Should I workout on the first day of my period? What the research says

Should I workout on the first day of my period? If you feel fine, yes. The best research we have finds that performance in the early part of your cycle is, at most, trivially lower than at other times, and the evidence behind even that is mostly low quality. What actually decides day one is how you feel: cramps, fatigue, a bad night's sleep. Those are real, and they're a reason to adjust the session, not to cancel the month.

Below: what the research says about training on your period, why symptoms matter more than the calendar, what the evidence says about exercise and period pain, and a simple way to decide what to do on the day. Whether you plan it yourself or use an app that does the programming for you, the decision rules are the same.

This post zooms in on one question from the hub guide on how to workout with menstruation. The hub covers the whole cycle; this one covers day one.

One ground rule first: this is about training, not medicine. If your periods are very heavy, painful enough to stop you functioning, irregular, or have stopped, see a doctor. That's not a programming question.

Should I workout on the first day of my period? The short answer

Yes, if you want to and you feel up to it. Nothing in the research reviewed below says women need to stop training during a normal period. The better question is whether to change today's session, and the honest answer is: sometimes, a little, based on symptoms rather than a date.

A sensible plan already has room for that. If your week has hard days, easy days and planned lighter weeks, a rough day one means swapping two sessions, not rewriting the program. A training plan built for women with running and lifting in the same week is one way to get that structure; any well-built plan with some flexibility will do.

What the research says about training on your period

Day one of your period is the start of what researchers call the early follicular phase. Both estrogen and progesterone are low, from the start of bleeding to about day 5 (Elliott-Sale et al., 2021). The full picture of menstrual cycle phases and hormones is its own post. Here's what matters for training.

Performance: a possible trivial dip

The biggest review so far, a 2020 meta-analysis of 78 studies by McNulty and colleagues, found exercise performance might be trivially reduced in the early follicular phase compared with all other phases. That applied to both endurance and strength outcomes. The authors rated the quality of evidence as mostly low, found large variation between studies, and concluded general guidelines can't be formed. Their recommendation: a personalized approach based on your own response.

"Trivially" is their word, not ours.

Strength: no reliable effect

A 2023 umbrella review by Colenso-Semple and colleagues looked across the published reviews on strength and resistance training. It found highly variable findings and poor, inconsistent methods for confirming cycle phase. Its conclusion was that it's premature to say short-term hormone fluctuations appreciably affect acute strength performance or longer-term strength and muscle gains.

So lifting heavy on day one is fine if you feel good. There's no evidence-based reason to cap your weights because of the date.

Effort: the session doesn't feel harder on average

A 2024 meta-analysis of perceived exertion during aerobic exercise pooled 17 studies with 160 women and found cycle phase did not impact rating of perceived exertion. That's a small evidence base, and the authors still suggest paying attention session by session. But on average, a steady run on day one didn't feel harder than the same run at other points in the cycle.

The catch

All of this is about averages. Group results can hide women who feel noticeably worse on their period and women who feel nothing at all. That's why every major review keeps landing on the same advice: track your own pattern.

Symptoms matter more than the date

For most women, the issue on day one isn't a hormone-driven drop in strength. It's symptoms.

In a 2021 survey of 6,812 exercising women not using combined hormonal contraception, the most common cycle symptoms were mood changes or anxiety (90.6%), tiredness or fatigue (86.2%), stomach cramps (84.2%) and breast pain or tenderness (83.1%). More frequent symptoms were associated with a greater likelihood of missing or changing training and missing competitions.

Those are symptoms across the whole cycle, not only during bleeding, but the point stands: when day one feels bad, it's usually because of something you can actually notice. Cramps, fatigue, poor sleep or low mood are reasons to adjust a session, the same way a cold or a rough night would be.

Does exercise help period cramps?

Possibly, but read the fine print.

A 2019 Cochrane review of 12 trials and 854 women with moderate-to-severe period pain found that exercise may have a large effect on reducing menstrual pain intensity compared with no exercise. The evidence was rated low quality. The studies used about 45 to 60 minutes of exercise three or more times a week, regularly across the month, and some asked women not to exercise during their period. None of them used resistance training.

