This quasi-experimental study was performed at Imam Reza Hospital, which is a University Hospital affiliated to Kermanshah University of Medical Sciences, Kermanshah, Iran. The study lasted from March to September 2017.

The study population consisted of female patients diagnosed with PCOS. The diagnosis was made by a board certified endocrinologist after obtaining laboratory tests, clinical examination and ultrasound of the ovaries using the Rotterdam criteria [15]. According to the criteria, two of three items namely oligo-and/or anovulation, clinical and/or biochemical signs of excess androgen, polycystic ovaries detected on ultrasound should be present to make the diagnosis of PCOS. Inclusion criteria included females with PCOS aged 20 to 40 years. Exclusion criteria were inability to perform physical exercise, cigarette smoking, infection and taking any medication by the patient which can affect laboratory tests. A total of 24 patients were consecutively included into the study. The subjects were divided into experimental group (aerobic exercise group, 12 patients) and control group (no intervention, 12 cases).

The details of the study and objectives of the protocol were explained to the patients and informed consent was obtained. The participants were allowed to leave the study whenever they were reluctant to continue. The study protocol was approved by our university Deputy of Research and Ethics Committee (Code: IR.KUMS.REC.1397.572).

The experimental group participated in a daily aerobic exercise program. The participants were asked to perform the stepping program at home following the schedule every morning at 11 o’clock in the morning. To guide the participants, an audio file was prepared and delivered to the experimental group subjects via cell phone which contained 88 acoustic signals per minute for a four-stroke stepping and a rhythm of 22 steps per minute. In order to monitor and ensure that the aerobic exercise program was completed correctly and on a daily basis, the exercises of five participants which were selected randomly every day were monitored.

The goal of the exercise program was to achieve the specific Exercise Energy Expenditure (ExEE) at each session. ExEE is amount of energy required by an individual to perform exercise. Specific ExEE during the first four weeks of the exercise program was equivalent to 4% of the estimated individual energy needed to maintain weight, which during the fifth to the eight weeks of the exercise increased to 6%, and during the weeks 9 to 12 increased to 8%, and during the weeks 13 to 16 increased by 10% [16]. The required energy was also calculated from the equation for the energy required to maintain weight for subjects with routine lifestyle [16]:

Energy requirement (kilocalories per day)=1625+31.8 (fat free mass in kilograms)+1.5 (fat mass in kilogram)–187 (for females).

Considering one minute of stepping with specific height and number of steps, the amount of oxygen consumed per minute was determined. With determining ExEE, by dividing it to VO2, the required time for stepping to reach exercise oxygen consumption was determined. After estimating the ExEE for each session, and after converting it to exercise oxygen consumption (VO2), the obtained value was put into a formula suggested by the American College of Sports Medicine to determine stepping ergometry, the required time for stepping to achieve the calculated required energy was determined [17]:

VO2 (mL.kg-1.min-1)=(0.2×f)+(1.33×1.8×f×h)+3.5 mL.kg-1.min-1, f is the stepping frequency in minutes; H is step height in metres; the height=16.25 inches or 41.275 cm for each step and a total number of 22 steps per minute.

After determining the required time for stepping for each individual, a table was designed which included schedule of stepping for the study period.

Blood samples were taken two times to measure fasting glucose, fasting insulin, and hs-CRP. First, blood samples were obtained 24 hours before the first exercise session. The second time that blood samples were obtained was 48-hours after the last session of the exercise program. In both the occasions, the blood samples were obtained after 12-hours of fasting via collection of 3 cc of anterior brachial vein blood. The blood samples were taken in certain hours of day (8-10 am) to ensure that diurnal variations do not affect blood insulin and hs-CRP levels. The blood samples were centrifuged for 15 minutes (3000 rpm) for plasma separation and were frozen and kept at -80°C. Insulin level was measured using Sandwich ELISA (Isotope, Sweden). To assess insulin resistance, Homeostatic Model of Assessment of Insulin Resistance (HOMA-IR) was derived using fasting glucose and insulin levels using the following formula [18]:

HOMA-IR={fasting plasma glucose (mmol/L)×fasting insulin concentration (μU/mL)}/22.5

Serum hs-CRP level was measured using immuno-turbidimetric method (Pars Azzmoon Co., Iran).

