#80 - Epigenetics of exercise adaptation and "muscle memory" with Dr Kevin Murach
Feb 14, 2024
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Dr Kevin Murach, an expert on muscle growth and adaptation to exercise training, discusses the concept of muscle memory and its relationship with epigenetics. The podcast explores studies on mice models, exploring endurance and strength effects, as well as the mechanisms of muscle memory such as epigenetics and microRNA. The importance of nuclei in muscle fibers for muscle growth and adaptation is also discussed.
Muscle memory is a phenomenon where muscles adapt faster when retrained after a period of detraining, suggesting long-term changes happening at the cellular level.
The use of a progressive weighted wheel running model in mouse studies allows for the investigation of muscle memory and the effects of training, detraining, and retraining.
Hind limb muscles, particularly the soleus and plantaris, exhibit different responses to detraining, indicating variations in muscle adaptation and fiber type transition.
Epigenetic factors, such as changes in gene expression and microRNA profiles, may play a role in muscle memory and influence adaptive changes in muscle mass and fiber types.
Deep dives
The podcast episode discusses the concept of muscle memory.
The podcast delves into the concept of muscle memory and its implications for exercise training. Muscle memory refers to the phenomenon where muscles adapt faster when retrained after a period of detraining. It is suggested that there are long-term changes happening at the cellular level in the muscle fibers themselves. The evidence for muscle memory is explored and the podcast discusses how it may be regulated, including factors like genetics, epigenetics, and changes in gene expression within the muscles.
A progressive weighted wheel running model is utilized in the research.
The podcast highlights the use of a progressive weighted wheel running model in mouse studies. This model allows for voluntary resistance training in mice, simulating the concept of exercise training. The mice are trained using magnetic weights on the running wheels, resulting in muscle growth and adaptations. The model is effective in studying muscle memory and investigating the effects of training, detraining, and retraining.
The podcast explores the specific muscle groups involved in the research.
The podcast focuses on the hind limb muscles, particularly the soleus and plantaris muscles, which are analyzed in the research. Findings show that the soleus muscle exhibits less detraining than the plantaris muscle, indicating differences in muscle responses and adaptive capabilities. The studies also reveal a fiber type transition towards slower twitch phenotypes in the trained muscles.
Epigenetics and muscle memory are discussed in relation to the research.
The podcast delves into the role of epigenetics in muscle memory. Epigenetics refers to the regulation of gene expression without alterations to the genetic code. The research suggests that epigenetic factors control the turning on and off of genes, determining whether they will be expressed. The podcast explores how epigenetics may be involved in the muscle memory phenomenon, influencing the adaptive changes observed in muscle mass, fiber types, and other cellular processes.
Muscle memory and the role of nuclei in muscle fibers
Muscle cells, unlike most cells in our body, are long cylinders with hundreds of thousands of nuclei, which contain DNA. These nuclei cannot divide or replenish themselves, but stem cells can contribute more nuclei to a muscle fiber to support its growth. Muscle memory is the idea that after training and subsequent detraining, the muscle can regain its previous size and strength faster when retrained. This muscle memory may be related to factors such as the number of nuclei gained during initial training, as well as potential epigenetic changes and microRNA involvement. The specific mechanisms and duration of muscle memory are still being studied, but there is evidence to suggest its existence in both mice and humans. Overall, muscle memory highlights the body's ability to adapt to and remember previous training stimuli.
The influence of age and sex on muscle memory
Studies have shown that muscle memory can occur in individuals of different ages. Older individuals may still experience the enhanced response to retraining, suggesting that the phenomenon of muscle memory can be observed across the lifespan. However, the specific effects of age and sex on muscle memory have not been extensively studied. Additionally, it is important to consider the limitations and differences in experimental design between mouse and human studies when interpreting research findings in this area.
Busting muscle myths: Understanding muscle memory
Muscle memory is not solely related to motor learning or the ability to remember exercise techniques. Instead, it refers to the phenomenon where muscles that have been trained and subsequently detrained can reacquire their previous size and strength faster when retrained. It is not necessary to go to extremes in training intensity to achieve muscle memory, as consistency and proper prescription of exercise are key. While the mechanisms behind muscle memory are still being explored, they may involve factors such as myonuclei gained during initial training, epigenetic changes, and microRNA profiles. It is important to critically evaluate training and exercise information from influencers and understand the limitations of single studies when considering muscle memory.
