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What Happens to Our Muscles When We Exercise? | The Evidence Exercise | Episode 6

What Happens to Our Muscles When We Exercise? | The Evidence Exercise | Episode 6

Welcome back to the evidence exercise. In our last video we talked about how taking part in regular muscle-strengthening activity, as recommended by the NHS PA guidelines, can contribute to the health of our bones. In this video, we are going to talk about the other part of our body that is majorly influenced by this kind of exercise and that is our muscles.
Obviously, this is closely related to the previous video, as we have already mentioned, the bones and the muscles work together to move objects (muscle-strengthening activity) so therefore, they share the consequences of that activity.

Why is muscle-strengthening activity so important, and why is it recommended by the NHS?

  • So we have already talked about reasons why the NHS recommend this activity due to the scientific evidence that shows it can help keep bones stronger, but does it have any beneficial effects on our muscles?
  • Many types of muscle strengthening activity can cause muscles to grow and become stronger, coupled with a proper diet that is, but that is not really what we will discuss in any great length in this video.

The benefits of muscle strengthening activity on maintaining a healthy weight

  • When we eat a balanced diet and take part in regular strength training, many people, not all (men more than women due to testosterone levels and greater initial muscle mass) may see increases in our overall lean muscle mass (that is muscle tissue that is low in fat) however, women are also capable of adding to their lean muscle mass (Avila et al., 2010).
  • Increasing the amount of muscle we have can actually be beneficial for burning excess calories which would otherwise be stored by the body as fat- in other words, having more muscle mass= having a higher basal metabolic rate, therefore your body will burn more calories even when at rest, thus meaning fat stores will be depleted (Dolezal and Potteiger, 1998, Campbell et al., 1994) (IF you eat a healthy balanced diet, which we will talk more about in other videos)
  • The basal metabolic rate basically describes the minimum amount of energy required by your body in order to keep it functioning properly. Basically, it is the amount of energy your body expends while at rest.
  • Because Muscle cells require more energy than fat cells, having more muscle cells= higher basal metabolic rate (in most cases) other things affect it such as age, genetics gender etc.
  • Some scientific studies have also shown that people who take part in regular muscle strengthening activity have lower cholesterol levels than those who don’t, and can also reduce their cholesterol levels by taking part in regular Muscle Strengthening Activity. (Remember our video on exercise and the heart? Well remember how dangerous cholesterol build-up was? Well that means strength exercise is also good for your heart and arteries too).

Who benefits most from muscle-strengthening activity?

  • As we said in the last video-everyone will benefit from taking part in appropriate levels of muscle-strengthening activity in line with the NHS guidelines.
  • Of course, again as we went over in the previous video, Muscle Strengthening Activity is of particular importance to women and older adults due to the added risks of developing osteoporosis (if you haven’t seen our previous video on skeletal health and exercise, check it out here). However, the added effects of certain types of Muscle Strengthening Activity on the muscles, and more specifically the way our muscles and our brain interact with each other, makes regular Muscle Strengthening Activity very important for anyone who is at increased risk of suffering serious injuries such as fractures due to falling-such as the elderly (both men and women).
  • So now we will explain exactly what happens within our muscles and nervous system when we take part in regular muscle strengthening activity (MSA), and just as importantly what happens when we don’t.

What happens to our muscles when we do MSA such as lifting weights?

  • To understand this, let’s think first in simple terms, how our brain controls our muscles.
  • Every muscle in our body is connected to our brain through the central nervous system, which runs from the brain, all the way through our spinal cord and branches out through openings in our spinal bones, the vertebras and then branch off further into nerves which connect directly into the muscles-which are called motor units. (have a look at our video to see a simplified diagram of this).
  • When we want to move, the brain sends an electrical impulse along these pathways/nerves to the muscle, basically giving it commands, and we get movement.
  • However, there are millions and millions of these nerves and pathways, and the brain gets used to the patterns we use on a daily basis and will recruit or use the nerves which are readily available or most used to do certain tasks, while the ones we hardly ever use, will be in a kind of “switched off” state, or the patterns in which the brain uses to make a muscle move may not be as efficient as they could be.
  • This principle applies to other movements in life also, and to MSA. A common thing to happen when people start to go to the gym for example with the intention to get stronger, is that in the first few weeks, they will see huge improvements in the amount of weight they can lift, but will not really see the size of their muscles change any great deal. Then as they continue to train for longer periods, the progress and gains decrease.
  • This is because in those first few weeks, the neural pathways between the brain and the muscle that were not being used to their full potential, have now been re-activated and are at the brain’s disposal if it needs to use the muscle. Now if the person then gives up and stops training, these pathways will gradually de-activate again and the brain will revert back to only using the nerves that it needs to in order to perform the every-day tasks just like before, and the person will lose that strength. But they can always get it back again. The more motor units we have at our disposal, the more relative strength a muscle will have (it also depends on the types of muscle fibres being developed, but that is something that is more complicated and can be discussed in another video series).
  • This is one reason why regular MSA is important and can benefit us, as in order to see the full benefit of the activity (i.e. stronger muscles, better balance, higher metabolism etc.) we have to be able to maintain this level of activity, or we will lose the benefits.

