'Training on Cycle': Hitting the Weights Frequently (5x/WK), Alone, Very Unlikely to Trigger the 'Female Athlete Triad'

The squat was not part of the training regimen in the study at hand - that's bad because it would certainly have made the workout more intense and might thus have affected the results.
If you don't remember what it was, I suggest you (re-)read the classic 'SuppVersity Athlete Triad'-Series (read it)... and if you don't have the time to devour those classics, here's the gist: While it is often accompanied by eating disorders, the athlete triad can also arise in periods of either low energy availability or high training loads. Next to an ongoing decline of physical (and eventually also cognitive performance), the main features of the female athlete triad are amenorrhoea / oligomenorrhoea (no, or a disturbed menstrual cycle, respectively), and - in the long(er) run, i.e. after months and years - an often highly significant decrease in bone mineral density (osteoporosis and osteopenia).

As et al. point out in their latest paper, the female athlete triad "has shown to be related to both training intensity and duration" (Wikström-Frisén. 2016). It is thus a threat for endurance athletes, strength athletes and gymrats alike; and a very similar effect can be observed in men when they're overtraining - even though, their fertility is not threatened as easily.
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"Intensive exercise-associated disorders, such as the female athletic triad, generally originate from hypothalamic dysfunction failing to initiate a normal hypothalamic-pituitary-ovarian function. This is leading to a decrease in pituitary secretion of luteinizing hormone (LH), and follicle-stimulating hormone (FSH), which in turn limits ovarian stimulation and estradiol production" (Wikström-Frisén. 2016).
In spite of everything we know, evidence pertaining to the effects of increased resistance training load on the athlete triad is scarce. The aim of the scientists from the  Umeå University in Sweden was thus to investigate potential exercise-related negative consequences on components in the female athlete triad following high-frequency leg resistance training.

So far, so good. What is new, or at least almost new, in this 2nd paper by Lisbeth Wikström-Frisén et al. addressing the issue of what I previously called tongue in cheek "training on cycle" (read my 2015 article of mine) is that the subjects' training regimen were periodized according to different parts of the menstrual/OC cycle. Practically speaking, the participants, all of whom had regular menstrual cycles (at pre-test 27.9 ± 1.9 days), or were taking oral contraceptives (OC cycles of 28 days), and had previous experience of leg press and leg curl resistance training, were randomized into either one of two periodized training groups or a control group:
  • one training group were allocated to high-frequency training (5 times per week) during the first two weeks of the menstrual/OC cycle (group 1), and 
  • the other training group to high-frequency training during the last two weeks of the menstrual cycles (group 2), 
  • the controls trained at a low frequency (3 times per week) during the whole cycle. 
During training, all participants performed leg resistance training according to current recommendations in order to achieve strength gains. The completed number of leg training sessions were logged and was equivalent in the three groups (group 1 = 41 ± 4.0, group 2 = 41 ± 4.8, control group = 42 ± 4.4).
Figure 2: While the relative changes (pre- vs. post-test) clearly indicate that training intensely in the latter phase of the menstrual cycle appears to have the most favorable effect on the women's hormonal profiles, none of the visible inter-group difference reached statistical significance - probably because of the rather small(ish) study size (N = 59 in three groups of 19, 19, and 21 subjects, respectively) as well as large inter-individual variation (Wikström-Frisén 2016).
At post-test, the participants reported how they perceived their leg training program during the four consecutive menstrual/OC cycles. Their perceptions were categorized on a three-graded scale; 1 = positive, 2 = neither positive nor negative, 3 = negative. The analysis revealed "a significant difference in regards to how the training was experienced, χ2(2) = 11.552, p = 0.003" with a significantly more positive perception of the leg training in the "on-cycle" group #1.
Figure 2: For those of you who are interested only in the takeaway messages, here are the implications of this (Study 2 / 2016) and the previous paper by Wikström-Frisén et al. (Study 1 / 2015) in a comprehensive form.
Now, the way you feel about your workouts is unquestionably important. The objectively measured hormonal response in Figure 1, however, is unquestionably a more objective measure of the training load or overload ... unfortunately, the lack of statistical inter-group differences (in spite of visible differences in the relative changes of the hormonal marker), doesn't allow for any definite conclusions on what's "best" hormone-wise (it's not even clear how to define "best" in this context, by the way). Nevertheless, the study does provide an important new insight, a result Wikström-Frisén et al. summarize as follows:
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"The results are in contrast to endurance training where negative exercise-related consequences are common when increasing the training load (Warren 2001). 
Thus, we observed no evidence that the high frequency periodized menstrual/OC cycle based resistance training resulted in exercise-related negative consequences which could contribute to a suppression of LH, FSH, and further decrease of the estradiol production (Meczekalski 2000)" (Wikström-Frisén 2016).
This conclusion is corroborated by the lack of changes in body composition and/or bone mineral density, but should still be taken with a large quantity of healthy skepticism.
Figure 3: Relative changes in lean mass (DXA data), measures power and strength (torque) in 59 trained women in response two weeks of frequent leg-training in the first or second two weeks of their estrous cycle (Wikström-Frisén. 2015).
After all, the long-term results of the 5-days-a-week approach to leg training cannot be accurately predicted based on these findings from a 4x28-day study and the higher motivation and previously detected performance increments (see Figure 3, from Wikström-Frisén 2015; learn more in my previous article about this study from 2015) speak in favor of a (maybe non-hormonal) advantage of training more intense in the first two weeks.
Read my analysis of the previous paper on this matter | learn more
So, how do I train, now? While the paper and hand suggests that it does not matter when you plan to increase the volume, a previously discussed study by the same researchers found that leg resistance training performed during the first two weeks of the menstrual/OC cycle will additionally improve physical performance in women (Wikström-Frisén 2015), the authors recommend to periodize accordingly: if you want to increase the training frequency, do it in the first two weeks of your menstrual cycle, ladies - your performance and, as the study at hand shows - your training experience will benefit! Comment on Facebook!
References:
  • Meczekalski, Blazej, et al. "Hypothalamic amenorrhea with normal body weight: ACTH, allopregnanolone and cortisol responses to corticotropin-releasing hormone test." European journal of endocrinology 142.3 (2000): 280-285.
  • Warren, M. P., and N. E. Perlroth. "The effects of intense exercise on the female reproductive system." Journal of Endocrinology 170.1 (2001): 3-11.
  • Wikström-Frisén, Lisbeth, Carl Johan Boraxbekk, and Karin Henriksson-Larsén. "Effects on power, strength and lean body mass of menstrual/oral contraceptive cycle based resistance training." Journal of Sports Medicine and Physical Fitness (2015).
  • Wikström-Frisén, Lisbeth, Carl J. Boraxbekk, and Karin Henriksson-Larsén. "Increasing training load without risking the female athlete triad: menstrual cycle based periodized training may be an answer?." The Journal of sports medicine and physical fitness (2016).
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