Exercising muscles in one wrist might help preserve strength in the other, according to a study published last month in the Journal of Applied Physiology, Gretchen Reynolds writes for the New York Times.
Previous studies have found that when a person exercises a muscle on one side of the body, the same muscle on the other side often contracts, Reynolds reports. However, previous studies, for the most part, did not entail completely immobilizing a limb or focus on specific muscles.
For the new study, researchers from the University of Saskatchewan in Canada gathered 16 right-handed male and female college students and measured the dimensions of two sets of muscles in their wrists: the flexors and the extensors. The researchers also tested each participant's wrist strength with a weight machine.
The researchers then covered each student's left forearm and wrist with a hard cast to immobilize it and attached small sensors above the flexors to measure any muscle contractions. The researchers asked half of the participants to begin an exercise plan specifically for their wrists, using a small weight machine to contract their flexors. The other half of the participants were asked to go about their lives normally, avoid exercise, and ignore the cast as much as they could.
After a month, the participants had their casts removed and their wrists measured.
The researchers found that group who had exercised their right wrists' flexor muscles maintained almost all of the original size and strength of the muscles on their left hand.
By contrast, the group who had not exercised their right wrist showed noticeable atrophy on their left wrist and lost about 3% of its mass. The researchers also found that the right flexors of the participants who didn't exercise their left were about 20% weaker than when the studied started.
However, the findings are specific to the flexor muscles. The flexor muscle exercises did little to preserve muscles participants' extensor muscles.
As for possible explanations for the findings, Jonathan Farthing, an associate professor of kinesiology at the University of Saskatchewan who conducted the study with a graduate student and other colleagues, said that he believes changes in the nervous system during exercise on one side might reach and influence the same body part on the other side. He also said that it's possible a number of different biochemical substances could be released by the muscles that could make their way to the contralateral muscles. How these substances would know to target a specific muscle, however, "is a mystery," said Farthing (Reynolds, New York Times, 5/16).
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