The effect of 8 weeks moderate-intensity continuous training on central hemodynamics and VO2max in non-athlete male

Background and Study Aim. Aerobic exercise improves fitness and quality of life and decreases mortality rate. Existence study determined the central hemodynamic adaptation after 8 weeks moderate-intensity continuous countryside jogging in non-athlete male. 
Material and Methods. Twenty-four untrained healthy male students (aged 20-22 years) volunteered and randomly divided into two groups: continuous training (CTG; n=12) and control (CG; n=12). Training program was countryside jogging for 45 min at 65-70% of Maximum Heart Rate (MHR), 3 days/week for 8-weeks performed. The CG group remained sedentary during the study period. Maximal oxygen consumption (VO2max) obtained using the step-test. Standard medical method impedance cardiograph was performed for hemodynamic parameters, during resting and after step-test conditions, before and after the study period. 
Results. Using t-test, after eight weeks: the resting heart rate (HR) in CTG group significantly decreased (P≤0.05). The systolic blood pressure (SBP) in CTG group decreased significantly at rest and after workload (P≤0.05). The diastolic blood pressure (DBP) did not change in both groups (P>0.05). The stroke volume (SV) increased significantly in CTG group at rest and after workload (P≤0.05).  The cardiac output (CO) did not change in both groups (P>0.05). The cardiac output (CO) did not change in both groups (P>0.05). The VO2max absolute and relative increased significantly in CTG group (P≤0.05). Significant difference between groups in SBP, SV, SVR and VO2max (absolute and relative) (P≤0.05). 
Conclusions. 8 weeks moderate-intensity continuous countryside jogging can improve the cardiac function and VO2max in selected healthy male. The regular exercise of aerobic with moderate intensity causes positive developments in systolic and diastolic blood pressures.

ORIGINAL ARTICLE with defining hemodynamic differences. Isotonic type, as endurance exercise increased in CO with normal or reduced peripheral vascular resistance. This type of exercise primarily represents a volume challenge for the heart, which affects all four chambers, specially increased left ventricular chamber size, with an increase in wall thickness caused by volume overload (eccentric left ventricular hypertrophy). In contrast, isometric exercise, as strength training, leads to increased peripheral vascular resistance, and normal or only little increased CO. The increase in peripheral resistance causes momentary but potentially marked systolic hypertension and left ventricular afterload. Athletes involved in mainly static or isometric exercise develop increased left ventricular wall thickness, with no change in left ventricular chamber size (concentric left ventricular hypertrophy) [12,13].
The CO is altered by regulating both heart rate (HR) and stroke volume (SV) [14]. Regular exercise and physical activity cause a reduction in resting heart rate (RHR) [15,16]. Cramer et al. [15] found a significant reduction in heart rate through yoga of 6.59 bpm in in healthy participants. In another studies Huang G, Shi et al. [17] showed that endurance training causes RHR reductions of 8.4% in older individuals. Furthermore, a decrease in RHR at quiet status was found after tai chi exercise in healthy adults in the research of Zheng Li et al. [18].

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The increase in maximal heart rate (MHR) is responsible for enhancement of the CO during exercise, and peak HR is a basically limiting factor of peak exercise capacity in healthy people. Maximal HR does not increase with training. In contrast, with prolonged physical training increases in stroke volume (SV) at rest and during exercise [19]. The initial increase in SV during training is as a result of an improved systolic and diastolic function as indicated by a raise in venous return and a stronger myocardial contractility. Additional research by Slordahl et al. [20] demonstrated that high intensity aerobic training at 90-95% of maximal oxygen consumption (VO 2max ) increased left ventricle heart mass by 12% and cardiac contractility by 13%, which is comparable to cardiovascular changes observed in continuous aerobic exercise. LV filling pressures and diastolic LV distension increase at the onset of exercise causing stretch-activation of myofibers according to the Frank-Starling mechanism and subsequently an increase in SV [21]. Findings about the CO help to develop physiological responses and mechanisms of adaptation due to the physical training, sedentary lifestyle and chronic disease [22].
Maximal oxygen consumption (VO 2max ) is considered the uppermost ability of the body to consume, distribute and utilize oxygen for energy production. It is commonly called maximal aerobic capacity and is a good predictor of exercise performance. Improvements in cardiovascular function will increase one's VO 2max . Daussin et al. [23] measured VO 2max responses among men and women who participated in an 8-week interval and a continuous cardiovascular training program. VO 2max increases in the interval group (15%) and in the continuous group (9%). Several study reported that the 4 × 4-min high-intensity interval training approach has been shown to be more effective than moderate exercise training for improving maximal oxygen uptake (VO 2max ) in both healthy subjects and patient groups [24][25][26]. Improving cardiovascular function and increasing VO 2max are major goals of patients that suffer from cardiovascular disease [27].
Many people who want to do sports practice in different exercises. But what kind of cardiovascular exercise more effective than it is important to clearly specify. The aim of this study determined the central hemodynamic adaptation after 8 weeks moderate-intensity continuous countryside jogging in non-athlete male.

