Interjoint coordination in lower limbs during different movements in humans

Abstract

Redundancy is associated with the ability of the nervous system to select different interjoint coordinations and movement trajectories to achieve the same motor goal. The nervous system may coordinate multiple degrees of freedom (DF) by combining them in a task-specific way to control them as a unit or synergy. Some movements may be accomplished using only one synergy, whereas other movements may employ several synergies. To investigate the problem of interjoint coordination, we applied principal component (PC) analysis to eight types of movement in healthy male subjects: forward squats, backward squats, sideways squats, squats on one leg, walking three steps, stepping in place, going up a step, and going down a step. Angular changes in four DF were analyzed: thigh flexion-extension, knee flexion-extension, ankle flexion-extension, thigh abduction-adduction, with the former three DF investigated in all movements. For many movements, two synergies were sufficient to account for more than 95% of DF angular excursions. Squatting on one leg could be described using only one synergy (99%). The angle between the vectors representing PCs for movements produced with the right and left legs could be less than 10 degrees for some movements but could reach 25 degrees for other movements. The nervous system may thus use somewhat different interjoint coordinations while producing movements on the right and the left sides. The angle between the first PCs of different movements could be smaller than 10 degrees. Thus there may be a common but adjustable basic synergy that is used to produce different movements. Additional synergies provide the transition from one movement to another.

Measurement Methods to Analyze Changes in Coordination During Motor Learning from a Non-linear Perspective

“…By using the mutual information the authors hoped to protect against nonlinearities and non-stationarities occurring in the input signals [46, p.180]. Other application of PCA include force tasks [48], reaching and grasping [42,49,50], muscle activation [51,52], gait [53][54][55][56], standing and squatting [40,57,58], and stair climbing [59]. Thus, many insightful applications of PCA are available in the literature.…”

Weightlifting Performance Is Related to Kinematic and Kinetic Patterns of the Hip and Knee Joints

“…In all, 4 fPCAs were performed; 2 for the normal angle and moment time-series data and 2 for the standardized angle and moment time-series data. To standardize the angle and moment time-series data, each matrix row had its mean subtracted and was then divided by its SD (15,16). The standardization procedure was performed to account for the fact that a larger variation for a given time series (e.g., hip) may dominate the results and overemphasize its importance with respect to the other time series (16).…”

“…To standardize the angle and moment time-series data, each matrix row had its mean subtracted and was then divided by its SD (15,16). The standardization procedure was performed to account for the fact that a larger variation for a given time series (e.g., hip) may dominate the results and overemphasize its importance with respect to the other time series (16). Principal component functions (PCFs) were then extracted from the covariance matrix of each of these 4 matrices.…”

“…The sum of the projections across the lift phase gave a set of PCF scores for each extracted PCF. Because the extraction of PCFs comes from the covariance matrix the pooled kinematic or kinetic hip, knee, and ankle data the extracted PCFs account for the fact that these joints are linked and covary during movement and therefore capture multijoint patterns common to the entire lower extremity (14,16,18). Subsequently, each PCF represents a kinematic or kinetic pattern, and the associated PCF score captures how much each pattern contributes to the motion or moment at each joint.…”

Coordenação postural em adultos e idosos durante movimentos voluntários na postura ereta

“…(COLLEDGE et al, 1994;COLLINS et al, 1995;HAY et al, 1996;TEASDALE et al, 1991) sejam mais afetados pela tarefa. Tal resultado é observado somente na relação entre tempo de movimento e índice de dificuldade efetivo.…”