How Lifting Weights Strengthens Your Nervous System

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How Lifting Weights Strengthens Your Nervous System

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Lifting weights at the gym might create bigger muscles but it may also hold the secret to better, more effective rehabilitation for the ill, the elderly and the disabled.

Going to the gym and lifting weights is not only good for building muscles. It is also beneficial in helping to strengthen the nervous system, new research shows.

Gym junkies have long lamented that they seem to get no material benefit from sweating it out lifting weights and that it takes years to get the bulging results they are after.

But, according to researchers from the United kingdom’s Newcastle University and University College London (UCL), some of the most spectacular benefits of weight lifting and resistance training are actually going on underneath the skin, deep in the body’s nervous system, which means that weight-lifting may provide extraordinary benefits in rehabilitating the ill, the disabled and the elderly.

For example, the bodily systems that young healthy weightlifters use to strengthen their muscles are essentially the same systems that a stroke victim might use to rehabilitate and strengthen a hand-rendered weak by a catastrophic stroke.

Although many scientists have theorised that this may be the case, the research undertaken by a joint team from Newcastle University and UCL, and published in the world-renowned Journal of Neuroscience shows a remarkable improvement in neurological stimulation when trained monkeys pulled on weights each day during a three-month period. The monkeys completed a total of 50 trials with weights progressively increased. The final weight was 6kg, close to the animal’s body weight.

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The brain sends movement signals to the body via two distinct neural pathways originating in the spinal cord. The first is known as the corticospinal tract (CST). The second is known as the reticulospinal tract (RST). Scientists believe the CST is the dominant movement pathway, with RST controlling posture.

However, previous research has shown that the CST does not change during strength training, which logically means that increased strength must originate from the RST, which is considered the older, more primitive, and evolutionary pathway.

Professor Stuart Baker from Newcastle University and Dr Isabelle Glover from UCL trained two female macaque monkeys to pull a weighted handle using one arm, with the weight gradually increasing over 12 weeks. Each day, the scientists stimulated the motor cortex and the two motor tracts, measuring the resulting electrical activity in the arm muscles. 

During training, the electrical response from stimulating the cortex and RST increased — a sign of strengthened signalling. Significantly, these changes persisted in the monkeys during a two-week layoff period without weight training.

After training the monkeys for a further three months, the researchers examined the monkeys under anaesthetic and found that stimulating the RST had provoked a greater response in the side of the spinal cord connected to the trained arm.

They found outputs from the RST became more powerful during weight training and could be the driving force behind increases in strength.

Professor Baker explains: “We know that movement is controlled by different pathways. In primates, the major pathway forms a direct line from the cerebral cortex to the spinal cord and sends instructions for fine movements like threading a needle or playing the piano. A second pathway takes a more circuitous route via the brainstem and seems to be more involved in gross movements like making a fist or walking. 

“It is known that when people start working out at the gym, they initially get stronger by increasing connections in the nervous system, not by growing bigger muscles, but the details of which pathways change wasn’t clear. We showed that the more indirect pathway seemed to be responsible.

“This is important since we’ve shown in the past that this pathway also helps people recover after a stroke. Improving the function of a hand-rendered weak by a stroke might be using the same mechanisms as strength-training in a healthy young bodybuilder.”

Dr Isabel Glover at UCL added: “We found significant increases in the strength of the evolutionary old pathway and no change in the main pathway. Therefore, although the main pathway is typically associated with our most sophisticated or complex movements, the evolutionary old pathway appears to be the driving force behind strength. These results are not just relevant to bodybuilders pushing for a new personal best. If we understand the neural mechanisms of strength then we can start to think about how to help individuals suffering from a loss of strength, such as following a stroke.”

It is well-known from other studies that strength training benefits patients suffering from emphysema and cardiovascular diseases. A new study from the Aarhus University in Denmark also indicates that strength-training can be effective for patients suffering cirrhosis, a disease that is particularly aggressive towards the body’s muscles.

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