ABSTRACT:

The autonomous nervous system controls one’s heart rate and blood pressure. This can be

affected by gravity, exercise, temperature and submergence. These factors were all varied and

observed in this experiment.

Male and female subjects were then subjected to various tests, each varying a different variable

factor. The results of altering these variables were recorded and results contrasted between

males and females. It is postulated that these variables alter the heart rate and blood pressure

in some discernible way.

Due to the vast differences in the class data set. Observed results were anomalous and

discernible trends difficult to analyse.

INTRODUCTION:

The autonomous nervous system controls involuntary processes within the body, such as the

heart rate and blood pressure. It is part of the peripheral nervous system. Due to external

pressures from the environment, [gravity or temperature] or changes in the body’s

requirements under stressful conditions can lead to a change in these processes.

Blood, in our circulatory system, exerts pressure on the walls of the blood vessels as it traverses

through them about the body via systemic circulation. This pressure can be measured using a

sphygmomanometer. The units of measurement for blood pressure are millimetres of Mercury

[mmHg], written as systolic blood pressure over diastolic blood pressure. Normal blood

pressure is considered to be 120/80 mmHg.

Within the heart there are 4 chambers, the left and right atrium, and the left and right ventricle.

Blood, on entering the atrium contracts and pushes blood into the ventricles. The ventricles are

larger compared to the atria of the heart. This pumping action of the heart is known as the

cardiac cycle and in this cycle there are two phases, the systole and the diastole. Systolic

pressure is the pressure received by the arteries from the contraction of the ventricles during a

heartbeat, whereas diastolic pressure is the pressure exerted by the blood in the arteries in-

between heart beats while the muscle relaxes.

The systolic phase is coincided with contraction of the hear muscles. This occurs when

deoxygenated blood enters the right atrium which contracts, pushing the blood into the right

ventricle. The right ventricle then contracts to push the deoxygenated blood to the lungs to be

oxygenated. The blood which has been oxygenated then eneters the left atrium which

contracts, forcing the blood into the left ventricle. From the left ventricle, via contraction the

blood is then pushed throughout the body.

Diastolic pressure is the minimal pressure exerted by the blood on the arteries during relaxation

of the ventricles as they fill up with blood

An electrocardiogram [ECG] is a test used which functions by recording the electrochemical

activity of the heart as it beats. The ECG illustrates the rhythm of the heartbeat, the strength

and timing of the electric signals as they pass through the heart and also how fast the heart is

beating.

Figure 1 : Example of a Normal ECG (Practical Clinical Skills, 2013)

The ECG gives a chart of peaks which correspond to the different stages of the cardiac cycle.

The P wave symbolizes the atrial depolarization; the PQ segment represents the atrial systole.

The QRS complex shows the ventricular depolarization whilst the ventricular systole is given by

the ST segment. The T wave illustrates ventricular repolarization.

Figure 2 : ECG Waves, Intervals and Segments (Chest, Heart and Stroke Scotland, 2014)

The pulse pressure is deduced by the stroke volume of the heart, the expansive ability of the

arterial system due to the aorta other large arteries and the resistance of flow in the arteries.

The elasticity of the arteries aid in the reduction of the blood pressure hence reducing the pulse

pressure. . Pulse pressure is derived from the blood pressure readings. Higher blood pressure

gives rise to a stronger pulse and vice versa. Thus pulse pressure if proportional to blood

pressure.

Pulse Pressure = Diastolic pressure – Systolic Pressure

The body responds to vasoconstrictions in the extremities when exposed to cold stress to

maintain the core temperature. This alter blood pressure. This is tested using the cold pressor

test in which the subjects hand is immersed in ice water for a certain period of time before

pulse rate and blood pressure are measured.

Gravity affects blood flow distribution depending on one’s positioning. When laying down,

blood flow is even from the base to the apex i.e. feet to head. Gravity gives rise to uneven

pulmonary blood flow in an upright person. Due to the downward pull of gravity, a lower blood

pressure is seen at the apex of one’s lungs.

Exercising has tendencies to offset the gravitational effects in an upright person. With exercise,

ventilation is increased as the oxygen demands of the body are greater than before in the

resting state. More oxygen is needed to respire as the body requires more energy. Thus heart

rate and blood pressure rise in order to facilitate the heightened requirements of the body.

When the body is submerged underwater, when one is holding their breath, the body enters a

state of oxygen conservation known as the mammalian diving reflex. To stimulate this effect,

subjects were required to hold their breath. This affects both the blood pressure and heart rate.

