The Surprising Fitness Shift Midlife Women Can’t Afford to Ignore

And that includes the experts.

Photo by Rinke Dohmen on Unsplash

At age 49, Alison, an experienced marathoner and triathlete, didn't have the energy to run the way she used to during workouts. Her heart rate climbed, she fatigued easily, and she gained weight.

She also had joint pain and poor recovery.

“I hadn’t anticipated this at all,” she said in this piece in the NY Times. “I thought I would breeze through menopause.”

The story in the August New York Times was the familiar menopause narrative we expect to hear. Blame it on estrogen, cut back on running, and add weightlifting.

Digging into the research has helped me better understand why this happens and what we can do about it. And the answer doesn’t neatly fit the common menopause narrative, which might be why I haven’t found any experts addressing it.

Now that I’m officially in menopause, I’m taking my exercise tolerance more seriously. By exercise tolerance, I mean my body’s ability to adapt to the demands of exercise by delivering oxygen to my muscles and creating energy, or ATP.

Two very intriguing studies have really brought this message to light, along with potential answers. So, let’s get to it.

There’s more to the exercise story

Midlife women repeatedly hear that they need to build muscle and strength. It’s thought that losses in this area cause fatigue during exercise.

Researchers from Brigham Young University wanted to determine the actual cause of decreased exercise tolerance with age. They assessed this by measuring critical power, which is the maximum effort someone can sustain without reaching a point of fatigue.

Twenty healthy, active adults (half women) who had exercised regularly for six months and were free of health problems and medication participated in the small study. There was a young group (age: 24.4±4 years) and older group (age: 63.1±3 years).

They all participated in five days of testing to evaluate their fitness, body composition, and other health-related measures.

The older group showed 32% lower absolute critical power than the young group. Most surprisingly, this gap persisted after accounting for lean mass. In fact, the older group still exhibited 30% lower critical power than the younger group.

So, if it’s not because of muscle loss, what is it?

The investigators concluded that the decline in power was mostly because of reduced blood flow and vascular conductance to the working muscles during exercise. Vascular conductance is a measure of how easily blood flows through the vascular bed.

And the effect was greater in the older women.

The healthy older group showed decreased endothelial function in their resistance vasculature. Endothelial refers to cells that line blood vessels.

Resistance vasculature is just another way to say those small blood vessels needed to reach organs like muscles.

In short, it wasn’t about muscle quantity, but about muscle quality.

Most importantly, the vascular system seemed to play a major role in the difference in exercise tolerance among the young and older groups.

Dorff et al, Experimental Physiology, 2023

Why this matters for midlife women

Exercise tolerance decreases with age in both men and women.

Yet growing research shows this problem affects midlife women to a greater degree than age-matched men, especially postmenopausal women. Researcher Daniel Craighead mentioned this in my interview with him:

pretty consistently if you take a midlife or older man and have them do an exercise training intervention for let’s say three months and you measure their endothelial function before and after that exercise training, they’ll see an improvement in endothelial cell health. When women go through the same exercise intervention, we don’t as consistently see those improvements. For some reason, not all the benefits of aerobic exercise seem to be accrued by women who are postmenopausal.

A 2022 systematic review examining the effects of exercise in postmenopausal women show modest benefits to endothelial function. Sixty-one percent of the studies showed at least one positive measure of endothelial function.

Yet only about half found benefits to both macrovascular and microvascular systems.

Lew et al, Experimental Physiology, 2022

Variability in exercise training, the population studied, and other relevant factors may account for the mixed results.

So, we don’t have a clear picture of this phenomenon.

But we know that lower level of estrogen post menopause plays a key role. So, does hormone therapy work?

READ: Reevaluating menopause’s influence on heart health

What about hormone therapy?

Some researchers hypothesize that estrogen is necessary for women to get the full benefits from aerobic exercise, since it works to increase nitric oxide.

For instance, women athletes who lose their period have lower flow-mediated dilation (FMD) than those who don’t. And it’s restored when periods return.

Yet the effects of hormone therapy on exercise adaptation is controversial, and inconclusive.

And it’s not clear if the benefits of taking hormone therapy continue as women age, as most are short-term studies.

Further research is needed to address the mechanisms driving the interactions between exercise training and HT in postmenopausal women.- Lew et al, Experimental Physiology, 2022

But a new study gets at a tool, that just might help.

The BEESWEET STUDY

I’ve been looking forward to the results of the research into how beetroot juice affects postmenopausal women who exercise.

Quick review. Although the body produces NO, and estrogen and progesterone increase it, diet can also provide it. Supplements that provide a consistent amount of nitrates (400mg) can increase NO, which benefits the vascular system and blood flow. Read more here.

One group of late postmenopausal women ingested two 70ml bottles of nitrate rich beetroot juice (Beet-it Sport) two hours before exercise. They took part in 8-week circuit-based exercise training just over an hour, three times a week.

Researchers compared another group, who did the same exercise without beetroot juice, to the first group.

The beetroot juice plus exercise participants showed greater improvement in the 6-minute walk test—going twice as far as the exercise alone group. Heart rate recovery and VO2 peak showed significantly greater improvement.

The researchers estimated that the changes in VO2 peak were equivalent to undoing about 7.5 years of biological aging.

Of course, we need more studies, but this is a step in the right direction. Yet I’m amazed how virtually no one is talking about it.

The Midlife Fitness Shift

It’s sad to me that the experts in the NY Times article failed to address any of this on the topic of menopause and exercise.

We can lift heavy and ramp up protein until the cows come home, but if we don’t have good blood flow, the quality of our muscles and our already at-risk vascular system suffers.

We’re simply not maximizing the effects of exercise that worked for so long to keep us healthy.

Although more research is needed, pre-exercise beetroot juice looks like a promising approach for middle-aged, especially postmenopausal, women.

I’d love to see studies that look at why some women lose vascular function and others don’t. I’d also like to see the effect of a diet high in nitrates versus taking concentrated beetroot juice.

Could there be an optimal dietary pattern? What about the oral microbiome?

I’ve already started taking beetroot juice before some of my workouts. The problem is, I still get up at the crack of dawn a few times a week and there’s just not enough time.

I’m thinking about shifting at least some of my workouts to later in the morning.

If you decide to try beetroot juice, ensure that you buy beetroot juice tested for nitrates. Both the Beet-it and Super Beets fit this bill.

And do me a favor. The next time an expert or anyone for that matter goes on about protein and lifting heavy, inform them about the fitness shift that has been all but ignored in midlife women—until now.

Send them to this post. (and leave a comment about what you think about this)

The information on this Substack is meant to educate and not replace medical advice. Consult a healthcare provider for you’re own unique medical needs.