Effect of high and low intensities of aerobic training on rate pressure product.
Aerobic exercise is defined as "any activity that uses large muscle groups, can be maintained continuously, and is rhythmic in nature." It is also defined as exercise that increases the need for oxygen. Aerobic exercise is used interchangeably with the terms cardiovascular exercise, cardiorespiratory exercise, and cardio. 
Regular aerobic exercise improves health in the following ways: Reduces body fat and improves weight control and resting blood pressure (BP) (systolic and diastolic) blood supply to the muscles, reduces insulin resistance, and improves heart and lung functions. 
Basic aerobic endurance training that follows the ACSM's recommended guidelines  for cardiorespiratory fitness training is known to improve [VO2.sub.max] leads to strengthening and enlarging of the heart muscle, to improve its pumping efficiency and reduces the resting heart rate (RHR), known as aerobic conditioning also improves circulation efficiency and reduces BP. 
RPP is defined by RHR multiplied by systolic BP (SBP). Under resting conditions, safer RPP should range between 7000 and 9000 mmHg/min. Any total value >10,000 mmHg/min indicates an increased risk for heart disease. At the same time, low RPP value suggests the restricted coronary blood supply with inadequate ventricular function. There are few studies showing improved RPP after regular aerobic training. [5,6]
However, there are quite a few studies comparing the different intensities of aerobic exercise on cardiovascular system, so the current study was designed to compare the effect of high and low intensities of aerobic exercise on cardiovascular system.
The objective of this study was to study the effect of high and low intensities of aerobic training on rate pressure product (RPP).
MATERIALS AND METHODS
A total of 80 sedentary male aged between 18 and 40 years were recruited from two fitness centers. Subjects were informed about the study and informed written consent was taken. Subjects were allocated into two equal groups of low-intensity and high-intensity exercise regimen using random number table.
* Men aged between 18 and 40 years who volunteered to participate in
* Involvement in a regular exercise or weight loss program for at least 6 months before the recruitment.
* H/o cardiovascular disorders.
* H/o endocrinologic or orthopedic disorders.
The anthropometric measurements included weight, height, waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-stature ratio (WSR) following the recommendations of the World Health Organization. 
RHR: Radial pulse was taken after subject rests for 15 min, felt for full 1 min, and noted down.
BP of each subject was recorded using digital sphygmomanometer (ACCUMAM), which recorded both systolic, diastolic BP, and even heart rate. BP was recorded 3 times with 5 min gap between each recording and average of three readings was displayed and noted.
RPP: Calculated using the formula
Rate pressure product (mmHg/min) = Systolic blood pressure x heart rate
Exercise Training Protocol
Digital cycle ergometer (COSCO, MODEL-CEB-JK-7007 A) which displays heart rate and level of exercise was used for the aerobic exercise. The aerobic training was designed to exercise the upper and lower body: For high-intensity group--subject exercised at Level 5, at 50 rpm, accounting to 150 watts (900 kpm) for 15 min at 80% HR max (80% [VO2.sub.max]) and for low-intensity group--subject exercised at Level 3, at 75 rpm, accounting to 90 watts (540 kpm) for 30 min at 50 % HR max (50% [VO2.sub.max]).
Both the groups exercised at different duration so that the work done by both the groups were almost equal. Subjects used to exercise either in evening or morning depending on their convenience. All subjects used to exercise 5 days a week continuously for 12 weeks. At the end of 12 weeks, all the parameters (weight, body mass index [BMI], WC, WHR, RHR, and RPP) were measured again.
SPSS 16.5 version of the statistical package was used for analysis of the data. Descriptive statistics like mean and standard deviation were calculated. Paired t-test of significance was used to study the difference between the baseline and post-interventional values of study variables.
Majority of our study population (55%) were between 21 and 30 years of age group; very few were below 20 years [Table 1].
Mean BMI, RHR, and RPP decreased in both the groups being more significant (P < 0.05) in high-intensity group. Results summarized in Tables 2 and 3.
SBP and DBP decreased in both the groups but not statistically significant.
In our study, RHR and RPP decreased in both intensities of aerobic exercise but more significant in high-intensity group. The results were consistent with Shiotani et al. study which showed that aerobic exercise exerts beneficial effects on the circadian rhythm of heart rate, especially in the morning. 
Endurance-trained subjects are known to have a significant resting bradycardia. Vigorous-intensity exercise confers greater cardioprotective health benefits than moderate-intensity exercise, including a lower incidence of coronary heart disease that may be related to lower-risk factors. Clinical trials have found that higher intensity exercise resulted in greater reductions in resting BP than lower intensity. [9,10]
According to White WB, RPP of 12,000 or below with the HR of 60-120 bpm and SBP of 100-140 mmHg is considered to be normal without any existing or future risk of cardiovascular complications in normal individuals.  All our study participants, RPP was within normal levels.
