Identification of the Maximum Acceptable Frequencies of Upper-Extremity Motions in the Sagittal Plane

Abstract

The present study examined the maximum acceptable frequencies (MAFs; motions/min) of upper-extremity motions in the sagittal plane at different forces. A dumbbell of 9.8 or 39.2 N was rotated by the arm about the shoulder, the forearm about the elbow, and the hand about the wrist; a dynamometer was pressed to 2.45 or 9.8 N by the index finger. Seventeen right-handed Korean men in their 20s without any history of musculoskeletal disorders received 1 hour of individual training and conducted each upper-extremity task for 30 minutes a day, assuming they were on an incentive basis. The participants determined their MAFs for 8 hours of work by the self-adjustment method, and work pulse (change in heart rate; beats per minute [bpm]) and rating of perceived exertion (RPE) were measured. For a limited set of conditions, the reproducibility of the MAF experimental protocol was found satisfactory (r = 0.97; interclass correlation coefficient > 0.95). The average MAFs of arm, forearm, hand, and index finger motions were 24, 45, 56, and 128 at their low force level and 9, 20, 30, and 66 at their high force level. The average work pulses of arm, forearm, and hand motions were 3.0, 2.1, and 1.5 times that of index finger motion (4.2 bpm at their low force level and 5.7 bpm at their high force level). The maximum average RPEs at the upper-extremity regions ranged from 2.1 (weak) to 3.1 (moderate) in Borg's CR-10 scale. (C) 2009 Wiley Periodicals, Inc.