Table 2.

The effects of physical activity in healthy females.

Investigator, year	Participants	Study design	Intervention and PA assessment	Control group	Main findings
Williams et al. (11), 2015	34 premenopausal eumenorrheic women with a normal BMI, all aged between 18 and 30 y	Randomized controlled trial	3 intervention groups, all involving 3 mo of supervised vigorous aerobic exercise 5 d/wk, ranging from 20–75 min, and controlled diet to manipulate caloric intake. Group 1 experienced a mild exercise calorie deficit, group 2 experienced a moderate exercise calorie deficit, and group 3 experienced a severe exercise calorie deficit	The same exercise regimen as intervention groups without an energy deficit	85% of the moderate and severe energy deficit groups experienced at least 1 luteal phase defect in the 3 intervention menstrual cycles. In contrast, only 1 participant in the control group and 1 in the mild deficit group did A trend toward higher rates of anovulation (35%) in moderate and severe deficit groups (P = .07) relative to other groups (0)
De Souza et al. (8), 2003	35 eumenorrheic women aged between 18 and 36 y	Cross-sectional study	Comparison of sedentary women (n = 11) and active runners (n = 24) running at least 2 h/wk (average of 32 km/wk	N/A	Of the 3 menstrual cycles assessed, 16% of the running group was deemed anovulatory vs. none of the sedentary women. In addition, 42% of the running group exhibited a luteal phase abnormality (short or insufficient) vs. 9% of the sedentary group. Luteal progesterone was lower in intact ovulatory cycles among runners vs. sedentary women
Wise et al. (9), 2012	3,027 women aged 18–40 y, not receiving any type of fertility treatment	Prospective cohort study	Women reported the average number of hours per week that they engaged in PA during the past year, reporting moderate and vigorous activity separately	N/A	Dose-response relationship between the number of hours of vigorous PA and the time to pregnancy in women with normal BMIs. Time to pregnancy was significantly lower in participants engaging in moderate PA only. Lower fecundability in all women who engaged in vigorous PA
Gudmunds-dottir et al. (10), 2009	3,887 premenopausal women aged 20–45 y	Prospective cohort study	Weekly frequency, intensity, and duration of leisure-time PA were self-reported, and the amount of PA was categorized as either low, moderate, or high on the basis of divisions at the 33rd and 66th percentiles	N/A	Women who exercised every day were 3.2 times more likely to be infertile than inactive women, and exercising to exhaustion was associated with 2.3 times the odds of infertility compared with taking it easy. Exercising for 15–30 or 30–60 min was associated with lower odds of infertility compared to exercising for <15 min

Note: BMI = body mass index; N/A = not applicable; PA = physical activity.