Physiological Systems In Sports And Exercise

Function of Cardiovascular and Respiratory System

1. Describe the structure and function of the physiological systems studied and explain how these respond to sport and exercise.

2. Explain the integration of the physiological systems studied during sport and exercise.

3. Explain how the limitations of physiological response may limit sport and exercise performance.

Heart is comprised of the arteries, arterioles, capillaries and veins. Heart is a muscular organ acts as pump.  Through the arteries and arterioles, heart supplies oxygen and nutrients to the other parts of the body. At the same time heart, receives impure blood with carbon dioxide and waste material.  Upper chambers of the heart receive blood and lower chamber pumps out the blood. Respiratory system comprises of different parts like lungs, diaphragm and nasal cavity. Main function of the respiratory system is to transport oxygen to muscles and tissues as well carbon dioxide from muscles and tissues. At the time exercise, respiratory system helps to meet oxygen demand of working muscles (Larry et al., 2015).  

Exercise like running and swimming augments need of muscle for oxygen and nutrients. There is deep breathing and pulse rate increases when person is performing exercise. When a person’s physiology is not normal, then cardiovascular system doesn’t adopt to these changes easily. Hence, such persons feel tired very easily with moderate exercise also. There is increased production of energy during exercise because of skeletal movements and contractions. Body produces carbon dioxide as the toxic byproduct during exercise (Ehrman, 2009). 

At the time of exercise, adrenal gland increases production of adrenaline and noradrenaline which affects the functioning of heart. These hormones act on heart by influencing sympathetic nerves. During the duration of moderate to intense exercise, heart rate increases rapidly and heart pumps more volume of blood. At the time of exercise, sympathetic nerves act on veins and veins get constricted which results in the return of more blood to the heart. This results in the increase in stroke volume by approximately 30 to 40 %. Consequently, there is the increase in the systolic blood pressure and increase in the blood volume (Peçanha et al., 2016; Besnier et al., 2016).

Along with volume, there is also increase in the speed of the blood flow through the blood capillaries. Due to increased blood flow, there is the increase in diameter of the blood capillaries. During exercise, blood flowing through the veins should not flow in the reverse direction. Diastolic pressure falls during moderate exercise because capillaries and veins relax and dilate during the duration of exercise. Even though, there is increase in the heart rate during exercise, there is decrease in heart rate after long exercise (Bell, 2008).

Exercise

In normal person heart rate is around 72 beats per minute, however heart rate increase upto 200 beats per minute during exercise. Because heart is a muscle and it becomes acquired with the exercise activity and need less work to pump oxygenated blood. In long term exercise, this condition can be observed both during exercise and after completion of exercise. There can be increase in heart rate during long term exercise but it would not be sharp increase due to the strengthening of the heart (Roh et al., 2016). During exercise, working muscles are the main focus of the circulatory system. Circulatory system prevents blood flow to the resting organs and tissues like tissues of the digestive system. During exercise, circulatory system delivers maximum number of nutrients to the skeletal system. There is increase in the capillary bed in muscle during exercise and circulatory system delivers 12 times more blood during exercise. Main reason for increase in the blood pressure during exercise is nutrient rich blood (Larry et al., 2015).   

Due to the increased amount of oxygen and carbon dioxide during exercise, there is increased respiratory rate and rate of breathing also increased. During exercise, there is increased stimulation of sympathetic nerves which results in the stimulation of the respiratory muscles and increase in the respiratory rate. During exercise, respiratory rate increase form 14 beat per minute to around 32 beat per minute. Tidal volume also increases during exercise. During normal condition tidal volume is approximately 0.5 liter and during exercises this tidal volume increase upto 4-5 liter. In normal condition human can take up to 0.35 liter of Oxygen per minute however, in case of exercise it can increase up to 3.5 liter per minute. It has been reported that, oxygen intake can be increased up to 6 liters per minute based on the fitness level of the individual. There is increased work for ribcage muscles and diaphragm during exercise (Plowman and Smith, 2007).