So that's evidence about regular exercise over weeks, not proof that one workout on day one will fix today's cramps. Some women find gentle movement helps on the day; others want the sofa. Both are fine. And if your period pain is severe, getting worse, or not manageable, that's a question for a doctor, not for a training plan.

How to decide what to do on day one

Use symptoms, not the calendar. A simple rule set:

Lifting on your period

If you feel good, lift as planned. If you don't, keep the movements and cut the load or the number of hard sets. You keep the habit and lose nothing.

One scheduling rule still applies whatever day of your cycle it is: don't put a heavy legs session the day before intervals or your long run. If you move the heavy session, move it to a hard-run day (run first, lift later) or an easy day.

Running on your period

Easy runs are the simplest session to keep on a rough day. Run by effort: if it feels harder than usual, slow down. Easy is still easy. If you have intervals scheduled and you feel bad, swap them with an easy run later in the week.

Race or test day on your period

You can't always choose when your period lands. If there's a chance it falls on a race, a Hyrox, or a test, practice your kit, fueling and warm-up on a period day in training, so race day isn't the first time.

What about heart rate and HRV on day one?

If you track your numbers, day one is often a good day on paper. In a study of 91 women wearing wrist sensors during sleep, sleeping pulse rate was lower in the menstrual phase than in the fertile window or the mid-luteal phase: 3.8 beats per minute lower on average than mid-luteal. HRV tends to be lower in the premenstrual days than during your period (Schmalenberger et al., 2019), but the everyday shift is small. In a large app dataset, morning RMSSD changed by about 3.2% between the follicular and luteal phases (Altini & Plews, 2021).

So your watch may say you're ready while your cramps say otherwise. Believe the cramps. And compare your readings with the same point in previous cycles, not with last week. What a normal hrv for women looks like depends mostly on your own baseline.

The bigger picture

Your period is one factor among many, and usually not the biggest. Training consistency, sleep, total stress and eating enough to fuel your training all matter more for most women than which day of the cycle a session lands on.

It's also worth keeping cycle questions separate from broader questions about women's physiology. Whether you do women have more endurance than men is a different research question, and so is where you sit on a chart of VO2 max for women. Neither changes the day-one advice: train if you feel fine, adjust if you don't, and track your own pattern.

A low-effort way to track it:

1. ›Log day one of your period each cycle.
2. ›Rate each session quickly: effort (RPE 1–10), how you felt, any symptoms.
3. ›Review after three or four cycles. If day one or two is always rough, plan easier sessions there. If nothing shows up, carry on.

How exrsz handles this

exrsz builds a periodized plan from your goal, schedule, level and equipment, with running and lifting balanced in one plan. It adapts each week to how you actually trained and reshuffles missed sessions, so swapping a session on a rough day doesn't knock the whole week over. It doesn't give medical advice.

FAQ

Is it bad to work out on the first day of your period?

No. A 2020 meta-analysis found performance might be only trivially reduced in the early follicular phase, from mostly low-quality evidence. If you feel fine, train; if symptoms make it rough, swap in something easier.

Does working out help period cramps?

Regular exercise may help, on low-quality evidence. A 2019 Cochrane review found exercise done about three times a week across the month may reduce menstrual pain intensity. Severe or worsening pain is a reason to see a doctor.

Can I lift heavy on my period?

Yes, if you feel up to it. A 2023 umbrella review concluded it's premature to say cycle phase appreciably affects strength performance or gains.

Is it OK to run on your period?

Yes. A 2024 meta-analysis found cycle phase didn't impact perceived exertion during aerobic exercise. Run by effort, and swap a hard session for an easy one if you feel rough.

Why do I feel weaker on my period?

Usually symptoms like fatigue, cramps or poor sleep rather than a big change in strength. In a survey of 6,812 exercising women, tiredness or fatigue was reported by 86.2% and stomach cramps by 84.2%.