Cardiovascular Adaptations after a Six Week Aerobic Training - Term Paper Example

Exercise Physiology Name: Institution: Date: 1.0 Introduction Over the past decade or so, the role of physical activity in cardiovascular health has received increased attention. Numerous reports have attested to the unparalleled role of physical activity in reducing the prevalence of symptomatic coronary artery diseases and decreased mortality from other cardiovascular diseases. Extensive research has shown the direct relationship between physical activity and the ability of individuals to participate comfortable and safely in activities of daily living as well as recreational sports. Today, the role of exercise or physical activity assumes additional importance with increased global concerns about obesity and overweightness, as well as, increased prevalence of lifestyle related ailments such as Type 2 diabetes, cardiac heart diseases, cancers, and stroke among others. Moreover, advanced technology has over the years ventured into this area by innovating alternative ways such as surgery, dieting and pharmacy-induced body weight loss, to achieve these healthy outcomes. Upon this background, an understanding of the physiological adaptations that occur in the cardiovascular systems during aerobic training programs on cardiovascular responses is essential and relevant among individuals, physiologists, clinicians , health workers , physical exercise practitioners and sports professionals. The concept of this paper is to review the cardiovascular adaptations that occur after a six week aerobic training and how they contribute tor the overall trained state. 2.0 Literature Review Extensive research shows that regular physical training, mainly the aerobic physical activities, stimulates important cardiovascular benefits, whereby the heart’s functional capacity is improved by means of several adaptations. These adaptations occur in different components of the cardiovascular system, including central hemodynamic blood flow, Peripheral blood flow, Muscle Metabolism and the Lactate Threshold. 2.1 Central Blood Flow Studies show that, both acute and/or single bouts of aerobic exercise have significant effects on the central hemodynamic blood flow in an individual. Braith & Beck (2008) mention that aerobic training results in numerous adaptations that are linked to the overall function of the central blood flow system in the human body (Braith & Beck, 2008). Firstly, aerobic or endurance training is responsible for adaptation in the ventricular heart dimensions. Particularly, acute aerobic training leads to the increase in dimensions or thickening of the left ventricle wall, as a result of increased ventricular filling. The thickening of the left ventricular wall is essential to allow a more forceful contraction of the left ventricle. Secondly, aerobic training is associated with significant adaptation in the training figure stroke volume. According to Schjertve , Tyldum , Tjonna, et al. (2008) endurance or aerobic training increases the stroke volume at rest and during submaximal and maximal exercise. The study observes that the stroke volume in untrained individuals is 50-70ml at rest and at 80-110 ml maximal activity, while that of trained individuals is 70-90 ml at rest and 110-150 ml at maximal activity. Further, the study indicates that the resting and maximal stroke volumes for highly trained individuals are 90-110ml and 150-220ml, respectively (Schjerve, et al., 2008). Another study by Roque,Soci and De Angelis et al. (2011) attributes the increased stroke volume to increased diastolic volume induced by increases in blood plasma and prolonged diastolic filling time (Roque, et al., 2011). Additionally, stroke volume is attributed to increased ventricular heart size that allows the heart to expand more and fill with more blood, while wall thickness increases augment contractility. Consequently, declined systolic blood pressure reduces the resistance to the flow of blood pumped out of the left ventricle (Kochan, 2011). Another adaptation in the central blood flow system is the resting heart rate, which declines with increased aerobic training. Research shows that sedentary individuals are able to decrease their resting heart rate by 1 beat per minute every week during initial training. On the other hand, highly trained individuals may exhibit a resting heart rate of 30 to 40 bpm. Aerobic training also results in significant declines in the submaximal heart rate during exercise, which decreases by almost 10 to 30 bpm in a period of six months at moderate training (Roque, et al., 2011). Aerobic training has also been linked to variations in cardiac output. Specifically, studies have shown that cardiac output (Q) increases significantly at maximal exertion in response to the increased maximal stroke volume. At maximal exertion the absolute values for Qmax recorded range from 14-20L in untrained individuals, 25-35L in trained individuals and 40L+ in maximal endurance individuals. Schjerve et al (2008) attribute this increase in cardiac output to an increase in capillarization of trained muscles as compared to fibers (Schjerve, et al., 2008). Qmax also increases with enhanced opening of existing capillaries in trained muscles which in turn leads to efficiency in blood redistribution. Lastly, aerobic training is associated to a decline in mean blood pressure both at submaximal and maximal exertion (Sharman, McEniery, Coombles, Campbell, Wikinson, & Cockcroft, 2005). Notably, studies conducted on the impact of endurance training on individuals with borderline hypertension show that both systolic and diastolic resting blood pressure is reduced significantly (Sharman J. , McEniery, Dhakam, Coombes, Wilkinson, & Cockcroft , 2007). Conversely, similar studies during maximal exertion indicate slightly peaked values in both diastolic and systolic blood pressure, though the resting blood pressure after resistance exertion does not change and in fact may even decreases in some instances (Fowler, Maiorana, Jenkins, Gain, O'Driscoll, & Gabbay, 2012). 2.2Peripheral Blood Flow Extensive literature shows that aerobic training improves peripheral blood flow and augments the capacity of the muscle fibers to produce larger amounts of adenosine triphosphate (ATP). Indeed various adaptations are observed in three major components of the peripheral blood flow, including capillaries, metabolic reflex and types of muscle fibers. In their examination of capillary adaptations, Schjerve et al (2008) discovered a significant increase in capillarization of trained muscles as compared to fibers (5.9 capillaries per fiber for trained individuals and 4.4 per fiber for untrained athletes) (Schjerve, et al., 2008). The study also found that aerobic training also enhanced opening of existing capillaries in trained muscles which in turn leads to efficiency in blood redistribution. An increase in capillaries is linked to the adaptation in the central cardiac system which amplifies the overall systemic conductance. Increased capillary density in the muscle enhances and improves substances exchange between blood and muscle tissues (Smith & Fernhall, 2011). Chronic aerobic training also affects the metabolism reflex of the individual. This is evidenced by declined blood cholesterol levels, low-density lipoproteins (LDL) and triglycerides. Aerobic training also increases the high-density lipoprotein (HDL) to low-density lipoprotein ratio. Significantly, this helps decreases the risk associated with developing coronary heart disease by enhancing the protective effect of HDL (Vatansev & Cakmakci, 2010). Some research has shown evidence that skeletal muscle switches fiber types from fast twitch to slow twitch due to aerobic training (Karp, 2010). Skeletal muscle fibers are classified into three types. Type 1 muscle fibers are the Slow-twitch oxidative fibers, which contain large quantities of myoglobin, and large quantities of mitochondria and blood capillaries. The slow twitch oxidative fibers appear red in color, breakdown ATP at a slow rate, and are quite slow in contraction velocity. Conversely, this type of muscle is fatigue resistant and is efficient in its capacity to produce ATP by oxidative metabolic processes. Type 2A muscle fibers are the Fast-twitch oxidative fibers which contain an exceedingly large amount of myoglobin, and vast numbers of mitochondria and blood capillaries (Smith & Fernhall, 2011). The fibers are also red, possess a very high capacity for producing ATP by oxidative metabolic processes, very rapid ATP breakdown rate, fast contraction velocity and resistant to fatigue. The third type of fibers is the Type 2B or the Fast-twitch glycolytic fibers, which bear relatively low myoglobin content, few mitochondria and blood capillaries, and hefty amounts of glycogen. These fibers are white, naturally designed to generate ATP by anaerobic metabolic processes, fast ATP breakdown rate, fatigue easily and fast contraction velocity (Karp, 2010). Summary of muscle tissue adaptations to aerobic (endurance) training: Before Training After Training Mitochondria (size and number) Increased Glycogen Stores Increased Myoglobin Increased Triglyceride Stores Increased Oxidation (both glucose and fats) Increased Anaerobic Glycolysis (lactic acid system) Decreased Muscle Type Adaptation (number and type) Increased Some conversion of: Type 2B fibres to Type 2A fibres 2.3 Muscle Metabolism Chronic aerobic training adaptations within muscular tissue are best produced through continuous training or high-repetition resistance training. Research inquiries have identified various tissue-level variations that occur within skeletal muscles following extensive endurance training. Firstly, aerobic training develops the body’s ability to absorb oxygen into the muscle cells and then utilise it to generate adenosine triphosphate (ATP) necessary for muscle contraction. Here, adaptations occur in the form of an increased in the size and number of mitochondria and increased myoglobin stores (Harber, Konopka, Douglass, & Minchev, 2009). Secondly, aerobic training leads to increased muscular storage of glycogen, free fatty acids and triglycerides, alongside other oxidative enzymes essential to metabolise these fuel stores and generate ATP. Thirdly, aerobics training increases the oxidation of glucose and fats whereby, muscular adaptations result in an increase in the ability of muscle fibres to oxidate both glucose and fats. Accordingly, the ability of the aerobic system to metabolise these fuels is increased with oxidation of fats as a fuel source; mainly because of augmented storage of triglycerides and free fatty acids and the amplified levels of enzymes associated with fat metabolism. This means that at any given level of exertion, a trained individual depends less on glycogen, thus sparing his or her glycogen stores. In this way, the individual is able to delay the time to exhaustion resulting form glycogen depletion (Klausen, Andersen, & Pelle, 2008). Lastly, the improved capacity of muscles to aerobically, synthesize glucose and fats, alongside other muscular level adaptations, reduces the dependence on the anaerobic glycolysis system to generate energy for ATP resynthesis. As such, it allows athletes to perform at maximal intensities without exceeding the lactate threshold. Other studies also argue that aerobic training raises the lactate threshold that is; the athlete is required run faster so as to collect a similar amount of lactic acid as afore training (Plowman & Smith, 2007). 2.4 The Lactate Threshold Chronic aerobic activity generally increases the anaerobic or lactate threshold as a result of the respiratory adaptations that enhance the delivery and uptake of oxygen in the muscles tissues. These increases in the maximum oxygen uptake (VO2 max) and lung ventilation raise ta lactate threshold such that the anaerobic glycolysis system is not utilised frequently. In this way, accumulation of lactic acid and hydrogen ions is delayed thus allowing the athlete to perform at maximal exertion in prolonged durations (TT, et al., 2012). 3.0 The Aerobic Training Study 3.1 Subject The study was focused on the evaluation of only one subject who underwent strict medical checkup and physical ability examination. The inclusion criterion was that the study individual was the least physically fit as compared to the rest of the aerobic training group. Another criterion for inclusion was that the individual was able to comply with the program (about70%). 3.2 Baseline characteristics Once the subject was chosen, various tests were conducted to establish the baseline characteristics. The first test was to establish the baseline maximal aerobic capacity by obtaining the subjects’ VO2 max. VO2 max was measured during uphill shuttle treadmill walking or running using the Metamax II system . Before the test, the subject underwent a warm-up period for 10 min (50–60% of HRmax) . A levelling off of VO2, despite increased work load, and RER (respiratory exchange ratio) 1.05 were used as criteria for VO2max. HR was measured during the test and HRmax was defined by adding 5 beats/min to the highest HR value obtained during the VO2 max test (Kenney, Wilmore, & Costill, 2011). The next test conducted on the subject aimed to establish the baseline ventilatory and lactate thresholds. These were determined using the v-slope method and established by ventilatory equivalents. Blood lactate threshold was identified as the first inflection in the blood lactate-velocity curve as well as the incorporated speed at a blood lactate level of 4 mmol/l. Heart rate threshold was determined as the percentage of maximum heart rate, power output was calculated for each run on the treadmill. Another test was the time to exhaustion test based on the established VO2 max. The last tests conducted the subject at baseline level included the anthropometric battery to describe the subjects characteristics (Kokkinos, 2010). Baseline characteristics Characteristic Value Age Height Gender Body Weight BMI Waist/ hip Ratio HR max VO2 max Time to Exhaustion Lactate threshold 3.3 Aerobic Training After recording the baseline characteristics the subject began the aerobic training program conducted at moderate intensity on the treadmill. The program entailed 10 minute of warm-up a t 50-60% of HRmax followed by continuous walking on the treadmill for 47 minutes at 60-70% of HR max. The subject was instructed to regulate the intensity of the exercise by monitoring his heart rate to adjust the speed or incline. Further, the subject was asked to continue with home training such as outdoor walking especially uphill. The subject would regulate the intensity of the exercise using the Borg RPE scale. 3.4 Results After a period of six weeks of intensive aerobic training regiments, post tests were conducted on the subject. Characteristics Baseline or pre test Post tests The results exposed significant differences from pre to post-test measurements in the subject p for BW, BMI,VO2max, lactate threshold and time to exhaustion(p Read More