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Biomechanical Measures of Muscular Effort: Board #109 May 30 2:00 PM - 3:30 PM

Gregory, Robert; John, Emmanuel; Liu, Wen

Medicine & Science in Sports & Exercise: May 2007 - Volume 39 - Issue 5 - p S256
doi: 10.1249/01.mss.0000273978.36411.b2
B-29 Free Communication/Poster - Neuromuscular Control, Balance, and Gait: MAY 30, 2007 1:00 PM - 6:00 PM ROOM: Hall E

1University of Kansas, Lawrence, KS.

2University of Kansas Medical Center, Kansas City, KS.

Email: rwg@ku.edu

There has been little research in which ratings of muscular effort have been used to investigate the biomechanics of human movement. Given the importance of effort as it relates to movement control, it is necessary to develop a method for relating judgments of muscular effort to biomechanical quantities during a wide range of activities.

PURPOSE: To determine the validity and reliability of a method for quantifying the biomechanics of muscular effort during single-joint, isometric tasks.

METHODS: Twenty healthy adults participated in this study. All participants performed isometric elbow joint flexion and extension tasks in the horizontal plane using their dominant arm at three different elbow joint angles (45°, 90°, and 135°). The participants produced joint torques that corresponded to effort levels of 1, 3, 5, 7, and 9 on a modified Borg CR-10 scale. The 30 conditions (five effort levels × three joint angles × two tasks) were tested in random order. Elbow joint torque (EJT) was measured using a Biodex System 3 Pro dynamometer. Validity was determined by calculating the Pearson product moment coefficient of correlation between the EJT and the muscular effort associated with each condition. Between-day reliability was determined by calculating an intra-class correlation coefficient for the EJT associated with each condition.

RESULTS: As the level of muscular effort increased across all conditions, there were significant increases in elbow flexion (from 7.0±4.9-39.5±17.7 Nm; p<0.001) and extension (from 4.1±2.9-23.3±11.0 Nm; p<0.001) joint torques. The validity coefficients for EJT and muscular effort ranged between r=0.78-0.88 across all conditions; all correlations were significant at the p<0.01 level. The reliability coefficients for EJT ranged between r=0.89-0.96 across all conditions; all correlations were significant at the p<0.05 level.

CONCLUSIONS: The methodology developed in this study is both valid and reliable for the measurement of muscular effort. This method may be useful for basic and clinical research attempting to quantify the biomechanics of muscular effort. In addition, this study supports the hypothesis that muscular effort is most directly related to joint torque (Andrews, 1983). This investigation was supported by the University of Kansas General Research Fund allocation #2301758.

© 2007 American College of Sports Medicine