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Jeffrey M. Haddad, Richard E.A. van Emmerik, Jonathan S. Wheat, Joseph Hamill and Winona Snapp-Childs

A variety of kinematic and kinetic measures are typically used to examine gait symmetry. Here we make the argument that gait asymmetries may be most clearly revealed through higher-order coordinative measures such as continuous relative phase (CRP). Participants walked on a treadmill with a load attached to their nondominant limb. Gait symmetry was then assessed using spatial (angular), temporal (velocity), and higherorder (CRP) symmetry measures. It was found that higher-order measures were most sensitive at assessing asymmetries due to load manipulation at both the distal and proximal segments. Symmetry measures derived from velocity variables were more sensitive than angular measures at detecting asymmetries, but were less sensitive compared with CRP. Asymmetries were also more readily detected using segmental angles compared with joint angles. These results suggest that gait asymmetries that emerge from changing constraints manifest along both spatial and temporal dimensions.

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Aaron Nelson, Nathan Koslakiewicz and Thomas Gus Almonroeder

) motion capture is limited as a clinical tool because of the time and expertise required for data collection or processing. The development of surrogate measures to assess knee kinetic symmetry may help to improve rehabilitation. Analysis of ground reaction force (GRF) symmetry using force plate

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Matthew D. DeLang, Mehdi Rouissi, Nicola L. Bragazzi, Karim Chamari and Paul A. Salamh

There is an ongoing debate between the appropriateness of asymmetry versus a desire to promote symmetry in sport. In unilateral sports, asymmetry may not only be appropriate, but also necessary for elite performance. 1 – 3 For instance, chronic adaptations of young tennis players displaying

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Caroline Lisee, Lindsay Slater, Jay Hertel and Joe M. Hart

, health care providers must apply the best evidence when making a return-to-play decision after injury. Strength, 4 functional performance, 4 and limb symmetry 9 are common sources of objective information that often inform clinicians when making return-to-play decisions. 9 – 11 Clinicians can compare

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Rachel L. Wright, Joseph W. Bevins, David Pratt, Catherine M. Sackley and Alan M. Wing

be synchronized to auditory cues. 21 The use of a periodic auditory pacing stimulus has been investigated as a means to improve temporal symmetry after stroke by providing a time reference frame for gait events. 22 – 24 Chronic stroke participants are able to synchronize their step timing to a

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Silvia Cabral, Renan A. Resende, Adam C. Clansey, Kevin J. Deluzio, W. Scott Selbie and António P. Veloso

High levels of gait asymmetry are associated with many pathologies. Our long-term goal is to improve gait symmetry through real-time biofeedback of a symmetry index. Symmetry is often reported as a single metric or a collective signature of multiple discrete measures. While this is useful for assessment, incorporating multiple feedback metrics presents too much information for most subjects to use as visual feedback for gait retraining. The aim of this article was to develop a global gait asymmetry (GGA) score that could be used as a biofeedback metric for gait retraining and to test the effectiveness of the GGA for classifying artificially-induced asymmetry. Eighteen participants (11 males; age 26.9 y [SD = 7.7]; height 1.8 m [SD = 0.1]; body mass 72.7 kg [SD = 8.9]) walked on a treadmill in 3 symmetry conditions, induced by wearing custom-made sandals: a symmetric condition (identical sandals) and 2 asymmetric conditions (different sandals). The GGA score was calculated, based on several joint angles, and compared between conditions. Significant differences were found among all conditions (P < .001), meaning that the GGA score is sensitive to different levels of asymmetry, and may be useful for rehabilitation and assessment.

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Marko T. Korhonen, Harri Suominen, Jukka T. Viitasalo, Tuomas Liikavainio, Markku Alen and Antti A. Mero

Eighteen young (23 ± 4 yr) and 25 older (70 ± 4 yr) male sprinters were examined for ground reaction force (GRF) and temporal-spatial variables. The data were collected during maximum-speed phase, and variability and symmetry indices were calculated from a total of 8 steps. There was little variation (CV < 6%) in vertical and resultant GRF and kinematic variables, while impact loading had high variability (CV: 10–21%). Overall, the pattern of variability was similar in both groups. Yet, a small but significant age-related increase in CV was evident in horizontal GRFs. There was a variable-specific asymmetry between legs but it was not related to leg dominance. No age differences existed in the symmetry indices. Results indicate that only selected force platform variables are symmetric and repeatable enough so that their use for comparison purposes is appropriate. Data also suggest that aging may increase variability in certain biomechanical measures, whereas symmetry is not affected by age.

