Lee T. Atkins

Kinematic and ground reaction force accommodation during weighted walking.

Weighted walking is a functional activity common in daily life and can influence risks for musculoskeletal loading, injury and falling. Much information exists about weighted walking during military, occupational and recreational tasks, but less is known about strategies used to accommodate to weight carriage typical in daily life. The purposes of the study were to examine the effects of weight carriage on kinematics and peak ground reaction force (GRF) during walking, and explore relationships between these variables. Twenty subjects walked on a treadmill while carrying 0, 44.5 and 89 N weights in front of the body. Peak GRF, sagittal plane joint/segment angular kinematics, stride length and center of mass (COM) vertical displacement were measured. Changes in peak GRF and displacement variables between weight conditions represented accommodation. Effects of weight carriage were tested using analysis of variance. Relationships between peak GRF and kinematic accommodation variables were examined using correlation and regression. Subjects were classified into sub-groups based on peak GRF responses and the correlation analysis was repeated. Weight carriage increased peak GRF by an amount greater than the weight carried, decreased stride length, increased vertical COM displacement, and resulted in a more extended and upright posture, with less hip and trunk displacement during weight acceptance. A GRF increase was associated with decreases in hip extension (|r|=.53, p=.020) and thigh anterior rotation (|r|=.57, p=.009) displacements, and an increase in foot anterior rotation displacement (|r|=.58, p=.008). Sub-group analysis revealed that greater GRF increases were associated with changes at multiple sites, while lesser GRF increases were associated with changes in foot and trunk displacement. Weight carriage affected walking kinematics and revealed different accommodation strategies that could have implications for loading and stability.

An exploration of load accommodation strategies during walking with extremity-carried weights.

The strategies used by individuals to respond to loading perturbations have implications for both musculoskeletal health and statistical data analysis. The purpose was to explore load accommodation strategies during walking with extremity weights carried in different positions. Twenty subjects walked on an instrumented treadmill while carrying 0, 44.5 and 89 N at the wrists and ankles. Peak ground reaction force (GRF) during weight acceptance was extracted for analysis. The change in peak GRF due to the addition of weight was calculated and used to quantify strategies. Results indicated that on average GRF increased (p<.05) more than the increase in weight alone in two of three load carriage positions, and ranged from 0.95 to 1.45 N/N. The strategy for weights carried at the wrists with the arms unconstrained (M±SD, 1.06±.42 N/N) was significantly (p<.017) less than with the wrists constrained (1.35±.56 N/N) or with weights carried at the ankles (1.40±.72N/N). Individuals exhibited a range of strategies from greatly increasing to slightly decreasing GRF with the addition of weight. Ninety-six percent of strategies resulted in GRF increases. Subject strategies may affect tissue loading and their presence decreases the validity of group statistical analyses.

Effects of constrained arm swing on vertical center of mass displacement during walking

The purpose of this study was to determine the effects of constraining arm swing on the vertical displacement of the bodys center of mass (COM) during treadmill walking and examine several common gait variables that may account for or mask differences in the bodys COM motion with and without arm swing. Participants included 20 healthy individuals (10 male, 10 female; age: 27.8 ± 6.8 years). The bodys COM displacement, first and second peak vertical ground reaction forces (VGRFs), and lowest VGRF during mid-stance, peak summed bilateral VGRF, lower extremity sagittal joint angles, stride length, and foot contact time were measured with and without arm swing during walking at 1.34 m/s. The bodys COM displacement was greater with the arms constrained (arm swing: 4.1 ± 1.2 cm, arm constrained: 4.9 ± 1.2 cm, p < 0.001). Ground reaction force data indicated that the COM displacement increased in both double limb and single limb stance. However, kinematic patterns visually appeared similar between conditions. Shortened stride length and foot contact time also were observed, although these do not seem to account for the increased COM displacement. However, a change in arm COM acceleration might have contributed to the difference. These findings indicate that a change in arm swing causes differences in vertical COM displacement, which could increase energy expenditure.

Reliability and concurrent criterion validity of a novel technique for analyzing hip kinematics during running

Abstract Excessive frontal plane hip kinematics during running has been associated with numerous running pathologies. Traditionally, assessment of hip kinematics during running required expensive and complex equipment and procedures making objective running assessment difficult for practicing clinicians. The aim of this study was to establish the reliability and validity of a novel technique designed for clinicians that allows for objective assessment of frontal plane hip kinematics during running. Hip angles and excursions were measured using videos and jpeg images of 10 subjects (five males and five females) running. A 2-D motion analysis system and computer algorithm served as reference measures. Six raters (three licensed physical therapists and three student physical therapists) took measures on two instances. Reliability was examined using intraclass correlation coefficients (ICC). Validity was investigated with ICCs, 95% limits of agreement (LA), and mean absolute differences (MAD) by comparing each raters 2-trial average to the criterion reference values. The ICCs for interrater and intrarater reliability for angle and excursion measures ranged from 0.82 to 0.99. The validity ICCs of all measures ranged from 0.89 to 0.99 with acceptable LA. The MAD ranged from 0.5°–1.5°. These results indicate that this novel technique is reliable and valid for measuring hip kinematics compared to the reference measures making it suitable for broad-based clinical use.

