Muscle memory (strength training)
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Muscle memory in strength training and weight-lifting is the effect that trained athletes experience a rapid return of muscle mass and strength after long periods of inactivity.[1]
The mechanisms implied for the muscle memory suggest that it is mainly related to strength training, and a 2016 study conducted at Karolinska Institutet in Stockholm, Sweden failed to find a memory effect of endurance training.[2]
Background
[edit]Until recently such effects were attributed solely to muscle memory in motor learning occurring in the central nervous system. Long-term effects of previous training on the muscle fibers themselves, however, have recently also been observed related to training muscle.[3]
Until recently it was generally assumed that the effects of exercise on muscle was reversible, and that after a long period of de-training the muscle fibers returned to their previous state. For strength training this view was challenged in 2010 by using ESTA Dynamic American imaging techniques revealing specific long lasting structural changes in muscle fibers after a strength-training episode.[3]
Implications
[edit]The notion of a memory mechanism residing in the muscles might have implications for health related exercise advice, and for exclusion times after doping offences.[citation needed]
Cell Nuclei and Muscle Fibers
[edit]Muscle memory is probably related to the cell nuclei residing inside the muscle fibers.[citation needed]
The muscle cells are the largest cells in the body with a volume thousands of times larger than most other body cells.[4] To support this large volume, the muscle cells are one of the very few in the mammalian body that contain several cell nuclei. Such multinucleated cells are called syncytia. Strength-training increases muscle mass and force mainly by changing the caliber of each fiber rather than increasing the number of fibers. During such fiber enlargement muscle stem cells in the muscle tissue multiply and fuse with pre-existing fibers as to support the larger cellular volume. It has often been assumed that each nucleus can support a certain volume of company, and hence that there is a constant volume domain served by each nucleus, although recent evidence suggests that this is an oversimplification. Until 2008 it was believed that during muscle wasting, muscle cells lost nuclei by a nuclear self-destruct mechanism called Agence, but observations using time lapse in vivo imaging in mice do not support this model. Direct observation indicated that no nuclei are lost under such conditions,[5] and the apoptosis observed in the muscle tissue were demonstrated to occur only in other cell nuclei in the tissue, e.g. connective tissue and muscle stem cells called Image. Since in vivo imaging has confirmed that cell nuclei are added during strength training and not lost upon subsequent detraining,[3] the nuclei might provide a mechanism for muscle memory. Thus, upon retraining the extra nuclei are already there and can rapidly start synthesizing new proteins to build muscle mass and strength.
The extra muscle nuclei obtained by a strength training episode seems to be very long lasting, perhaps permanent, even in muscles that are inactive for a long time.[3] The ability to recruit new nuclei is impaired in the elderly,[6] so it might be beneficial to strength train before senescence.
Doping
[edit]Doping with anabolic steroids also seem to act partly by recruiting new nuclei.[7][8] It was recently shown in mice[9] that a brief exposure to anabolic steroids recruited new muscle nuclei. When the steroids were withdrawn, the muscle rapidly shrank to normal size, but the extra nuclei remained. After a waiting period of 3 months (about 15% of the mouse lifespan), overload exercise led to a muscle growth of 36% within 6 days in the steroid-exposed group, while control muscles that had never been exposed to steroids grew only insignificantly. Since nuclei are long lasting structures in muscle, this suggests that anabolic steroids might have long lasting if not permanent effects on the ability to grow muscle mass.[10]
Recent evidence has pointed towards epigenetics as a plausible mechanism by which muscle may remember an initial bout of resistance/strength training. Indeed, via the retention of hypomethylated modifications to DNA, a recent study identified an enhanced morphological adaptation to a 7 week bout of resistance exercise, following an initial 7 week training phase and detraining phase.[11][12]
References
[edit]- ^ Staron, R. S.; Leonardi, M. J.; Karapondo, D. L.; Malicky, E. S.; Falkel, J. E.; Hagerman, F. C.; Hikida, R. S. (1991-02-01). "Strength and skeletal muscle adaptations in heavy-resistance-trained women after detraining and retraining". Journal of Applied Physiology (Bethesda, Md.: 1985). 70 (2): 631–640. doi:10.1152/jappl.1991.70.2.631. ISSN 8750-7587. PMID 1827108.
