Adaptational and learning processes during human split-belt locomotion: interaction between central mechanisms and...

Area of Science:

• Neuroscience
• Biomechanics
• Motor Control

Background:

• Split-belt locomotion necessitates rapid adjustments in biomechanical parameters and electromyographic (EMG) activity.
• Understanding these adaptations and learning effects is crucial for motor control research.

Purpose of the Study:

• To investigate the adaptation process during the initial strides of split-belt locomotion.
• To examine motor learning effects induced by repetition in asymmetric gait.
• To explore the role of interlimb coordination and proprioceptive feedback.

Main Methods:

• 11 healthy volunteers performed split-belt locomotion with unequal leg speeds (0.5 m/s and 1.5 m/s).
• Biomechanical parameters and leg muscle EMG activity were recorded during adaptation.
• The experiment involved initial adaptation, repetition of the paradigm, and a 'mirror' condition with inverted speeds.

Main Results:

• Initial adaptation to split-belt locomotion required 12-15 strides, involving changes in stride duration and muscle activity.
• Repetition of the task led to a significant motor learning effect, with adaptation occurring within 1-3 strides.
• The short-time learning effect was not observed when the slow and fast sides were inverted (mirror condition), requiring 12-15 strides again.
• Adaptation of EMG activity paralleled biomechanical changes without increased co-contraction of antagonistic muscles.

Conclusions:

• Split-belt locomotion adaptation involves adjustments in stride cycle duration and muscle activation patterns.
• Motor learning significantly speeds up adaptation, but this learning is side-specific and not transferred contralaterally.
• Proprioceptive information from each leg is essential for adjusting centrally generated locomotor commands for controlled bipedal locomotion.