Body mass index [BMI] is utilized to determine how much fat a person has. This is also in

indicator of one’s health i.e. if one is underweight, healthy, overweight or obese.

BMI=weight (¿kilograms)height (¿metres)2

.

A BMI value of less than 18.5 is considered “underweight”, 18.5 to 24.9 is considered “normal”,

25.0 to 29.9 is considered “overweight” and values of over 30 are considered “obese” (Castro,

2013).

This experiment seeks to gain insight into the effects of the variable factors of gravity,

temperature, submergence and exercise on blood pressure and pulse by altering each factor

one at a time and observing the changes in data.

METHOD:

The radial pulse of the individual to be tested was taken by feeling their pulse with the palm

facing upward and feeling for the beating sensation with the index and middle fingers. The

number of beats in 15s was recorded and converted into beats per minute [BPM]. The height

and weight of the subject was also recorded.

The subject was placed in a seated position and the left arm placed upon the lab bench. The

sphygmomanometer was placed on the upper arm ensuring that the arrow was above the

brachial artery. The cuff was inflated until it did not fall and then with the stethoscope on, the

diaphragm placed on the antecubital space. The cuff was then inflated to 150 mmHg and the

valve on the runner ball opened slightly whilst listening for pressure sounds. The pressure at

which the sounds were detected were recorded the systolic pressure. The valve was then

opened further and the pressure at which the sounds disappeared taken as the diastolic

pressure. These sounds are referred to as the Korotkoff noises.

The blood pressure and heart rate were then determined while the subject stood quietly, and

after running in place for 1, 3 and 5 minutes. Then with the subject seated, the resting blood

pressure and heart rate were recorded. The subject then held his/her breath as long as

possible. The heart rate was measured whilst the subject held their breath. Once breathing was

resumed, readings for heart rate and blood pressure were taken at 1 minute intervals for five

minutes.

The subject was then laid back, in a lying position and the heart rate and blood pressure

recorded. This was also done for the subject in a seated position and a standing position.

With the subject seated comfortably, the heart rate and systolic and diastolic pressures were

recorded. Their free hand was submerged in ice water to a depth above the wrist. The hand

was rapidly removed from the ice bath and dried. The blood pressure and heart rate were then

recorded on the opposite arm. This was repeated at one minute intervals until the heart rate

and blood pressure returned to control values.

A fully annotated ECG was then done for a male and female subject in the normal resting state

using standard limb leads. Then immersing the palm in cold water, another ECG was done

ensuring the leads did not get wet. The subjects then underwent vigorous exercise for 5

minutes before producing another ECG chart.

RESULTS:

Table 1. Summarization of Male individuals tested

Subject

MALE Height: Weight Ratio cm/kg

BMI STATUSHeight/ cm

Weight/ kg

1 187 97 1.9 27.7 Overweight2 160 74 2.2 28.9 Overweight3 170.4 61 2.8 21.0 Normal4 181 75 2.4 22.9 Normal5 172 65 2.6 22.0 Normal6 194 79 2.5 21.0 Normal7 195 97 2.0 25.5 Overweight8 174 51 3.4 16.8 Underweight9 176 77.2 2.3 24.9 Normal

10 168 62 2.7 22.0 Normal11 182.5 93 2.0 27.9 Overweight

Table 2. Summarization of Female individuals tested

Subject

FEMALE Height: Weight Ratio cm/kg

BMI STATUSHeight/ cm

Weight/ kg

1 157 50 3.1 20.3 Normal2 156 82 1.9 33.7 Overweight3 162 56 2.9 21.3 Normal4 162 56 2.9 21.3 Normal5 149 30 5.0 13.5 Underweight

Table 3. Summary Table of Average Male and Female Blood pressure and Heart Rate in their respective catergories.

CLASS INTERVAL

MALE FEMALEAVERAGE

HEART RATE

AVERAGE BLOOD PRESSURE

AVERAGE HEART RATE

AVERAGE BLOOD PRESSURE

SYSTOLIC DIASTOLIC SYSTOLIC DIASTOLICUNDERWEIGHT 64 12 22 96 108 68

NORMAL 65.3 107 74 81.3 111.3 76OVERWEIGHT 81 126.25 90 80 130 105

UNDERWEIGHT NORMAL OVERWEIGHT0

20

40

60

80

100

120

140

Resting Systolic Blood Pressure of Males vs Females

SYSTOLIC MALE SYSTOLIC FEMALE

The figure above illustrates the systolic blood pressure of males and females in the resting state. Both the Normal and Overweight categories are quite similar with the males being just a slight bit less than the females. With the underweight category, with males there was only one person which gave a very low reading which most likely is anomalous. Also being only one underweight female in the data set, the systolic value read may also be anomalous.

