Abstract Cardiovascular health in different populations within American societies has been studied very scarcely, however, it is common knowledge that regular exercise is important to cardiovascular fitness. In this study, we wanted to answer the question, how does the number of layers of clothing affect a subjects fitness index? In this experiment we conducted the Harvard Step Test, which involves a subject stepping up and down a 23cm high platform to the rhythm of a metronome that’s ticking 120 times a minute for three minutes. After the step test is completed, the subjects pulse rate is then taken one, two, and three minutes after the conclusion of the test. The results indicated that the experimental group (the group wearing three layers) had higher pulse rates and lower fitness index scores than the control group, which led us to the conclusion that multiple layers of clothing has a negative relationship with cardiovascular fitness and fitness index scores. Introduction The Center of Disease Control (CDC), and the Department of Health and Human Services (HHS) are concerned with the correlation between a sedentary lifestyle and obesity and chronic illness. Consequently, the HHS came up with guidelines for the average American to follow to improve physical fitness, which they believe will decrease obesity and chronic illness rates. The guidelines include 150 minutes of moderate physical activity, including some form of strength training two or more times a week. The HHS believes that following these guidelines will increase cardiovascular fitness within the American population, however there are many other factors that can affect a person’s cardiovascular fitness. A person’s diet, whether or not they smoke, whether or not they drink excessively or use illegal drugs, and whether or not they had a preexisting genetic condition can all affect a person’s fitness levels. Luckily, there are standards that can be met to determine a person’s level of cardiovascular fitness. For example, a person’s resting pulse and respiratory rates and how quickly these rates return to their average resting rate can be a good indicator of their level of fitness. The most widely used method to test someone’s fitness based on these two factors is the Harvard Step Test (Simon, 2005). This test involves taking a subject stepping up on a step that is 8 to 14 inches high at a fixed rate, then the subjects pulse rate is taken before, one minute, two minutes, and three minutes after the activity. According to the test, a healthier person’s heart rate will come back down to their normal resting heart rate more quickly than someone who is not physically fit. This data can then be used to calculate the subject’s fitness index score. In this investigation, the question we set out to answer was whether or not the amount of layers of clothing a subject was wearing would affect their pulse rate after exercise. We hypothesized that a subject who was wearing three layers of clothing would have a higher pulse rate after exercise, thus a lower fitness index score. We had seven groups perform the Harvard Step Test with two subjects from each group, one subject with only one clothing layer and another subject with three clothing layers. Before the step test began, each subjects resting heart rate was measured. Each subject was instructed to step to the beat of a metronome which ticked 120 times per minute for three minutes. After the three minutes was over, the subjects heart rates were measured one minute, two minutes, and three minutes after. Then, this data was used to calculate the fitness index of each subject. The predicted outcome of this experiment is that if the subject was wearing three layers of clothing, then it would take a longer amount of time for their heart rate to return to their normal resting rate, thus causing them to have a lower fitness index score. Materials and Methods To begin the experiment, seven lab groups of four to five people were formed. Two people from each group volunteered to be subject and two people volunteered to record the data taken from the subjects. One subject was assigned to only wear one layer of clothing (the control group), while the other subject was instructed to wear three layers of clothing (the experimental group). After roles were assigned, each group acquired a step or platform that was 23cm high, a metronome set to 120 beats per minute, and a cell phone that included a timer. After all materials were gathered, the groups split up to conduct the same experiment separately. Before the Harvard Step Test began, each recorder took each subjects pulse rate to determine their resting heart rate. Then, the experiment was conducted by having each subject step up on the platform at the same rate as the metronome, to the rhythm of right foot up, left foot up, right foot down, left foot down. The subjects were instructed to maintain this rhythm for three minutes. Once the three minutes was completed, the subjects had their pulse measured one minute, two minutes, and three minutes after the end of the experiment. This data was recorded and shared between all seven of the groups in order to compare data and find averages in heart rate and fitness index scores. Results This research consisted of gathering quantitative data, the heart rate of each subject, which was then used to calculate the fitness index of each subject. These values were used to find averages across each group, including the one layer and three layer groups. The data collected from the experiment has been expressed through bar and line graphs and well as tables. As evidenced by Figure 1.1, the experimental group had a higher heart rate consistently throughout the entire course of the experiment. As demonstrated by Figure 1.2, each control group, except for Group Three, had higher fitness index scores than their experimental group counterparts. The data from group three indicates that that the experimental group had a higher fitness index score than the control group by 0.04, which makes Group Three the outlier.