FSE 01 The Effect of Body Position on Blood Pressure Regulation After Exercise

This experiment explores how different body positions—standing, sitting, lying down, kneeling, and standing on one leg—affect systolic blood pressure recovery after exercise, revealing how posture influences cardiovascular homeostasis.

Introduction

How does the regulation of blood pressure relate to homeostasis in our cardiovascular system? Firstly, we must understand what blood pressure is. Blood pressure is the effort your blood must exert to pass through your arteries. The role of the cardiovascular system is to maintain constant blood flow through the capillaries, which reach every tissue and cell in our body. Blood pressure in humans fluctuates throughout the day depending on the activities we participate in. When you’re exercising or excited, your blood pressure goes up. When you’re resting, your blood pressure is lower. Blood pressure regulation is a negative feedback loop. Baroreceptors near the heart and neck arteries sense lower blood pressure and send signals to the brain. This causes the heart to beat more quickly and pump more blood, bringing the blood pressure down.

How does body position also relate to the body’s homeostasis of blood pressure? Body posture affects blood circulation, which is necessary to preserve homeostasis. Because of gravity, blood flows toward the lower extremities when you are sitting or standing. The body responds to this through the use of muscular contractions and vasoconstriction, which helps return blood to the heart. These systems help maintain a healthy supply of oxygen and nutrients while also ensuring that blood reaches necessary organs and avoiding blood accumulation in the lower limbs. The results we get from this lab can help inform practices going forward because if we find trends that certain body positions cause higher/lower blood pressure, we can conclude that certain body positions can affect the distribution of blood within the body and the time it takes our cardiovascular system to reach homeostasis.

In this experiment, we will be measuring systolic blood pressure in mmHg (millimeters of mercury), which measures the blood pressure when the heart ventricles contract. A systolic blood pressure of 115 millimeters of mercury is usually considered normal.

Hypothesis

When our body is in a more relaxed position, such as lying down (supine), our blood pressure will be lower.

Variables

Independent Variable

Body Position of person in experiment (Standing, Sitting, Lying Down, and Standing on One Leg)

Dependent Variable

Blood Pressure of a person after doing exercise and staying in a selected body position (mmHg)

Controlled Variable

Time of Exercising

The time of exercising is controlled at 2 minutes. An increased time of exercising could lower the blood pressure and cause the body’s homeostasis to take a longer time for the blood pressure to rise back up. A lower time of exercise would take our homeostasis a shorter time to return blood pressure to a higher state.

Time Standing in Selected Body Position

The time standing in the selected body position is controlled at 2 minutes. If we were to increase the time, that would give our homeostasis in the cardiovascular system more time to regulate blood pressure.

Same Blood Pressure Monitor

Using the same blood pressure monitor is crucial to maintain consistency throughout all trials. Different monitors could have small discrepancies in their accuracy and range. Blood Pressure Model Used: HEM-7121

Same Rowing Machine

Using the same rowing machine allows us to eliminate the potential influence of machine-specific errors on the outcome of the experiment. This allows us to focus on the specific variables of interest and draw more accurate conclusions. Rowing Machine Model Used: Concept 2 Rower

Same Rowing Machine Resistance

Rowing machine resistance affects the intensity of the exercise and lowers our blood pressure accordingly. Changing the resistance would change the blood pressure significantly.

Equipment

• Rowing Machine

• Blood Pressure Monitor

• Timer

• Person Volunteer * 3

Methodology

1. Row on the Rower for 2 minutes on Resistance 10

2. Get off the rower and choose a body position (independent variable)

3. Stay in the selected body position for 2 minutes

4. Record systolic blood pressure (dependent variable)

5. Keep track of all data in an Excel spreadsheet

   
   

Body Position	Person 1	Person 2	Person 3	Qualitative Data/Observations
Standing	109	128	103	This position felt more tiring, and the heart rate appeared to drop more slowly.
Sitting	115	148	113	This position was comfortable, and the body seemed to recover from exercise more efficiently.
Laying Down	126	150	130	This was the most relaxing position, with the fastest recovery from exercise.
Standing on One Leg	100	122	105	This position felt slightly more tiring than standing.
Kneeling	110	135	116	This position felt somewhat more tiring than sitting, but not as exhausting as standing.

