The effects of age and task demand on dynamic mean ankle moment arm during walking.

Background: Older adults walk with a diminished foot and ankle push-off compared to younger adults and this difference may be a target for assistive devices. Dynamic mean ankle moment arm (DMAMA) is an aggregate measure of foot and ankle control that varies in younger adults across walking speeds and inclines.

Research Question: Does age affect DMAMA across a range of walking tasks designed to challenge power output from the ankle and foot?

Methods: We enrolled 12 healthy younger adults and 10 healthy older adults.

Reduced Achilles tendon stiffness in aging associates with higher metabolic cost of walking.

The mechanisms responsible for increased metabolic cost of walking in older adults are poorly understood. We recently proposed a theoretical premise by which age-related reductions in Achilles tendon stiffness (k) can disrupt the neuromechanics of calf muscle force production and contribute to faster rates of oxygen consumption during walking. The purpose of this study was to objectively evaluate this premise.

Foot-Ankle Mechanical Transmission: Age Effects and the Relation to Ankle Push-Off During Walking.

Older adults walk with less push-off power than younger adults. Principally attributed to plantar flexor dysfunction, growing evidence implicates interactions between the foot and ankle as critical for generating effective push-off. Our purposes were to measure age effects on foot-ankle mechanical transmission (FAMT, ie, the ratio between metatarsal phalangeal extension and medial gastrocnemius fascicle length change), and its association with ankle push-off during walking.

Reduced Achilles tendon stiffness in aging persists at matched activations and associates with higher metabolic cost of walking.

The mechanisms responsible for increased walking metabolic cost among older adults are poorly understood. We recently proposed a theoretical premise by which age-related reductions in Achilles tendon stiffness (k ) can disrupt the neuromechanics of calf muscle behavior and contribute to faster rates of oxygen consumption during walking. The purpose of this study was to objectively evaluate this premise.

In Vivo Comparison of Backscatter Techniques for Ultrasonic Bone Assessment at the Femoral Neck.

Ultrasonic techniques are being developed to detect changes in cancellous bone caused by osteoporosis. The goal of this study was to test the relative in vivo performance of eight backscatter parameters developed over the last several years for ultrasonic bone assessment: apparent integrated backscatter (AIB), frequency slope of apparent backscatter (FSAB), frequency intercept of apparent backscatter (FIAB), normalized mean of the backscatter difference (nMBD), normalized slope of the backscatter difference (nSBD), normalized intercept of the backscatter difference (nIBD), normalized backscatter amplitude ratio (nBAR) and backscatter amplitude decay constant (BADC). Backscatter measurements were performed on the left and right femoral necks of 80 adult volunteers (age = 25 ± 11 y) using an imaging system equipped with a convex array transducer.

Ultrasonic Bone Assessment Using the Backscatter Amplitude Decay Constant.

Ultrasonic backscatter techniques are being developed to detect changes in bone caused by osteoporosis. The present study introduces a new technique that measures the exponential decay in the amplitude of the backscatter signal quantified by a parameter called the backscatter amplitude decay constant (BADC). Measurements were performed on 54 specimens of cancellous bone from 14 human femurs using a 3.