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The effects of grade and speed on leg muscle activations during walking.

ABSTRACT: Compared to level walking, additional muscle actions are required to raise and lower the center of mass during uphill and downhill walking, respectively. However, it remains unclear which muscle recruitment strategies are employed at typical grades when walking over a range of speeds. Based on previous reports, we hypothesized that, across a range of walking speeds, hip, knee, and ankle extensor muscle activations would increase with steeper uphill grade, but only knee extensor muscle activations would increase with steeper downhill grade. We also hypothesized that these changes in muscle activations with grade would become more pronounced at faster walking speeds. To test these hypotheses, 10 young adults (5M/5F) walked on a standard treadmill at seven grades (0°, ± 3°, ± 6°, and ± 9°) and three speeds (0.75, 1.25, and 1.75 ms(-1)). We quantified the stance phase electromyographic activities of the gluteus maximus (GMAX), biceps femoris (BF), rectus femoris (RF), vastus medialis (VM), medial gastrocnemius (MG), and soleus (SOL) muscles. On average, compared to level walking, hip (BF: 635%, GMAX: 345%), knee (RF: 165%, VM: 366%), and ankle (MG: 175%, SOL: 136%) extensor muscle activities increased to walk up 9°, but only knee (RF: 310%, VM: 246%) extensor muscle activities increased to walk down 9°. Further, these changes in muscle activations with grade became greater with faster walking speed. We conclude that people employ distinct uphill (hip, knee, and ankle extensors) and downhill (knee extensors) muscle recruitment strategies generally across walking speeds and progressively with steeper grade.

SUBMITTER: Franz JR

PROVIDER: S-EPMC3262943 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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The effects of grade and speed on leg muscle activations during walking.

Franz Jason R JR Kram Rodger R

Gait & posture 20111002 1

Compared to level walking, additional muscle actions are required to raise and lower the center of mass during uphill and downhill walking, respectively. However, it remains unclear which muscle recruitment strategies are employed at typical grades when walking over a range of speeds. Based on previous reports, we hypothesized that, across a range of walking speeds, hip, knee, and ankle extensor muscle activations would increase with steeper uphill grade, but only knee extensor muscle activation ...[more]

PMID: 21962846

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Project description:BackgroundSuccessful walking requires the execution of the pre-swing biomechanical tasks of body propulsion and leg swing initiation, which are often impaired post-stroke. While excess rectus femoris activity during swing is often associated with low knee flexion, previous work has suggested that deficits in propulsion and leg swing initiation may also contribute. The purpose of this study was to determine underlying causes of propulsion, leg swing initiation and knee flexion deficits in pre-swing and their link to stiff knee gait in individuals post-stroke.MethodsMusculoskeletal models and forward dynamic simulations were developed for individuals post-stroke (n = 15) and healthy participants (n = 5). Linear regressions were used to evaluate the relationships between peak knee flexion, braking and propulsion symmetry, and individual muscle contributions to braking, propulsion, knee flexion in pre-swing, and leg swing initiation.ResultsFour out of fifteen of individuals post-stroke had higher plantarflexor contributions to propulsion and seven out of fifteen had higher vasti contributions to braking on their paretic leg relative to their nonparetic leg. Higher gastrocnemius contributions to propulsion predicted paretic propulsion symmetry (p = 0.005) while soleus contributions did not. Higher vasti contributions to braking in pre-swing predicted lower knee flexion (p = 0.022). The rectus femoris had minimal contributions to lower knee flexion acceleration in pre-swing compared to contributions from the vasti. However, for some individuals with low knee flexion, during pre-swing the rectus femoris absorbed more power and the iliopsoas contributed less power to the paretic leg. Total musculotendon work done on the paretic leg in pre-swing did not predict knee flexion during swing.ConclusionsThese results emphasize the multiple causes of propulsion asymmetry in individuals post-stroke, including low plantarflexor contributions to propulsion, increased vasti contributions to braking and reliance on compensatory mechanisms. The results also show that the rectus femoris is not a major contributor to knee flexion in pre-swing, but absorbs more power from the paretic leg in pre-swing in some individuals with stiff knee gait. These results highlight the need to identify individual causes of propulsion and knee flexion deficits to design more effective rehabilitation strategies.

Project description:BACKGROUND:Chronic kidney disease is associated with malnutrition and inflammation. These processes may lead to loss of skeletal muscle and reduced physical performance. Associations of kidney function with muscle composition and longitudinal measures of physical performance are unknown. STUDY DESIGN:Prospective cohort study. SETTING & PARTICIPANTS:We evaluated 826 community-dwelling older adults enrolled in the Invecchiare in Chianti (InCHIANTI) Study who were free of baseline stroke or activities of daily living disability. PREDICTOR:Baseline creatinine clearance (Clcr) based on 24-hour urine collection. OUTCOMES:Cross-sectional and longitudinal trajectories of physical performance measured by 7-m usual gait speed, 400-m fast gait speed, and knee extension strength using isometric dynamometry. Calf muscle composition assessed by quantitative computed tomography. RESULTS:Mean age of participants was 74 ± 7 (SD) years, with 183 having Clcr < 60 mL/min/1.73 m(2). After adjustment, each 10-mL/min/1.73 m(2) decrement in Clcr was associated with 0.01 (95% CI, 0.004-0.017) m/s slower 7-m usual walking speed and 0.008 (95% CI, 0.002-0.014) m/s slower 400-m walking speed. Each 10-mL/min/1.73 m(2) decrement in Clcr was associated with 28 (95% CI, 0.8-55) mm(2) lower muscle area and 0.15 (95% CI, 0.04-0.26) mg/cm(3) lower muscle density. After adjustment, lower Clcr was associated with slower mean 7-m (P=0.005) and 400-m (P=0.02) walk and knee extension strength (P=0.001) during the course of follow-up. During a mean follow-up of 7.1 ± 2.5 years, each 10-mL/min/1.73 m(2) lower baseline Clcr was associated with 0.024 (95% CI, 0.01-0.037) kg/y greater decline in knee strength. LIMITATIONS:Single baseline measurement of Clcr and 3-year interval between follow-up visits may lead to nondifferential misclassification and attenuation of estimates. CONCLUSIONS:Among older adults, lower Clcr is associated with muscle atrophy, reduced walking speed, and more rapid declines in lower-extremity strength over time.

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The effects of grade and speed on leg muscle activations during walking.

Publications

The effects of grade and speed on leg muscle activations during walking.

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