The epidemiology of upper extremity musculoskeletal symptoms on a college campus.

OBJECTIVE: The study examines temporal variations in upper-extremity musculoskeletal symptoms throughout the day, over a week and throughout the semester. METHODS: 30 undergraduates were followed in a repeated measures study throughout a semester. Upper extremity musculoskeletal symptoms data were collected on handheld computers randomly throughout the day for seven days over three data collection periods. Multilevel statistical models evaluated associations between time-related predictors and symptoms. RESULTS: In adjusted models, pain reported at baseline was associated with increased odds of experiencing both any symptoms (OR=15.64; 90% CI 7.22-33.88) and moderate or greater symptoms (OR=16.44; 90% CI 4.57-29.99). Any symptoms were less likely to be reported if responses occurred at 58-76 days (OR=0.66; 90% CI 0.49-0.86), 77-90 days (OR=0.29; 90% CI 0.20-0.42) and 91-117 days (OR=0.54; 90% CI 0.39-0.75) into the semester compared to 35-57 days. Similarly, responding after midnight was associated with greater odds of reporting moderate or greater symptoms (OR=21.33; 90% CI 6.49-65.97). There was no association observed for day of week and symptoms. CONCLUSION: This pilot work suggests upper extremity musculoskeletal symptoms exhibit temporal variations related to time of day and days into semester. Understanding the natural history of musculoskeletal symptoms and disorders is needed when designing epidemiologic research and/or intervention studies using symptom outcome measures.

Evaluation of two posture survey instruments for assessing computing postures among college students.

OBJECTIVE: To determine agreement between two posture assessment survey instruments and which, if any, were correlated with experiencing upper extremity musculoskeletal symptoms. METHODS: Thirty undergraduate participants had three postural assessment surveys completed, one each for three separate 7-day data collection periods during a semester. Two observation assessment tools were used, a modified Rapid Upper Limb Assessment (mRULA) for computer users for the right and left limbs and the University of California Computer Use Checklist. Concurrently, upper extremity musculoskeletal symptom experience paired to each postural assessment was measured. Lin's concordance correlation coefficient evaluated survey agreement and multi-level statistical models described associations between survey responses and symptoms. RESULTS: There was no agreement between the two postural assessment tool scores (p> 0.85). In adjusted models, the UC Computer Use Checklist was positively associated with symptoms occurrence (OR=1.4, 90% CI 1.2-1.6 for any symptoms; OR=1.3, 90% CI 1.0-1.6 for moderate or greater symptoms). Associations with mRULA scores were inconsistent in that they were sometimes protective and sometimes indicators of risk, depending on the covariates included in the models. CONCLUSION: The mRULA for computer users and the UC Computer Use Checklist were independent of each other; however, due to the inconsistent associations with symptoms we cannot conclude one instrument is superior to the other. Our data do suggest the UC Computer Use Checklist demonstrates a traditional relationship with symptoms, where increasing scores signifiy greater risk. We observed a nontraditional relatioship with symptoms for the mRULA for computer users that needs to be further examined. This is a pilot study and, thus, findings should be interpreted as exploratory. Associations observed in the current study will be used to test hypotheses in the cohort study recently conducted.

Typing keystroke duration changed after submaximal isometric finger exercises.

A repeated-measures laboratory experiment tested whether keystroke duration during touch-typing changes after a finger performs submaximal isometric flexion exercises. Fourteen right-handed touch-typists used right ring finger to perform three 15-min exercise conditions, two isometric exercises and a no-force condition, each on a separate day. Before and after each exercise condition, typing keystroke duration and isometric force elicited by electrical stimulation were measured for right ring finger. Keystroke duration of right ring finger decreased by 5% (6 ms, P < 0.05) immediately after the exercises but not after the no-force condition. Peak isometric finger force elicited by electrical stimulation decreased by 17-26% (P < 0.05) for the flexor digitorum superficialis and decreased by 4-8% for the extensor digitorum communis after the isometric exercises. After the finger was exposed to isometric exercises, changes in typing keystroke duration coincided with changes in the physiological state of the finger flexor and extensor muscles.