Striking the right balance with muscle control

February 28, 2014
Figure 1: The human body maintains balance thanks to well-coordinated muscles controlled by the central nervous system. Credit: sognolucido/iStock/Thinkstock

The central nervous system (CNS) comprises the brain and spinal cord, and coordinates all our bodily activities. One of the functions of the CNS is to choose the most efficient muscle movements in order to conserve energy and allow the body to move smoothly, and it is believed that the CNS trains itself through experience to narrow down the number of options. Fady Alnajjar and colleagues from the Intelligent Behavior Control Unit of the RIKEN Brain Science Institute have now modeled the behavior of muscles during balance tests to illustrate how the human CNS trains itself to maintain balance1.

"Modeling of the computational mechanisms between the CNS and , which we call muscle synergy, is challenging," explains Alnajjar. "Our study concerns the muscle synergy behind basic motor skills, such as maintaining balance, in healthy humans."

Alnajjar's team developed a model of 'muscle synergy' by devising two novel parameters: the synergy stability index (SSI), which measures the similarities between muscle usage in repeated behaviors and therefore the stability of the neural command, and the synergy coordination index, which measures the overall size of the synergy space required to carry out a movement and therefore the level of coordination between muscles.

The researchers used these two parameters to measure the interactions between the human CNS and muscles during balance tests. Eight participants were asked to stand on a randomly moving platform, using only their hips and ankles to maintain balance, with electrodes attached to their major leg and .

Both indices were found to successfully characterize the muscle synergy associated with balance skill. "Participants with strong balancing ability showed high SSI levels," notes Alnajjar, "implying that their CNSs were aware of the best muscle synergy for responding to balance disturbances. Participants with low balancing ability had low SSI levels. Also, good balancers used tightly coordinated muscles, resulting in smoother movements."

In each case, the CNS appeared to search for a narrow muscle-synergy space of stable neural commands and coordinated muscle reactions. In a second set of experiments using the lowest scorers from round one, each person completed five more sessions on the platform. The participants showed significant improvement on completion, suggesting that with training, the CNS can narrow its muscle-synergy space and thus improve coordination.

Alnajjar hopes that an advanced version of these indices could be used to develop therapies for post-stroke motor function recovery as a means of creating targeted, effective neuro-rehabilitation systems.

Explore further: How neurons control fine motor behavior of the arm

More information: Alnajjar, F., Wojtara, T., Kimura, H. & Shimoda, S. "Muscle synergy space: Learning model to create an optimal muscle synergy." Frontiers in Computational Neuroscience 7, 136 (2013). DOI: 10.3389/fncom.2013.00136

Related Stories

How neurons control fine motor behavior of the arm

January 31, 2014
Motor commands issued by the brain to activate arm muscles take two different routes. As the research group led by Professor Silvia Arber at the Basel University Biozentrum and the Friedrich Miescher Institute for Biomedical ...

Tweaking energy consumption to combat muscle wasting and obesity

December 16, 2013
Using a new technique to evaluate working muscles in mice, researchers have uncovered physiological mechanisms that could lead to new strategies for combating metabolism-related disorders like muscle wasting and obesity. ...

Key mechanism links exercise to muscle growth

October 24, 2013
Scientists from King's College London have identified a mechanism by which exercise – or lack of it – controls the growth and loss of muscle mass.

Protein illustrates muscle damage

November 11, 2013
Researchers at McMaster University have discovered a protein that is only detectable after muscle damage, and it may serve as a way to measure injury.

Researchers rejuvenate stem cell population from elderly mice, enabling muscle recovery

February 16, 2014
Researchers at the Stanford University School of Medicine have pinpointed why normal aging is accompanied by a diminished ability to regain strength and mobility after muscle injury: Over time, stem cells within muscle tissues ...

High-intensity strength training shows benefit for Parkinson's patients

January 27, 2014
(Medical Xpress)—Researchers at the University of Alabama at Birmingham say that high-intensity strength training produced significant improvements in quality of life, mood and motor function in older patients with Parkinson's ...

Recommended for you

Molecular hitchhiker on human protein signals tumors to self-destruct

July 24, 2017
Powerful molecules can hitch rides on a plentiful human protein and signal tumors to self-destruct, a team of Vanderbilt University engineers found.

Researchers develop new method to generate human antibodies

July 24, 2017
An international team of scientists has developed a method to rapidly produce specific human antibodies in the laboratory. The technique, which will be described in a paper to be published July 24 in The Journal of Experimental ...

New vaccine production could improve flu shot accuracy

July 24, 2017
A new way of producing the seasonal flu vaccine could speed up the process and provide better protection against infection.

A sodium surprise: Engineers find unexpected result during cardiac research

July 20, 2017
Irregular heartbeat—or arrhythmia—can have sudden and often fatal consequences. A biomedical engineering team at Washington University in St. Louis examining molecular behavior in cardiac tissue recently made a surprising ...

Want to win at sports? Take a cue from these mighty mice

July 20, 2017
As student athletes hit training fields this summer to gain the competitive edge, a new study shows how the experiences of a tiny mouse can put them on the path to winning.

'Smart' robot technology could give stroke rehab a boost

July 19, 2017
Scientists say they have developed a "smart" robotic harness that might make it easier for people to learn to walk again after a stroke or spinal cord injury.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.