Rhythmic arm movement paradigms utilized in this experiment. The arm cycling paradigm (left panel) involves subjects performing circular movements with the arms on an upper limb ergometer. This is similar to leg cycling but while seated upright or standing and using the arms to cycle the cranks. Arm swing while standing (right panel) involves pendular movement of the arms while holding the handles of an arm swing apparatus that allows free shoulder flexion and extension yet restricts other arm movements.
General conceptual overview for the regulation of rhythmic human movement. Note that the effect of feedback encodes the neuromechanical interactions and projects to the motoneuronal pools, interneuronal pathways (IN), and the CPG yin-yang itself, and is subsumed in the output of the shared common oscillator. The effect of supraspinal input is taken as regulatory but is not shown. (Adapted from Zehr, 2005.)
Rhythmic CPG neural oscillator controllers (yin-yang) for all four limbs interacting with the mechanical environment (gears) meant to represent the regulation and coordination among and between all four limbs during movement. (Adapted from Zehr, 2005.)
(a) Schematic diagram relating the phases of movement for arm cycling, arm swing while standing, and arm swing while walking. The movement cycle was normalized to 100% of shoulder flexion/extension and displayed in reference to the clock face movement cycle from arm cycling (1–12) Note: the arm cycling and arm swing devices are not shown. (b) Sign conventions at the right arm and ergometer hand crank. , , and represent shoulder abduction/adduction, shoulder flexion/extension, and elbow flexion/extension, respectively. Participants performed all three tasks while EMG, kinetic, and kinematic data were recorded.
Comparative EMG traces for muscles of the right arm and trunk averaged across all subjects for cycle, swing, and walk tasks. Significant differences between cycle and walk, swing and walk, and swing and cycle are denoted by #, $, and %, respectively. Vertical dashed lines denote the 3 o’clock (shoulder flexion) and 9 o’clock (shoulder extension) positions during the movement cycle, respectively.
(a) Kinematic changes at the right shoulder and elbow during arm cycling, swinging, and walking for shoulder flexion/extension , shoulder abduction/adduction , and elbow flexion/extension . (b) Kinetics measured at the right hand during arm cycling and swinging. (c) Moments calculated about the shoulder and elbow during arm cycling, swinging, and walking. Vertical dashed lines denote the 3 o’clock and 9 o’clock positions during the movement cycle, respectively.
(a) The averaged cumulative percentage of the variance explained by each of the first four factors is shown for the three tasks for -direction, (b) -direction, (c) and EMG. (d) The average factor loadings for the first factor in the -direction (flexion/extension) for shoulder and elbow and the average factor loadings for the first factor in the -direction (adduction/abduction) for the shoulder for all tasks. (e) The average factor loadings for all muscles from the EMG PCA analysis. Asterisks denote significant differences between factor loading and the cycle.
The correlation coefficients (± standard error) of the first factor between tasks for separate -kinematic, -kinematic, and EMG PCA analysis. Asterisks denote significant difference between the cycle vs swing correlation.
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