Cardiovascular System and Physical Fitness

Cardiovascular System and Physical Fitness
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Cardiovascular System and Physical Fitness
1. Introduction
1.1. Background
Sports and exercise physiology is a growing science and has major implications towards athletic performance. It lays the foundation for assessment of various physiological, psychological and anatomical variables that influences the performance of an athlete on the field (Haskell et al., 2012). Understanding such variables is extremely important from the perspective of designing various training programs as an individualistic approach for each athlete (Haskell et al., 2012).
One such physiological variable that needs to be regularly assessed for evaluating the cardiovascular fitness of an athlete is Cardiac Output. Cardiac Output refers to the volume of blood pumped out by the ventricles per minute. The average cardiac output of a normal person is approximately 5 litres per minute (Brandon, 2009).
Often the cardiac output is expressed as cardiac index. Cardiac index is calculated as cardiac output per square meter of the body (or simply body surface area). Cardiac output is calculated as a product of stroke volume and heart rate. Stroke volume represents the volume of blood pumped out by the ventricles per heart beat (Brandon, 2009). The average stroke volume of normal heart is approximately 70ml per beat and the average heart rate is 72 beats per minute. Therefore, the cardiac output approximately amounts to 5 litres per minute.

However, cardiac output increases in case of moderate and heavy exercise and it is normally much higher in trained athletes (Brandon, 2009).
Cardiac output is dependent on various factors. Increased venous return causes an increase in cardiac output. The exercising muscles exert increased venous return that in turn increases the end-diastolic volume (Brandon, 2009). The increase in end diastolic volume stretches the myocardium and as per the Starlings law of the heart, an increase in length of the myocardium within physiological limits increases the force of contraction of the ventricles (Brandon, 2009). This phenomenon leads to increase in stroke volume, and hence the cardiac output also increases (Brandon, 2009). On the other hand, atherosclerosis and hypertension causes an increase in peripheral resistance of the arterioles which leads to an increased after-load. Such phenomenon leads to a decreased cardiac output (Tremblay et al., 2010).
Cardiac output can also be increased by an increase in heart rate. Such compensations are possible in an individual with decreased stroke volume or in conditions of moderate exercise (Brandon, 2009). However, in conditions of heavy exercise the heart rate is increased further, which leads to a decreased cardiac filling. As a result, the stroke volume decreases and the product of stroke volume and heart rate also decreases. In other words, cardiac output gets decreased (Brandon, 2009).
Trained athletes have improved efficiency in venous return, and hence the ventricles are hypertrophied due an increased end-diastolic volume in each cardiac cycle. Hence they meet the increased demand of exercise through an increased stroke volume and not by an increase in heart rate, otherwise noted in non-athletes. Such modification in the anatomy of the heart of an athlete reduces the work done by the heart, and the cardiac stress is minimized during heavy exercise (Haskell et al., 2012).
1.2. Aims and Objectives
The present study was done to evaluate the findings discussed in the background literature survey. The research would try to evaluate the average resting heart rate of an individual. Further, the present study will try to evaluate whether there is a difference in heart rate of individuals who exercise routinely compared to individuals who do not exercise at all, after performing a standard moderate exercise. Such findings will help to endorse physical activity programs since a lowered heart rate is considered as an aspect of cardiac fitness. The lower the heart rate, lesser is the stress placed on the heart during strenuous activities. Since, review of literature indicated that athletes have a lower heart rate, so the individuals who exercise regularly, may be perceived as athletic. Hence, exercising individuals perhaps meet their demand for increased cardiac output with an increased stroke volume.
1.3. Methodology
Five individuals were randomly selected for assessing the resting heart rates and five observations were noted. Their heart rates were measured for 15 seconds and extrapolated to 1 minute. Further, ten individuals and 16 individuals were selected separately, on the basis of their exercise habits. The former numbers indicated individuals who exercised regularly and the latter figure indicated individuals who did not exercise regularly. The individuals from both the groups were exposed to a moderate exercise program, which involved brisk walking for 2 minutes.
1.4. Hypothesis Testing
Two hypotheses were tested through the present study. The first hypothesis proposed that the average resting heart rate of an individual should be near to 72 beats per minute. The second hypothesis that the study proposed was that the heart rate of individuals who exercise regularly should be lesser than the heart rate of individuals who do not exercise regularly.
1.5. Data Analysis
Data collections and analysis were done through Microsoft Excel software, as per the current version uploaded in Windows 2007. The common descriptive variables like mean, median, range, maximum and minimum were represented. Comparisons were done for the exercise and non-exercise groups after calculating the mean heart rates of the individuals from the two different groups.
2. Results
The results were reflected to exhibit a clear documentation of the raw data collected and its analysis, through Microsoft excel software, as per the current version uploaded in Windows. 2007. The common descriptive variables like mean, median, range, maximum and minimum were estimated. Such variables were measured to objective and portray the validity of the hypotheses considered for the study. For example, the exercise group should reflect a lower mean compared to the non-exercise group. Moreover, the median value will indicate the number of individuals below or above a certain heart rate. The exercise group is expected to have a lower median too. Further the comparisons in the form of bar charts and pie-diagram provided a clear visual depiction of the results and the proposed analysis in a compatible way. The results of the experimentation are represented through the various figures and legends described below.

