Is the association between physical activity and fatigue mediated by physical function or depressive symptoms in symptomatic knee osteoarthritis? The Multicenter Osteoarthritis Study

Objectives: To examine whether physical activity (PA) was associated with fatigue, and quantify the extent of potential mediation through depressive symptoms or physical function (PF) on the relationship between PA and fatigue in symptomatic knee osteoarthritis (KOA).Method: This longitudinal study used data from the Multicenter Osteoarthritis Study (n = 484), comprising subjects aged ≥ 50 years. Baseline PA was quantified via an ankle-worn accelerometer. The outcome was fatigue, measured using a 0-10 rating scale at 2 year follow-up. Mediators included gait speed as a measure of PF and depressive symptoms at 2 year follow-up. Mediation analysis was carried out after adjustment for baseline confounders. Stratified analysis by baseline fatigue status [no/low (< 4) and high (≥ 4) fatigue] was performed.Results: A significant direct association was found between PA and fatigue at 2 years [unstandardized coefficient (B) = -0.054; 95% confidence interval (CI) -0.107, -0.002, p = 0.041]. The PA-fatigue relationship was not mediated by gait speed (B = -0.006; 95% CI -0.018, 0.001) or depressive symptoms (B = 0.009; 95% CI 0.009, 0.028). In the subgroup with high baseline fatigue, direct associations were found between PA and fatigue (gait speed model:, B = -0.107; 95% CI -0.212, -0.002, p = 0.046; depressive symptoms model: B = -0.110; 95% CI -0.120, -0.020, p = 0.017); but in the no/low baseline fatigue group, no significant association was found between PA and fatigue.Conclusion: In the symptomatic KOA population, higher baseline PA was directly associated with reduced fatigue 2 years later, especially in those with high baseline fatigue. However, this relationship was not mediated by depressive symptoms or PF.

Functional foot symmetry and its relation to lower extremity physical performance in older adults: the Framingham Foot Study

BACKGROUND

While many studies use gait symmetry as a marker of healthy gait, the evidence that gait symmetry exists is limited. Because gait symmetry is thought to arise through laterality (i.e., limb preference) and affects gait retraining efforts, it is important to understand if symmetry exists during gait in older adults. Therefore, the purpose of this study was to evaluate foot and gait symmetry in the population-based Framingham Foot Study as well as to determine the effects of vertical force symmetry on physical performance measures.

METHODS

Members of the Framingham Foot Study were included in this analysis (N=1333). Foot function and force data were collected using the Tekscan Matscan during self-selected gait, with symmetry evaluated using the symmetry index. The short physical performance battery (SPPB) measures of balance, chair stands and gait speed assessed lower extremity physical function. Participants were evaluated using quartiles of gait speed and foot symmetry to determine the effects of symmetry on lower extremity physical function.

RESULTS

Individuals with faster gait speed displayed greater foot function asymmetry; individuals with -3.0% to -9.5% asymmetry in foot function performed better on the short physical performance battery (SPPB). Further, with aging, the degree of asymmetry was reduced.

CONCLUSIONS

While this research suggests that a moderate degree of foot asymmetry is associated with better lower extremity function, the causes of vertical force asymmetry are unknown. Future studies should evaluate the causes of foot asymmetry and should track the changes in symmetry that occur with aging.

Strategies of stepping over obstacles: The effects of long-term exercise in older adults

BACKGROUND

Stepping over obstacles challenges stability and is a leading cause of falls in older adult populations. As walking and Tai Chi (TC) exercise have been suggested practices for older adults for fall prevention, the purpose of this study was to evaluate the obstacle-crossing strategies of long-term TC practitioners and exercise walkers.

METHODS

Thirty healthy older women (average age: 65.7 years) with either TC (n=15) experience (average experience: 8.2 years) or walking exercise (n=15; average experience: 8.8 years) participated in this study. We used three trial conditions: (1) normal walking, (2) crossing a 15cm (20% of leg length) obstacle, and (3) crossing a 23cm (30% of leg length) to assess obstacle-crossing strategy. Sagittal plane obstacle-crossing kinematic parameters and plantar pressures were used to evaluate the obstaclecrossing strategy. A MANOVA assessed differences between groups.

RESULTS

Individuals with a TC background crossed the obstacle significantly faster with a significantly longer step relative to the exercise walkers. Plantar pressure profiles between the two groups also differed. Exercise walkers showed greater plantar pressure in the forefoot; TC practitioners demonstrated greater medial heel plantar pressure during obstacle-crossing.

CONCLUSIONS

Our results suggest that obstacle-crossing strategies were affected by the type of longterm exercise. The strategies each group used had important attributes that affect stability during obstacle-crossing. Future studies are needed to understand how obstacle-crossing strategies are adopted and how exercise may influence the strategy used.

Design and Validation of a Knee Brace With Feedback to Reduce the Rate of Loading

The repetitive nature of walking can lead to repetitive stress and associated complications due to the rate of loading (ROL) experienced by the body at the initial contact of the foot with the ground. An individual’s gait kinematics at initial contact has been suggested to give rise to the ROL, and a repetitive, high ROL may lead to several disorders, including osteoarthritis. We present the design, development, and validation of a knee brace that provides feedback to the user during gait. The feedback consists of an auditory signal when the specific parameters of knee angle or tibial acceleration 50 ms prior to contact are exceeded. Nine women were recruited for the gait analysis, and the gait characteristics with and without the brace and feedback are analyzed. Our results indicate that using a knee brace with feedback can effectively change the gait kinematics used during walking, leading to a reduced ROL experienced at initial contact. Using a knee brace with feedback is a novel approach to gait retraining. Al-though the kinetics of how the subjects change in gait pattern is unknown, the reduced ROL experienced is significant and warrants further investigation.

Proprioception, gait kinematics, and rate of loading during walking: are they related?

The cyclic nature of walking can lead to repetitive stress and associated complications due to the rate of loading (ROL) experienced by the body at the initial contact of the foot with the ground. An individual's gait kinematics at initial contact has been suggested to give rise to the ROL, and a repetitive, high ROL may lead to several disorders, including osteoarthritis. Additionally, proprioception, the feedback signaling of limb position and movement, may play a role in how the foot strikes the ground and thus, the ROL. Our goal was to explore the relationship between proprioception, gait kinematics and ROL. Thirty-eight women were recruited for gait analysis, and the gait characteristics 50 ms prior to and at initial contact were examined. Two proprioception tests, joint angle reproduction and threshold to detect passive motion were used to examine the subject's proprioceptive acuity. Our results indicate that individuals with a larger knee angle (i.e., greater extension) 50 ms prior to initial contact (IC) experience a higher ROL during gait and have poorer proprioceptive scores. However, it remains unclear whether poor proprioception causes a high ROL or if a high ROL damages the mechanoreceptors involved in proprioception, but the apparent relationship is significant and warrants further investigation.