Menstrual cycle and training

How hormonal phases shape your performance and weight — and, just as importantly, how much they don't. This is the deep-dive behind the Cycle phase context shown in your Trends & Review, alongside your weight and energy data. Cycle tracking is opt-in and stays on your device; when it's on, the app shows which phase a day falls in so you can interpret your weight and appetite — not so it tells you what to do. In the app, tap the (i) on the cycle card to land here.

The cycle and its phases

The menstrual cycle is the roughly monthly hormonal rhythm that prepares the body for a possible pregnancy. It's counted from day 1 = the first day of bleeding. A "textbook" cycle is about 28 days, but the normal range runs roughly 21 to 35 days, and the phases stretch or shrink with it.

The phases, with the caveat that the day numbers below assume a ~28-day cycle:

• Menstruation (bleeding), ~days 1–5 — the shedding of the uterine lining. This overlaps with the start of the follicular phase; it isn't a separate "fifth" phase.
• Follicular phase, ~days 1–13 — from day 1 up to ovulation. So menstruation sits inside the early follicular phase — worth knowing so the overlap doesn't confuse you.
• Ovulation, around mid-cycle — the release of the egg (about day 14 in a ~28-day cycle).
• Luteal phase, ~days 15–28 — from ovulation to the next period.

What this means for the phase label in Strathlon. The phase shown in Trends & Review is an estimate from your dates — most accurate for regular ~28-day cycles, and fuzzier for longer or irregular ones. Use it as a lens, not a stopwatch. If your cycles are long or variable, the label may not line up perfectly with your actual hormones; that's the estimate being approximate, not your body being "wrong." This is also why cyclical water and appetite patterns read most clearly when you compare the same phase across cycles rather than day to day — the same logic behind reading your weight trend over weeks instead of mornings.

The hormone pattern behind everything

Two ovarian hormones do most of the work you'll actually feel. Almost every effect on this page traces back to them:

• Estrogen (estradiol) — rises through the follicular phase and peaks just before ovulation. It then dips, has a smaller second rise in the mid-luteal phase, and falls before the period.
• Progesterone — low in the follicular phase, rises after ovulation, peaks in the mid-luteal phase, then falls sharply just before menstruation. That final progesterone drop is what triggers the period.

One idea ties the rest of the page together: the luteal phase is the high-progesterone half of the cycle (with a raised estrogen:progesterone interplay), and the estrogen peak sits around ovulation. When a later section says "in the luteal phase you may notice X," you can anchor it to that: this is the high-progesterone half.

Water retention and the pre-period scale bump

This is the most reassuring and highest-value section for anyone tracking weight. Many people gain roughly 1–2 kg (about 2–4 lb) of water weight in the days before their period, often with bloating or breast tenderness. It is temporary.

The mechanism — stated carefully

In the luteal phase, progesterone interacts with the mineralocorticoid (aldosterone) system in the kidney. Progesterone competes at the mineralocorticoid receptor; the body responds with a compensatory rise in aldosterone, and aldosterone promotes sodium — and therefore water — reabsorption. The net effect is that the body holds onto a bit more fluid in the high-progesterone luteal phase. When progesterone falls before and at the start of the period, the retained fluid is released.

The honest one-liner is: progesterone rises → the body compensates with higher aldosterone → more sodium and water are held onto. The tidy version you'll see everywhere — "progesterone directly causes water retention" — is an oversimplification and partly backwards, because progesterone's own direct receptor action is mildly the opposite; it's the aldosterone compensation that nets out to retention. The safe way to say it is that the luteal phase is associated with higher aldosterone activity and fluid retention.

Why this matters for the scale

For a weight-tracking app this is the crux: a late-luteal, pre-period scale bump is water, not fat. Gaining 1–2 kg of actual fat in a few days is physiologically implausible on any normal diet — it would take a surplus of thousands of calories a day. The number resolves on its own once the period starts. This is exactly why Strathlon shows cycle phase alongside your weight: so you can read a normal fluid swing for what it is, instead of mistaking it for lost progress or a broken diet. A fair, non-alarming way to hold it: water retention can mask real fat-loss progress on the scale; it doesn't erase it.

Be honest about the range. The 1–2 kg figure is a typical range, not a rule. Some people notice almost nothing; some notice more. Salt intake, heat and training all move body water independently of the cycle too, so the pre-period bump sits on top of everyday fluctuation. For the full picture of why the daily scale is mostly water and food rather than fat, see weight trend.

Appetite and cravings across the cycle

Many people feel hungrier in the luteal phase, often with a stronger pull toward carbohydrate- and fat-rich or sweet foods, most noticeably in the days before the period. This is a real, hormonally driven shift — not a lapse in willpower.

Why it happens

Two established threads:

• Progesterone tends to increase appetite, and losing estrogen's appetite-suppressing effect in the luteal phase adds to it. At the level of the body's hunger and fullness signalling, the luteal shift is associated with less satiety and more hunger drive (research points to changes in the ghrelin/leptin balance and in appetite-regulating pathways — the direction is clear even if the exact detail isn't).
• Serotonin tends to dip in the late luteal phase, and because eating carbohydrate transiently supports serotonin, this is a plausible contributor to the carb cravings people report before a period.

