Menstrual Cycle Strength Variations: What the Evidence Actually Shows
Table of Contents
Key Takeaways: Menstrual Cycle Strength Variations
- Menstrual cycle strength variation may exist, but the average effect appears small and inconsistent.
- The early follicular phase may be less favorable for some types of maximal strength, but the evidence is not strong enough to build rigid training plans around it.
- Cycle-phase testing is a major limitation in the research. Counting days from the last period is practical, but it does not confirm ovulation or hormone levels.
- Hormonal mechanisms involving estrogen, progesterone, and testosterone are biologically plausible, but they are better viewed as context than as direct training instructions.
- ACL laxity may increase around ovulation, but the evidence is very low certainty and should not be used alone to change training or competition plans.
- In practice, menstrual cycle information is best used as one piece of context alongside sleep, recovery, training load, nutrition, injury history, and how the athlete actually feels.
- I would not use menstrual cycle phase alone to justify medication, cycle manipulation, or major changes to competition planning.
- The practical message is not “train hard in one phase and deload in another.” It is: track your own patterns, interpret them cautiously, and avoid turning small population-level effects into rigid rules.
Introduction: Menstrual Cycle Strength Variations
Many female athletes already know that their bodies do not feel exactly the same every day of the month.
In my clinical experience, many female patients are actually quite aware of their menstrual cycle — they often know where they are in their cycle, how long it usually lasts, and how their energy levels or perceived performance during exercise tend to fluctuate. Some have an intuitive sense that certain phases feel better or worse for training, even though far fewer systematically adjust their exercise programming based on cycle phase.
But this raises the important question: are these subjective changes meaningful enough to guide athletic training?
For decades, female athletes were often excluded from studies or tested in ways designed to minimize hormonal variability — which meant researchers had limited data on what those hormonal fluctuations actually mean for performance. That’s finally changing, and the picture emerging on menstrual cycle strength is far messier than the popular “train hard in the follicular phase” narrative suggests.
A 2024 systematic review pooling 22 studies and 433 women found that the early follicular phase was unfavorable across all three categories of maximal strength tested — isometric, isokinetic, and dynamic [1]. A separate umbrella review of five reviews concluded that menstrual-cycle phase has, at most, limited or trivial effects on strength performance, and that low-quality studies, poor methodology, and between-study variability make broad phase-based training recommendations premature [2].
These reviews aren’t necessarily contradicting each other. They are answering slightly different questions with different tolerances for uncertainty — and understanding that difference matters for how athletes, coaches, and clinicians should interpret menstrual cycle strength data.
The Problem: Why Menstrual Cycle Strength Research Is So Hard to Get Right
Testing women only at low-hormone points minimizes confounding — but it also means training science was built almost entirely on male physiology and then extrapolated to female athletes without checking whether that transfer was valid, as measurements were often taken at low hormone levels specifically to minimize potential hormonal influence, and results from male-body research were transferred to female training programs without examining whether they actually applied [1].
The core methodological problem behind inconsistent menstrual cycle strength findings is cycle-phase verification. In the 2024 maximal strength meta-analysis, nine of the 22 included studies determined cycle phase using blood samples, six using urine samples, three by counting days, and one each using saliva samples, self-report, body temperature, or an unreported method — and only one of the 22 studies was rated high quality overall [1]. The umbrella review authors add further complications: the follicular phase can range from roughly 10 to 22 days and the luteal phase from roughly 7 to 17 days, so the common assumption of a uniform 28-day cycle is a serious oversimplification [2]. Compounding this, basal body temperature — one of the more common phase-detection methods — coincided with the actual LH surge in only 22% of menstrual cycles in one evaluation of 98 women [2]. If a study can’t reliably confirm which phase a woman was actually in, any strength difference it reports is built on sand.
In clinical practice, however, this level of cycle-phase verification is rarely available. Most of the time, the discussion is based on counting the number of days since the last menstrual period and combining that with the patient’s own understanding of her usual cycle length.
That can still be useful, because many women have a reasonably good sense of how long their cycle typically is. But it remains an estimate. Counting days from the last period does not confirm ovulation, hormone levels, or the true biological phase of the cycle. It gives a practical approximation — not the same level of certainty as blood or urine hormone testing.
Mechanisms Behind Menstrual Cycle Strength Variations
The physiological argument for cycle-based strength variation centers on estrogen and progesterone acting on the neuromuscular system in opposite directions. Estrogen has been proposed to have a neuroexcitatory effect that influences activity potential, force production, and performance positively, while progesterone inhibits cortical excitability and represents a negative influence on the same pathway [1]. At the cellular level, the proposed mechanism involves estrogen’s effect on myosin: in animal (mouse) models, removing ovarian hormones reduced the number of active myosin heads bound to actin, diminishing the muscle’s capacity to generate force — a mechanism the review cites as a plausible explanation, though it has not been directly demonstrated in humans [1].
Testosterone adds a second layer to menstrual cycle strength physiology. A brief spike in testosterone occurs during the ovulatory phase, and an acute rise in testosterone can enhance physical performance through improved neural activation and better electrophysiological and contractile properties of muscle [1] — one proposed explanation for why isokinetic strength tends to peak around ovulation rather than in the late follicular phase where isometric and dynamic strength peak.
Body composition adds a further wrinkle to menstrual cycle strength interpretation. Body mass and total body water increase from the follicular to the luteal phase in both athletes and healthy non-athletes [1], which the review authors attribute partly to fluid retention driven by rising aldosterone and partly to appetite changes as progesterone increases and insulin decreases [1].
In practice, this is where the distinction between physiology and usefulness becomes important. Many women are aware of the idea that higher estrogen levels may be linked with better force production, and some may recognize that certain days simply feel stronger than others.
