In the final part of this series we will look at how altering exercise programming based on the menstrual cycle actually affects strength in athletes. Previous parts of this series are available here (Part III), here (Part II), here (Part I).
The Science on Periodizing Training Based on The Menstrual Cycle
The evidence that points to differences in training capabilities during different phases of the menstrual cycle has spurred another area of research relevant to female strength athletes. There are four studies that have looked at how changing training based on the menstrual cycle affects strength performance.
Reis et al. compared the maximal strength of 7 untrained women who trained based on their menstrual cycle. For the training protocol, subjects completed 3 sets of 12 reps of leg press 3 times a week during the follicular phase and one time per week during the luteal phase (Menstrual Cycle Triggered Training (MCTT)). The women acted as their own controls, training every third day on one leg and performing the MCTT on the other leg. At the beginning and end of the training they tested strength using the leg press and collected blood samples to analyze estradiol, testosterone, sex hormone binding globulin, progesterone, and cortisol. They found that both groups increased strength and muscle size with the MCTT leg showing greater strength increase than the control leg. Interestingly, the researchers did not present significance levels or p-values for the differences in percent strength gains. Additionally, the MCTT leg has a decreased training load (volume) prior to every testing session which could increase the strength display in the MCTT leg due to reduced fatigue. There also may be issues with assessing strength and size differences between limbs in an individual, as the crosstalk between sides can drive improvements as well. One important outcome of the study was that the authors were (apparently) able to do is implement a strategy to determine what menstrual phase each individual was in. Reis et al 1995 They used body temperature and ovulation strips, which could probably be done at home by individuals wanting to adjust training based on their menstrual phase. Overall, the study shows promise for identifying menstrual phase at home, but the small sample size and confounding variables make it hard to be very confident in these findings without more data suggesting similar findings.
Sung et al recruited 20 untrained women with normal cycles to train each leg according to one phase of their cycle. One leg trained high volume during the luteal phase and one leg trained high volume during the follicular phase. The authors measured muscle strength and size before and after the interventions. The legs that completed the training with high volume during the follicular phase demonstrated a significant increase in strength and muscle size compared to the legs doing the high volume in the luteal phase. Some may take these findings at face value and implement higher volume, lower intensity training in the follicular phase and lower volume, higher intensity during the luteal phase to maximize training adaptations. When looking at the data a bit more closely however, the rate of change in performance is similar in all weeks of the study except for the first and last two weeks of training. It is the initial exposure to training (the first two weeks) and the taper at the end that seem to have fairly large effects across groups. The methodological challenges in this study are potentially confounding the data. Sung et al., 2014 Because the women served as their own control, there is also similar concerns that contralateral strength increases are occurring due to the unilateral resistance training, e.g. crosstalk as described above Munn et al., 2004. To eliminate this potential confounder, we’d have groups of women doing bilateral resistance training using different periodization schemes based on their menstrual phase and see what differences in training outcomes there are, if any.
A 2016 study from Sakamaki- Sunaga et al recruited 14 untrained women to investigate the effect of different programming for different menstrual phases on strength and muscle size. The subjects’ menstrual cycles were determined using basal body temperature and their 1-repetition max dumbbell curl were tested before beginning the training program and then again at 4, 8, and 12 weeks during the study. Training frequency was moderated by the women’s menstrual cycle phase, either luteal or follicular. Researchers used subjects as their own comparisons and had them train both arms differently. One arm trained high volume (3 times a week) during the follicular phase low volume during the luteal phase (1 time per week) and the other arm trained high volume during the luteal phase and low volume during the follicular. Women did significantly increase their elbow flexor cross sectional area and strength from baseline. The researchers found no differences in muscle size or strength differences between the two arms indicating that training load based on the menstrual cycle does not significantly increase strength or cross sectional area. Sakamaki-Sunaga et al., 2016 Again, the methodology raises concerns over the applicability of varying unilateral training protocols to more traditional resistance exercise programming.
