Jocelyn F. Hafer

Variability of segment coordination using a vector coding technique: Reliability analysis for treadmill walking and running

Coordination variability (CV) quantifies the variety of movement patterns an individual uses during a task and may provide a measure of the flexibility of that individuals motor system. While there is growing popularity of segment CV as a marker of motor system health or adaptability, it is not known how many strides of data are needed to reliably calculate CV. This study aimed to determine the number of strides needed to reliably calculate CV in treadmill walking and running, and to compare CV between walking and running in a healthy population. Ten healthy young adults walked and ran at preferred speeds on a treadmill and a modified vector coding technique was used to calculate CV for the following segment couples: pelvis frontal plane vs. thigh frontal plane, thigh sagittal plane vs. shank sagittal plane, thigh sagittal plane vs. shank transverse plane, and shank transverse plane vs. rearfoot frontal plane. CV for each coupling of interest was calculated for 2-15 strides for each participant and gait type. Mean CV was calculated across the entire gait cycle and, separately, for 4 phases of the gait cycle. For running and walking 8 and 10 strides, respectively, were sufficient to obtain a reliable CV estimate. CV was significantly different between walking and running for the thigh vs. shank couple comparisons. These results suggest that 10 strides of treadmill data are needed to reliably calculate CV for walking and running. Additionally, the differences in CV between walking and running suggest that the role of knee (i.e., inter-thigh- shank) control may differ between these forms of locomotion.

Changes in coordination and its variability with an increase in running cadence

ABSTRACT Alterations in joint mechanics have been associated with common overuse injuries. An increase in running cadence in healthy runners has been shown to improve several parameters that have been tied to injury, but the reorganisation of motion that produces these changes has not been examined. The purpose of this study was to determine if runners change their segment coordination and coordination variability with an acute increase in cadence. Data were collected as ten uninjured runners ran overground at their preferred cadence as well as a cadence 10% higher than preferred. Segment coordination and coordination variability were calculated for select thigh–shank and shank–foot couples and selected knee mechanics were also calculated. Paired t-tests were used to examine differences between the preferred and increased cadence conditions. With increased cadence, there was a decrease in peak knee flexion and a later occurrence of peak knee flexion and internal rotation and shank internal rotation. Segment coordination was altered with most changes occurring in mid-late stance. Coordination variability decreased with an increase in cadence across all couples and phases of gait. These results suggest examination of coordination and its variability could give insight into the risk of intervention-induced injury.

The effect of a cadence retraining protocol on running biomechanics and efficiency: a pilot study

Abstract Many studies have documented the association between mechanical deviations from normal and the presence or risk of injury. Some runners attempt to change mechanics by increasing running cadence. Previous work documented that increasing running cadence reduces deviations in mechanics tied to injury. The long-term effect of a cadence retraining intervention on running mechanics and energy expenditure is unknown. This study aimed to determine if increasing running cadence by 10% decreases running efficiency and changes kinematics and kinetics to make them less similar to those associated with injury. Additionally, this study aimed to determine if, after 6 weeks of cadence retraining, there would be carryover in kinematic and kinetic changes from an increased cadence state to a runner’s preferred running cadence without decreased running efficiency. We measured oxygen uptake, kinematic and kinetic data on six uninjured participants before and after a 6-week intervention. Increasing cadence did not result in decreased running efficiency but did result in decreases in stride length, hip adduction angle and hip abductor moment. Carryover was observed in runners’ post-intervention preferred running form as decreased hip adduction angle and vertical loading rate.