But what does this mean for our health?

  • Well, just as we lose bone mass naturally as we age, we also naturally lose muscle mass too. This means that we will gradually become weaker and weaker as we age, and will lose all the benefits that come with having increased muscle mass such as strength, balance and a higher metabolic rate.
  • Taking part in regular MSA will reduce the rate at which loss of muscle mass happens, and can also reverse it, and cause the development of more muscle mass (coupled with genetics, a good diet and intensity of training).
  • But for at risk populations such as the elderly, who may already have weaker bones and be at risk of fractures, MSA can not only make their bones stronger, but by training the brain to use more of the muscle that is already available to it, it can make every-day tasks such as walking, climbing stairs, lifting grandchildren etc. that big bit easier and less dangerous (Liu and Latham, 2009).
  • So we are not saying that everyone should become a bodybuilder-far from it, but there are plenty of exercises and activates that constitute muscle –strengthening activity that don’t involve the gym, and it’s important to remember that what constitutes MSA will differ for different ages and abilities. For some such as elderly people who maybe have not taken part in a lot of MSA for a long time, simple bodyweight exercises such as tai-chi are sufficient to create these benefits (Wolfson et al., 1996), while others, usually younger people will notice more benefit from lifting free-weights in a gym.
  • Numerous studies have found that regular MSA or resistance training has improved elderly participants balance, reduced the amount of falls they have and increased their feelings of confidence and independence, as they feel safer walking around and going about their daily business without worrying about falling (Hunter et al., 2004).
  • Make sure you consult a medical professional if you are not sure about what type of MSA is suitable for you, especially if you have a pre-existing medical condition. The good news is there is an activity out there to suit just about anyone, so have a go and see the benefits!

Thanks for watching!
AVILA, J. J., GUTIERRES, J. A., SHEEHY, M. E., LOFGREN, I. E. & DELMONICO, M. J. 2010. Effect of moderate intensity resistance training during weight loss on body composition and physical performance in overweight older adults. European journal of applied physiology, 109, 517-525.
CAMPBELL, W. W., CRIM, M. C., YOUNG, V. R. & EVANS, W. J. 1994. Increased energy requirements and changes in body composition with resistance training in older adults. The American journal of clinical nutrition, 60, 167-175.
DOLEZAL, B. A. & POTTEIGER, J. A. 1998. Concurrent resistance and endurance training influence basal metabolic rate in nondieting individuals. Journal of applied physiology, 85, 695-700.
HUNTER, G. R., MCCARTHY, J. P. & BAMMAN, M. M. 2004. Effects of resistance training on older adults. Sports medicine, 34, 329-348.
LIU, C. J. & LATHAM, N. K. 2009. Progressive resistance strength training for improving physical function in older adults. The Cochrane Library.
WOLFSON, L., WHIPPLE, R., DERBY, C., JUDGE, J., KING, M., AMERMAN, P., SCHMIDT, J. & SMYERS, D. 1996. Balance and strength training in older adults: intervention gains and Tai Chi maintenance. Journal of the American Geriatrics Society, 44, 498-506.
“The Evidence Exercise” is a nine-part series focusing on the research and evidence for including physical activity in our lives.
You can watch the series here on the SCPHRP website or subscribe to the SCPHRP YouTube channel to be alerted when new videos go up. Be sure to follow us on Instagram, Facebook or Twitter for behind the scenes photos and information.
Made with funding from The University of Edinburgh’s ‘Innovation Initiative Grant’.



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