Muscle activation patterns are bilaterally linked during split-belt treadmill walking in humans

There is growing evidence that human locomotion is controlled by flexibly combining a set of basic muscle activity patterns. To explore how these patterns are modified to cope with environmental constraints, 10 healthy young adults 1st walked on a split-belt treadmill at symmetric speeds of 4 and 6...

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Bibliographic Details
Published in:Journal of neurophysiology 2014-04, Vol.111 (8), p.1541-1552
Main Authors: Maclellan, M J, Ivanenko, Y P, Massaad, F, Bruijn, S M, Duysens, J, Lacquaniti, F
Format: Article
Language:English
Subjects:
Adult
Biomechanical Phenomena
Exercise Test
Female
Gait - physiology
Humans
Lower Extremity - physiology
Male
Muscle, Skeletal - physiology
Walking - physiology
Young Adult
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Summary:There is growing evidence that human locomotion is controlled by flexibly combining a set of basic muscle activity patterns. To explore how these patterns are modified to cope with environmental constraints, 10 healthy young adults 1st walked on a split-belt treadmill at symmetric speeds of 4 and 6 km/h for 2 min. An asymmetric condition was then performed for 10 min in which treadmill speeds for the dominant (fast) and nondominant (slow) sides were 6 and 4 km/h, respectively. This was immediately followed by a symmetric speed condition of 4 km/h for 5 min. Gait kinematics and ground reaction forces were recorded. Electromyography (EMG) was collected from 12 lower limb muscles on each side of the body. Nonnegative matrix factorization was applied to the EMG signals bilaterally and unilaterally to obtain basic activation patterns. A cross-correlation analysis was then used to quantify temporal changes in the activation patterns. During the early (1st 10 strides) and late (final 10 strides) phases of the asymmetric condition, the patterns related to ankle plantar flexor (push-off) of the fast limb and quadriceps muscle (contralateral heel contact) of the slow limb occurred earlier in the gait cycle compared with the symmetric conditions. Moreover, a bilateral temporal alignment of basic patterns between limbs was still maintained in the split-belt condition since a similar shift was observed in the unilateral patterns. The results suggest that the temporal structure of these locomotor patterns is shaped by sensory feedback and that the patterns are bilaterally linked.
ISSN:0022-3077
1522-1598
DOI:10.1152/jn.00437.2013