Potential impact of muscle memory on overall health
While the specific impact of muscle memory on overall health benefits beyond muscle adaptation is not yet fully understood, previous research has shown that both strength training and endurance training can have positive effects on health markers such as glucose regulation and blood pressure. The extent to which these health benefits persist after detraining and retraining remains an area of investigation. It is possible that some health benefits may be regained more quickly with retraining due to the phenomenon of muscle memory, but further research is needed to fully understand the relationship between muscle memory and overall health.
Dr Glenn McConell chats with Assistant Professor Kevin Murach who is a rising star from the University of Arkansas, USA. Kevin is an expert on muscle, muscle growth, adaptation to exercise training, “muscle memory”, the regulation of muscle growth and muscle memory and the effect of aging etc. Muscle memory definitely seems real (especially in slow muscle fibers). Looks like epigenetics involved more than changes to muscle fibers nuclei. But more work needs to be done, especially in humans. We had a really great chat. I enjoyed it a lot. A very smart chap. Twitter: @KevinMurachPhD 0:00. Introduction and welcome 2:16. How Kevin got into exercise research 6:53. What is “muscle memory”. 9:15. Human evidence of muscle memory 13:58. Mice models to investigate resistance training 19:30. Training, detraining and retraining 20:35. Comparing rodents and human re their different lifespans 22:30. Evidence for muscle memory in mice after ex training 31:05. Mouse model that has both endurance and strength effects 33:25. Voluntary wheel running: matching the training 35:45. 10% greater hypertrophy with retraining 39:25. Mice slow postural muscles didn’t detrain! 44:45. Mechanisms: epigenetics 49:50. Muscle nuclei and exercise training/muscle memory 1:02:00. Muscle memory and epigenetics in the nuclei 1:05:40. MicroRNA and muscle memory 1:07:30. Epigenetics 1:08:35. Exercise training and each bout of exercise 1:11:20. MicroRNA and muscle memory 1:16:20. Balance of protein synthesis and breakdown 1:20:20. Muscle memory: Endurance vs resistance training 1:21:35. Time course of muscle memory 1:23:55. How much training need to get muscle memory 1:25:18. Specificity of ex training muscle memory 1:26:40. Nature and nuture 1:27:25. Dutch famine and epigenetics 1:28:18. Age and muscle memory 1:29:38. Biological sex and muscle memory 1:30:40. Common misconceptions: use it or lose it 1:31:38. Identical twins 1:32:25. Don’t need to go hard or go home. 1:33:05. Research experts vs influencers etc 1:37:15. Takeaway messages 1:39:44. Do health benefits have a memory too? 1:41:45. Outro
Inside Exercise brings to you the who's who of research in exercise metabolism, exercise physiology and exercise’s effects on health. With scientific rigor, these researchers discuss popular exercise topics while providing practical strategies for all. The interviewer, Emeritus Professor Glenn McConell, has an international research profile following 30 years of Exercise Metabolism research experience while at The University of Melbourne, Ball State University, Monash University, the University of Copenhagen and Victoria University. He has published over 120 peer reviewed journal articles and recently edited an Exercise Metabolism eBook written by world experts on 17 different topics (https://link.springer.com/book/10.1007/978-3-030-94305-9). Connect with Inside Exercise and Glenn McConell at: Twitter: @Inside_exercise and @GlennMcConell1 Instagram: insideexercise Facebook: Glenn McConell LinkedIn: Glenn McConell https://www.linkedin.com/in/glenn-mcconell-83475460 ResearchGate: Glenn McConell Email: glenn.mcconell@gmail.com Subscribe to Inside exercise: Spotify: shorturl.at/tyGHL Apple Podcasts: shorturl.at/oFQRU YouTube: https://www.youtube.com/@insideexercise Anchor: https://anchor.fm/insideexercise Google Podcasts: shorturl.at/bfhHI Anchor: https://anchor.fm/insideexercise Podcast Addict: https://podcastaddict.com/podcast/4025218 Not medical advice
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