Association between muscle strength, upper extremity fatigue resistance, work ability and upper extremity dysfunction...

Upper extremity musculoskeletal disorders negatively affect ability to perform activities of daily living, self-care and work. Therefore, outcome measurements that address muscle strength, fatigue resistance, functionality and work physical capacity must be defined to assess and plan specific actions to minimize them.

To investigate the association of upper extremity muscle strength with upper extremity fatigue resistance, work ability and upper extremity dysfunction in a sample of workers from a tertiary hospital.

Shoulder and elbow isokinetic strength were assessed by Biodex System 4™, isometric hand grip by JAMAR™, upper extremity fatigue resistance by Functional Impairment Test Hand and Neck/Shoulder/Arm (FIT-HaNSA), ability to work by the Work Ability Index and upper extremity dysfunction by the Quick-Disabilities of the Arm, Shoulder and Hand QuickDASH-Br questionnaire. The Nordic questionnaire and Numeric Pain Rating Scale (NPRS) were used for pain description. The associations were analysed by Spearman's correlation coefficient (rho) (p < 0.05).

Twenty-seven participants: 59.2% women; mean age 46 years old; 70.3% obese/overweight; 62.9% active with predominantly dynamic muscle contraction work. Besides predominance of good to moderate work ability (81.4%) and comorbidities (37%), all participants had symptoms of the upper extremities for at least 12 months, with a predominance of low-intensity in the shoulder (55.5%). In addition, 88.8% reported pain in other segments. Muscle strength of abduction (rho = 0.49), adduction (rho = 0.40), internal rotation (rho = 0.44) and hand grip (rho = 0.68) presented moderate correlation with FIT-HaNSA. Hand grip (rho = - 0.52) showed moderate correlation with upper extremity dysfunction.

The results of this preliminary study suggested the association of shoulder strength with fatigue resistance. Also, hand grip strength was associated with upper extremity dysfunction and fatigue resistance. No association was found with the Work Ability Index in this sample. So, it is suggested that hand grip and shoulder strength could be outcome measurements used for future interventions focused on upper extremity preventive exercises to improve strength and fatigue resistance of workers at risk for the development of musculoskeletal disorders. Other individual, psychosocial and organizational risk factors must also be considered as influences on upper extremity function.