'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.
"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).