As the body absorbs oxygen and releases carbon dioxide, the heart rate adjusts to keep up with the demand of tissues for oxygen. The standard rate for an adult at rest, 60-80 beats per minute, is important to know for a number of reasons. Medical conditions like tachycardia, or bradycardia, can be recognized as faster or slower (respectively) than the normal 60-80 bpm. Heart rate is also important for an athlete to know, specifically resting heart rate, from which target maximum heart rate can be found and a workout adjusted for different physical benefits.
The heart rate determining need for oxygen by tissues is in turn determined by variables such as body position, weight, age, consumption of caffeine, gender, and time of day. This study looks specifically at resting heart rate in connection to these variables. Because heart rate is known already to be affected by these variables it was hypothesized that a clear connection could be found in our data to each of these variables. We tested the heart rate and pulse of twenty college students and calculated their HRV. Each HRV was tied to an anonymous survey covering the variables we were looking at. From our results we were able to identify different rates and conclude that heart rate is affected by each of the variables we tested.
Resting heart rate is known to be affected by different variables. Published research has shown that maximum heart rate decreases as age increases and increases again as one approaches their late forties to early fifties. Weight also affects heart rate. It has been found to affect heart rate through a strong correlation between adiposity, the measure of fat carried by an individual, and a higher resting heart rate. Another variable we looked at was exercise. Research has shown that with exercise, over time, the average resting heart rate drops significantly. This is due to the fact a larger, stronger heart is able to pump out more ml/min. than a smaller, weaker heart thus needing to beat fewer times per minute to achieve the 5000 ml required. When it comes to the effects of caffeine, much controversy exists over its effects on heart rate. Some research shows that caffeine consumption raises blood pressure and therefore heart rate, while other research proved an insignificant difference between resting heart rate with and without caffeine. The last variable we looked at, gender, affects resting heart rate. Articles on heart rate show that women, in comparison to men, have a higher resting HR up to the age of 55 years.
The purpose of this study is to identify the effect of each different variable on human heart rate in ECG patterns.
Methods and Materials
For our study of heart rate and pulse we used an electrocardiogram to read both pulse and rate. Twenty subjects were tested while supine and during a 5-min period. Volunteers were asked to remove any jewelry from their arms, right leg, and hands where it could interfere with any electrical readings. The electrodes were then attached and the subjects asked to remain still and relaxed for a five minute period. Our data was collected from the last 2 minutes of the 5 minute recording in order to account for any fluctuations due to nervousness or other outside factors. After the ECG reading subjects were given a survey to fill our anonymously which had their number on it only so that we could connect the heart rate with the variables on the survey. Our survey covered the variables:
- Activity level
- Last time of caffeine consumption
- Time of ECG reading
- Medical conditions (pertaining to heart rate)
- Marital Status
Twenty-one subjects were tested around the same time in mid afternoon. After collecting all of the data we correlated the information by graphing and statistical analysis. All of the data collected was stored into an excel document where the correlative tests were calculated and graphs were made. HRV was