The purpose of this paper is to discuss the role of variability in human movement, with emphasis on locomotion variability. Based on the assessment of stride characteristics, movement variability has been associated with reduced gait stability and unsteadiness. However, based on the measure of joint coordination during locomotion, variability has been suggested to provide a source of adaptation. Therefore, it would appear that the assessment of movement coordination from either the task outcome (i.e., stride characteristics) or the joint coordination patterns provide distinctly opposing views of variability. This paper will discuss the use of the variability measures, specifically joint coordination variability, from a clinical perspective. Investigations will be presented in which a reduction in joint coordination variability has been associated with pathology. Finally, the clinical implications of these measures as well as treatment suggestions are discussed.
Bryan C. Heiderscheit
Bryan C. Heiderscheit, Joseph Hamill and Richard E.A. van Emmerik
The purpose of this investigation was to determine whether individuals with patellofemoral pain (PFP) display a reduction in intralimb joint coordination variability compared to nonimpaired persons. In addition, it was hypothesized that the variability of the stride characteristics would be similar between groups. Eight individuals with unilateral PFP and 8 nonimpaired participants ran on a treadmill at a fixed (2.68 m·s–1) and preferred speed while stride characteristics and 3-D kinematics of the bilateral lower extremities were recorded. Intralimb coordination variability was measured using a vector coding technique applied to relative motion plots of various joint couplings. The PFP group displayed greater stride length variability during running at the preferred speed. However, this was not the case during running at the fixed speed. When averaging across the entire stride cycle, coordination variability for all joint couplings was consistent between the two groups. However, further analysis about heel-strike revealed reduced joint coordination variability for the thigh rotation/leg rotation coupling of the PFP group’s injured limb compared to that of the nonimpaired group. With the exception of the transverse plane rotations at heel-strike, it would appear that the level of pain experienced by the PFP participants may not be great enough to produce a change in the intralimb coordination patterns during running.
Jason Brumitt, Bryan C. Heiderscheit, Robert C. Manske, Paul Niemuth, Alma Mattocks and Mitchell J. Rauh
The Lower-Extremity Functional Test (LEFT) has been used to assess readiness to return to sport after a lowerextremity injury. Current recommendations suggest that women should complete the LEFT in 135 s (average; range 120–150 s) and men should complete the test in 100 s (average; range 90–125 s). However, these estimates are based on limited data and may not be reflective of college athletes. Thus, additional assessment, including normative data, of the LEFT in sport populations is warranted.
To examine LEFT times based on descriptive information and off-season training habits in NCAA Division III (DIII) athletes. In addition, this study prospectively examined the LEFT’s ability to discriminate sport-related injury occurrence.
189 DIII college athletes (106 women, 83 men) from 15 teams.
Main Outcome Measures:
LEFT times, preseason questionnaire, and time-loss injuries during the sport season.
Men completed the LEFT (105 ± 9 s) significantly faster than their female counterparts (117 ± 10 s) (P < .0001). Female athletes who reported >3–5 h/wk of plyometric training during the off-season had significantly slower LEFT scores than those who performed ≤3 h/wk of plyometric training (P = .03). The overall incidence of a lower-quadrant (LQ) time-loss injury for female athletes was 4.5/1000 athletic exposures (AEs) and 3.7/1000 AEs for male athletes. Female athletes with slower LEFT scores (≥118 s) experienced a higher rate of LQ time-loss injuries than those with faster LEFT scores (≤117 s) (P = .03).
Only off-season plyometric training practices seem to affect LEFT score times among female athletes. Women with slower LEFT scores are more likely to be injured than those with faster LEFT scores. Injury rates in men were not influenced by performance on the LEFT.
Christine D. Pollard, Bryan C. Heiderscheit, Richard E.A. van Emmerik and Joseph Hamill
The purpose of this study was to determine if gender differences exist in the variability of various lower extremity (LE) segment and joint couplings during an unanticipated cutting maneuver. 3-D kinematics were collected on 24 college soccer players (12 M, 12 F) while each performed the cutting maneuver. The following intralimb couplings were studied: thigh rotation (rot)/leg rot; thigh abduction-adduction/leg abd-add; hip abd-add/knee rot; hip rot/knee abd-add; knee flexion-extension/knee rot; knee flx-ext/hip rot. A vector-coding technique applied to angle-angle plots was used to quantify the coordination of each coupling. The average between-trial standard deviation of the coordination pattern during the initial 40% of stance was used to indicate the coordination variability. One-tailed t-tests were used to determine differences between genders in coordination variability for each coupling. Women had decreased variability in four couplings: 32% less thigh rot/leg rot variability; 40% less thigh abd-add/leg abd-add variability; 46% less knee flx-ext/knee rot variability; and 44% less knee flx-ext/hip rot variability. These gender differences in LE coordination variability may be associated with the increased incidence of ACL injury in women. If women exhibit less flexible coordination patterns during competition, they may be less able to adapt to the environmental perturbations experienced during sports. These perturbations applied to a less flexible system may result in ligament injury.