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Timothy J. Suchomel, Kimitake Sato, Brad H. DeWeese, William P. Ebben and Michael H. Stone

The purposes of this study were to examine the effect of ballistic concentric-only half-squats (COHS) on subsequent squat-jump (SJ) performances at various rest intervals and to examine the relationships between changes in SJ performance and bilateral symmetry at peak performance. Thirteen resistance-trained men performed an SJ immediately and every minute up to 10 min on dual force plates after 2 ballistic COHS repetitions at 90% of their 1-repetition-maximum COHS. SJ peak force, peak power, net impulse, and rate of force development (RFD) were compared using a series of 1-way repeated-measures ANOVAs. The percent change in performance at which peak performance occurred for each variable was correlated with the symmetry index scores at the corresponding time point using Pearson correlation coefficients. Statistical differences in peak power (P = .031) existed between rest intervals; however, no statistically significant pairwise comparisons were present (P > .05). No statistical differences in peak force (P = .201), net impulse (P = .064), and RFD (P = .477) were present between rest intervals. The relationships between changes in SJ performance and bilateral symmetry after the rest interval that produced the greatest performance for peak force (r = .300, P = .319), peak power (r = –.041, P = .894), net impulse (r = –.028, P = .927), and RFD (r = –.434, P = .138) were not statistically significant. Ballistic COHS may enhance SJ performance; however, the changes in performance were not related to bilateral symmetry.

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Kim Bennell, Kay Crossley, Tim Wrigley and Julie Nitschke

The aim of our study was to assess the interday test-retest reliability (focussing on the separate contribution of systematic and random error) of selected 10-trial mean ground reaction force (GRF) parameters and GRF symmetry indices measured during running. Ten competitive male heel-strike runners (aged, 26.2 ± 5.7 years) performed 10 successful running trials across the force platform at a constant velocity of 4.0 m · s-1 ±10% wearing their customary running footwear. The testing procedure was repeated under similar conditions 1 week later. The results showed no statistically significant differences between the means of Test 1 and Test 2 for most GRF parameters and symmetry indices, indicating non-significant systematic error. Correlation coefficients ranged from 0.73 to 0.99 for GRF parameters. Random error was small with SEmeas less than 10% of the Test 1 mean value for almost all GRF parameters. Symmetry indices displayed correlation coefficients ranging from −0.44 to 0.91. Based on these and the size of the SEmeas, the symmetry indices displayed variable reliability, with the most reliable being those associated with peak vertical active force and peak horizontal propulsive force.

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Louis A. DiBerardino III, Chantal A. Ragetly, Sungjin Hong, Dominique J. Griffon and Elizabeth T. Hsiao-Wecksler

The regions of deviation method has been proposed as a technique for identifying regions of the gait cycle where joint motion deviates from normal (Shorter et al., 2008). The original statistical analysis distinguished only peak values during stance and swing. In the current article, we extend the approach by examining deviations from normal throughout the entire gait cycle using pointwise t tests. These methods were demonstrated on hind-limb joint angles of 21 Labrador Retrievers without and with cranial cruciate ligament disease. Results were compared with peak difference analysis previously performed on these subjects. All points in the gait cycle where symmetry deviations were significantly affected by cranial cruciate ligament disease (via pointwise t tests) were defined as regions of deviation from symmetry. Discriminant function analysis was used to consider single subjects and validate that these regions were truly areas of difference between groups. Regions of deviation encompassed previously determined significant peak differences, while extending analysis to additional areas of asymmetry. Discriminant function analysis suggested that the region of deviation method is a viable approach for distinguishing motion pattern differences. This enhanced method may help researchers better understand the mechanisms behind lameness and compensation.