In a 2017 study by Wikstom-Frisen et al., 59 resistance-familiar women (32 on oral contraceptives and 27 without oral contraceptives) were split into 3 groups:
- Group 1 (follicular phase training): high frequency training (5x/week) during the first two weeks of the menstrual cycle and low frequency the second two weeks (once per week)
- Group 2 (luteal phase training): low frequency training (1x/week) during the first two week and high frequency training (5x/week) during the second two weeks of the menstrual cycle.
- Group 3 (control): trained 3x/week during the whole menstrual cycle.
The study period lasted 4 months and the following outcomes were measured before and after the training interventions : squat jump (ST), countermovement jump (CMJ), isokinetic peak torque and LBM were collected for each of the groups. Groups with higher volume during the follicular phase (Groups 1 and 3) had increased ST, CMJ, and peak hamstring torque but not quadriceps torque, while training with higher frequency during the luteal phase did not result in increases. While this looks like Group 1 got better than Group 2 during the course of the training, each went into the post-testing at different points in their training cycle. Group 1 entered into their training cycle on a week where they had completed 5 training sessions, Group 2 entered into testing on the week where they completed 1 training session, and Group 3 had 3 training sessions the week of testing. Wikström-Frisén et al., 2017 There appears to be an effect of volume the week of testing, the follicular phase training group only trained 1 time and the relative decrease in volume may have acted like a taper while the luteal phase training group had high volume. These differences in volume the week of testing might be confounding these results and again is not clear evidence of a training effect.
In these four studies on periodized training, there is weak but converging evidence pointing to a benefit of periodized training with some limitations in the methodology. Performance potential will vary day to day based on biological, psychological, social, and environmental inputs. The small performance differences that are seen in these multi-week studies don’t necessarily persist over many years of training and may be absent in larger sample sizes. Long term, the rate of strength gain is dependent on many more factors than just training during the menstrual cycle. Existing evidence on training response indicates that individuals will vary greatly in their response to training. Ahtiainen et al 2016 . Some variation or noise in training may be due to menstrual symptoms, possibly due to central fatigue, but most likely not directly influenced by hormone levels. To determine if there are additional effects of the menstrual cycle and specific periodization techniques on inter-individual training responses, we need strong evidence.
Another important drawback of these studies is that none actually measured hormone levels. Not every woman has a 28 day cycle Fehring et al., 2006, there are variations in hormone timing and concentration from cycle to cycle. Menstrual cycles vary between women and vary additionally with age and BMI. Bull et al., 2019, Fehring et al., 2006 Many of the aforementioned studies assumed a 28-day cycle and thus it isn’t possible to know if women were training or testing during the correct phase during the studies. Hormone ovulation sticks are capable of signaling ovulation and thus determining cycle phase, luteal or follicular, but breaking this down further to early, mid, and late is more complex and would require daily analysis of exact hormone concentrations. Many women don’t have the time or financial availability to measure their hormone levels to know exactly what phase of their menstrual cycle they are in. Doing so is probably excessive, as we have seen in previous articles hormone concentrations do not correlate with performance. This is particularly relevant for team sports athletes. These athletes are more likely to be lumped with a large group that trains together, and while some women might have similar cycles, it is probably best to train according to the competition schedule, and to train together. The best training is going to be consistent and utilize progressive overload based on competitions.
Additionally, the studies reviewed used small sample sizes of women with methods that may not be generalizable, e.g. the different unilateral training protocols. This makes it difficult to be confident that the results are meaningful and should be used to influence coaching practices. One strategy we can use to overcome the small sample size issue is to pool these studies together via a systematic review and meta analysis and see if there are differences in performance and training responses across the menstrual cycle.
Multiple recent systematic reviews and meta-analyses agree there is inconclusive evidence that the hormonal changes occurring during different menstrual cycle phases have an effect on training response or performance. Blagrove et al., 2020; McNulty et al., 2020; Thompson et al., 2020 Carmichael et al., 2021. Unfortunately, the majority of the evidence is of low-quality, which limits the ability to find a consensus. McNulty et al., 2020.
