Midlife Reset Series, Part 1
Introduction
Distinct changes start happening to our bodies in our forties, and then again in our fifties and beyond. I wake up with “bed injuries.” I’m sore for two days after going out dancing. And I’ll be honest, I haven’t fully embraced aging. Some days, it just sucks.
Midlife is a major transition. I always take a moment to reflect, whenever I arrive at a new decade. Suddenly, we’re the experienced ones at work, and we’re the caretakers for our families. We have more responsibilities, and to make matters worse, without any warning, we are not as strong, perky or energetic. We can be doing more of the same exercise, and sadly, achieve less.
That’s why I created The Midlife Reset Series — a trilogy of articles designed to explain what’s happening in the body during midlife.
We’ll start by breaking down what muscle actually does beyond moving your skeleton. Next, we’ll explore why exercise starts to feel different after 40. Finally, we’ll end with a minimalist, effective workout approach, since, let’s face it, most of us are busy humans.
Muscle: More Than Strength
In medical school, I did not learn about the importance of muscle in controlling many organ systems of our bodies.
Muscle is not just tissue that helps you move, lift things, or look fit. Skeletal muscle also acts like an endocrine organ, meaning it plays a role in hormone signaling. Hormones are messengers, and when muscle contracts, it releases signaling molecules called myokines.
These myokines travel through the bloodstream to communicate with the liver, fat tissue, the brain, and the immune system. Effectively, your muscles are sending out the orders that regulate your blood sugar, fat breakdown, and inflammation. It is a massive physiological job description that most of us completely ignore.
In 2020, a group of endocrinologists highlighted that muscle signaling also affects bone, the pancreas, and the immune system. They suggested that myokines may help protect against age-related diseases.
Different types of exercise trigger different myokine responses. Strength training and endurance exercise do not send the same signals. These muscle-derived messages help explain many of the benefits we associate with exercise, including better metabolism and lower inflammation.
This is where midlife changes become apparent. As metabolism and internal signaling begin to shift, the body needs a clearer message from exercise. That means the workouts that worked for us before, may no longer be the ones that serve us best now.
The Cost of Losing Muscle
So what happens when muscle activity drops?
Some researchers have suggested something striking: physical inactivity itself can be thought of as a disease state. It suggests that spending much of the day sitting and not moving is linked to a higher risk of many chronic diseases. This idea was described by Dr. Bente Pedersen, who showed that low muscle activity is strongly associated with conditions like diabetes, heart disease, and metabolic syndrome.
When muscles are inactive, they stop releasing protective signals called myokines. Without these signals, inflammation rises and the body becomes less sensitive to insulin. Over time, this increases the risk of metabolic disease, including type 2 diabetes. Inactive muscle also changes how the body handles blood sugar and fat, making it harder to keep levels stable.
Muscle also communicates directly with fat tissue. When muscle activity drops, fat tissue releases more inflammatory signals into the bloodstream. This leads to low-grade, chronic inflammation, which plays a role in heart disease, diabetes, and other age-related conditions. Once I understood this, it made sense why exercise affects so much more than strength, including metabolism and inflammation.
The takeaway point here is that losing muscle doesn’t just affect strength or appearance. It changes how the body works on the inside. Losing muscle can affect memory, mood and resilience to chronic disease.
This helps explain why staying physically active supports both physical and mental health as we age.
Why This Matters in Midlife
As a clinician, I see how the muscle is like a communication system, especially when patients lose muscle. When this happens, patients will complain not only about mobility issues, but issues with mood and memory. They are confused as to why many things change at once.
Once you understand what muscle really does, the other changes in your body start making sense.
In the next article in The Midlife Reset Series, we’ll talk about how midlife actually affects your muscles, bones and tendons, and also touch upon hormones, so that you have a solid understanding of your baseline. I will end the trilogy with a minimalist workout regimen, since, personally, I like optimizing everything.
References
Pedersen BK, Febbraio MA (2012)
https://pubmed.ncbi.nlm.nih.gov/22473333/
Pedersen BK (2009)
https://pubmed.ncbi.nlm.nih.gov/19752112/
Hoffmann C, Weigert C (2017)
https://pubmed.ncbi.nlm.nih.gov/28389517/
Severinsen MCK, Pedersen BK (2020)
https://pubmed.ncbi.nlm.nih.gov/32393961/
Siparsky PN et al. (2014)
https://pubmed.ncbi.nlm.nih.gov/24427440/
Louis J et al. (2009)
https://pubmed.ncbi.nlm.nih.gov/19685414/
Frontera WR et al. (2012)
https://pubmed.ncbi.nlm.nih.gov/22985613/
Hunter SK et al. (2016)
https://pubmed.ncbi.nlm.nih.gov/26660447/
Daly RM et al. (2013)
https://pmc.ncbi.nlm.nih.gov/articles/PMC6367240/
Gaps to Acknowledge
Even strong science has limits. Here are important gaps to keep in mind when reading this research:
- Much myokine research comes from lab or animal studies, which don’t always translate perfectly to real-life humans.
- Human exercise studies are often short-term, so long-term effects are often inferred rather than directly measured.
- Individual myokines are still being mapped, and scientists are still learning how they interact.
- Strength training and endurance exercise send different signals, and the ideal balance is still being studied.
- Sex-specific data are limited, especially for perimenopause and menopause.
- Many studies focus on adults over 60, even though changes often begin earlier.
- “Masters athlete” studies may not reflect everyday midlife adults.
- Mechanistic studies often involve small sample sizes.
- Modern factors like chronic stress, poor sleep, sedentary work, and screen-heavy lifestyles are underrepresented.