Approximately 40 – 50 % changes occur in the intrathorasic pressure during exercise. This increased respiratory rate helps in allowing more oxygen to enter lungs and blood. Consequently, blood can deliver more oxygen to the working muscles during exercise (Porcari et al., 2015). In long term, exercise helps respiratory system to adapt to the physiological adaptations. As a result, there is augmentation in the efficiency of the respiratory system and removal of metabolic by-products. With this increased efficiency, respiratory system can transport and deliver more oxygen to the working muscles. Long term oxygen efficiency of respiratory system generally measured using VO2 max test which is a test for maximum rate of oxygen consumption during incremental exercise. During exercise, there is improvement in the VO2 max. During exercise, there is increased metabolic by-product due to cellular respiration. At the same time, there is increase in the carbon dioxide due to compensate for these acidic byproducts. As there is increased production of carbon dioxide in the body, person should breath faster to expel produced carbon dioxide (West, 2012).

Cardiovascular System

During long term exercise, there could be intensified respiratory rate however, there would not be difficulty in the respiration due to strengthening of the lungs. Respiratory rate of the body remains elevated after the completion of the exercise. This event is known as Excess Post-Exercise Oxygen Consumption (EPOC). This EPOC phenomenon occurs because, body tries to bring back physiology to normal homeostatic condition and resting state similar to prior to exercise. This surplus oxygen consumption helps body to refill energy reserve, make oxygen and hormone level in the blood to normal level, maintain normal body temperature and ventilation. Duration of EPOC can vary from few minutes to 24 hrs based on the type of exercise (Larry et al., 2015).          

2. Exercise enforces enormous stress on the physiology of the person. Hence, different physiological functions should act in coordination to get maximum benefit with lesser stress. Exercise produces multiple effects on the cardiopulmonary system. There is increased work load on the cardiopulmonary system during exercise. Both cardiovascular and respiratory system works towards the same goal. Goal of these two systems is to delivery oxygen to the tissues and extract carbon dioxide form the tissues during exercise. Respiratory system gets fresh oxygen from the air during inhalation. This oxygen transported to the blood with low oxygen level through alveoli. At the same time, carbon dioxide from the blood gets transported to the lungs. This fresh oxygen received by the respiratory system gets transported to the different parts of the body by virtue of cardiovascular system. In this way, both cardiovascular and respiratory systems work together. If there is hypertrophy of muscle, blood capillaries and mitochondria, it would lead to the increased circulatory capacity and increased oxygen transport to the tissues. However, increase in the circulatory function to the greater extent during exercise may lead to the requirement of the greater structural demand. This increase in the structural demand lead to the exercise induced pulmonary hemorrhage (Gregory and Travis, 2015).      

Respiratory system utilize parts of cardiovascular system like heart, blood and blood vessels for the transport of the oxygen and carbon dioxide. During exercise, there is increase in both the heart beats and breathing rate. This is due to increased demand for the oxygen. Circulatory system has chemoreceptors and these chemoreceptors detect alteration in the oxygen and carbon dioxide concentration in the blood. These chemoreceptors send danger signal of increased carbon dioxide level in the blood. Brain sends signals to increase respiration rate, in response to increased carbon dioxide level in the blood (Hawley et al., 2014). During exercise, veins of the circulatory system should work more to circulate waste product to the heart. Consequently, heart contracts and pumps blood into the pulmonary artery. Lungs absorb this carbon dioxide and exhale this carbon dioxide outside the body. It has been observed that, there is increase in the pulmonary vasodilation during exercise (Margaritelis et al., 2016).   

