Regular physical exercises are associated with a decrease in mortality and the risk of developing various cardiovascular diseases. Physical exercises have also been found to slow aging, reduce physiological dysfunctions, and decrease DM complications by improving endurance, metabolism, muscle strength, circulation, and decreasing body fat mass [24, 25]. Besides, physically active individuals have higher insulin sensitivity, lower blood pressure, and a more favorable plasma lipoprotein profile . However, to the best of the author’s knowledge, no previous data documented the effect of regular long-term swimming program on patients with chronic diseases like T2DM and HTN from the West Bank area of Palestine.
In the current study, the statistical analysis results between groups (experimental vs. control) showed that the TC, HDL, LDL, TG, BMI, body fat percent, BG, SBP and DBP variables on the posttest were significantly improved (p < 0.05) with effect size of partial eta squared were 43.7, 21.1, 39.8, 55.7, 11.5, 13.2, 12, 15.5, and 14.7%. While, no significant difference was found at p < 0.05 on the pretest of all studied variables compared to the control group.
Moreover, comparing the pre- and post-tests results, the findings of this study showed that there were statistically significant differences (p < 0.05) in all conducted variables (TC, HDL, LDL, TG, BMI, body fat percent, SBP and DBP) in favor of posttests in the experimental group, as the effects size of partial eta squared were 32.7, 29.6, 31.1, 48.8, 15.8, 22.9, 34.8, 27.3 and 27.9%, respectively. Whereas, no significant differences were found at p < 0.05 between pre- and post-tests of the studied variables in the control group.
In addition, in the case of interaction (group* time), there was statistically significant interaction (p < 0.05) for all of studied variables. However, the value of HDL in the post test for patients (experimental group) was significantly the greatest compared to these values of pretest (for patients in both groups) and the post test for patients of the control group, as the effects size of partial eta squared was (27.3%). Furthermore, the values of posttest for the variables (TC, LDL, TG, BMI, body fat percent, BG, SBP and DBP) among patients (experimental group) were significantly the lowest in comparison with these values of pretest for patients in both groups and in the post test for patients (control group), as the effects size of partial eta squared were 35, 32.8, 49.4, 15.1, 20.6, 21.7, 16.7 and 16.5%, respectively.
These results indicate that the participating in swimming sessions regularly has positive impact on the biochemical variables for the experimental group according to TC, HDL, LDL, TG, BG, BMI, and body fat percent tests.
It is known that physical exercises decrease blood glucose levels by increasing the sensitivity to insulin in the exercised muscle and enhancing muscle contraction-induced glucose uptake in these muscles. The mechanisms include increased hexokinase activity, increased glycogen synthase activity, decreased release and enhanced clearance of free fatty acids, increased post-receptor insulin signaling, GLUT4 mRNA and protein, and enhanced influx of glucose to the muscles due to enhanced muscle capillarization and blood flow. Also, the physical exercises enhanced the ability of the muscles to burn fat to a greater extent instead of glycogen. This is mediated by activation of a number of enzymes in the skeletal muscles that are necessary for lipid metabolism which affect positively in decreasing TG, TC and LDL and increasing the levels of HDL [27, 28].
In addition, regular training contributes into the enhancement of glucose uptake into skeletal muscles and could activate hormones like adiponectin. The higher circulating levels of adiponectin is beneficial during exercise and favors the oxidation of fat and glucose uptake into muscles. The decrease in fat and blood pressure could also be critical elements of decreasing T2DM complications .
In the experimental group of the current study, we noticed that the body fat percent and BMI significantly decreased as verified by the difference in results before and after the change within the group. However, the control group showed no significant difference. In fact, physical exercises can increase energy consumption and enhance lipolysis, thereby reducing the body fat mass and BMI .
The improvements in blood lipid profiles for experimental group lead to improvements in the blood pressure parameters while did not change significantly in the control group. In contrast, the lack of exercise causes disorder in the lipoprotein metabolism in the blood to result in an increase in the density of TC and LDL in the blood, and decrease in the HDL density which can cause various cardiovascular disorders. In fact, although the blood pressure-lowering effect of physical exercises is considered to be multifactorial, but seems to be independent of weight loss and energy expenditure. The mechanisms include neurohumoral, vascular and structural adaptation. The antihypertensive effect is believed to be mediated via reduced sympathetically induced vasoconstriction in the trained state, and decreased catecholamine levels .
These observations are in agreement with previously published studies which concluded that participating in aerobic exercises can improve the metabolic risk factors significantly, as well as the associated reductions in the levels of TC, LDL, TG, BG, SBP, DBP, BMI, and body fat percent and elevated the HDL level [19,20,21, 31,32,33,34].
Predominantly, recreational swimming exercise is based on aerobic metabolism because both lipids and carbohydrates are the primary sources of energy. For that, aerobic exercises have a positive effect on the metabolism of these substances . Several published studies demonstrated a positive relationship between aerobic aquatic exercise and the right physiological and psychological conditions. These studies showed that regular physical exercises could reduce musculoskeletal disorders, many metabolic risk factors, anxiety, insomnia, depression, and stress [35,36,37,38]. Briefly, these results emphasize that practicing swimming regularly by patients suffering from Type II DM and HTN has a significant positive effect on TC, HDL, LDL, TG, BG, SBP, DBP, BMI, and body fat percentage compared to those who never participated in swimming sessions. In addition, regular swimming exercises improved metabolism rates, life style, boosting mood also increased the burning a lot of calories for these patients.
In conclusion, we recommended that T2DM, and HTN patients should regularly follow different types of training, including swimming, to have optimal health benefits .
Considerable difficulty was to recruit patients that were free from other complicating disorders and disabling conditions like the patients who have a history of chronic pulmonary diseases, stroke, peripheral artery diseases, and nephropathy. Moreover, the patients who have severe infections, peripheral ulcers, or have problems with glycemic control, which are more common in patients with the combination of T2DM and HTN, were excluded from the current study. Therefore, the sample size of the participants was small as planned by researchers. Furthermore, the current study was planned to be carried out for 12 months. Unfortunately, due to the COVID-19 pandemic, which started in our country in May 2020, we stopped the current study to protect the participants and researchers from this lethal infectious disease. A future study required to test all the metabolic risk factor markers, maximal oxygen uptake (VO2), and heart rate monitoring parameters for a more extended with a larger sample size.