Effect of exercise on blood pressure among medical students, in relation to duration of exercise and body mass index

 

 

Abstract               Background and Objectives: Exercise testing provides valid information about physiological systems of individuals that may help identify healthy individuals at risk of developing future cardiovascular diseases. Physical exercise is a relevant non-pharmacologic option for the prevention and treatment of high Blood Pressure. Scientific evidence in some literatures have demonstrated that after an acute exercise bout, BP levels are reduced for minutes or hours in relation to pre-exercise levels. Materials and Methods: Our study included 120 normal healthy untrained young male medical students in the age group of 18-22 years were selected randomly. Out of 120 students, 60 students were considered as control group and reaming students were involved in exercise group. Cardio-respiratory responses to different exercise sessions were observed on a stationary exercise bicycle and treadmill, in the exercise group. Results: The present study demonstrated that in the exercise group with normal Body Mass Index (BMI), the Systolic Blood Pressure was increased linearly with increasing intensities and duration of exercise when compared to the students with abnormal BMI. The Systolic Blood Pressure had a steady decline during recovery period. Systolic Blood Pressure is slightly above the resting value at the end of 30 minutes in the recovery period and returned to resting value at the end of 60 minutes. Conclusion: In the students with normal BMI, the Systolic Blood Pressure increased linearly with increasing intensities and duration of exercise and it reflects the normal sympathetic drive on cardiovascular system, when compared to the students with abnormal BMI. Decrease in Diastolic Blood Pressure was interpreted due to decrease in peripheral resistance. Mean arterial Blood Pressure remained unchanged. There was steady decline in Systolic Blood Pressure during recovery period. Cardio-respiratory responses to different exercise sessions, on a stationary bicycle and treadmill, in the exercise group with normal BMI, were in the range of physiological limits when compared to the students with abnormal BMI.

Key Words: Blood Pressure, Body Mass Index (BMI), Intensity and Duration of exercise, Stationary bicycle, Treadmill.

 

 

INTRODUCTION

Exercise testing provides valid information about physiological systems of individuals that may help identify healthy individuals at risk of developing future cardiovascular disease (CVD). ¹ Cardiovascular markers such as, resting heart rate (HR) respiratory rate (RR) and Blood Pressure (BP) have been used as simple non-invasive and useful biomarkers of the fundamental status of Blood circulation and the cardiovascular system (CVS) in healthy people.² Exercise which is the increase in bodily movement involving all major muscle groups, challenges all physiological systems including the cardiovascular system. Exercise would be referred to as an acute session, and training, the chronic effect (repeated acute bouts that lead to a conditioning effect). Heart rate Respiratory rate and Blood Pressure are hemodynamic variables that are easily measured during exercise in different populations. ³ Physical exercise is a relevant non-pharmacologic option for the prevention and treatment of Hypertension. Scientific evidence in the literature have demonstrated that after an acute exercise bout, Systolic and Diastolic Blood Pressure levels are reduced for minutes or hours in relation to pre-exercise levels. ^4–6 This phenomenon is called post-exercise hypotension (PEH) and considered as an important strategy in the control and reduction of Blood Pressure. ^{4, 6, 7, 8} Although the first report on Post Exercise Hypotension ⁹ was published over 100 years ago, systematic investigations of this phenomenon did not begin until the 1980s. The interest in the Post Exercise Hypotension has been mainly motivated by its clinical implications; it has potential as a non-pharmacological agent that can treat several cardiovascular disorders, such as hypertension. ^{10, 11} Only a few studies have investigated the BP responses following resistance exercise, and these have shown increase ^{12, 13}, maintenance ^[14-16], and even decrease ^17-20 in post-exercise Blood Pressure. Although occurrence of Post Exercise Hypotension in resistance exercises is demonstrated by some studies, however there is still no consensus on an ideal protocol to enhance this effect^[4,21].According to results of some studies, resistance exercise intensity affects the duration (longer Post Exercise Hypotension in the protocol with the highest intensity), but not the magnitude of Post Exercise Hypotension ^22,23, and different training methodologies (set repetition vs. circuit format) does not affect the magnitude or duration of the post-resistance exercise hypotensive response ²³.In addition to exercise intensity, volume and sequence that were previously studied, other variables such as the amount of muscular mass involved, number of repetitions, type of training and rest interval (RI) between the exercise sets can affect the hemodynamic responses to a bout of resistance exercises.^24,25 Despite the physiological mechanisms involved, Post Exercise Hypotension may depend on the specific type of the exercise session. The relationship between the intensity and duration of the exercise session and Post Exercise Hypotension is still controversial; several studies have reported a positive correlation between the intensity ^26-28 and duration ^{26, 29, 30} of the session and the magnitude and/or duration of the Post Exercise Hypotension, whereas other experiments have shown no such relationship ^31-33, particularly in normotensive subjects. The majority of these experiments, however, were designed to investigate the effect of only one variable (the intensity or duration of the session) on Post Exercise Hypotension. Because the intensity and duration of exercise can be adjusted simultaneously, the relationship between the interaction of these two variables and Post Exercise Hypotension is of interest. Therefore, the present study was aimed to investigate the effects of different endurance exercise sessions with different intensities and durations on the Blood Pressure in healthy male medical students with different BMI.

