Abstract
The study has been conducted to assess the effect of aerobic exercise on the heart rate and this involves recording of resting, exercise and recovery heart rate of the subjects of the study. A group of students have been selected as subjects and their heart beats were recorded with the help of equipment attached to display pulse rate on screen to test the hypothesis that aerobic exercise reduces the heart rate. Heart rate in resting period, during exercise and in recovery period was recorded for five consecutive weeks. The readings were recorded and analyzed statistically using SPSS and excel. The results demonstrated that the heart rate decreases by few beats per minute after 5 weeks of aerobic exercise which means that for an average person, every week of aerobic exercise in the initial months of exercise would lead to decrease in heart rate by 1 beat per minute. This experiment, therefore establishes that aerobic exercises reduces the heart rate.
Introduction
It is extremely important to assess the impact of exercise on heart rate as every exercise has impact on heart. The heart responds to exercise with an increase in cardiac output that is heart rate. Exercising muscles extract more oxygen from the blood purifying them, but the response of the heart rate is the ultimate determinant of delivery of oxygen to tissues and is the limiting factor for aerobic exercise.
As a result of exercise, heart rate increases immediately and with further exercise, the heart rate and cardiac output responses level off whilst additional increases in oxygen consumption occur by increased oxygen extraction. Exercise disrupts the homeostatic state or dynamic equilibrium of the body. These homeostatic disruptions or changes represent the body’s response to exercise. An exercise response is the pattern of change that physiological variables exhibit during a single acute bout of physical exertion. A physiological variable is any measure of bodily function that changes or varies under different circumstances. Heart rate is a variable which determines the impact of exercise on body. Increase of heart rate during exercise does not describe the full pattern of the response. For example, the heart rate response to a 400-m sprint is different from the heart rate response to a 50 mi-bike ride. Three factors need to be considered to determine or describe the acute response to exercise; these are exercise modality, exercise intensity and exercise duration.
Exercise modality means the type of activity or the particular sport. For example, rowing has a very different effect on the cardiovascular-respiratory system than does football. Modalities are often classified by the type of energy demand (aerobic or anaerobic), the major muscle function (continuous and rhythmical, dynamic resistance or static), or a combination of energy system and muscle action. Walking, cycling and swimming are examples of continuous, rhythmical aerobic activity; jumping, sprinting, and weight lifting are anaerobic and dynamic resistance activities.
Exercise intensity is most easily described as maximal or sub-maximal. Of these, maximal exercise is most straightforward: it simply refers to the highest intensity, greatest load or highest duration an individual is capable of doing. Motivation plays a large part in the achievement of maximal levels of exercise. Most maximal values are reached at the endpoint of an incremental exercise test to maximum, that is, the exercise task begins at a level the individual is comfortable with and gradually increases. The values for the physiological variables measured at this time are labeled as max. Sub-maximal exercise is defined as the set load which is a load known or measured to be below an individual’s maximum.
Exercise duration is simply a description of the length of time the muscular action continues. Duration may vary from a short a time as 1-3 seconds for an explosive activity such as jump, to as long as 12 hours for a full triathlon bicycle ride. Thus, the amount of homeostatic disruption is a function of both the duration and intensity of the exercise.
For this experiment to determine the heart rate response to 5 weeks of aerobic exercise training, the experiment has been conducted in two labs; In Lab 1 and 3. This experiment is conducted on the students of BIO3333. Lab 1 is the pre-test, following by 5 weeks of self-organized aerobic exercise training and Lab 3 is the post-test, in which the effects of exercise training will be evaluated. The data has been analyzed using Excel and SPSS. The hypothesis which is tested for this study is that the aerobic exercise reduces the heart rate.
Aerobic exercise reduces the resting heart rate
Aerobic exercise does not reduces the resting heart rate
Method
The resting, exercise, and recovery-heart rate in a moderate exercise is being recorded. These measurements are made using the Powerlab system as outlined in previous practical. Prior to the collection of test data the equipment was prepared with the attachment of pulse set, and heart rate was shown on the screen. The Monark exercise bike was adjusted so that the subjects could ride comfortable.
The recording was commenced by clicking on the “Start” icon. At each of the time intervals information was recorded in the data collection tables.
Experimental Plan
Students were allocated into small groups. An informed consent was signed before the testing.
Protocol:
1. The subject was instrumented with the pulse set and the heart rate was shown on the screen.
2. The subject rested on the cycle ergometer for 3 minutes (pre-exercise). Heart rate was recorded at the end of every minute into the table provided.