Different cognitive functions discriminate gait performance in younger and older women: A pilot study

AIM Cognitive dysfunction is associated with slower gait speed in older women, but whether cognitive function affects gait performance earlier in life has yet to be investigated. Thus, the objective of this study was to test the hypothesis that cognitive function will discriminate gait performance in healthy younger women. METHODS Fast-pace and dual-task gait speed were measured in 30 young to middle-aged (30-45y) and 26 older (61-80y) women without mild cognitive impairment. Visuoperceptual ability, working memory, executive function, and learning ability were assessed using neuropsychological tests. Within each age group, women were divided by the median into lower and higher cognitive function groups to compare gait performance. RESULTS Younger women with higher visuoperceptual ability had faster fast-pace (2.25±0.30 vs. 1.98±0.18m/s, p≤0.01) and dual-task gait speed (2.02±0.27 vs. 1.69±0.25m/s, p≤0.01) than women with lower visuoperceptual ability. The difference in dual-task gait speed remained significant (p=0.02) after adjusting for age, years of education, and other covariates. Dividing younger women based on other cognitive domains showed no difference in gait performance. In contrast, working memory and executive function discriminated dual-task gait speed (p<0.05) in older women after adjusting for age and education. CONCLUSION To our knowledge, this is the first study to show that poorer cognitive function even at a relatively young age can negatively impact mobility. Different cognitive functions discriminated gait performance based on age, highlighting a possible influence of aging in the relationship between cognitive function and mobility in women.

The relationship between various anatomical landmarks used for localizing the first rib during surface palpation

Abstract Objectives: To assess the relationship between anatomical landmarks used to locate the first rib during surface palpation. One currently cited technique suggests locating the width of the transverse processes (TPs) of the first cervical vertebrae (C1) to determine the estimated width of the first thoracic vertebrae (T1) TP, allowing for subsequent palpation of the first rib laterally to the transverse process of T1. Based on anatomical structural relationships, the authors propose an additional method of locating the first rib, lateral to T1 TP, by palpating through the trapezius muscle at the width of the mastoid process (MP). Methods: Overlying tissue of the bilateral MP, C1 TPs, and T1 TPs of 28 cadavers were removed. Measurements of the left to right spans at the following structures were collected using a digital caliper: mastoid process, C1 TP, and T1 TP. Measurements were used to determine the agreement between each anatomical structural span. Results: The mean absolute difference (standard deviation, SD) between C1 TP span versus T1 TP span was 3·9 (±2·58) mm with an intraclass correlation coefficient (ICC) of 0·88 (95% CI = 2·9–4·9). The mean absolute difference between MP span and T1 TP span was 35·4 (±6·46) mm with an ICC of 0·71 (95% CI = 33·0–37·8). Discussion: This study confirms the anatomical accuracy and feasibility of using the C1 TP span to determine the general width of the T1 TP span while palpating for the first rib just lateral to the T1 TP. Additionally, this study demonstrates that the more easily palpated mastoid process serves as an effective landmark to identify a width sufficiently lateral to the T1 TP, appropriate for first rib palpation through the trapezius muscle.

Effects of arm weight on gait performance in healthy subjects

Previous studies have investigated how additional arm weights affect gait. Although light weights (0.45 kg) seemed to elicit performance improvements in Parkinsonian patients, it was not studied how light weights affect gait parameters in healthy individuals. It is important to understand normal responses in a healthy population so that clinical effects might be better understood. Therefore, the purpose of this study was to investigate the effects of arm weights on arm swing amplitude, gait performance, and muscle activity in healthy people. Twenty-two subjects walked overground at their preferred speed under different weight carriage conditions (C1: no weight; C2: unilateral arm weight; C3: bilateral arm weights; C4: waist weights). Gait speed increased in C2 (p = 0.018) and C4 (p = 0.013) when compared with C1(C1: 1.21 ± 0.08; C2: 1.25 ± 0.11; C3: 1.24 ± 0.11; C4: 1.25 ± 0.11 m/s) with an increase in cadence during C2 (p < 0.001), C3 (p = 0.008), and C4 (p < 0.001) (C1: 105.5 ± 5.2; C2: 108.5 ± 5.6; C3: 107.9 ± 5.6; C4: 108.5 ± 5.3 steps/min) and in tibialis anterior electromyographic activity on the unweighted side in C2 (p = 0.048) (C1: 21.05 ± 4.59; C2: 25.10 ± 6.10; C3: 23.93 ± 4.75; C4: 24.33 ± 6.32 μV). The results indicate that an additional sensory input with the application of the weights may result in an overcompensation with the whole body and facilitate faster walking speed when applied on one arm or around the waist. The locations of the weights and amount of the weights may elicit different responses. Various strategies of adding weights should be further investigated as a potential intervention to improve performance in individuals with various gait impairments. Although there is evidence for benefits of this intervention in Parkinsonian patients, further study is warranted in other patient populations, such as stroke patients, who might benefit from this intervention to improve gait performance.