AIMS AND OBJECTIVES

Our study was aimed to observe the effect of isotonic exercise on Blood Pressure among Medical students with different BMI, by using stationary exercise bicycle and treadmill at different intensities and durations.

 

MATERIALS AND METHODS

The present study was conducted on Male Medical Students at our medical college in the month of August 2019. Study protocol was approved by the Institutional Ethical Committee. Our study included 120 normal healthy untrained young male medical students in the age group of 18-22 years were selected randomly. Out of 120 students, 60 students were considered as control group and reaming students were involved in exercise group.

 

Inclusion Criteria-:

1. Male Medical students aged between 18-22 years, who were given informed consent
2. Medical students who were non-smokers, non-alcoholics and had no history of lower body injuries, cardiovascular disease, orthopedic problems or other medical problems.

Exclusion Criteria-:

1. Students who were on drugs that could influence cardiovascular responses
2. Students who were with musculoskeletal deformities

It was instructed to the participants that, not to change their eating, sleeping and drinking habits during the study period.

Procedures

Initially, the volunteers remained seated in a comfortable chair for 10 min, after which BP was measured at 5^th and10th minute to obtain average resting values. Then, the subjects who were randomly selected for one of the eight sessions underwent 5 minute warm-up consisting of static stretching and performed one of the eight sessions in a randomized order.

(1) Stationary bicycle exercise-light intensity-2 min,

(2) Stationary bicycle exercise-light intensity-5 min,

(3) Stationary bicycle exercise-moderate intensity-2 min,

(4) Stationary bicycle exercise-moderate intensity-5 min

(5) Treadmill exercise-light intensity-2min

(6) Treadmill exercise-light intensity-5min

(7) Treadmill exercise-moderate intensity-2min

(8) Treadmill exercise-moderate intensity-5min

After performing the exercise, subjects came back to laboratory and rested in the supine position for 60 min, with Blood Pressure being measured at 10 min, 30 min, 60 min of post-exercise. Blood Pressure was recorded by the same observer in all exercise trials, using a standard mercury sphygmomanometer. The participants carried out eight experimental sessions with a minimum of 24 hour intervals between different sessions. Pre and post-exercise values of Blood Pressure were measured. Gradation of exercises in to light and moderate intensities was based up on the classifications according to Christensen Classification of grading of exercises (Table 1).

Table 1: Gradation of exercise based according to Christensen

Following anthropometric measurements were used to calculate the Body mass index (BMI). Body weight was measured with human weighing machine (Kruups) in a standing position without shoes to the nearest 100 gm with minimal clothes. Height was measured with measuring tape meter in standing position without shoes while the shoulders were in normal position, to the nearest 1 cm. Blood Pressure (BP) was measured manually using a standard mercury sphygmomanometer during rest, after exercise at 10 min, 30 min and 60 minutes in supine position. Equipment used in our study were STEX stationary exercise bicycle ( S25ux Upright Bike S25 Series) and Treadmill (STEX S25T), equipped with digital sensors for constant monitoring of Heart Rate in beats / minute, Power in watts and Time in minutes.

 

RESULTS

The present study included a total of 120 healthy male medical students (60 controls and 60 subjects). The various parameters of controls and subjects (exercise group), which include their age and their physical characteristics, were shown in Table 2.

Table 2: Physical Characteristics of Controls and Subjects

The Mean of Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP) of controls at rest and after 10 min, 30 min, and 60 min were presented in Table 3. The Mean SBP and DBP of exercise group at rest, after two minute and five minute exercise of light and intensity on Stationary Exercise Bicycle were shown in Table 4. The Mean SBP and DBP of students in exercise group were recorded at rest and after five minute exercise of light intensity on Stationary Exercise Bicycle were shown in Table 5. The Mean SBP and DBP of students in exercise at rest and after two minute and five minute exercise of moderate intensity on Stationary Exercise Bicycle were shown respectively in Table 6 and Table 7.

