Sometimes it feels as if your body is trying to whisper something to you — or perhaps shout it — but it’s not always easy to listen before it’s too late. I’d like to share a recent experience, and at the same time highlight a concept many people with fibromyalgia recognize, yet one that doesn’t always get the attention it deserves: PEM — post-exertional malaise — also known as activity-induced symptom worsening.
A completely ordinary weekend?
Last weekend I was on a girls’ trip. There was chatting, laughter, a couple of glasses of wine, some unhealthy food, lots of noise and plenty of sensory impressions — all in all, a fantastic weekend. On the surface, it probably looked like any other weekend for many people.
But for me, and for many others with fibromyalgia, experiences like these often come with a price — a price that isn’t paid immediately, but creeps in during the days that follow.
The Monday after, I felt it in my whole body. Not necessarily as pain right away, but as a deep exhaustion. Not only physical, but mental too. And my Garmin watch confirmed what my body already knew: my HRV status had been low all week, far outside my normal range. It didn’t climb back up until Sunday — and even then, only barely into “imbalanced.” My BodyBattery stayed low and never went above 40, even after nights of what seemed like decent sleep. And sleep quality? More orange stress lines than calming blue ones.
What exactly is PEM?
Post-exertional malaise is described as a worsening of symptoms after physical, mental, or emotional exertion — often with a delayed onset. PEM is most often discussed in relation to ME/CFS, but more and more people report PEM as part of their fibromyalgia experience as well.
Common symptoms include:
• Increased fatigue, pain, and sleep disturbances
• “Brain fog” — difficulty concentrating or remembering
• Worsening of other symptoms, such as digestive issues or headaches
• Reduced recovery — the body simply doesn’t bounce back the way it used to
What makes PEM so challenging is that it isn’t necessarily triggered by exercise or heavy physical exertion. It can just as easily be caused by a social weekend, a demanding meeting, or emotional stress. That makes it hard to predict — and even harder to explain to others.
“But you looked so energetic this weekend?”
Yes — and maybe I did. But my body had a bill to send, and it arrived on Monday.
How do you know it’s PEM — and not just “a bad week”?
It’s not always easy to tell the difference. For me, things became clearer when I started tracking my body’s signals more systematically. I use my Garmin to monitor HRV, BodyBattery, sleep, and stress levels. It’s not a perfect science, but it gives me insight.
When HRV stays low for an entire week, when BodyBattery doesn’t rise, and when stress levels remain high even while I “rest” — that’s when I know it’s more than random fluctuations.
And then, of course, there’s the body itself. When it feels like I’m “stuck in place,” no matter how much I rest. When my thoughts slow down, pains become heavier and more diffuse, and the sense of being “completely drained” just doesn’t lift.
What can we do?
There are unfortunately no miracle cures for PEM. But there are strategies — and perhaps a kind of understanding, both from ourselves and from those around us. Here are a few reflections:
• Plan your recovery: After social activities or other strains, schedule downtime. Don’t wait for your body to demand it.
• Use your data: If you have tools that measure HRV or stress, use them as support. They can validate what you feel — and help you set boundaries.
• Dare to say no — or “maybe.” It’s okay not to know how your body will react.
• Talk about it: PEM is still unfamiliar to many. The more openly we discuss it, the easier it becomes for both patients and loved ones to understand and support.
A small hope
I hope this text resonates with some of you — and maybe offers a bit of comfort if you recognize these patterns in your own body. You are not alone. And it is not “just you” being overly sensitive or weak. These are real, physiological reactions to exertion that might seem harmless to others.
At Helfi, we’re working to develop digital tools that help people understand and manage their health on their own terms. Not to “fix” us — but to help us find acceptance, control, and balance in a demanding everyday life.
Sources:
• NHI.no – Fibromyalgia
• Norwegian ME Association on PEM
• UpToDate– Clinical manifestations and diagnosis of fibromyalgia(demands access)