Participants.
The study was performed on 24 non-athletic healthy male students aged from 18-22 years. Selected participants were randomly divided into two groups as continuous training group (CTG; n=12) and control group (CG; n=12). They did not attend regularly sports activities (more than one hour per week), before this study. The criterion for cardiovascular health was the data obtained from the questionnaire devised by the researcher. Before the initiation to participate in the study, all subjects were informed of the process and filled out the medical sport questionnaire and the соnsent form.

Research Design. Training programme.
Training program was designed including a 45-minutes countryside continuous jogging with 65-70% of the maximum heart rate (MHR), three times a week for eight weeks. Training session was of 65min duration and consisted of warm-up (10min), main program (45min) and cold-down (10 min). All the training sessions were supervised by the researcher. The control group remained sedentary during the study period.
Blood pressure (BP) were recorded in the sitting position. BP at rest was obtained from the right arm was resting on a table with the elbow in a flexed position by manually using mechanical aneroid sphygmomanometer and a quality stethoscope (MDF ® Calibra Professional Aneroid Sphygmomanometer and Stethoscope). The resting heart rate (HR) was recorded by 60-s count, maximum heart rate was determined by the formula: HR max = 220 − age.
Step-test uses as a 40 cm high step bench. Subjects try with a step frequency of 22.5 steps per minute under the metronome for 6 minutes. Aerobic capacity was expressed as estimated maximal oxygen consumption (VO 2max ), obtained using the step-test and the Astrand-Ryhming nomogram from the steady state heart rate (HR) and workload [28].
Statistical analysis. SPSS 19.0 packet program. Means and standard deviation were calculated with this program. Test of normality for the data's were made by Kolmogorov-Smirnov test. And then parametric tests applied. The evaluation inside the group was made by Paired Samples-t test, and evaluations between-group differences in baseline values and intervention induced changes were tested by independent-t test. Statistical significance was accepted as and p ≤ 0.05.

Results
General features and demographic characteristics of the participants are summarized in Table 1. Values of central hemodynamic variables participants are summarized in Table 2. After eight weeks the resting heart rate (HR) in the CTG significantly decreased (P≤0.05). The systolic blood pressure (SBP) in CTG decreased significantly at rest and after workload (P≤0.05). The diastolic blood pressure did not change in both groups (P>0.05). The systemic vascular resistance (SVR) in both groups did not change (P>0.05). The stroke volume (SV) increased significantly in CTG at rest and after workload (P≤0.05). The cardiac output (CO) did not change in both groups (P>0.05). The VO 2max absolute and relative increased significantly in CTG (P≤0.05).
Significant difference observed between groups in SBP, SV, SVR and VO 2max absolute and relative (P≤0.05).

