Integrating the Spine into Full Body Movement: Motor Synergies and Skill

Abstract

Skilled movers effectively use their spine and pelvis to facilitate limb motions during full body tasks. One method of spine-body integration is through motor synergies, which are central nervous system processes that coordinate the motions of body segments to stabilize key features of performance. The overall aim of this dissertation was to examine the relationship between motor synergies and skilled performance for the integration of the spine and pelvis into full-body athletic movements. To address this aim, three studies were completed. In Study #1, potential limitations associated with choosing discrete time points and focusing on spatial performance variables when using Uncontrolled Manifold analysis to quantify the presence of motor synergies were explored. Motor synergies stabilizing hand kinematics (position, velocity, and acceleration) were studied in experienced Nordic skiers during a simulated skiing ergometry task. Kinematic motor synergies were observed for all of position, velocity, and acceleration and fluctuated throughout the entire skiing cycle. These results suggested that a) higher order kinematics need to be studied as potential performance variables, and b) the entire movement cycle should be considered when analyzing motor synergies during continuous human movements. In Study #2, the stability of hand, upper arm, trunk centre of mass, and wholebody centre of mass was examined in experienced Nordic skiers and novice persons during a simulated skiing ergometry task. Trunk centre of mass position and velocity were stabilized for portions of the skiing cycle by experienced skiers but not novices. These results highlight that different trunk control strategies are present in skilled versus unskilled people. In Study #3 the effects of a brief bout of video game-based spine and pelvis movement experience on trunk motor synergies and coordination were examined. No changes in motor synergies were observed, but participants tended to increase their coordination variability in response to the short-term intervention. In sum, Studies #1-3 suggest that the ability to stabilize trunk kinematics across repetitions of movements is important for skill development. Although this might not develop after a single short-term session of targeted trunk and pelvis movement, when these opportunities to experience different movement patterns are provided over the long-term, they may eventually access motor synergies to stabilize spine motion and become more skillful.