Fig 1: represents heart rate of 5 individuals who were randomly selected for assessing the resting heart rates in 5 observations.

Fig 2: represents the measured average individual heart rate as per figure 1, compared to the expected average individual heart rate as evidenced in review of literature.
Exercise Group Non-Exercise Group
81 94
84 96
85 99
70 80
72 82
75 83
60 86
62 89
65 71
54 73
  74
  76
  77
  79
  67
  69

Table 1: Reflects the raw data collected from individuals with different exercise habits. The figures represent individual heart rates after a moderate exercise intervention.
  Exercise Group Non-Exercise Group
Mean 70.8 80.9375
Median 71 79.5
Maximum 85 99
Minimum 54 67
Standard Deviation 10.59140112 9.698582371
Range 54 to 85 67 to 99
Table 2: Reflects the descriptive statistics as per the raw data of table 1.

Fig 3: Represents the mean heart rates of 10 individuals (exercise group) and 16 individuals selected separately (not- exercise group), on the basis of their exercise habits.

Fig 4a: Represents percentage of Different individuals with range of Heart Rates in the Exercise Group

Fig 4b: Represents percentage of Different Individuals with range of Heart Rates in the Exercise Group
4. Discussion
From the above results as per Fig 1 and Fig 2, it clearly satisfies our hypothesis that resting heart rate of an individual is approximately 72 beats per minute. Our findings endorsed the literature recommendations (70.4 beats per minute versus 72 beats per minute). The descriptive statistics represented in table 2 which were based on table 1 endorsed the second hypothesis of the study. This is because the mean heart rate of individuals who exercise regularly was found to be lesser than the heart rate of individuals who did not exercise regularly (70.8 beats per minute versus 80.93 beats per minute).
Such difference and comparison were reflected too in Fig 3 and such difference was significant. From this present finding it may be interpolated that individuals who exercised regularly were athletic and must have had a greater stroke volume. Hence, to meet the demands of exercise they did not have to increase their heart rate to a great extent for achieving the necessary cardiac output. On the other hand, it can also be interpolated that individuals who did not exercise regularly were non- athletic and must have had a lesser stroke volume. Hence, to meet the demands of exercise they did not have to increase their heart rate more than the exercising group for achieving the necessary cardiac output (Malina., 2010).
Moreover, it is evidenced from literature that trained athletes have improved efficiency in venous return, and hence the ventricles are hypertrophied due an increased end-diastolic volume in each cardiac cycle which leads to their greater stroke volume. Hence, the individuals in exercise group may be considered athletic. Such findings are further potentiated by the fact that athletic training or routine exercise stimulates the parasympathetic nervous system. This leads to release of acetylcholine that acts as an inhibitory neurotransmitter (Wisloff, Ellingsen & Kemi., 2012).
Acetylcholine acts on the SA node and inhibits them. Hence, the resting heart rates in athletes or individuals who exercise are lower than non-athletes or individuals who do not exercise regularly. In this present experimentation it must have been possible that the individuals in the exercise group already had a lower heart rate. Hence, as per the demand of exercise their heart rates were not increased unlike individuals who did not exercise regularly.
Fig 4a and Fig 4b, endorsed the above literature findings and explanations because the percentage of individuals in higher ranges of heart rate (> 80) were more in the non-exercise group compared to the exercise group. Interestingly, 18% individuals in the non-exercise group belonged to the heart rate range of 90-99, which once gain confirms that individuals who exercise regularly have lower heart rates compared to individuals who do not exercise regularly.
The study was robust; however, chances of elemental bias cannot be undermined. Moreover, the resting heart rates were not noted in the two groups before start of exercise. This situation may have impacted the outcome validity of our study.
1.5 Conclusion
The present study endorsed the need of routine physical activity and exercise for maintaining cardiac fitness, which will help individuals to sustain physical activity and stress (Malina., 2010). Hence, physical fitness is higher in individuals engaged in routine exercise than individuals who do not exercise routinely. Such fitness is required for proper delivery of oxygen to the exercising tissues and prevention of fatigue. Such implications are equally important in routine activities and professional athletic performance.

References
Brandon, Leigh (2009). Anatomy of Strength and Fitness Training for Speed. McGraw-Hill.
Haskell, W. L.; Troiano, R. P.; Hammond, J. A.; Phillips, M. J.; Strader, L. C.; Marquez, D.
X.; Grant, S. F.& Ramos, E. (2012). “Physical Activity and Physical
Fitness”. American Journal of Preventive Medicine 42 (5): 486
Malina, R (2010). “Physical activity and health of youth”. Constanta: Ovidius University
Annals, Series Physical Education and Sport/Science, Movement and Health.
Tremblay, M; Colley, R; Saunders, T; Healy, G ; & Owen, N. (2010). “Physiological and
health implications of a sedentary lifestyle”. Applied Physiology, Nutrition, and
Metabolism 35 (6): 725–740.
Wisløff, U; Ellingsen, Ø; & Kemi, O. (2009). “High-intensity interval training to
maximize cardiac benefits of exercise training?”. Exercise and Sport Sciences
Reviews 37 (3): 139–46