Taken together, it’s probably best to avoid making prospective changes to a training program based on menstrual-phase-related hormone fluctuations while monitoring an individual’s response to the training and adjusting as needed. Anecdotes in these situations are useful to exemplify the range of responses to the menstrual cycle women have specifically as it relates to training. However, one woman’s experience is not another’s diagnosis. Women are resilient and they will overcome a range of obstacles and be highly successful athletes regardless of the phase of their menstrual cycle. Women should continue to train in a way that promotes their independence through consistent, auto-regulated, and progressively loaded training.
At the beginning of this article series, we set out to see whether or not the existing scientific evidence rejected the hypothesis that there is no reliable effect of the different phases of the menstrual cycle on performance in strength sports. Based on the above evidence and the previous articles, there are 4 main reasons we cannot reject this hypothesis and therefore we accept it:
1) There are not reliable or repeatable cycle phase induced differences in training adaptation or performance or compound movement performance. Fluctuations in estrogen observed during the menstrual cycle do not tend to have a robust effect on training performance, or adaptations in strength training. While they may exert some effect, these effects are either too small or too unreliable to characterize, particularly in comparison to physiological parameters (age, training status etc.), and environmental factors all work in concert to alter adaptation to training.
2) There is a high degree of inter-individual variability in response to cycle phase, contraceptives, and training. Women have high inter-individual variability between menstrual cycles and intra-individual variability between women. Women respond to training with a heterogeneity of responses. Training should not automatically start at a lower intensity, frequency, or volume at the start of the luteal phase. Women have reported a range of increases and decreases in their performance variables across the menstrual cycle. The use of an auto-regulated program and consulting with a coach is the best way to ensure consistent progress.
Coaches should be comfortable with what a menstrual cycle is, and the physiological processes occurring across the cycle. If you have made it this far you probably are now well-versed. A coach’s main job in this situation is to support the athlete they are working with and help them troubleshoot. A good coach will interpret outcomes and determine patterns in training, if present, to meet you where you are, which is going to be more efficacious than automatically planning based on the menstrual cycle. An athlete should not be in severe pain or discomfort during training, nor should there be a complete deload based on menstrual cycle symptoms. Coaching requires developing a strong relationship with an athlete and sometimes that includes talking about healthcare topics.
3) Other inputs on performance/adaptation are seemingly more reliable, more important, and more modifiable than altering training based on cycle phase. Time is best spent focusing on proper sleep, nutrition and training that is appropriately programmed via adjustments in volume, intensity, exercise selection, frequency, etc. in order to drive fitness adaptations without outstripping recovery resources.
Symptoms of the menstrual cycle may have an impact on training, however these symptoms tend to be unique to the individual, vary within individuals, and learning to work with them will serve athletes in the long term. Start training, stay training, and don’t be discouraged by small setbacks that happen from week-to- week. Overall, athletes are human first, female second; there are a range of fluctuations experienced in life and training that have a greater chance of changing outcomes than the menstrual cycle.
4) Accurately tracking and managing training based on cycle phase has costs ($$ + potential nocebo). Tracking training accurately with serum hormones is costly and ultimately challenging to complete. Telling female athletes her cycle is changing her training may be potentially harmful based when coaches and subject matter experts seed negative expectations within individuals. This sets the individual up to have negative expectations and through training may be more likely to fulfill those negative expectations, which may have downstream effects pertaining to long-term training adaptations.
Overall, being physically active and reducing the barriers to physical activity is far more important than the menstrual cycle; by telling women they need to periodize their training based on their period, we are actually creating barriers by complicating training. These barriers reduce the likelihood that a woman will train. The goal should be to optimize the variables that will provide the greatest outcomes, which includes consistency and well-designed training programs utilizing progressive overload. Focus on getting to the gym and strength training at minimum twice a week to meet the WHO guidelines of physical activity.