However, I have not commonly seen training plans built rigidly around this idea, nor have I seen athletes trying to shift their menstrual cycle with progestogen medication simply to make a theoretical hormonal “peak” land on competition day. From a clinical perspective, this makes the estrogen-strength connection more useful as context than as a direct planning tool. It may help explain why one training day feels better than another, but it does not automatically translate into a reason to redesign an athlete’s entire program around the menstrual cycle.
Menstrual Cycle Strength Data: What the Studies Actually Show
Here’s where the two review families genuinely diverge on menstrual cycle strength — not because one is wrong and one is right, but because they’re measuring different things with different tolerances for noise.
The 2024 maximal strength meta-analysis found phase-dependent patterns for all three strength types. For isometric strength, the late follicular phase showed a medium effect size favoring greater force output compared to the early follicular phase, while the luteal phases showed decreased values [1] — a pattern the authors tie to peak estrogen and low progesterone around day 11. For isokinetic strength, the pattern flips: the ovulation phase showed a small effect favoring better performance, while the late follicular phase actually underperformed relative to the early follicular phase [1]. For dynamic strength (1RM-type lifts), the late follicular phase again showed a small favorable effect — though this finding rests on only three studies, the thinnest evidence base of the three strength categories [1].
The umbrella review, which specifically scrutinized five prior meta-analyses using formal quality-appraisal criteria, reached a more cautious verdict on menstrual cycle strength claims. Within that review, one of the largest prior meta-analyses (Blagrove et al.) is described as finding a trivial effect of menstrual cycle phase on maximal voluntary contraction force, isokinetic peak torque, and explosive strength (Hedges’ g < 0.2) [2]. A separate analysis included in the same umbrella review (McNulty et al.) found that once only moderate-to-high-quality studies were considered, 90% of studies showed no difference in strength performance between menstrual cycle phases — the significant findings clustered almost entirely in the lower-quality studies [2].
Read together: there may be a small biological signal here, but it’s frequently smaller than the noise generated by inconsistent phase-verification methods, small sample sizes, and high study heterogeneity. The 2024 meta-analysis’s own authors acknowledge this directly, noting that the included studies are of low overall quality due to imprecise cycle-phase determination and should be interpreted with caution [1].
In my view, this is where the practical conclusion becomes quite conservative. If the average effect is small and the evidence is still uncertain, I would be cautious about trying to manipulate the menstrual cycle for performance reasons alone.
For example, I would not see a strong rationale for using progestin medication simply to move a theoretical performance window, and in some cases that approach could create more confusion than benefit. From a clinical perspective, sport performance alone is not usually a medical indication for menstrual suppression, cycle shifting, or hormone-based medication. Those decisions should be based on the individual patient’s broader clinical situation, symptoms, preferences, risks, and appropriate medical indications — not just the hope of aligning a hormonal peak with a training session or competition.
In practice, I would usually treat menstrual cycle information as context rather than as a scheduling rule. It may help an athlete understand why some days feel different, but I would not build training blocks, competition plans, or medication decisions around it without a much stronger reason.
Beyond Strength: Menstrual Cycle and Injury Risk
Strength output isn’t the only variable that moves with the cycle — connective tissue does too, with real injury implications relevant to anyone tracking menstrual cycle strength changes. A meta-analysis of 21 studies covering 68,758 participants examining ACL injury and laxity found that four of five studies in women not using hormonal contraception indicated the luteal phase was least associated with ACL injuries, and six of twelve studies on ACL laxity found significantly increased laxity during the ovulatory phase compared with the follicular phase [3]. This is described in the source literature as an association rather than a fully established causal mechanism. The review itself rated the overall strength of this evidence as “very low” under GRADE criteria, so this should be treated as a risk signal worth watching rather than a settled rule [3].
The injury-risk discussion should also be interpreted cautiously. From a clinical perspective, I see this more as useful context than as something that leads to clear, actionable conclusions on its own.
It may be interesting to know that ACL laxity has been reported to vary across the menstrual cycle, especially around ovulation, but I would not use this alone to make major clinical, training, or competition decisions. In real-world sport and medical practice, injury prevention still depends far more on established fundamentals: appropriate training load, strength, landing mechanics, recovery, previous injury history, and sport-specific risk management.
So, for me, the practical value of this finding is mainly explanatory. It may help us understand one possible layer of biological variability, but it does not mean an athlete should avoid certain movements, skip competition, or redesign training around the ovulatory phase.
Conclusion: Menstrual Cycle Strength Variations
The honest conclusion is that menstrual cycle strength variation is real enough to be worth understanding, but not strong or reliable enough to treat as a rigid training rule.
Some women may notice that certain days feel better for strength, energy, or coordination, and there are plausible physiological reasons why this can happen. The early follicular phase appears to be less favorable in some strength research, while ovulation may be linked with small changes in strength and ACL laxity. But the evidence is still limited by small studies, inconsistent cycle-phase verification, and very low certainty in some injury-risk findings.
In practice, I would use menstrual cycle information as context, not as a command. It may help an athlete understand why performance feels different from one day to another, but I would not use it alone to redesign a training program, move competitions, or manipulate the cycle with medication for performance reasons. For most athletes, the bigger priorities remain training quality, recovery, sleep, nutrition, load management, strength, and sport-specific injury prevention.
So the practical takeaway is not “train hard in one phase and avoid another.” It is more cautious: know your own cycle, pay attention to repeated individual patterns, verify cycle phase properly if it truly matters, and do not mistake a small population-level signal for a rule that applies to every athlete.
Bibliography
[1] https://doi.org/10.3390/sports12010031