UNDERWEIGHT NORMAL OVERWEIGHT0

20

40

60

80

100

120

Resting Diastolic Blood Pressure of Male vs Female

DIASTOLIC MALE DIASTOLIC FEMALE

The trend in the resting diastolic pressure shows females having higher values than the males

across all categories. Due to the Underweight category having only one male and female, the

readings may be inaccurate.

UNDERWEIGHT NORMAL OVERWEIGHT0

20

40

60

80

100

120

Average Heart Rate of Male vs Female

HR MALE HR FEMALE

The resting heart rate of the males and females in the overweight category are quite similar and

almost equal. The underweight and normal categories of males have almost equal heart rates

as well. The females in the underweight and normal categories however had higher values than

the males.

S t an d i n g Qu et l y

I mm

ed i a t e l y After

1 mi n u t e aft er

3 mi n u t es aft er

5 mi n u t es aft er

0

20

40

60

80

100

120

140

Eff ect of Exercise on Heart rate in MalesUnderweight Normal Overweight

The trend of these results with the effect of exercise on heart rate across the categories of male

subjects in the calls data are quite similar. The heat rate increases initially during and after

exercise before slowly returning back to the resting state with time. The overweight category

followed the trend however, had a higher heart rate that both the normal and underweight

male categories.

S t a n d i n g Q u et l y

I m m ed i a t e l y A ft er

1 m i n u t e a ft e r

3 m i n u t es a ft er

5 m i n u t es a ft er0

20

40

60

80

100

120

140

160

Eff ect of Exercise on Heart Rate in FemalesUnderweight Normal Overweight

With the female categories, similar trends with heart rate were seen as compared to the males.

However, the overweight and underweight categories had very similar rates of increase and

decrease of heart rate with time with a fast decrease back to resting heart rate. The normal

category however, even though following the general trend, returned to resting heart rate at a

slower rate.

S t a n d i n g Q u i e t l y

I m m ed i a t e l y A ft er E x er c i s e

1 m i n u t e a ft e r e x er c i s e

3 m i n u t es a ft er ex er c i s e

5 m i n u t es a ft er ex er c i s e0

20

40

60

80

100

120

140

160

Eff ect of Exercise on Systolic BP [M]UnderWeight Normal Overweight

The systolic pressure across the three categories in males all followed the same trend.

Overweight males showed a higher systolic pressure as compare to the normal and

underweight males. Normal males showed very little variation in systolic pressure as compared

to the underweight and overweight males with the effect of exercise.

S t a n d i n g Q u i e t l y

I m m ed i a t e l y A ft er E x er c i s e

1 m i n u t e a ft e r e x er c i s e

3 m i n u t es a ft er ex er c i s e

5 m i n u t es a ft er ex er c i s e0

20

40

60

80

100

120

Eff ect of Exercise on Diastolic BP [M]UnderWeight Normal Overweight

All categories here showed the same general trend with regards to the fluctuations of diastolic

pressure with time after exercise. The males which were classed as normal showed the least

fluctuation whilst those who were underweight showed the most.

S t a n d i n g Q u i e t l y

I m m ed i a t e l y a ft er ex er c i s e

1 m i n a ft e r e x er c i s e

3 m i n u t es a ft er ex er c i s e

5 m i n u t es a ft er ex er c i s e0

20

40

60

80

100

120

140

Eff ect of Exercise on Systolic BP [F]Underweight Normal Overweight

All categories of females followed the general trend in change of systolic pressure with exercise

and recovery. However, the overweight category of females showed the least fluctuation in the

systolic pressure and stayed almost constant throughout the recovery period.

S t a n d i n g Q u i e t l y

I m m ed i a t e l y a ft er ex er c i s e

1 m i n a ft e r e x er c i s e

3 m i n u t es a ft er ex er c i s e

5 m i n u t es a ft er ex er c i s e0

20

40

60

80

100

120

Eff ect of Exercise on Diastolic BP [F]Underweight Normal Overweight

All females in the data set followed the general trend in fluctuation of diastolic pressure with

exercise and recovery time. However, the normal and underweight categories of females

showed the least variation in the diastolic pressure with exercise and recovery time.