RPP really illustrates the oxygen demands of the heart for a person who is in a good physical condition like a trained athlete, the oxygen demands of the heart place less contributing stress in a workout, whereas an untrained individual experiences an elevated stress from cardiac demand and the fatigue of respiratory muscles attempting to satisfy this demand. Hence, a trained person with less RHR and less resting BP will have effective myocardial oxygen consumption and ultimately later onset of fatigue when compared to an untrained person.
Lesser RPP is an indicator of more parasympathetic activity and increased parasympathetic tone is believed to be cardioprotective.  Hence, our study shows the cardioprotective effects of aerobic training.
Regarding the role of the exercise's intensity on health parameters, despite the increasing interest on high-intensity training, there is still no accordance between researchers. Clinical trials generally reported greater improvements after vigorous (typically > or = 60% aerobic capacity) compared with moderate-intensity exercise for diastolic BP, RHR glucose control, and aerobic capacity, but reported no intensity effect on improvements in SBP, lipid profile, or body fat loss. 
Many studies show that high-intensity aerobic training improves aerobic capacity ([VO2.sub.max]) and physical fitness index in comparison with low-intensity training. [14,15,16]
Even though regular aerobic training offers cardioprotection, high-intensity method of training seems to be more beneficial when compared to the low-intensity method.
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[13.] Swain DP, Franklin BA. Comparison of cardio protective benefits of vigorous versus moderate intensity aerobic exercise Am J Cardiol 2006;97:141-7.
[14.] Madhusudhan U. Effect of high and low intensities of aerobic exercise on physical fitness index. J Evid Based Med Health Care 2015;2:3296-300.
[15.] Madhusudhan U, Bhanuprakash. Effect of high and low intensities of aerobic training on maximal oxygen consumption. Biomedicine 2015;35:163-6.
[16.] Bassi R, Sharma S, Sharma A, Kaur D, Kaur H. The effect of aerobic exercises on peak expiratory flow rate and physical fitness index in female subjects. Natl J Physiol Pharm Pharmacol 2015;5:376-81.
Department of Physiology, DM Wayanad Institute of Medical Sciences, Wayanad, Kerala, India
Correspondence to: Madhusudhan U, E-mail: email@example.com
Received: November 24, 2017; Accepted: December 02, 2017
How to cite this article: Madhusudhan U. Effect of high and low intensities of aerobic training on rate pressure product. Natl J Physiol Pharm Pharmacol 2018;8(4):550-553.
Source of Support: Nil, Conflict of Interest: None declared.
Table 1: Age wise distribution of study population Age groups High-intensity Low-intensity (in years) Group n=40 (%) Group n=40 (%) <20 3 (7.5) 5 (12.5) 21-30 23 (57.5) 21 (52.5) 31-40 14 (35) 14 (35) Table 2: Parameters in high-intensity group Parameters Baseline After t 12 weeks BMI (kg/[m.sup.2]) 26.39[+ or -]1.17 25.6[+ or -]1.2 2.58 RHR (beats/min) 79.79[+ or -]7.71 74.05[+ or -]6.10 7.33 (*) SBP (mmHg) 132.25[+ or -]7.52 127.1[+ or -]6.88 4.33 DBP (mmHg) 76.6[+ or -]5.94 73.8[+ or -]5.43 1.64 RPP (mmHg/min) 10574.31[+ or -]1312.21 9419.1[+ or -]1008.63 7.68 (*) (*) Statistically significant (P<0.05). BMI: Body mass index, RHR: Resting heart rate, SBP: Systolic blood pressure, DBP: Diastolic blood pressure, RPP: Rate pressure product Table 3: Parameters in low-intensity group Parameters Baseline After t 12 weeks BMI (kg/[m.sup.2]) 28.57[+ or -]2.44 27.39[+ or -]2.46 6.58 (*) RHR (beats/min) 79.75[+ or -]7.74 73[+ or -]6.43 7.68 (*) SBP (mmHg) 128.15[+ or -]10.96 122.1[+ or -]7.73 4.37 DBP (mmHg) 76[+ or -]5.80 74.95[+ or -]5.63 1.68 RPP (mmHg/min) 10344.31[+ or -]1484.21 8930.4[+ or -]1126.61 9.24 (*) (*) Statistically significant (P<0.05). BMI: Body mass index, RHR: Resting heart rate, SBP: Systolic blood pressure, DBP: Diastolic blood pressure, RPP: Rate pressure product
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|Title Annotation:||RESEARCH ARTICLE|
|Publication:||National Journal of Physiology, Pharmacy and Pharmacology|
|Date:||Apr 1, 2018|
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