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Etude sur la mémoire musculaire
Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining
J. C. Bruusgaard, I. B. Johansen, I. M. Egner, Z. A. Rana, and K. Gundersen1
Effects of previous strength training can be long-lived, even after prolonged subsequent inactivity, and retraining is facilitated by a previous training episode. Traditionally, such “muscle memory” has been attributed to neural factors in the absence of any identified local memory mechanism in the muscle tissue. We have used in vivo imaging techniques to study live myonuclei belonging to distinct muscle fibers and observe that new myonuclei are added before any major increase in size during overload. The old and newly acquired nuclei are retained during severe atrophy caused by subsequent denervation lasting for a considerable period of the animal’s lifespan.
The myonuclei seem to be protected from the high apoptotic activity found in inactive muscle tissue.
A hypertrophy episode leading to a lasting elevated number of myonuclei retarded disuse atrophy, and the nuclei could serve as a cell biological substrate for such memory. Because the ability to create myonuclei is impaired in the elderly, individuals may benefit from strength training at an early age, and because anabolic steroids facilitate more myonuclei, nuclear permanency may also have implications for exclusion periods after a doping offense.
L’étude complète :
Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining
Problèmes des suppléments de ginseng
Five out of 11 ginseng supplements recently selected for testing contained less ginseng than expected from their labels or were contaminated with lead and/or pesticides, according to a report from ConsumerLab.com, White Plains, NY.
ConsumerLab.com has reported problems with the quality of ginseng supplements since 2000. Ginseng is a popular herb with U.S. sales last year of $83 million according to Nutrition Business Journal.
“Consumers need to be wary of the quality of ginseng supplements,” said Tod Cooperman, MD, president of ConsumerLab.com. “People should also recognize that there is enormous variation in the amount of ginsenosides—key ginseng compounds—in marketed supplements. We found most products to provide approximately 10 to 40 mg of ginsenosides per day, but some yielded much higher amounts, including one that delivered a whopping 304 mg. We are not aware of human studies with the higher amounts. The effects might certainly differ from one product to another.”
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