How much, and what to do about it

Studies report higher energy intake in the luteal phase — commonly a few hundred extra calories a day for some people — but the reported range is wide and individual variation is large, so it's not a fixed number to bank on. Two accurate, useful points:

• The extra hunger is partly matched by a small rise in energy expenditure (next section), so it isn't purely "extra."
• Fighting it with an aggressive calorie cut in exactly the phase when hunger and cravings peak is a recipe for poor adherence and a rebound — which does more damage to a fat-loss goal than the calories themselves.

So the practical move is to plan for it: keep protein and fibre up, don't try to set a diet-cut personal best that week, and judge your intake over the whole cycle rather than day to day. A higher-intake luteal stretch inside an otherwise-on-track cycle is completely fine. Protein in particular is one of the strongest levers on fullness — see energy balance for how the deficit is built and why day-to-day intake is best read as a trend.

Metabolism — the small, overstated bump

Resting metabolic rate — the energy you burn at rest — is slightly higher, on average, in the luteal phase than the follicular phase in many people. But this effect is real on average yet small and genuinely uncertain, and it's one of the most overstated numbers in cycle content online.

What the evidence actually looks like:

• Pooled analyses find a small increase in luteal resting metabolism — but when restricted to studies using better modern measurement methods, the effect shrinks and often stops being statistically significant.
• Individual studies land all over the map, from a few tens of calories a day up to somewhat more, with many finding no meaningful difference at all, and most on small samples.
• The popular "your metabolism spikes ~100–150 kcal a day before your period" is too confident. The defensible version is: a small amount — often on the order of tens of calories a day for many people, if anything, and some people show no measurable change.

The takeaway is not "you burn a lot more in the luteal phase, so eat whatever you want." The bump is small, inconsistent, and easily exceeded by the luteal appetite increase — so it doesn't create a real free-eating window. Its only practical value is to reinforce that a slightly higher luteal intake isn't automatically a surplus.

Training performance — read this carefully

This is where popular content most outruns the evidence, so it's worth being deliberately careful. The familiar claim is: follicular phase (low progesterone) = stronger and faster; luteal phase = better endurance but lower max strength. The research tells a more sober story.

• For maximal strength, systematic reviews find small, inconsistent, low-certainty effects. Some hint at a slight tendency toward better strength in the late follicular phase and a poorer early-follicular phase, but the effect sizes are small and the evidence quality is low.
• A recent review restricted to high-quality studies concluded that the majority found no menstrual-cycle-phase effect on strength, power, or endurance performance.
• For endurance and aerobic capacity, results are mixed, and most studies find no marked, consistent phase effect. The claim that "the luteal phase gives you better endurance" is not well supported — if anything, some studies show endurance is unchanged or slightly reduced in the luteal phase (partly from higher perceived effort and heat load). So don't expect a luteal endurance advantage.
• Crucially, research does not show that periodising your training to your cycle beats ordinary, well-run training. Phase-based programming is an appealing idea that doesn't yet have solid outcome evidence behind it.

The one genuinely established difference

There is a modest, real shift in fuel use across the cycle: the higher-hormone luteal phase is associated with somewhat greater reliance on fat and less on carbohydrate at rest and during moderate exercise, driven mainly by estrogen (progesterone partly opposes it). But even here the caveat matters — peak fat-oxidation studies are inconsistent, and this substrate shift does not reliably translate into better or worse endurance performance. It's a nice "your metabolism runs a little differently across the month" fact, not evidence for a luteal endurance advantage.

What this means for how you train

The strongest real-world signal isn't a fixed performance curve — it's that many people subjectively feel different across the cycle (see the next section). That felt difference is a legitimate reason to self-adjust, even though group-average performance barely moves. So the honest message is: listen to your body and adjust if you want to; don't expect a hormone-dictated performance schedule.

• If you feel strong, train hard — regardless of phase.
• On days you feel flat (often but not always luteal or pre-period), it's completely reasonable to pull back intensity or volume, swap a max-effort session for something moderate, and not read it as regression. Seeing the phase label next to a low-energy day just gives that decision context.
• Judge training progress over whole cycles, not day to day — the same way you'd read strength progress, which naturally zig-zags week to week.
• Phase-tracking is a self-awareness tool, not a prescription. Some elite programmes experiment with cycle-based periodisation, but there's no strong evidence it beats training by how you actually feel and perform.

Energy, mood and perceived effort

Some people feel flatter, more fatigued, or lower-energy in the luteal phase and pre-period, and workouts can feel harder even when the actual output is similar. This is partly physiological and partly perceptual, and it's the honest reason phase-awareness is useful.