Table 3: Controls baseline levels of Blood Pressures

*Blood Pressure in mm Hg

 

Table 4: Post Exercise (Stationary Exercise Bicycle - Light Intensity - 2 minutes duration) changes in Blood Pressure

^ Significant, *Blood Pressure in mm Hg

 

Table 5: Post Exercise (Stationary Exercise Bicycle - Light Intensity - 5 minutes duration) changes in Blood Pressure

^ Significant, *Blood Pressure in mm Hg

 

Table 6: Post Exercise (Stationary Exercise Bicycle - Moderate Intensity- 2 minutes duration) changes in Blood Pressure

^ Significant, *Blood Pressure in mm Hg

 

Table 7: Post Exercise (Stationary Exercise Bicycle - Moderate Intensity - 5 minutes duration) changes in Blood Pressure

^ Significant, *Blood Pressure in mm Hg

The Mean SBP and DBP of subjects at rest and after two minute and after five minute exercise of light intensity on Treadmill were shown in Table 8 and Table 9 respectively. The Mean SBP and DBP of subjects at rest and after two minute exercise and after five minute exercise of moderate intensity on Treadmill were shown in table 10 and Table 11.

 

Table 8: Post Exercise (Treadmill-Light Intensity - 2 Minutes duration) changes in Blood Pressure

 

^ Significant, *Blood Pressure in mm Hg

 

Table 9: Post Exercise (Treadmill - Light Intensity - 5 minutes duration) changes in Blood Pressure

^ Significant, *Blood Pressure in mm Hg

 

Table 10: Post Exercise (Treadmill - Moderate Intensity - 2 minutes duration) changes in Blood Pressure

^ Significant, *Blood Pressure in mm Hg

 

Table 11: Post Exercise (Treadmill-Moderate Intensity - 5 minutes duration) changes in Blood Pressure

^ Significant, *Blood Pressure in mm Hg

 

DISCUSSION

The present study demonstrated that in medical students with normal BMI the Systolic Blood Pressure increased linearly with increasing intensities and duration of exercise and it is statistically significant, when compared to the students with abnormal BMI. Exercise induced significant rise in Systolic Blood Pressure reflects the normal sympathetic drive on cardiovascular system which enables the heart to pump more Blood to the active tissues in the body, as physical conditioning of person greatly influences the heart rate, Blood Pressure and rate of Blood flow of the individual. Similar increase in Systolic Blood Pressure during graded exercise were reported by Wolthuis et al, ³⁶ Bhave et al, ³⁹ Sharma et al, ⁴¹ and Venkatesh et al. ⁴² In our study, the Systolic Blood Pressure had a steady decline during recovery period. Systolic Blood Pressure was slightly above the resting value at the end of 30 minutes in the recovery period and returned to resting value at the end of 60 minutes in the students with normal BMI. Wolthuis et al. ^[36] also reported the similar findings. Systolic Pressure slightly above the pre-exercise value at the end of 30th minute was reported by Thomas et al. ³⁷ and Madan et al. ⁴³ Similar findings were reported by Fraser Robert et al, ³⁴ Bhave et al.³⁸ and Biswas et al. ⁴⁰ Stevenson et al, ⁴⁴ also found that return of both Systolic and Diastolic Pressure to pre-exercise values generally did not occur until 30 minutes of recovery. In the present study, there was a minimal increase in Diastolic Blood Pressure in both the light intensity exercises and there was a decrease in Diastolic Blood Pressure in both the moderate intensity exercises. This decrease is thought to be due to decrease in systemic vascular resistance which occurs during exercise. Change in the Diastolic Blood Pressure was minimal (1-4 mm of Hg) as compared to the change in Systolic Blood Pressure (20-40 mm of Hg). This result is consistent with the earlier work done by Fraser Robert et al. ³⁴ Biswas Dalia et al.⁴⁰ and Bhave et al. ³⁹ In the present study, mean arterial Pressure was found to change very little since changes in Systolic and Diastolic Blood Pressure are opposite in direction. This finding is in consistency with the earlier work done by Lars Hermansen et al. ³⁵ and Fraser Robert et al. ³⁴ In consistent to the results of the present study, Veloso et al ^[45] observed no change in SBP and DBP after three exercise protocols with rest interval of 1, 2 and 3 minutes between the sets, that consisted of three sets of eight repetitions in six exercises. De Salles et al ⁴⁶ reported no changes of SBP and DBP after exercise with 2 min rest interval between different exercise sets. Rodriguez et al ⁴⁷ observed no significant variance in the SBP and DBP after both of traditional multiple set and tri-set methods that six upper limb exercises were used for two distinct muscular groups (chest and back). Also Polito et al ⁴⁸ failed to induce a hypotensive response in SBP and DBP following three series of 12 maximal repetitions of knee extension unilaterally and bilaterally .Similar results were also observed by Roltsch et.al. ⁴⁹

 

CONCLUSION

The Systolic Blood Pressure increased linearly with increasing intensity and duration of exercise in the students with normal BMI. Exercise induced significant rise in Systolic Blood Pressure reflects the normal sympathetic drive on cardiovascular system. Changes in the Diastolic Blood Pressures were minimal as compared to the change in Systolic Blood Pressures. The SBP and DBP at the end of different exercise models, intensities and durations returned to the pre-exercise levels and there was no post exercise Hypotension or Hypertension in the students with normal BMI when compared to students with high BMI.

 

REFERENCES