The participants were weighted using Seca Digital Weigh with 0.1-kg precision. The subject’s height was measured by using measurement tape fixed on the wall with minimum 0.1 centimetres. The Body mass index (BMI) was calculated as body weight in Kg divided by height in metres squared.

To study the changes of hs-CRP and HOMA-IR index before and after the study, the paired t-test was used. To determine the differences of hs-CR and HOMA-IR index between the experimental and control groups, the independent t-test was used. The significance level was set at 0.05. All analyses were performed by SPSS software (ver. 22.0, IBM, US).

The [Table/Fig-1] presents characteristics of the subjects. As observed, no significant difference was detected regarding age, height, weight, and BMI between the two groups.

Mean (±SD) fasting glucose and insulin levels at baseline in the experimental group decreased after 16-weeks of home-based aerobic exercise. However, in control group, no such decrease was observed. There was a significant decrease in hs-CRP (38.03% decrease from baseline) and HOMA-IR (42.2% decrease from baseline) in the experimental group after the aerobic exercise program. However, no significant change was observed in hs-CRP (0.42% change from baseline) and HOMA-IR (4.2% change from baseline) in control group [Table/Fig-2].

PCOS not only leads to infertility, but also can cause cardiovascular diseases [19]. Non-pharmacologic interventions in particular physical exercise and diet are the primary modalities to prevent cardiovascular diseases [20]. The goal of the present research was to study the effects of a 16-week home-based aerobic exercise program on hs-CRP and insulin resistance in PCOS women. The findings showed that the aerobic exercise program had significant effect on decreasing hs-CRP and insulin resistance index among PCOS females. However, no significant difference was found in control group who did not receive any intervention. Thus, improvement in insulin resistance index in the experimental group could be attributed to the aerobic exercise program implemented in this group. Studies on the role of physical exercise in PCOS patients have not been done sufficiently. Vizza L et al., investigated the effect of Progressive Resistance Training (PRT) in PCOS women and reported mean hs-CRP level at baseline as 8.9 mg/L which decreased to 8 mg/dL after 12 weeks of PRT which statistically was not significant (p=0.38) [21]. The authors also investigated HOMA-2 which decreased from 2.62 to 2.56, a small non-significant decrease. This discrepancy can be related to the nature of the PRT which is different from aerobic exercise. Strenuous exercise may in fact cause a short-term increase in CRP but chronic habitual physical activity decrease CRP levels [22]. In another study, including 94 obese women with PCOS, three interventions (diet, diet and aerobic exercise, diet and mixed aerobic-resistance exercise) resulted in decrease in HOMA-IR from 1.87 at baseline to 1.4 after 20 weeks of diet and aerobic exercise [11]. In the present study, calorie intake and diet of the patients were not studied. Although diet alone as intervention in the mentioned study [11] also led to decrease in HOMA-IR, according to our findings aerobic exercise for 16 weeks also decreased HOMA-IR significantly in PCOS patients.

Insulin resistance is a pathologic situation in which, the normal amount of blood insulin is unable to provide a normal biologic response. In fact, insulin signalling is impaired. This decreased response could affect the entire metabolic effects of insulin [23]. As 70-80% of the uptake of circulating glucose is done by the muscles, this tissue has specific importance in insulin resistance development [24]. Glucose absorption in target tissues is carried out by Glucose Transporter 4 (GLUT4). By activating phosphoinositide kinase, insulin changes phosphatidylinositol 4,5-bisphosphonate to phosphatidylinositol (3,4,5-triphosphate and activates other cytosol mediators such as PDK1 (phosphoinositol-dependent kinase-1), AS160 protein, GTPase, protein kinase B, protein kinases C [25].

The findings of the current study showed that aerobic exercise improved insulin resistance in PCOS patients reflected by significant decrease in HOMA-IR after 16 weeks.

Aerobic exercise help in physiologic compatibility such as increasing oxidation enzymes, lowering fat tissues, reducing inflammatory markers such as hs-CRP [26], increasing anabolic hormones such as dihydrotestosterone [27], increasing capillary density, increase in the number of mitochondria, improving maximum oxygen intake and efficiency of cardiovascular system [28]. Increase in resistin level occurs following physical exercise and acts as an antioxidant [29]. Resistin acts as a pre-inflammatory mediator and stimulates release of tumour necrosis factor-alpha, monocyte chemotactic protein-1 and endothelial adhesion molecules [30].

