What happens to our muscles after exercise?

Analysis: Knowing how muscles respond to exercise helps us understand the changes that lead to improved performance and health

The way our muscles respond to exercise is similar, whether you’re new to exercise, out of shape, or an elite athlete looking to maximize your performance. If you walk, run or participate in a strength training session today, you will be stressing your body in some way and this will initiate a response.

Exercise affects a number of organs within the body by altering our resting state. For example, we see immediate changes such as elevated heart rate and increased blood flow to key areas of the body, including the muscles, brain, and liver, as well as increased metabolism in other tissues. Here, we are going to focus on the impact of exercise on our muscles.

‘Wow, that was hard!’

We’ve all been that soldier after a workout where we’ve pushed our body to or near its limits and said ‘wow! That was hard afterwards. Given the choice, we may have liked to go faster or further, but we just weren’t capable and will likely feel the effects with potential fatigue and soreness as we recover over the next two or three days.

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This marks the early stages of the response in our muscles that will ultimately lead to better exercise. Our muscles are very smart and effectively respond by saying ‘I wasn’t ready for that.’ If you ask me to do it again, I’ll be better prepared next time. What don’t I have ready that I need for the next day?’ Then the muscle is about putting those support systems and infrastructure in place.

Here is an analogy that may explain this better. Equate our current exercise ability or “capacity” in terms of our recent vaccine release schedule, that is, our ability to administer X number of vaccines per week represented as our “vaccine capacity.” Many of you will remember January 2021 when we looked enviously at the UK and lamented our own vaccine launch when we were administering just shy of 1,000 vaccines a week.

That is the equivalent of an unfit or out of shape muscle. That “vaccine capacity” was so low because the infrastructure and support systems were not yet in place, limited by vaccine supply, number of vaccinators, cold storage, vaccination centers, IT, software and other factors. Once we identified each week what was limiting our deployment, we were able to act on it, implement the necessary tools, and ultimately build our capacity to the point where we were deploying 250,000 vaccines per week by the summer of 2021.

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That efficient system is the equivalent of a trained and fit muscle. When our muscle lacks the necessary infrastructure, it also has limited capacity. After just one exercise session, the muscle will build that infrastructure to ultimately improve our exercise capacity. This involves building the machinery in the muscle that allows it to contract and dictate the amount of force it can generate, increasing our supply of accessible energy and the number and efficiency of compartments where this energy is generated. This requires muscle remodeling by breaking down old proteins and making new ones. Exercise acts as the stimulus that initiates these processes.

How do we build muscle capacity?

We house our DNA or genetic library in the core of our muscle. This is a recipe book, so to speak, for the different genes that give us the code for the proteins we need. We make a copy of the codes we need to make new proteins. These copies are known as messenger RNA or mRNA for short.

Research at the University of Limerick shows that this process begins immediately and we see an increase in these gene copies in the muscle, peaking around three hours after a single exercise session. We then ‘translate’ that code to assemble the correct combination of amino acids that are the building blocks of new proteins.

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Each of these new proteins that we generate has a specific function. Some will enhance our ability to produce accessible energy to power exercise, others will enhance our ability to create larger forces. Ultimately, this new infrastructure and support system provided by these new proteins will improve our exercise capacity, making us fitter, faster, taller, and stronger.

Why is this important?

You may be surprised to learn that muscle is the largest organ in the body, making up about 40% of our body mass. Muscle is extremely important to our daily lives and our independence. In fact, the strength and function of our muscles is an indicator not only of our Life expectancy, but also the period of life spent in good Health.

Muscle is also interesting as it is a very metabolically active tissue that is important for our health. For example, muscle acts as a sponge for glucose, or blood sugar, which has implications for metabolic diseases such as Type 2 diabetes. By maintaining the size and health of our muscles through exercise, this helps regulate blood glucose levels after a meal or snack. Even a single exercise session reduces blood glucose spike that we see around meals like breakfast and throughout the day.

Knowing how muscles respond to exercise allows us to understand what changes are occurring that lead to better performance and health. This has implications not only for athletes, but also for the possible prevention and treatment of diseases such as type 2 diabetes, Cancer Y heart disease. If you haven’t already, I suggest you get some exercise and build some new protein in your muscle today. Your muscles will thank you.

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The views expressed herein are those of the author and do not represent or reflect the views of RTÉ

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