Primary dysmenorrhea (PD) is the most common cause of cyclic pelvic pain and is defined as painful menstrual cramps among adolescents and young adult females (1). In PD, it is stated that the overproduction and release of endometrial prostaglandins (PGs) during menstruation can cause uterine hypercontractility, decrease uterine blood flow, and result in uterine hypoxia and hypersensitivity in pain fibers (1). It is known that exercise reduces the severity of menstrual pain by decreasing the level of prostaglandins (2). It is also reported that exercise in PD causes changes in body temperature and metabolism, hormonal changes and affects aerobic capacity, muscle strength, and flexibility. On the other hand, some studies have found no changes in flexibility, muscle strength and endurance, aerobic performance or reaction time over the menstrual cycle (2). In the literature, it is stated that aerobic exercise is the gold standard treatment approach to improve cardiovascular fitness, and yoga is frequently recommended for increasing flexibility and strength (3).  However, there is no study in the literature comparing the effects of aerobic exercise (AE) and yoga exercise (YE) on physical fitness parameters in PD. To the best of our knowledge, this is the first study compare the effectiveness of AE and YE on pain and physical fitness parameters in PD.

The present study was designed as a prospective randomized clinical study with two parallel arms (Group I: AE, Group II: YE). Individuals without systemic or metabolic disease who were scanned using a 3-6 MHz transabdominal probe and a Mindray DC80 (USA) colour Doppler ultrasound device were included in this study. The primary outcome measure of our study was determined as the "Visual Analogue Scale (VAS)" score. Based on reference studies in the literature, the reduction in menstrual pain severity was predicted to be 2 units in one study group and 3 units in the other.  Thus, in the two-way hypothesis test design, the sample size was calculated as 34 participants in total (17 participants per group), with 80% power and 5% type 1 margin of error. Considering a total 20% dropout rate, the final total sample size required was calculated as 44 individuals, with 22 individuals per study group.
Individuals were randomly assigned to 2 groups according to an online computer-generated (sealedenvelopeTM, Pocock 1983) block randomisation list. Menstrual pain, physical fitness parameters including cardiovascular fitness, muscle strength and endurance, and flexibility were evaluated with VAS, 6-minute walk test (6-MWT), quadriceps muscle strength ((Lafayette Instrument Company, Lafayette, Indiana), hand grip strength (Jamar® Plus, Paterson Medical, Green Bay, WI, USA), static and dynamic abdominal endurance test and sit-and-reach test, respectively.
All outcome measurements were performed before and after interventions (after the 2nd cycle). AE adjusted according to the Karvonen protocol (heart rate reserve percentage-% HRR) was applied to the first group for 8 weeks, 3 days a week, on a treadmill ergometer. Exercise intensity was adjusted according to weeks as follows: 30 min at 50% of HRR in weeks 0-2, 45 min at 50% of HRR in weeks 2-4, 45 min at 60% of HRR in weeks 4-6, and 60 min at 60% of KHR in weeks 6-8. YE including breathing and warming exercises, suryanamaskar, asanas, and various relaxation techniques was applied to the second group for 8 weeks, 3 days a week with the same duration as the first group. Since numerical characteristics did not show normal distribution, intergroup and intragroup differences were evaluated with nonparametric tests. For this purpose, aerobic and yoga groups were compared by Mann-Whitney U test. The Wilcoxon test was used in the analysis of within-group changes. A p-value less than 0.05 was considered to be statistically significant.

Forty-four individuals (mean age:18.00 ±3.59 years, BMI: 26,93±3,41 kg/m2) were randomized to AE and the YE groups. The baseline values of all outcome measures were similar between the study groups (p>.05). All outcome measures (VASmean, 6-MWT, quadriceps muscle strength, hand grip strength, static and dynamic abdominal endurance test, sit-and-reach test) had significantly improved over time in both groups (p<0.05). In the inter-group comparisons, other parameters were similar except for cardiovascular fitness. However, in terms of 6-MWT, Group I demostrated significant improvements (p:0.024) (Table 1).

An eight-week and supervised aerobic exercise or yoga training program were found to be similarly effective in reducing the severity of menstrual pain, static and dynamic abdominal strengths, quadriceps and hand grip strengths, and flexibility. Cardiovascular fitness, assessed by 6-MWT distance, improved more in the AE group.

Both AE and RE were found to be effective in increasing physical fitness in individuals with PD over time, but AE was found to be more effective in increasing cardiovascular fitness, in line with the literature. Considering that the majority of participants in our study were young adults, it is believed that YE can be used in combination with AE in the management of PD in terms of the principles of participation and enjoyment of exercise. Further studies should also show long-term effects.

1.	Won, H. R., & Abbott, J. (2010). Optimal management of chronic cyclical pelvic pain: an evidence-based and pragmatic approach. International journal of women's health, 2, 263.
2.	Wiecek M, Szymura J, Maciejczyk M, Cempla J, Szygula Z. Effect of sex and menstrual cycle in women on starting speed, anaerobic endurance and muscle power. Acta Physiol Hung. 2016;103(1):127-32.
3.	Aghjayan SL, Lesnovskaya A, Esteban-Cornejo I, Peven JC, Stillman CM, Erickson KI. Aerobic exercise, cardiorespiratory fitness, and the human hippocampus. Hippocampus. 2021 Aug;31(8):817-844. doi: 10.1002/hipo.23337. Epub 2021 Jun 8. PMID: 34101305; PMCID: PMC8295234.

Continence 12S (2024) 101446
DOI: 10.1016/j.cont.2024.101446