Cycle Syncing Training, What Dr. Stacy Sims Reconsiders

When cycle syncing feels like it should work, but does not

If you have ever planned a “follicular phase PR week” and a “luteal phase deload,” only to feel amazing right before your period or wiped out mid cycle, you are not alone.

The frustration is real because the idea sounds so clean. Hormones rise and fall, training stress rises and falls, results improve.

This video takes a more nuanced stance: science evolves, and so should the advice. Dr. Stacy Sims, speaking as a scientist, steps back from blanket cycle syncing rules and acknowledges that some of the earlier messaging was built on what was known 5 or 6 years ago.

What is interesting about this approach is that it does not throw the biology away. It keeps the molecular insights, but it questions whether we can reliably map them onto real life training calendars when cycles are variable and ovulation is not guaranteed.

Before vs After: the shift in perspective

Before: Use cycle phases like a fixed schedule, go hard in low hormone weeks, back off in high hormone weeks.

After: Use cycle information as personal feedback. Track your own patterns first, then adjust training based on how your body actually responds.

What the biology still suggests about low vs high hormone phases

The discussion highlights that some foundational physiology still “holds true,” especially when you look at what is happening at the molecular level.

Low hormone (follicular) phase, why it can feel more resilient

In the low hormone or follicular phase, the body is often described as more stress resilient. The framing here is that carbohydrate use can be more efficient, and there is an “impetus” for muscle protein synthesis.

That combination can matter in the gym. If you tend to feel more robust, recover faster, or tolerate intensity better during this time, it may line up with these mechanisms.

What the research shows: Exercise performance across the menstrual cycle is highly individual, and research reviews emphasize that responses vary widely, even when hormone patterns look similar on paper. See discussion in a peer reviewed review in Sports MedicineTrusted Source.

High hormone (luteal) phase, why needs may shift

After ovulation, in the high hormone or luteal phase, the video points to several changes that also “hold true.” Protein needs may increase. Metabolism may shift toward relying more on free fatty acids. Immune function can tilt toward a more pro inflammatory response.

Those are not just trivia points. If you notice more soreness, more sluggishness, or more sensitivity to training load in this window, it may be partly explained by these systemic shifts.

Did you know? A normal looking bleed does not automatically confirm ovulation. Anovulatory cycles can still include bleeding, which is one reason rigid phase based plans can miss the mark.

The big update, ovulation and variability change the whole plan

Here is the pivot point: ovulation is the critical component that creates distinct hormonal phases. Without ovulation, the “two week low hormone, two week high hormone” story can fall apart.

The newer research lens emphasized in the video is variability. Cycles can vary within the same person from month to month, and even more across the general population. That means a phase based plan can accidentally become a plan based on assumptions.

A key insight is that “very few women have ovulatory cycles,” as stated in the video. Even if you still have a bleeding phase, it could be an anovulatory bleed.

That is why the speaker cautions against absolutes. Taking molecular science and applying it to the whole person, without confirming ovulation or noticing personal patterns, can lead to mismatched training decisions.

One common misinterpretation is especially important: some people heard “high hormone phase” and translated it into two weeks of barely training, then going very hard in the low hormone phase. That does not make sense for someone who frequently has anovulatory cycles. It also does not make sense for someone who feels “bulletproof” a few days before their period.

Important: If your cycle length changes noticeably, or your usual pattern suddenly shifts, this can be a clue that your stress load (training, life stress, under fueling, poor sleep) is exceeding your current resilience. Consider discussing persistent changes with a licensed clinician.

How to train with your cycle without rigid rules

This perspective suggests a different goal. Instead of “train by calendar,” you “train by pattern recognition.” The practical tool is self tracking, not as a perfection project, but as a way to learn your own signals.

What to track first, according to the video

Start with the bleed itself and the nuances of how you feel.

Pro Tip: If you already log workouts, add two quick notes: “bleed day and flow” and “how training felt.” Over 2 to 3 cycles, patterns often become clearer than you expect.

How to dial training up or down, without assuming phases

Instead of assigning workouts to a phase, match training to your current readiness.

Q: Do I need to confirm ovulation to train “the right way”?

A: You do not necessarily need to confirm ovulation to exercise safely, but ovulation is what creates true phase differences. If you are using strict phase based training, confirmation becomes more relevant because bleeding alone cannot tell you which hormonal pattern you are in.

If you are noticing repeated fatigue, big performance swings, or major cycle changes, consider discussing ovulation tracking options with a clinician.

Dr. Stacy Sims, PhD

»MORE: Create a simple “cycle and training” tracker, include bleed pattern, symptoms, sleep, and perceived exertion. Bring it to your next sports medicine, primary care, or gynecology visit for more individualized guidance.

Key Takeaways