Systematic review and meta-analysis of gait mechanics in young and older adults

Background Age‐related gait changes may play a critical role in functional limitations of older adults. Despite sizable interest in determining how age alters walking mechanics, small sample sizes and varied outcome measures have precluded a comprehensive understanding of the impact of age on lower extremity joint kinematics and kinetics. Objective The aim of this study was to perform a systematic review and meta‐analysis of the aging gait mechanics literature. Methods The overall standardized effect of age on walking mechanics was computed for 29 studies (200 standardized effects). To account for variation in reported outcome variables, analyses were carried out for comparisons between young and older adult results using all discrete kinematic or kinetic variables reported for the ankle, knee, or hip. Different variables reported for a given joint were then analyzed as separate categorical moderators. Results The overall standardized effect of age was large for ground reaction forces, moderate for ankle and small for knee and hip kinematics and ankle and hip kinetics. When the analysis was restricted to studies with similar or matched walking speed, the standardized effects of age remained similar except for hip power generation and knee kinematic variables. Conclusions The results of this meta‐analysis provide evidence to support moderate standardized effects, with and without consideration of walking speeds, for changes in lower extremity kinematics, joint moments and powers at the ankle, and ground reaction forces. The standardized effects of age for knee mechanics are less conclusive and would benefit from further research. HighlightsMeta‐analysis examining 30 years of gait biomechanics comparing age groupsResults support the hypothesis that ankle function diminishes with age.Older adults display altered ankle and hip kinematics through gait cycle.Propulsive ankle kinetics and ground reaction forces are decreased in older adults.Differences in knee kinematics are more apparent when walking speeds are matched.

Age related differences in segment coordination and its variability during gait

BACKGROUND Aging is associated with a loss of mobility and altered gait mechanics. Loss of function and mobility may be due to or exacerbated by low levels of physical activity in the aged. The mechanisms linking age-related changes in physiology, altered mobility and gait may be elucidated by examining movement coordination and coordination variability. RESEARCH QUESTION The purpose of this study was to examine the impacts of age and habitual physical activity level on segment coordination and coordination variability during gait. METHODS A modified vector coding technique was used to calculate segment coordination and coordination variability during treadmill gait for three groups of healthy adults: young (21-35 years), older highly active (55-70 years), and older less active (55-70 years). Segment couples of interest included those whose coordination could contribute to typical age-related changes in gait mechanics at the hip, knee, and ankle. RESULTS Differences in coordination and its variability occurred mainly during terminal swing and midstance and in couples across the hip and ankle. Across the hip, coordination differed between older highly active adults and the other cohorts, while variability was higher in young compared to all older adults. Across the ankle, young adults displayed different coordination and greater variability than all older adults except for the sagittal couple in midstance, where older highly active adults had greater coordination variability than the other cohorts. SIGNIFICANCE These results suggest that older adults, independent of habitual physical activity, may use a different strategy to control hip and ankle motion during periods of single-limb stance.

Exertion and pain do not alter coordination variability in runners with iliotibial band syndrome

Background Iliotibial band syndrome is a common overuse running injury which results in altered mechanics. While injuries alter discrete mechanics, they may also cause a change in coordination variability, the stride‐to‐stride organization of runners’ movement patterns. Uninjured and injured runners may experience a change in coordination variability during a run to exertion due to fatigue, pain, or a combination of these factors. The aim of the current study was to determine if runners with iliotibial band syndrome and uninjured runners display different segment coordination variability across the course of a run to exertion. Methods 3D kinematics were collected as 13 uninjured runners and 12 runners with iliotibial band syndrome ran on a treadmill. A modified vector coding technique was used to calculate coordination variability during stance for segment couples of interest. Coordination variability was compared between uninjured and injured runners at the beginning and end of the run. The influence of pain on coordination variability was also examined. Findings There were no differences in coordination variability at the beginning or end of the run between uninjured runners and those with iliotibial band syndrome. The change in coordination variability due to the run was not different between uninjured runners, injured runners who experienced no change in pain, and injured runners who did experience a change in pain. Interpretation Runners do not constrain the patterns of segment motion they use in response to exertion nor does it appear that occurrence of pain during running results in a differential change in coordination variability. HighlightsCoordination variability was similar between uninjured and injured runners.Exertion had minimal impact on coordination variability in all runners.Presence or absence of pain did not appear to alter coordination variability.Runners with iliotibial band syndrome had variable responses to the run to exertion.