Table 4. ECG Calculations for Male subject

SEX: MALE Weight: 162 lBS Height: 182cm

Duration Amplitude

ActivityP

wave

PR-segme

nt

QRS-wave

ST-segme

nt

T-wave

Heart rate/bp

m

Pwave QRS T

Normal resting

.06 .08 .12 .04 2.0 68 0.5 0.1 ---

Immediately after exercise

.08 .08 .04 .04 .16 136 --- 0.4 ---

1 min after exercise

.08 .08 .04 .12 .12 125 --- 0.3 ---

3 min after exercise

.08 .08 .04 .04 .20 125 --- 0.6 ---

5 min after exercise

.06 .12 .04 .04 .12 125 0.2 0.5 ---

8 min after exercise

.04 .08 .04 .08 .12 115 --- 0.5 ---

Immediately after

cold press.06 .08 .05 .10 .12 125 0.15 0.4 0.3

1 min after cold press

.04 .08 .04 .08 .18 125 --- 0.4 ---

3 min after cold press

.06 .12 .04 .08 .10 107 0.1 0.2 0.3

5 min after cold press

.04 .12 .04 .08 .12 115 --- 0.2 ---

8 min after cold press

.08 .10 .04 .04 .12 107 --- 0.2 ---

Table 5. ECG Calculations for Female Subject

Sex: Female Weight: 146 lBS Height: 166.5

Duration Amplitude

ActivityP

wave

PR-segme

nt

QRS-wave

ST-segme

nt

T-wave

Heart rate/bp

m

Pwave QRS T

Normal resting

.08 .04 .06 .16 .12 83 0.1 0.4 0.2

Immediately after exercise

.04 .06 .04 .16 .12 107 0.1 0.6 0.3

1 min after exercise

.06 .06 .08 .08 .16 83 0.1 0.5 0.3

3 min after exercise

.08 .06 .06 .10 .20 79 0.05 0`.5 0.2

8 min after exercise

.06 .06 .06 .14 .12

Immediately after

coldpress.08 .08 .06 .18 .08 68 0.05 0.4

0.1

1 min after coldpress

.04 .05 .06 .18 .12 71 0.05 0.5 0.1

3 min after cold press

.04 .06 .06 .16 .12 78 0.05 0.4 0.1

8 min after cold press

.06 .08 .04 .16 .10 83 0.05 0.4 0.1

SAMPLE CALCULATIONS:

Rate of paper= 25mm/sDistance between interval= 23mmDuration between interval = 23/25 = 0.92 sHeart rate = 60/0.92 = 65.2 beats per minute

Duration of P wave=3/25 = 0.12sDuration of PR segment = 1.5/25 = 0.06sDuration of QRS wave=2/25 = 0.08s

Duration of ST segment=2.5/25 = 0.10sDuration of T wave=5/25 = 0.20s

10mm = 1mV 1mm = 0.1mVTherefore the amplitude of the P wave is = 2 x 0.1 = 0.2mVThe amplitude of the QRS wave is = 11.5 x 0.1 = 1.15mVThe amplitude of the T wave is = 3 x 0.1 = 0.3mV

DISCUSSION:

The body mass index [BMI] was used on all individuals in this class data set to determine their

general health from their BMI results. This allowed for the separation of individuals into

“normal/healthy”, “underweight”, “overweight” and “obese” categories. Male subjects were

contrasted against female subjects. By utilizing BMI information, the data set was standardized,

thus allowing all data to correlate correctly with each other.

Pulse rate and blood pressure would expectedly be lowest when the individual was in a laying

position as compared to sitting and standing positions. In the seated position, the hydrostatic

influence acts on the carotid sinus of the heart. The blood pressure and heart rate would also

be higher upon standing as the heart has to work against the force of gravity to pump blood up

towards the head as well as everywhere else in the body.

In all male subjects, in the laying position the heart rate and blood pressure were lowest. ON

sitting up the heart rate increased slightly, and on standing the heart rate was highest.

However the readings on blood pressure for all on standing were fluctuated from those of the

seated position. This is most likely due to anomalous readings from those taking

measurements. Some blood pressures rose while others dropped. The blood pressure readings

should drop when moved from seated to standing position as standing upright can lead to 500

– 700 mL of blood pooling into the legs due to the forces of gravity. The systolic pressure of the

males ranges from 84 – 140 mmHg. The differences in the values between each category were

prevalent. The lowest blood pressures were seen from the males in the “normal” category.

