Exercise, inverted

the year i was most exhausted was the year i trained hardest, and for a long time i could not see that those two facts were holding hands.

This is the third of the Thyroid Letters. The first, the year I did everything right and felt worse, is where the story starts. The second covered the blood tests to ask for, which is the more important of the two. Read that one first if you have not had bloods done.

What I was doing, and why it was the wrong thing to double

When I started feeling flattened, I assumed the tiredness was a discipline problem. So I trained harder. Longer sessions, more of them, on less sleep, with a toddler and a business and a body that had given birth eighteen months earlier.

Every week I felt slightly worse, and every week I read that as confirmation I was not doing enough.

That is a tidy trap, because the cure and the cause look identical from the inside. Ours is the generation told the answer to almost everything is to push.

Hypothyroidism and exercise: what is actually known

This is where wellness writing usually goes wrong, so let me be careful.

Exercise is good for you. That is not in dispute, and it is well evidenced for mood, cardiovascular health, bone density and sleep. Nothing here is an argument for stopping.

What is not settled is the claim I am making about myself: that in a body already running a hormonal deficit, high intensity training acts as another demand on the same stress system, the hypothalamic-pituitary axis, and that a system struggling to regulate does not answer that demand the way a well-regulated one would. Mechanistically plausible. Not proven. There is no large trial establishing that reducing training intensity improves thyroid function.

So take it as one woman's experience plus a plausible mechanism. That is a weaker claim than most of what you will read on this subject, and I would rather give you the weaker true one.

And if your thyroid is untreated or under-treated, no exercise adjustment fixes that. Getting the medication right is the work. This is what you do alongside it, never instead of it.

The inversion, in practice

What changed was not the amount of movement. It was the order.

I had been building the week the way most of us do: intensity at the base, rest as the reward if I had earned it. I turned it upside down. Rest became the base, the thing scheduled first, and intensity became what I added on top when there was something left to add.

• Walking, most days. Unglamorous, and the single change that did the most. Forty minutes, not fast, usually before the heat.
• Strength twice a week, not five times. Heavy enough to be worth doing, short enough to leave the room with something in reserve. I stopped training to failure.
• One genuinely hard session a week, only if the week had gone well. Some weeks there was not one, and that stopped being a moral event.
• Restorative work in the evening, which I had filed under "not real exercise" and which turned out to be what my nervous system was asking for.

The measure I use now is embarrassing in its obviousness. Do I feel better ninety minutes after training than I did before it? If the answer is consistently no, that is information, not weakness.

The sauna and the cold plunge, where I was silly

I added both at exactly the wrong moment. Sauna in the afternoon, cold plunge after, when I was already depleted and sleeping badly.

I was silly. I was reaching for the most demanding thing available because demanding things had always worked before.

Heat and cold both have interesting research behind them and I am not telling you to avoid them. I am telling you they are stressors, which is the entire mechanism by which they are meant to help, and stacking stressors onto a system already failing to cope is not obviously a good idea. Again: plausible reasoning, not established fact. I stopped both for months, brought them back slowly, and they sit fine now.

What none of this replaces

Being a woman is complicated, and we were not given any kind of user's manual. But the manual for this part is short, and it is not the exercise part.

If you are tired in a way sleep does not touch, ask for the bloods. Do not let anyone tell you it is just motherhood or just your forties without testing first. If you are already on thyroid medication, keep taking it exactly as prescribed, and take any question about the dose to the person who prescribed it. Movement is worth adjusting, but never instead of that.

Frequently asked questions

Can exercise make hypothyroidism worse?

There is no good trial evidence that exercise worsens thyroid function, and exercise remains broadly beneficial. What I experienced, and what some women describe, is that high intensity training during under-treatment left them feeling worse rather than better. The proposed mechanism is added load on an already strained stress axis: plausible and unproven. If training consistently leaves you flattened for days, raise it with your doctor.

What is the best exercise for an underactive thyroid?

There is no established best workout for hypothyroidism. What helped me was daily walking, strength work twice a week stopped short of failure, and restorative movement in the evening, with hard sessions kept occasional. The usual adult guidance, a mix of aerobic and resistance work, still applies. The adjustment is to intensity and recovery, not to the type of exercise.

Should I stop exercising if I have Hashimoto's or hypothyroidism?

No. Nothing here is an argument for stopping. Exercise is well evidenced for mood, bone density and cardiovascular health, all of which matter here. The change I made was to the intensity and the ordering of my week, not to whether I moved.

Does cortisol affect thyroid function?

The stress and thyroid systems are connected through the hypothalamic-pituitary axis, and chronic stress influencing thyroid function is considered mechanistically plausible. The human evidence is not strong enough to treat as settled, and be cautious of anyone presenting it as such.

How long did it take you to feel different?

Several months, and it was not dramatic. The medication being correct did the heavy lifting. Inverting the week stopped me undoing that progress every time I felt better and immediately overspent it.

Loves, we really need to take care, let go of many expectations, and get back to the basics. The basics here were walking, sleeping, and being willing to look at the thing I was proudest of and ask what it was costing me.

Part Four is about the minerals, and why the brazil nut advice you have read is very nearly right and then goes one nut too far.

With love from Bali,
Myrah