Respiratory System

There are three different phases of cardiorespiratory response occurs during exercise. Phase 1 response is rapid and it occurs prior to initial 15 seconds. This rapid response in phase 1 is mainly due to the neural control mechanisms. Second phase of cardiorespiratory response occurs between 15 s to 3 minute and in this phase 2 there is slower increase in the cardiorespiratory response. Generally, period after 3 minutes is considered as the steady state for the cardiorespiratory response. At the end of the exercise, both breathing rate and heart gradually return to the normal. This gradual normalization of the heart rate and breathing rate is called as recovery period. This recovery period for cardiovascular and respiratory system is faster in people who exercise as compared to the people who do not perform exercise. After completion of the exercise, this cool down period is necessary for heart and lung. This cooling down period should be gradual and light exercise like stretches and motion exercises can be incorporated during this period. Sudden stopping of the muscle activity can result in the decrease in the blood pressure below normal level and results in the dizziness and lightheadness. This steady state of the cardiorespiratory system can be achieved by integration of neural and humoral mechanisms. Nueral mechanisms involved in the regulation of the cardiorespiratory system are feedback reflex from the working muscle and feedforward motor action generated from the central nervous system. It reflects central nervous system command and muscle afferent information work in coordination during exercise for effective utilization of the cardiorespiratory system. If there is more exercise, this system become more efficient. These two system work together for efficient transport of oxygen and carbon dioxide during exercise. During exercise there is more production of heat in the body (Periard et al., 2016). During this period of EPOC, bodies necessitate surplus energy to activate the cooling system of the body. Ventilation and heart rate also requires more energy during the period of EPOC.   

3. In persons with chronic blood pressure, there is damage of the blood vessels and this lead to the arteries with plaque. Due to the presence of this plaque, there is limitation of the blood flow to the muscles. As a result, muscles don’t receive oxygen during the exercise.  More serious case occurs, when there is narrowing of coronary artery, which result in the pain in chest during the exercise. In persons with univentricular circulation, there is significant decrease in the exercise capability of the person. During exercise, there is increased work demand on the right ventricle (RV). There is decreased cardiac output in the patients with heart failure during exercise. To increase cardiac output, there should be more contractibility for RV as compared to the LV. In case of hypoxic pulmonary vasoconstriction, pulmonary circulation prevents cardiac output. Generally impairment in the tolerance of exercise, is due to the diastolic dysfunction. This diastolic dysfunction is due to the insufficient filling of LV and damage to the LV myocardium. Insufficient filling of LV is due to the reduction in preload. As compared to the systemic circulation, there is increased pulmonary vascular pressure. It reflects there is more workload on the RV and cardiac fatigue due to exercise (Brown et a., 2012; LeMura and Von Duvillard, 2004).

As compared to the heart, respiratory system of the heart is not usually considered as the limitation for exercise in the normal person. This strength of respiratory system is due to capacity of the system to manage increased requirement for ventilation and gas exchange during heavy exercise (Szabo et a., 2015). There are different reasons for the impaired transport of oxygen to the working muscles in the exercise. First, is the failure of the respiratory system to prevent arterial desaturation and there is alteration in the oxygen content in the arteries. This increased Arterial Oxyhaemoglobin desaturation is due to the inadequate hyperventilation during exercise. This inadequate hyperventilation is due to decreased chemo responsiveness as a result of  decreased circulating chemical agents like adenosine, catecholamines and proteins. Second, is the respiratory muscle work fatigue due to heavy exercise. This respiratory muscle fatigue mainly occurs due to the increase in activity of both inspiratory and expiratory muscle. This results in the sympathetic system mediated limb-muscle vasculature vasoconstriction and alteration in the blood flow to the leg. Third, is the unwarranted fluctuations in the intrathoracic pressure and consequent alteration in the cardiac output and blood flow to the leg. These fluctuations in the intrathoracic pressure also results in the exposure of heart and large blood vessels to the considerable oscillatory pressure. Due to this impaired oxygen transport, there is decreased VO2 max and reduced endurance capacity of the individual. At higher altitude, limitations of respiratory system are more during exercise. At higher altitude, there is decreased arterial content and increased fatigue of the respiratory muscle (Ehrman, 2009; Amann, 2012).    