Corrigendum to “Changes in patellofemoral pain resulting from repetitive impact landings are associated with the magnitude and rate of patellofemoral joint loading” [Clin. Biomech. 53 (2018) 31–36]

a Department of Physical Therapy, Angelo State University, San Angelo, TX, USA Department of Rehabilitation Sciences and Center for Rehabilitation Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA c Kinesiology and Sport Management Division, University of South Dakota, Vermillion, SD, USA d Division of Biokinesiology & Physical Therapy, University of Southern California, Los Angeles, CA, USA

Changes in patellofemoral pain resulting from repetitive impact landings are associated with the magnitude and rate of patellofemoral joint loading

Background Although a relationship between elevated patellofemoral forces and pain has been proposed, it is unknown which joint loading variable (magnitude, rate) is best associated with pain changes. The purpose of this study was to examine associations among patellofemoral joint loading variables and changes in patellofemoral pain across repeated single limb landings. Methods Thirty‐one females (age: 23.5(2.8) year; height: 166.8(5.8) cm; mass: 59.6(8.1) kg) with PFP performed 5 landing trials from 0.25 m. The dependent variable was rate of change in pain obtained from self‐reported pain scores following each trial. Independent variables included 5‐trial averages of peak, time‐integral, and average and maximum development rates of the patellofemoral joint reaction force obtained using a previously described model. Pearson correlation coefficients were calculated to evaluate individual associations between rate of change in pain and each independent variable (&agr; = 0.05). Stepwise linear multiple regression (&agr;enter = 0.05; &agr;exit = 0.10) was used to identify the best predictor of rate of change in pain. Findings Subjects reported an average increase of 0.38 pain points with each landing trial. Although, rate of change in pain was positively correlated with peak force (r = 0.44, p = 0.01), and average (r = 0.41, p = 0.02) and maximum force development rates (r = 0.39, p = 0.03), only the peak force entered the predictive model explaining 19% of variance in rate of change in pain (r2 = 0.19, p = 0.01). Interpretation Peak patellofemoral joint reaction force was the best predictor of the rate of change in pain following repetitive singe limb landings. The current study supports the theory that patellofemoral joint loading contributes to changes in patellofemoral pain. HighlightsJoint loading variables were examined for their association with patellofemoral pain.Peak patellofemoral joint force was the best predictor of increases in pain.Interventions that reduce peak joint force may benefit persons with patellofemoral pain.

Prediction of calcaneal bone competence from biomechanical accommodation variables measured during weighted walking

Carrying weight while walking is a common activity associated with increased musculoskeletal loading, but not all individuals accommodate to the weight in the same way. Different accommodation strategies could lead to different skeletal forces, stimuli for bone adaptation and ultimately bone competence. The purpose of the study was to explore the relationships between calcaneal bone competence and biomechanical accommodation variables measured during weighted walking. Twenty healthy men and women (10 each; age 27.8 ± 6.8 years) walked on a treadmill at 1.34 m/s while carrying 0, 44.5 and 89 N weights with two hands in front of the body. Peak vertical ground reaction force and sagittal plane angular displacements of the trunk and left lower extremity during weight acceptance were measured and used to quantify accommodation. Calcaneal bone stiffness index T-score (BST) was measured using quantitative ultrasound. Correlation and stepwise multiple regression were used to predict calcaneal BST from the accommodation variables. Accommodations of the foot and ankle explained 29 and 54% (p ≤ .015) of the variance in calcaneal BST in different regression models. Statistical resampling using 1000 replications confirmed the strength and consistency of relationships, with the best model explaining 94% of the variance in calcaneal BST. Individuals who change foot and ankle function when carrying heavier weight likely alter the control of gravitational and muscular forces, thereby affecting calcaneal loading, bone adaptation and bone competence. These novel findings illustrate the importance of gait accommodation strategies and highlight a potential clinical consequence that requires further investigation.