Regular physical activities could improve glucose tolerance in individuals; however, people do not have sufficient time to spend on sports [31]. Aerobic exercises affect fat tissues and stimulate muscular peroxisome Proliferator-activated receptor Gamma Coactivator 1-alpha (PGC-1α), which increases fat oxidative capability and capacity. By aerobic exercise, perhaps the systemic inflammation reduces and insulin function increases; followed by reducing insulin resistance index in subjects; and ultimately, due to increase in tissues reactions towards insulin, the insulin amount of serum is consequently reduced [32]. Physical exercise improves insulin resistance via increase in transfer of glucose transporter (GLUT4) in cell membrane via activating intra-cellular messages after muscle contractions, increase in activity of glycogen synthesise insulin and protein kinase B receptors, and trans-regulation of components engaged in insulin signalling flow [33].

In addition, the results of the research showed that the aerobic exercises resulted in significant differences between hs-CRP of PCOS patients. However, no significant changes were observed in control group. This improvement in hs-CRP level in experimental group could be attributed to the aerobic exercise. CRP activates the classic complement pathway and, similar to antibodies, causes opsonization, phagocytosis and lysis of invading organisms. It has been an accepted claim in the past decade that inflammatory mechanism plays a key role in the pathologic process of PCOS. It has been well established that PCOS patients show mild chronic inflammatory symptoms [11]. In fact, these findings support the idea that there is a close relation between mild chronic inflammation and high levels of metabolic indices in PCOS women [34]. Most studies have suggested that it is weight reduction, rather than the effect of training itself, that decrease CRP [16]. It has been claimed that small weight loss in obese patients reduces visceral fat mass more than subcutaneous fat mass and this factor is followed by an improvement in all cardiovascular disease risk factors [16]. Weight loss in women has been shown to prevent increase in the inflammatory cytokines and improvement of endothelial disorders [33]. Therefore, it seems that weight loss is one of the main mechanisms in CRP reduction [35]. Due to direct relationship between CRP production with IL-6, serum IL-6 level should also decrease [35]. Some researchers have introduced IL-6 as an inducing factor of insulin excretion in pancreatic beta cells. Constant engagement in intensive interval activities reduces fat. Since fat tissue is one of the major sources in IL-6 production. By lowering fat tissue, the serum level of this cytokine decreases as well. The reduction of serum IL-6 level weakens the signalling path of CRP and insulin production [35].

Many researchers have claimed that improving physical fitness due to the physiology of exercise is the main factor in lowering the CRP level [36]. The relation between increase in physical activities level and decreasing CRP has observed even after controlling BMI and waist-hip-ratio [36]. Therefore, it seems other factors, besides body composition, can be effective in lowering post-interval exercise inflammatory factors; and researchers attribute those factors to the anti-inflammatory characteristics of physical activities [35,36].

Some possible anti-inflammatory characteristics of aerobic exercise could be associated with regulating the cytokines produced from fat tissue, muscles and mononuclear cells [37]. In addition, perhaps intensive interval activities decrease TNF-α, IL-1-α and Interferon Gamma (INFG) production by mononuclear cells and increases the anti-atherogenic cytokines (IL-10, IL-4 and TGF-β-11) [37].

Along those mechanisms, although aerobic exercises lead to an increase in oxidation stress; in long-term, it improves anti-oxidant defense of body by increasing anti-oxidant enzymes. These anti-oxidant characteristics prevent HDL cholesterol oxidation and ultimately prevent endothelial damage and inflammation [38].

This study had certain limitations. The study period was not long enough to establish long-term effect of aerobic exercise. Authors were not able to include other methods of physical exercise to compare different exercise programs (resistance training, mixed aerobic and resistance exercise). The present authors did not assess weight change or lipid changes in the patients. Finally, randomisation was not used here to allocate the women to experimental or control groups.

A 16-week home-based aerobic exercise program led to decrease in HOMA-IR and hs-CRP in a sample of female patients with PCOS. Although the effect of aerobic exercises in PCOS need more studies, these findings confirm the effective role of aerobic exercises in decreasing inflammation and improving insulin sensitivity in these patients. The present authors recommend aerobic exercise in PCOS patients. Future studies can be done to investigate the effect of aerobic exercises in PCOS patients who have diabetes mellitus to determine whether by improving insulin resistance, similar effects can be seen regarding blood glucose level.