Processed Data

Table 02: Quantifying the Impact of Resting Body Position (IV) on Systolic Blood Pressure After Exercise (DV): A Statistical Analysis of Averages and Standard Deviations.

Body Position	Average	Standard Deviation
Standing	113.3	13.0511813
Sitting	125.3	19.65536398
Laying Down	135.3	12.85820101
Standing on One Leg	109.0	11.53256259
Kneeling	120.3	13.0511813

Graph 1: Systolic Blood Pressure of People After Resting in a Certain Body Position After Exercise.

Claim

When our body is in more relaxed positions, such as lying down (supine), our systolic blood pressure will increase.

Conclusion

By analyzing Graph 1, we can see that when a person is lying down or sitting, the average blood pressure is the highest (125-135 mmHg). When a person is standing or standing on one leg, blood pressure is the lowest (109-113 mmHg). This means that there is a trend between more relaxed body positions, such as lying down and sitting, that increases a person’s blood pressure. Therefore, we can conclude that relaxed body positions, such as the supine position (lying down), increase your blood pressure, and that tenser positions, such as standing and kneeling, lower your blood pressure.

Another key part to consider is the standard deviation of our data. Standard deviation is a measure of how significant our data is from each other. A higher standard deviation means that our data could be inconsistent and less significant. Overlapping error bars can tell us that our data doesn’t have any significant difference. We can see that the error bars for lying down and the error bars for standing on one leg have no overlap, meaning that their data have a significant difference. However, we can also see that the error bars for sitting and lying down do overlap quite a bit, meaning that the data between the two don’t have a very significant difference. This means that justifying claims between sitting and lying down could be hard because overlapping error bars mean there isn’t a strong trend present.

The reason for blood pressure to rise in more relaxing positions or blood pressure to drop in standing positions is due to a condition called orthostatic hypertension. Orthostatic hypotension is a drop in blood pressure that happens when a person stands up from a lying or sitting position. Gravity causes blood to accumulate in the legs and stomach when one stands up from a seated or lying posture, which reduces the amount of blood returning to the heart. Reduced blood flow means that there is less force needed to push the blood through your arteries, leading to a decrease in blood pressure. Once our blood pressure drops, our baroreceptors kick in to maintain homeostasis and narrow the blood vessels to increase blood pressure.

Evaluation

Although my partner and I tried our best to maintain consistency throughout our experiments by setting multiple constant variables, there are limitations to our accuracy. For example, because each one of our test subjects has a different resting blood pressure, we tried to even out the inconsistencies by taking the averages of each independent variable to see a general trend of the data. However, there are outliers in our data that can make the trend not as clear, which affects our confidence in our claim. A way that we could solve this inconsistency is to have the same person do multiple trials on each

independent variable, and only use the data for a single person. Although this method is time-consuming, it is the only way to ensure consistency across test subject homeostasis systems.

Another factor to consider is the intensity at which each test subject rowed on the rower. Even though we set the resistance value on the rower at 10 for all trials, each test subject could have rowed at different intensities and paces. A resistance of 10 could be at 80% energy for one test subject, but only 60% for the other. These are all factors that could influence a person’s final blood pressure. A way we would ensure that all test subjects put in the same effort across all test trials is to measure their heart rate. For example, we could tell them to stop every time they reach a bpm of 150.

Another limitation that we came across was the accuracy of our timing. Although we set a controlled variable of the time we rest after exercise, different test subjects took different times to get ready once the time was up. This extra rest that some subjects got could cause discrepancies in our data and lead us to make inaccurate conclusions. A way to solve this in future experiments is to have very strict timings and watch our test subjects throughout all trials. If they don’t follow a certain controlled variable, we would have to cancel the trial, and the data recorded can’t be used.

A strength we had during our experiment was having a variety of participants as test subjects. We can’t generalize a physical phenomenon by looking at the trends of a singular person. We chose 3 different people who have different fitness abilities to best represent the public.

Bibliography Citation

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Mayo, Staff. “Orthostatic Hypotension (Postural Hypotension).” Mayo Clinic, Mayo Foundation for Medical Education and Research, 2022, www.mayoclinic.org/diseases- conditions/orthostatic-hypotension/symptoms-causes/syc-20352548.

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