Discussion
Hypertension is the most important risk factor for cardiovascular morbidity and mortality [29] and it is also known that increased resting heart rate is an independent risk factor associated with cardiovascular fatality [30]. In addition, increased heart rate may also increase atherosclerosis, cardiac ischemia, cardiac hypertrophy and heart failure [31,32]. Studies showed that the patients with high-normal blood pressure (systolic blood pressure 130-139 mmHg, diastolic blood pressure 85-89 mmHg, or both) were twice as likely to have a cardiovascular disease risk compared to those at low levels [33,34,35]. Liu S et al. [36] reported significantly decrease in SBP and DBP after acute and chronic exercise. In our study SBP decreased from 125.0±8.7 to 115.7±4.1 mmHg at rest and decreased from 143.6±5.9 to 135.0±8.4 at workload (step-test) in training group significantly, along with decrease in DBP, but there was no significant mode. It was also observed that systolic and diastolic blood pressures of CTG were closed to cardiovascular disease risk before training, but at the end of the study there was a positive improvement indicating that subjects in exercise group were away from the risk of cardiovascular disease. It can be argued that the regular exercise of aerobic with moderate intensity causes positive developments in systolic and diastolic blood pressures [37,38]. Jennings et al. [39] and Whelton et al. [40] reported that higher exercise more than five times per week and >60 min did not produce a greater reduction in BP in hypertensive patients compared with three to four times per week and 30-60 min. The relation of long term training intensity to BP reductions is unclear, with some authors observing more change with an intensity >70% VO 2max [41], whereas another sees no intensity effect [11]. Nevertheless, the time course of the resting BP change allowed us to verify that the greatest BP reduction was achieved at the end of the 8 weeks of training [36].
Duncker and Bache, [42] reported that during physical activity increase in HR is highest of myocardial oxygen consumption is responsible. In the present study, HR decreased significantly at rest. It is consonant with research of Rodrigues et al. [43] and Chaudhary et al. [44]. SV increased at rest and workload. Trilk et al. [45] demonstrated that interval training improved cardiac function by reducing HR and increasing SV. After 8 weeks continuous training the CO showed no significantly increase. In result of endurance training is eccentric reformation change on heart. It is highlight with increase the internal dimension and a reason of the large left ventricular volume, and high SV [46,47]. In addition, in the CTG was shown an increase in SV with a decrease Step-test 4.1±0.6 4.7±0.5* , ** 3.6±1.1 3.7±0.7 VO 2max relative, ml.kg -1 .min -1 Step-test 52.6±8.8 62.9±6.3* , ** 48.1±10.9 51.4±11.5 Note: Significantly different from beginning at statistical level: * in groups, ** between groups -P≤0.05 in heart rate. This mechanism was shown as the result that might maintain a stable resting CO. It can be said, increasing SV is maintained with decreasing heart rate, and conversely. Also, regular exercise makes the flow of the venous blood, thus increasing the amount of blood returning to the heart, which increases CO [48].
Mean arterial blood pressure increases in result of dynamic exercise. Increase in mean arterial pressure results from an increase in CO and decrease in total peripheral resistance [49,50]. The long term exerciseassociated BP reduction is mainly due to decreased total peripheral resistant that is not met by an increase in CO [8]. The mechanism in which exercises have effect on blood pressure is different depending on intensity, time, and training types, but it is known that decreasing blood pressure happens due to decreasing activity of sympathetic nervous system and decreasing the peripheral resistance [51]. That confirmed with decrease in SVP at rest and after step-test. After 8-weeks the SVP in CGT was significantly less than control group. VO 2max is accepted as a demonstration of cardiovascular health and cardiopulmonary fitness [52]. One of the aims of our study was to increase VO 2max by applying moderateintensity continuous programs at 65-70% in addition, improving left ventricular cardiac parameters (CO & SV) [54]. At the end of the study, there was a positive increase in VO 2max (absolute and relative) in CTG (at rest and after workload) and resulting in positive improvements in SV. For this reason, we can say that regular exercises on young male in training group benefit cardiorespiratory fitness and primary and another protection of cardiovascular diseases [54]. Mazurek K et al. [55] reported significantly increase in VO 2max absolute and VO 2max related in college females after interval and continuous aerobic training. Tjonna et al. [56] showed the intensive endurance training significantly improves VO 2max after 10-week of training in healthy men. After 8-weeks VO 2max in CGT was significantly higher than CG.
In response to aerobic training, the body reacts by increased oxygen uptake, HR, CO, initial peak and then plateau in SV. Peripheral vascular resistance is reduced and SBP progressively increases along with a decreased DBP [57]. It is consistent with the result of our study in terms of step-test.

Conclusion
The result of this study demonstrated that a positive effect through moderate-intensity continuous countryside jogging on VO 2max and cardiac function. Also, the exercise duration (45 min) and intensity (65-70% VO 2max ) prescribed in this study were expected to yield the optimal BP reduction as well as improvement in aerobic power especially for sedentary people.