Reasonable contributors to mention gently — as plausible factors, not proven switches:

• Higher progesterone has mild sedative and thermogenic effects (a slightly higher core temperature in the luteal phase), which can raise perceived effort and heat strain.
• The shifting hormone picture in the late luteal phase is associated with changes in mood- and motivation-related brain chemistry (including serotonin), which can make some people feel lower-energy.
• Sleep quality and the broader pre-period symptom load feed in too — poor sleep alone can flatten energy and make adherence harder, independent of the cycle.

A note on the neurotransmitter detail: you'll see very specific "dopamine down, serotonin up" claims online, and those are too precise and partly backwards. The more established late-luteal picture is a serotonin dip (linked to lower mood and carb cravings), with real but complex dopamine and estrogen interactions on top. It's more honest to say the changes affect mood and motivation than to assign a confident up/down to each chemical.

Why this matters: the felt-energy dip is the genuine reason phase-awareness helps — not because your muscles are weaker, but because motivation, perceived effort and adherence really do move for many people. Anticipating a flat stretch means you plan a lighter week instead of quitting. A low-energy luteal week is normal and self-limiting; it's a good week to prioritise consistency over personal records, protect sleep, and be kind to your adherence rather than forcing an aggressive cut.

Putting it to use in Strathlon

The cycle phase in Trends & Review sits next to your weight and energy trends so you can interpret them. It doesn't prescribe. Here's how to use it well:

• Track for context, not commands. Phase is a lens on your weight and energy, not a set of instructions.
• Expect the pre-period scale bump and don't panic. It's usually water and it resolves within days of your period starting.
• Plan for higher luteal appetite. Keep protein and fibre up, don't schedule your hardest calorie cut that week, and judge intake across the whole cycle.
• Avoid hard calorie cuts in the luteal phase — not because it's metabolically dangerous, but because adherence suffers most exactly when hunger and cravings peak, and a blown week costs more than the calories. Think of it as an adherence strategy.
• Adjust training intensity or volume by feel if you want to. Pulling back on a flat day is smart self-regulation, not weakness — but don't expect a rigid hormone-timed performance schedule, and remember that formal cycle-periodisation isn't proven to beat training by feel.
• Zoom out. Weight, appetite and performance all read more clearly over full cycles than day to day.

On-device and opt-in

Cycle tracking in Strathlon is opt-in and stays on your device. It's used only to add context to your weight and energy data in Trends & Review — it isn't uploaded and isn't used for anything else. If you'd rather not use it, you don't have to; the rest of the app works exactly the same without it.

If you're on hormonal contraception

Hormonal contraceptives — the combined pill, progestogen-only pill, hormonal IUD, implant, injection, ring and patch — change or suppress the natural cycle. Combined methods in particular typically suppress the body's own estrogen and progesterone rhythm and replace it with steadier synthetic levels; any "bleed" on the pill is usually a withdrawal bleed, not a true menstrual period.

Because of that, the cycle-linked effects described on this page — water, appetite, the small metabolic shift, mood and any performance changes — may be muted, altered, or absent, and a "phase" estimated from dates may not map to real hormone swings. Effects also differ by method and by person, so treat this as "may be reduced or absent," not "will be gone."

Practical takeaway. If you're on hormonal birth control, treat the cycle-phase context as less applicable to you, and lean more on your own observed weight, energy and appetite trends. This is general education only — a clinician can speak to your specific method.

Myths worth correcting — a quick reference

• "Ovulation is always day 14." It's about 14 days before the next period; timing varies with cycle length.
• "A pre-period scale gain is fat." Almost always water — it resolves after the period. This is the page's most valuable correction.
• "Progesterone directly causes water retention." It's the compensatory aldosterone rise that nets out to retention; say "associated with," not "directly causes."
• "Your metabolism spikes ~100–150 kcal a day in the luteal phase." Real on average but small, inconsistent, and it shrinks in better studies — keep it qualitative.
• "Follicular = stronger/faster, luteal = better endurance." Best-quality reviews find mostly no consistent phase effect on strength, power or endurance; the luteal "endurance advantage" is not supported.
• "Periodise your training to your cycle for better results." Not shown to beat ordinary training — frame it as optional self-adjustment.
• "The luteal phase is a bad training phase." Different or sometimes flatter-feeling is not worse; measured performance often barely changes.
• "Luteal cravings mean no willpower." They're hormonally driven and expected; naming them improves adherence.
• "Precise dopamine-down, serotonin-up drives the luteal slump." Too specific and partly backwards — the established signal is a late-luteal serotonin dip.
• "The pill gives you a normal cycle." Most hormonal methods suppress or override the natural cycle; the effects here may be muted or absent.

This is general educational information, not medical advice. The physiology here is well established in broad terms, but individual variation is large — cycle length, phase timing and hormone amplitude differ between people and between cycles in the same person — and mechanisms are described as tendencies and associations rather than certainties. Menstrual, metabolic, appetite and mood patterns can also be affected by medications and by conditions such as PCOS, thyroid disorders, endometriosis and others. Anyone with a menstrual, metabolic or other health condition, anyone who is pregnant or trying to conceive, or anyone with irregular, absent or unusually heavy or painful periods should consult a qualified professional. See our Terms for more.

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