To facilitate stable trunk kinematics, humans must generate appropriate motor patterns to effectively control muscle force and stiffness and respond to biomechanical perturbations and/or neuromuscular control errors. Thus, it is important to understand physiological variables such as muscle force and stiffness, and how these relate to the downstream production of stable spine and trunk movements. This study was designed to assess the local dynamic stability of spine muscle activation and rotational stiffness patterns using Lyapunov analyses, and relationships to the local dynamic stability of resulting spine kinematics, during repetitive lifting and lowering at varying combinations of lifting load and rate. With an increase in the load lifted at a constant rate there was a trend for decreased local dynamic stability of spine muscle activations and the muscular contributions to spine rotational stiffness; although the only significant change was for the full state space muscle activation stability (p < 0.05). With an increase in lifting rate with a constant load there was a significant decrease in the local dynamic stability of spine muscle activations and the muscular contributions to spine rotational stiffness (p ≤ 0.001 for all measures). These novel findings suggest that the stability of motor inputs and the muscular contributions to spine rotational stiffness can be altered by external task demands (load and lifting rate), and therefore are important variables to consider when assessing the stability of the resulting kinematics.
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December 2014
Research-Article
Local Dynamic Stability of Spine Muscle Activation and Stiffness Patterns During Repetitive Lifting
Ryan B. Graham,
Ryan B. Graham
1
School of Physical and Health Education,
e-mail: ryang@nipissingu.ca
Nipissing University
,100 College Drive, Box 5002
,North Bay, ON P1B 8L7
, Canada
e-mail: ryang@nipissingu.ca
1Corresponding author.
Search for other works by this author on:
Stephen H. M. Brown
Stephen H. M. Brown
Department of Human Health
and Nutritional Sciences,
e-mail: shmbrown@uoguelph.ca
and Nutritional Sciences,
University of Guelph
,50 Stone Road East
,Guelph, ON N1G 2W1
, Canada
e-mail: shmbrown@uoguelph.ca
Search for other works by this author on:
Ryan B. Graham
School of Physical and Health Education,
e-mail: ryang@nipissingu.ca
Nipissing University
,100 College Drive, Box 5002
,North Bay, ON P1B 8L7
, Canada
e-mail: ryang@nipissingu.ca
Stephen H. M. Brown
Department of Human Health
and Nutritional Sciences,
e-mail: shmbrown@uoguelph.ca
and Nutritional Sciences,
University of Guelph
,50 Stone Road East
,Guelph, ON N1G 2W1
, Canada
e-mail: shmbrown@uoguelph.ca
1Corresponding author.
Manuscript received February 6, 2014; final manuscript received September 30, 2014; accepted manuscript posted October 16, 2014; published online October 30, 2014. Assoc. Editor: Kenneth Fischer.
J Biomech Eng. Dec 2014, 136(12): 121006 (9 pages)
Published Online: October 30, 2014
Article history
Received:
February 6, 2014
Revision Received:
September 30, 2014
Accepted:
October 16, 2014
Citation
Graham, R. B., and Brown, S. H. M. (October 30, 2014). "Local Dynamic Stability of Spine Muscle Activation and Stiffness Patterns During Repetitive Lifting." ASME. J Biomech Eng. December 2014; 136(12): 121006. https://doi.org/10.1115/1.4028818
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