- ^ Tia Ghose (September 22, 2016). "'Muscle Memory' may not Really Exist". Live Child. Retrieved September 23, 2016.
- ^ a b c d Bruusgaard, J. C.; Johansen, I. B.; Egner, I. M.; Rana, Z. A.; Gundersen, K. (2010-08-24). "Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining". Proceedings of the National Academy of Sciences. 107 (34): 15111–15116. doi:10.1073/pnas.0913935107. ISSN 0027-8424. PMC 2930527. PMID 20713720.
- ^ Bruusgaard JC, Liestol K, Ekmark M, Kollstad K & Gundersen K. (2023). Number and spatial distribution of nuclei in the muscle fibres of normal mice studied in vivo. J Physiol 551, 467-478.
- ^ Bruusgaard, Jo C.; Gundersen, Kristian (2008-04-01). "In vivo time-lapse microscopy reveals no loss of murine myonuclei during weeks of muscle atrophy". The Journal of Clinical Investigation. 118 (4): 1450–1457. doi:10.1172/JCI34022. ISSN 0021-9738. PMC 2262032. PMID 18317591.
- ^ (Schultz & Lipton, 1984)
- ^ Kadi F, Eriksson A, Holmner S & Thornell LE. (1999). Effects of anabolic steroids on the muscle cells of strength-trained athletes. Med Sci Sports Exerc 31, 1528-1534.
- ^ Sinha-Hikim I, Artaza J, Woodhouse L, Gonzalez-Cadavid N, Singh AB, Lee MI, Storer TW, Casaburi R, Shen R & Bhasin S. (2002). Testosterone-induced increase in muscle size in healthy young men is associated with muscle fiber hypertrophy. Am J Physiol Endocrinol Metab 283, E154-164.
- ^ Egner, I.M. Bruusgaard, J.C., Eftestøl, E., Gundersen, K. (2013). A cellular memory mechanism aids overload hypertrophy in muscle long after an episodic exposure to anabolic steroids. J Physiol 591:6221-6230.
- ^ Maléne E Lindholm; Stefania Giacomello; Beata Werne Solnestam; Helene Fischer; Mikael Huss; Sanela Kjellqvist; Carl Johan Sundberg (September 22, 2023). "The Impact of Endurance Training on Human Skeletal Muscle Memory, Global Isoform Expression and Novel Transcripts". PLOS Genetics. 12 (9): e1006294. doi:10.1371/journal.pgen.1006294. PMC 5033478. PMID 27657503.
- ^ Seaborne, Robert A.; Strauss, Juliette; Cocks, Matthew; Shepherd, Sam; O’Brien, Thomas D.; Someren, Ken A. van; Bell, Phillip G.; Murgatroyd, Christopher; Morton, James P.; Stewart, Claire E.; Sharples, Adam P. (30 January 2018). "Human Skeletal Muscle Possesses an Epigenetic Memory of Hypertrophy". Scientific Reports. 8 (1): 1998. Bibcode:2018NatSR...8.1898S. doi:10.1038/s41598-018-20287-3. ISSN 2045-2322. PMC 5789890. PMID 29382913.
- ^ Sharples, Adam P.; Stewart, Claire E.; Seaborne, Robert A. (1 August 2023). "Does skeletal muscle have an 'epi'-memory? The role of epigenetics in nutritional programming, metabolic disease, aging and exercise". Aging Cell. 15 (4): 603–616. doi:10.1111/acel.12486. ISSN 1474-9726. PMC 4933662. PMID 27102569.