Katherine A. Boyer

Running Mechanics and Variability with Aging.

INTRODUCTION As the elderly population in the United States continues to grow, issues related to maintenance of health become increasingly important. Physical activity has positive benefits for healthy aging. Running, a popular form of exercise, is associated with the risk of developing injury, especially in older runners. Initial differences between older and younger runners have been observed, but these were observed without consideration of other differences between groups, such as running mileage. PURPOSE This study aims to compare running mechanics and lower-extremity coordination variability in matched groups of healthy younger and healthy older runners. METHODS Three-dimensional kinetics and kinematics were collected while 14 older adults (45-65 yr) and younger adults (18-35 yr) ran overground at 3.5 m·s. Knee, ankle, and hip joint angles and moments were determined. Discrete measures at foot strike (maximum and minimum) were determined and compared between groups. Segment angles during stance were utilized to calculate segment coordination variability between pelvis and thigh, thigh and shank, and shank and foot, using a modified vector coding technique. RESULTS Knee and ankle joint angles were similar between groups (P > 0.05). Older runners had greater hip range of motion (P = 0.01) and peak hip flexion (P = 0.001) at a more extended hip position than younger runners. Older runners had smaller ankle plantarflexion moment (P = 0.04) and hip rotational moment (P = 0.005) than younger runners. There were no between-group differences in any of the variability measures (P > 0.05). CONCLUSIONS Runners appear to maintain movement patterns and variability during running with increasing age, indicating that running itself may be contributing to maintenance of health among older runners in the current study.

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.

Do footfall patterns in forefoot runners change over an exhaustive run

ABSTRACT The purpose of this study was to investigate possible footfall pattern changes in habitual forefoot runners over a prolonged, exhaustive run. A prolonged run was performed to exhaustion in 14 habitual forefoot runners. Vertical ground reaction forces (VGRFs) and kinematics were collected at the beginning and end of the run. Ankle plantar flexor torque and triceps surae electromyographic activity were measured during pre- and post-run isometric contractions. By run’s end, there was an increase in VGRF loading rate and impact peak magnitude, greater dorsiflexion at foot contact and greater knee flexion angle throughout stance. Ankle plantar flexor torque decreased significantly from pre- to post-run tests. This was accompanied by a decrease in the integrated electromyographic activity (iEMG) output for the lateral and medial gastrocnemius. There were significant changes in landing mechanics for forefoot runners that indicate a transition towards more midfoot footfall patterns. A contributing factor may be ankle plantar flexor muscle fatigue that, at touchdown, is exposed to exaggerated eccentric loading. These findings suggest that a forefoot running pattern may become difficult to maintain in longer endurance events, and thus runners should pay attention to this in training to improve performance and mitigate potential injury.

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 and sex influences on running mechanics and coordination variability

ABSTRACT The purpose of this study was to examine the impact of age on running mechanics separately for male and female runners and to quantify sex differences in running mechanics and coordination variability for older runners. Kinematics and kinetics were captured for 20 younger (10 male) and 20 older (10 male) adults running overground at 3.5 m · s−1. A modified vector coding technique was used to calculate segment coordination variability. Lower extremity joint angles, moments and segment coordination variability were compared between age and sex groups. Significant sex–age interaction effects were found for heel-strike hip flexion and ankle in/eversion angles and peak ankle dorsiflexion angle. In older adults, mid-stance knee flexion angle, ankle inversion and abduction moments and hip abduction and external rotation moments differed by sex. Older compared with younger females had reduced coordination variability in the thigh–shank transverse plane couple but greater coordination variability for the shank rotation–foot eversion couple in early stance. These results suggest there may be a non-equivalent aging process in the movement mechanics for males and females. The age and sex differences in running mechanics and coordination variability highlight the need for sex-based analyses for future studies examining injury risk with age.

Comparison of classification methods to determine footfall pattern

dition compared to the indoor shoe condition on turf suggests that the main reason for the increase in performance was due to the increased compliance of the artificial turf. When wearing the same indoor shoes, less peak traction was utilised to accelerate on the turf compared to the lab floor, and even less was utilised when wearing cleats on the turf. It is not clear why maximal effort acceleration required less traction on the artificial turf, especially given that the subjects sprinted faster. The ground reaction impulse data do not explain the performance differences. This study has shown that artificial turf allows athletes to accelerate faster, and that this is likely related to increased surface compliance. However, kinetic data of one foot-strike were unable to further explain the mechanism by which this performance enhancement occurred.

The Nature of Age-Related Differences in Knee Function during Walking: Implication for the Development of Knee Osteoarthritis

Background Changes in knee kinematics have been identified in the early stages of osteoarthritis (OA). However, there is a paucity of information on the nature of kinematic change that occur with aging prior to the development of OA, This study applied a robust statistical method (Principal Component Analysis) to test the hypothesis that coupling between primary (flexion) and secondary (anterior-posterior translation, internal-external rotation) joint motions in walking would differ for age groupings of healthy subjects. Methods Seventy-four healthy participants divided into three groups with mean ages of 24 ± 2.3 years (younger), 48 ± 4.7years (middle-age) and 64 ± 2.4 years (older) were examined. Principal Component Analysis was used to characterize and statistically compare the patterns of knee joint movement and their relationships in walking. Results There were significant differences between the younger group and both the middle-age and older groups in the knee frontal plane angle and the coupling between knee flexion (PC1, p≤0.04) and the relative magnitudes of secondary plane motions in early and late stance (PC3, p<0.01). Two additional principal components (PC2, p = 0.03 and PC5, p<0.01) described differences in early stance knee flexion and relationship with secondary plane motion through-out stance for the older compared with middle-age group. Conclusions It appears there are changes in knee kinematics that occur with aging. The kinematic differences were identified for middle-aged as well as older adults suggesting midlife changes in neuromuscular physiology or behavior may have important consequences. These kinematic measures offer the potential to identify early markers for the risk of developing knee OA with aging.

A comparison of the ground reaction force frequency content during rearfoot and non-rearfoot running patterns

Running with a non-rearfoot pattern has been claimed to reduce injury risk because the impact peak in the vertical ground reaction force (GRF) is visually absent in the time-domain compared with a rearfoot pattern. However, running results in a rapid deceleration of the lower extremity segments immediately following initial contact with the ground, regardless of footfall pattern. Therefore, the frequency content of the GRF is expected to contain evidence of this collision. The purpose of the present study was to characterize the waveform components of the GRF generated during the impact phase by habitual rearfoot and habitual non-rearfoot pattern groups using the continuous wavelet transform. Twenty rearfoot and 20 non-rearfoot participants ran over-ground at a standardized speed with their habitual footfall pattern. The continuous wavelet transform was performed on the resultant GRF vector and the vertical GRF. GRF signals generated by the non-rearfoot pattern group during early stance had maximum signal power of 15.4±9.1Hz occurring at 23.1±6.3% of stance, which is within the 10-20Hz range previously associated with impact in rearfoot runners. Maximum signal power occurred earlier in the impact phase (11.5±1.5%) and with a higher frequency (27.2±3.9Hz) in the rearfoot pattern group verses the non-rearfoot pattern group (P<0.05). While the impact force transient may not appear as a prominent feature within the time-domain GRF with a non-rearfoot pattern, the results indicate that both footfall patterns generate frequencies associated with the impact peak in the resultant and vertical GRF.

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.