Hip, Knee, and Ankle Functional Demand During Habitual and Fast-Pace Walking in Younger and Older Women.

This study compared functional demand (FD) between older and younger women walking at habitual and fast speed and determined strength thresholds necessary to maintain FD below 80%. FD was calculated by expressing walking flexion and extension joint torques of the ankle, knee, and hip as a percentage of maximal strength. Young women had an average FD of 65% across joint actions and speeds, whereas older women had FD of 90%. In older women, the greatest FD occurred in the hip musculature. The hip, knee, and ankle extensor strengths required to maintain FD below 80% were 1.66, 1.86, and 0.57 Nm/kg, and flexor strengths were 1.24, 0.49, and 0.69 Nm/kg, respectively. Older women have limited functional reserve to increase gait speed and rely heavily on available hip strength during walking. This study identifies strength targets for the hip, knee, and ankle that will assist in maintaining FD of older women at a sustainable level.

Discriminatory Ability of Lower-Extremity Peak Torque and Rate of Torque Development in the Identification of Older Women With Slow Gait Speed.

The aim was to compare torque and rate of torque development of lower limb muscles between older women with functional and slow gait speeds to determine which muscle group is the best predictor of functional gait speed, and to establish strength thresholds needed for functional walking speed. Torque and rate of torque development of hip, knee, and ankle muscles were measured in older women who were divided in 2 groups according to gait speed: slow gait speed (<1.22 m·s-1) and functional gait speed (≥1.22 m·s-1). For each muscle group, 3 maximal isometric contractions were performed, and peak torque and rate of torque development were recorded. Older women with slow gait speed had lower peak torque than older women with functional gait speed for hip extension (28%), knee flexion (15%), knee extension (14%), and plantar flexion (16%) (all Ps < .05). Older women with slow gait speed had lower peak rate of torque development for hip flexion (29%), hip extension (37%), knee flexion (34%), knee extension (33%), and plantar flexion (19%) (all Ps < .05). Knee extension peak rate of torque development and hip extension peak torque were the better predictors of functional gait speed with thresholds of 2.96 N·m·s-1·kg-1 and 1.26 N·m·kg-1, respectively.

Neuromuscular performance in the hip joint of elderly fallers and non-fallers.

BACKGROUNDS: Low strength and neuromuscular activation of the lower limbs have been associated with falls making it an important predictor of functional status in the elderly. AIM: To compare the rate of neuromuscular activation, rate of torque development, peak torque and reaction time between young and elderly fallers and non-fallers for hip flexion and extension. METHODS: We evaluated 44 elderly people who were divided into two groups: elderly fallers (n = 20) and elderly non-fallers (n = 24); and 18 young people. The subjects performed three isometric hip flexion and extension contractions. Electromyography data were collected for the rectus femoris, gluteus maximus and biceps femoris muscles. RESULTS: The elderly had 49 % lower peak torque and 68 % lower rate of torque development for hip extension, 28 % lower rate of neuromuscular activation for gluteus maximus and 38 % lower rate of neuromuscular activation for biceps femoris than the young (p < 0.05). Furthermore, the elderly had 42 % lower peak torque and 62 % lower rate of torque development for hip flexion and 48 % lower rate of neuromuscular for rectus femoris than the young (p < 0.05). The elderly fallers showed consistent trend toward a lower rate of torque development than elderly non-fallers for hip extension at 50 ms (29 %, p = 0.298, d = 0.76) and 100 ms (26 %, p = 0.452, d = 0.68).The motor time was 30 % slower for gluteus maximus, 42 % slower for rectus femoris and 50 % slower for biceps femoris in the elderly than in the young. DISCUSSION: Impaired capacity of the elderly, especially fallers, may be explained by neural and morphological aspects of the muscles. CONCLUSION: The process of senescence affects the muscle function of the hip flexion and extension, and falls may be related to lower rate of torque development and slower motor time of biceps femoris.

Association between energy cost of walking, muscle activation, and biomechanical parameters in older female fallers and non-fallers.

OBJECTIVE: To determine the nervous activation, muscle strength, and biomechanical parameters that influence the cost of walking in older fallers and non-fallers. METHODS: Maximal voluntary isokinetic torque was measured for the hip, knee and ankle of older women. Oxygen consumption was measured at rest and during 8min of walking at self-selected speed. An additional minute of walking was performed to collect kinematic variables and the electromyographic signal of trunk, hip, knee, and ankle muscles, which was analyzed by the linear envelope. Cost of walking was calculated by subtracting resting body mass-normalized oxygen consumption from walking body mass-normalized oxygen consumption. Stride time and length, and ankle and hip range of motion were calculated from kinematic data. FINDINGS: Older adult fallers had 28% lower knee extensor strength (p=0.02), 47% lower internal oblique activation at heel contact (p=0.03), and higher coactivation between tibialis anterior and gastrocnemius lateralis in each of the gait phases (p<0.05). For fallers, a higher activation of gluteus maximus was associated with a higher cost of walking (r=0.55, p<0.05 and r=0.71, p<0.01, before and after heel contact, respectively). For non-fallers, an association between cost of walking and age (r=0.60, p=0.01) and cost of walking and thigh muscle coactivation (r=0.53, p=0.01) existed. INTERPRETATION: This study demonstrated that there may be links between lower-extremity muscle weakness, muscle activation patterns, altered gait, and increased cost of walking in older fallers.