Assessing trunk motor variability in a changing spinal environment: an experimental study.

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Motor variability is an important feature of human movement which can be measured using multiple parameters such as performance measures, kinematic and kinetic components of the movement pattern, muscle activity and muscle recruitment patterns. The main objective of this proposal is to identify and characterize trunk neuromuscular and kinematic adaptations to a “changing spinal environment”. The proposed research program will include a series of experiments designed to each address a specific hypothesis related to trunk and spinal motor variability under varying mechanical and neurophysiological conditions. The results of these studies will provide critical information regarding the development of acute and long term motor adaptation in the complex musculoskeletal spinal system. The results and knowledge derived from these studies could, in the long run, provide new insights on how intrinsic spinal variability can be exploited as a source of biomechanical variation without compromising work-related or other type of performances. Potential long term applications of this specific work include risk assessment in ergonomics, objective “return to work algorithm” as well as the development of standardized functional spinal evaluation and clinical diagnostic tools. METHODS All the proposed experiments will be based on a similar experimental protocol aimed at quantifying neuromechanical adaptations to various experimental conditions using trunk muscular activity recordings with large surface electrode matrices as well as lumbar spine and pelvis movements. A flexion-extension task and trunk muscle endurance will be studied as they both offer the possibility to investigate a standardized neuromuscular response with highly reproducible muscle activity and movement characteristics. Independent groups of healthy adult participants will be recruited to participate in each of these experiments (N= 40 per experiment) and will be asked to perform a series of standardized trunk flexion and extension under varying experimental conditions. With regard to motor variability, the various experiments suggested will try to answer the following research questions: [1] How does erector spinae muscle fatigue change trunk muscle recruitment strategies and kinematics? [2] How does abdominal muscle fatigue change trunk muscle recruitment strategies and kinematics? [3] How do changes in passive spinal stability affect trunk muscle recruitment strategies and kinematics? [4] How do nociceptive segmental inputs affect trunk muscle recruitment strategies and kinematics? Neuromuscular motor variability will be quantified using the spatial representation of muscular activity in EMG matrices during the various experimental tasks. Spatial reorganization of muscular activity in erector spinae and abdominal muscles will be assessed using multiple features of motor variability. Motor variability related to trunk movement will also be assessed by studying the movement interaction between the lumbar spine and the pelvis. My goal, with the present proposal, is to create an educational environment for graduate students that will foster interdisciplinary collaboration in order to ensure both diversified and high quality training of young researchers in the fields of motor control, biomechanics and signal processing. Current collaborations with the electrical engineering department have already led to the development of innovative approaches to the study muscle recruitment and movement organization.