Enhanced oxygen delivery to the tissues during exercise is mainly limited by the central factors such as heart, lung and blood vessels and peripheral factor such as tissue extraction of oxygen.  There are also physiological factors responsible for the limitation of the oxygen delivery and these include pulmonary diffusion, efficiency of cardiac output, amount of blood flow and rate of blood flow (Bassett and Howley, 2000). During exercise, there is the increased amount of cardiac output. Due to this, there are fewer periods for blood to accept oxygen in the lungs and consequently lower oxygen saturation in the blood. It has been estimated that around, 80 % of the limitation of the oxygen delivery to the tissues is due to increased cardiac output. In peripheral region main limiting factors responsible for the oxygen extraction of tissue are muscle diffusion capacity, mitochondrial enzymes responsible for the ATP production and blood capillary density at the muscle. Oxygen delivery to the muscle mainly depends on the gradient mechanism. During exercise there is increase in the mitochondrial enzymes and consequently peripheral limitation to the oxygen delivery to the muscle. Central factors are more important for delivery of oxygen to tissues as compared to the peripheral factors (Robergs, 2001).      

Thus, cardiovascular and respiratory systems are two most important systems plays important role in the exercise and sports in an individual.

References:

Amann, M. (2012). Pulmonary System Limitations To Endurance Exercise Performance In Human Experimental Physiology, 97(3), pp. 311–318. 

Bassett, D.R., JR., and Howley, E.T. (2000). Limiting factors for maximum oxygen uptake and determinants of endurance performance. Medicine and Science in Sport and Exercise, 32(1), pp. 70-84. 

Bell, C. (2008).  Cardiovascular Physiology in Exercise and Sport. Elsevier Health Sciences. 

Besnier, F., Labrunée, M., Pathak, A., Pavy-Le, T.A., Galès, C., Sénard, J.M., and Guiraud, T. (2016). Exercise training-induced modification in autonomic nervous system: An update for cardiac patients. Annals of Physical and Rehabilitation Medicine,  pii: S1877-0657(16)30081-1. 

Brown, S. P., Miller, W.C., and Eason, J. M. (2012).  Exercise Physiology: Basis of Human Movement in Health and Disease. Lippincott Williams & Wilkins. 

Ehrman, J. K. (2009). Clinical Exercise Physiology. Human Kinetics. 

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Hawley, J.A., Hargreaves, M., Joyner, M.J., and Zierath, J.R.  (2014). Integrative biology of exercise. Cell, 159(4), pp. 738-49.

 Larry, K. W., and Jack, W., David, C.  (2015). Physiology of Sport and Exercise. Human Kinetics. 

LeMura, L. M., and Von Duvillard, S. P. (2004).  Clinical Exercise Physiology: Application and Physiological Principles. Lippincott Williams & Wilkins. 

Margaritelis, N.V., Cobley, J.N., Paschalis, V., Veskoukis, A.S., et al., (2016). Principles for integrating reactive species into in vivo biological processes: Examples from exercise physiology. Cell Signaling, 28(4), pp. 256-71.

Peçanha, T., Bartels, R., Brito, L.C., Paula-Ribeiro, M., Oliveira, R.S., and Goldberger, J.J. (2016). Methods of assessment of the post-exercise cardiac autonomic recovery: A methodological review. International Journal of Cardiology, pii: S0167-5273(16)33138-2.

Périard, J.D., Travers, G.J., Racinais, S., Sawka, M.N. (2016). Cardiovascular adaptations supporting human exercise-heat acclimation. Autonomic Neuroscience, 196, pp. 52-62.

Plowman, S., and Smith, D. (2007).  Exercise Physiology for Health, Fitness, and Performance. Lippincott Williams & Wilkins.

Porcari, J., Bryant, C., and Comana, F.  (2015). Exercise Physiology. F.A. Davis. 

Robergs, R.A. (2001). An exercise physiologist’s “contemporary” interpretations of the “ugly and creaking edifices” of the VO2max concept. Journal of Exercise Physiology online, 4(1), pp.  1-44.

Roh, J., Rhee, J., Chaudhari, V., and Rosenzweig, A. (2016). The Role of Exercise in Cardiac Aging: From Physiology to Molecular Mechanisms. Circulation Research, 118(2), pp. 279-95.

Szabo, A., Griffiths, M.D., de La Vega Marcos, R., Mervó, B., and Demetrovics, Z. (2015).  Methodological and Conceptual Limitations in Exercise Addiction Research. Yale Journal of Biology and Medicine, 88(3), pp. 303-8.

West, J. B. (2012).  Respiratory Physiology: The Essentials. Lippincott Williams & Wilkins.