6 months and 1 year after injury. RESULTS: Notable reductions (23-30%) of neck strength in both directions were seen for whiplash-exposed subjects at all time points, compared with controls. Also, extensor endurance was reduced at 1 week, 1 month, 3 months, 6 months* and 1 year* (*non-significant). Within the whiplash group, non-recovered individuals (individuals who had not returned to pre-injury work capacity at one year) displayed ~50% reductions in cervical strength in both directions at all time points, compared with recovered whiplash individuals. CONCLUSION: Cervical muscular functioning is impaired for at least one year after whiplash injury, well beyond the time course of recovery of neck mobility and pain sensations. In whiplash-exposed individuals, non-recovery is associated with considerable muscular weakness. There is a need for increased clinical focus on early neck function after whiplash injury.