Muscular endurance exercise therapy for work-related chronic neck pain in computer users

Resumen

Background and Purpose. Work-related chronic neck pain (CNP) is common in computer users. Moderate intensity pain, pain-related disability, reduction of strength of neck and shoulder muscles, and limitation of range of movement (ROM) have been identified in symptomatic office workers. Exercise therapy for neck pain is not common in the occupational setting and it is unclear which type and intensity of exercises are more effective for treating active workers who suffer that affection. This study compared the effects of two programs of therapeutic exercises on pain, pain-related disability and muscular function in computer users with work-related CNP. The aim is to evaluate the efficacy of a moderate endurance exercises for neck and shoulder girdle muscles in active employees with CNP. Design. A single-blinded randomized trial was conducted between January and June 2012. Setting. Occupational setting. Participants were recruited by the Prevention Work Risks Service in a Spanish public university. The study was conducted at the Physiotherapy and Ergonomics Service at the same university. Participants. Thirty-seven healthy and active employees (age range between 29 and 51 years) with chronic non-specific neck pain related to computer use. Those were the subjects selected after an initial sample of 106 potential participants. Interventions. Selected participants were randomly assigned to a neck and shoulder endurance exercise program (NSEE group, n = 18), or to a stretching and postural exercise program (SPE group, n = 17). Exercises took place twice a week for a seven-week period for both groups. The NSEE group performed specific moderate-intensity resistance training to improve endurance of neck and shoulder girdle muscles. The SPE group performed passive stretching exercises for neck and shoulder muscles and postural re-education. Advices and information on active management of neck pain and on workstation ergonomic adaptations were provided to both groups. Outcome Measures. A numerical rating scale (NRS) and the Vernon Neck Disability Index (NDI) were used to assess neck pain intensity and neck pain-related disability, the main outcome measures. Cervical active range of movement (AROM), on saggital, frontal and transverse planes, was measured with a gravity goniometer. Endurance of deep neck flexor muscles was assessed with the Grimmer craniocervical flexion test. Maximal strength of shoulder abductor muscles was assessed with a submaximal repetitions test (10-RM test). The impact of treatment on health related quality of life was measured with the Short Form-36 Health Survey (SF-36). Results. 27 subjects concluded the seven-week period of treatment. As effect of treatment, both pain and disability were significantly reduced in both groups (p < 0.01) compared to baseline. The reduction was similar in NSEE (pain: -63%, disability -49%) and in SPE (pain -68%, disability -47%;) and no statistically significant differences between groups for both outcomes were found. AROM improved significantly in the three movements assessed in both groups (p < 0.01 in all movements, except for rotation in the NSEE group, with p < 0.05). Differences between groups were not statistically significant for the three movements. Endurance of deep neck flexor muscles improved significantly only in NSEE group (p < 0.01). Shoulder abductors strength did not change in a statistically significant way. The same happened for the physical component summary (PCS) and mental component summary measures (MCS) of SF-36. Even though the differences between the mean values of the NSEE group and the SPE group after the treatment were not statistically significant in all but endurance of cervical flexor muscles variable, the comparison of the effect size points out the presence of some differences. In particular, the improvement in the NSEE group was six times that of the SPE group regarding strength of shoulder abductors and range of flexion-extension, and around twice regarding lateral flexion and rotation. Concerning the remaining variables, NSEE shows slightly better improvements with respect to neck pain-related disability and endurance on neck flexors and similar values with respect to pain intensity. Concerning the effect size of the summary values of the SF-36, we observe a moderate effect in both groups, with slightly better values for the SPE group regarding the MCS. Adherence was similar in both groups and no relevant adverse effects have been found in both training groups. Conclusions. A seven-week program of specific moderate endurance exercise for neck and shoulder muscles has shown to be effective on improving subjective symptoms, cervical ROM and endurance of deep cervical flexor muscles, in active computer workers with CNP. The resistance training has proven safe and readily accepted by participants. Compared with a stretching and postural re-educative program, endurance training was more effective on neck flexor muscles function. The effect size showed similar results for subjective symptoms and substantially better outcomes in the NSEE group than in the SPE group regarding muscular function and cervical mobility, and may be recommended to treat active employees with neck pain in an occupational setting. Key words: Chronic neck pain; Therapeutic exercise; Visual display unit; Resistance training; Work-related musculoskeletal diseases.