3. The subject commenced exercise 5 minutes at the workload of 100 Watts (50RPM x 2kp for females) and 150 Watts (50RPM x 3kp for males). Heart rate was recorded at the end of every minute.
4. Exercise stopped. The subject remained sitting on the bike for another 3 minutes (post-exercise). Heart rate was recorded at the end of every minute.
5. Once the protocol was completed, the subject was allowed to cool down at 0.5kp for 2-3 minutes.
Results
The results demonstrate that the heart rate after 5 weeks of aerobic exercise decreases at resting and at exercise. The p value is obtained at 0.001 which is lower than the significance value of 0.05. This leads to rejection of null hypothesis and this can be stated that aerobic exercise decreases the resting heart rate. The Resting heart rate after 5 weeks of aerobic exercise decreased from 86 beats per minute to 83 beats per minute. Similarly, during exercise the heart rate decreased from pretest to post test.
Discussion
Aerobic training has a major impact on heart rate at rest, during sub-maximal exercise and during the post-exercise recovery period. The effect of maximal training on heart rate was not tested for in this experiment. As has been demonstrated by t value of 0.966 and p value of 0.001, the aerobic exercise decreases the heart rate.
Resting Heart Rate: the heart rate at rest can decrease markedly as result of endurance training. A sedentary individual with an initial resting heart rate of 74 beats per minute can decrease resting heart rate by approximately 1 beat/min with each week of aerobic training, at least for the first few weeks (Earle & Baechle 2004, p. 103). After 5 weeks of moderate aerobic training, resting heart rate can decrease from 74 to 69 beats per minute or lower, which 68 beats per minute is as demonstrated in below table showing pretest and post-test data of aerobic training of one of the subjects in experiment. As displayed in the results, the null hypothesis is rejected because heart rate is decreased with the aerobic exercise.
During sub-maximal exercise, aerobic conditioning results in proportionally lower heart rates at a given absolute exercise intensity. This is illustrated in Graph 1 which shows the average heart rate of class exercising both before and after training. At each specified intensity; indicated here by the speed at which the subject is training, the post-training heart rate is lower than the heart rate before training. As per literature on exercise, after a six month endurance training program of moderate intensity, decreases in heart rate of 10 to 30 beats per minute are common at the same absolute sub-maximal workload, the training-induced decrease being greater at higher intensities.
These decreases indicate that the heart becomes more economical through training. In carrying out its necessary functions, a trained heart performs less work (lower heart rate, higher stroke volume) than an unconditioned heart at the same absolute workload.
During exercise, heart rate must increase to increase cardiac output to meet the blood flow demands of the active muscles. When the exercise bout is finished, heart rate does not instantly return to its resting level. Instead, it remains elevated for a while, slowly returning to its resting level. The time it takes for heart rate to return to its resting rate is called the heart rate recovery period. Following a period of training, as illustrated in graph 2, heart rate returns to its resting level much more quickly after exercise than it does before training. This is true after standardized sub-maximal exercise as well as after maximal exercise.
Conclusion
With the help of this experiment, it has been established that resting heart rate decreases as a result of endurance training by acceptance of the hypothesis. In a sedentary person, the decrease is about 1 beat/minute per week during the initial weeks of training. Heart rate during sub-maximal exercise is also lower and the magnitude of decrease is greater at higher exercise intensities. The heart rate during the recovery period decreases more rapidly after training. Hence, it deduces that cardiac output at rest and at sub-maximal levels of exercise remains unchanged or decreases slightly after endurance training.
References
Hitchcock, H., 2010. The Effect of Steady-State Exercise on the Body. [Online] [Accessed 27 Septemberhttp://www.livestrong.com/article/339455-the-effect-of-steady-state-exercise-on-the-body/#ixzz1ZLLaSR76 2011].
Iaizzo, P.A., 2009. Handbook of Cardiac Anatomy, Physiology, and Devices. Springer.
Idelle M. Weisman and R. Jorge Zeballos, 2002. Clinical Exercise Testing. Karger Publishers.
LeMura, L.M. and Von Duvillard, S.P., 2004. Clinical exercise physiology: application and physiological principles. Lippincott Williams & Wilkins.
Roger W. Earle & Thomas R. Baechle, 2004. NSCA's essentials of personal training. USA: Human Kinetics.
Sharon A. Plowman and Denise L. Smith, 2007. Exercise Physiology for Health, Fitness, and Performance. Lippincott Williams & Wilkins.
William D. McArdle, Frank I. Katch and Victor L. Katch, 2006. Essentials of exercise physiology, Volume 1. Lippincott Williams & Wilkins.
