title: The influence of task frequency and force direction on psychophysically acceptable forces in the context of the biomechanically weakest links.
abstract: This study examined the influence of frequency and direction of force application on psychophysically acceptable forces for simulated work tasks. Fifteen male participants exerted psychophysically acceptable forces on a force transducer at 1, 3, or 5 repetitions per minute by performing both a downward press and a pull toward the body. These exertions were shown previously to be strength and balance limited, respectively. Workers chose acceptable forces at a lower percentage of their maximum voluntary force capacity during downward (strength-limited) exertions than during pulling (balance-limited) exertions at all frequencies (4% to 11%, P = .035). Frequency modulated acceptable hand force only during downward exertions, where forces at five repetitions per minute were 13% less (P = .005) than those at one exertion per minute. This study provides insight into the relationship between biomechanically limiting factors and the selection of acceptable forces for unilateral manual tasks.
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Canada.
authors.forename: Alan C
authors.initials: AC
authors.lastname: Cudlip
authors.forename: Steven L
authors.initials: SL
authors.lastname: Fischer
authors.forename: Richard
authors.initials: R
authors.lastname: Wells
authors.forename: Clark R
authors.initials: CR
authors.lastname: Dickerson
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena; D006804:Ergonomics; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D018709:Statistics, Nonparametric; D013647:Task Performance and Analysis