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.
Background:The purpose of this investigation was to determine neuromuscular failure via pre-to-post exercise amplitude changes of the M-wave following a Calf-Raise Exercise (CR). Methods:In a balanced crossover design and separated by one week, eight participants (Males = 5; Females = 3) performed the CR with either one repetition (CR1) or five repetitions (CR5).Electromyography of gastrocnemius were recorded both pre-and post-CR1/CR5 in order to determine changes in M-wave amplitude. Results:The main effect for exercise was not statistically significant (p = 0.7590) where the M-wave amplitude for CR1 (5.50±6.16mV) and CR5 (4.88±5.59mV) were similar when pooled across pre-/post-exercise.Likewise, the main effect for time was not statistically significant (P = 0.6310) where the M-wave amplitude for pre-exercise (5.24±5.33 mV) and post-exercise (5.13±5.08 mV) were similar when pooled across CR1 and CR5.The exercise x time interaction was not statistically significant (P = 0.3440) as M-wave amplitude did not change differently from pre-to post-exercise between the CR1 and CR5 trials. Conclusion:We conclude that M-wave amplitude was not statistically different from pre-exercise to post-exercise for either one repetition or five repetitions of the CR exercise.
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