These males were deemed healthier than the others according to the BMI and as such, should

have stronger heart able to pump blood more efficiently. The highest heart rates were seen in

the overweight males.

The females showed the lower heart rate to belong to the overweight category. The healthy

females had heart rates which showed no discernible trend whilst the underweight female had

a heart rate which fell within the range of the healthy females. Having only one overweight and

underweight subject introduced a great deal of difficulty in discerning any trends from the data.

Discerning any trends from the females with regard to blood pressure with relation to body

orientation also proved difficult as values were scattered.

Exercise raised the heart rate and blood pressure of all individuals who were tested; however,

the responses following the bout of exercise were very different. The heart rate of healthy

males increased rapidly during exercise, a heart rate (105 beats per minute), and then quickly

returned to close to normal after 5 minutes. A similar situation occurred with respect to the

blood pressure of the healthy males. Their blood pressure increased only slightly and quickly

returned to normal after 5 minutes. The underweight males’ heart rate increased more slowly.

Their blood pressure also increased slightly and did not return to normal after 5 minutes. The

obese male had a heart rate which increased rapidly, higher than that of the other males before

returning to normal rate at a much slower rate. The blood pressure of the obese individual also

fluctuated and varied more than both the healthy and underweight males. This is most likely

due to the heart attempting to satiate the demands of the body.

The healthy females had a similar reaction to the healthy males. Their heart rate spiked quickly

during exercise (from 80.7 BPM to 114 BPM) and then returned to close to normal at a

moderate pace after 5 minutes. The blood pressure of the healthy females increased slightly,

and gradually decreased as time passed. The underweight and overweight category in females

showed a rapid spike with exercise before returning to close to normal much faster than that of

the healthy females. This most like is due to there being only one female for the overweight

and underweight classes respectively giving rise to biased data.

Individuals classed as healthy have faster recovery rates due to the autonomous nervous

system being trained to have such a response. It is assumed that healthier or healthy individuals

exercise more often than those who are overweight or underweight. The parasympathetic

nervous system allows for the slowing of the heart rate and lowering of blood pressure after

exercise. It becomes more efficient due to the outcome of exercise.

When underwater, one must hold one’s breath. The body enters a state known as the

mammalian diving reflex. Submergence in this case was stimulated by the subject simply

holding their breath for as long as possible. From the results for males, no discernible trends

were observed with heart rate or blood pressure. Some individuals had values which remained

constant, and others fluctuated with no discernible reason. The same fluctuations were seen in

females and thus made observing trends difficult. The mammalian diving reflex stimulates

peripheral constriction of the blood vessels in the outer extremities of the body. This avoids the

circulation of blood to non-vital parts of the body while maximizing the supply of oxygen to vital

organs, such as the brain (Cheng, 2010). This causes the lowering of heart rate and blood

pressure when holding breath which should have been observed in the data set.

The cold pressor test triggers a vascular sympathetic activation and an increase in blood

pressure in healthy persons. However the heart rate has high variability from person to person

(Mourot, 2007). After the healthy males removed their hands from the ice water, there was a

slight increase in blood pressure, and then a steady decrease as time progressed. Heart rate for

the individuals fluctuated too greatly to discern any trends. The ECG of the male corresponded

with these results. The underweight males had a very fluctuating heart rate.

Healthy females had a steady decrease in heart rate and blood pressure, which started to

increase back to normal from the minute after. The underweight female had a fluctuating heart

rate. Her blood pressure increased a bit and then decreased gradually. The cardiac cycle was

most affected by the cold pressor test, as it caused the most variance in the ECG.

Key sources of error could have been introduced every time blood pressure was taken. This is

subjective as to which point the blood was heard through the stethoscope i.e. the Korotkoff

sounds. Error may have also been introduced through pulse readings. Also with regards to

exercise, the exercise done by each individual was not standardized and as such some

individuals may have exerted themselves to a greater extent than others. This experiment may

be improved by using a digital sphygmomanometer to take readings of blood pressure and

pulse rate. Also a larger sample size with equal amounts of individuals in the various BMI

classes would allow for less discrepancy in data collection and give rise to more accurate

results. Also standardization of the exercises by controlling the amount and the intensity should

be implemented to give greater validity to the results.