Prolonged trapezing during sailing often results in low back pain among elite sailors. Modifications of the trapeze harness have been proposed as one approach to ameliorating this problem. To evaluate six harnesses incorporating novel features that had tested well during pilot work, myoelectric activity was monitored at C5, T6, and L5 levels of sacrospinalis and at an abdominal site while five elite sailors wore the harnesses. Integrated EMG (IEMG) values were stored by a microcomputer at periodic intervals during each 10-min trial, as each subject maintained a static horizontal trapezing position in the laboratory. Factorial repeated-measures ANOVA indicated no change in IEMG values over time, but significant (p<0.001) differences among harnesses at all four electrode sites. Features of trapeze harness design that appear to minimize muscular tension include heavy, rigid padding throughout the harness, full-length shoulder-to-buttocks support of the trunk, and adjustable leg strap supports as opposed to a crotch strap.
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- Author: Jane A. Kent x
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Comparative Assessment of Novel Sailing Trapeze Harness Designs
Susan J. Hall, Jane A. Kent, and Vern R. Dickinson
Muscle Torque–Velocity Relationships and Fatigue With Reduced Knee Joint Range of Motion in Young and Older Adults
Zoe H. Smith, R. Anthony Martin, Erica Casto, Carol Bigelow, Michael A. Busa, and Jane A. Kent
The purpose of this study was to evaluate the influence of knee joint range of motion (RoM) on the torque–velocity relationship and fatigue in the knee extensor muscles of 7 young (median = 26 y) and 7 older (68 y) adults. Each leg was assigned a RoM (35° or 75°) over which to perform a torque–velocity protocol (maximal isokinetic contractions, 60–300°·s−1) and a fatigue protocol (120 maximal contractions at 120°·s−1, 0.5 Hz). Six older participants were unable to reach 300°·s−1 over 35°. Therefore, the velocity eliciting 75% of peak torque at 60°·s−1 (V 75, °·s−1) was calculated for each RoM from a fit of individual torque–velocity curves (60–240°·s−1), and ΔV 75 (35°–75°) was determined. Fatigue (final torque/initial torque) was used to calculate Δfatigue (35°–75°). ΔV 75 was not different from 0 in young (−28.3°·s−1 [−158.6 to 55.7], median [range], P = .091) or older (−18.5°·s−1 [−95.0 to 23.9], P = .128), with no difference by age (P = .710). In contrast, fatigue was greater for 75° in young (Δfatigue = 25.9% [17.5–30.3], P = .018) and older (17.2% [11.9–52.9], P = .018), with no effect of age (P = .710). These data indicate that, regardless of age, RoM did not alter the torque–velocity relationship between 60 and 240°·s−1, and fatigue was greater with a larger RoM.