2Lower heart rate during sub-maximal workloads: Mainly a result of increased stroke volume.The heart works more efficiently - (More blood is pumped with each beat, and therefore the heart doesn’t have to work as hard to supply the required blood flow and oxygen supply)Slower increase in heart rate during exercise and a lower and faster attainment of steady state during exercise
4Improved heart-rate recovery rates: Heart rate of a trained athlete will return to pre-exercise levels (resting rate) in a much shorter time than that of an untrained individual.
5Increased cardiac output at maximum workloads Cardiac output – unchanged at rest and even during sub-maximal exercise regardless of training status.Does increase during maximal exercise.Maximal exercise – may increase to values of:· litres per minute for untrained male· litres per minute for untrained· 30 litres per minute or more – highly trained athletes females
6Lower blood pressure:May lower blood pressure, especially among people who suffer from hypertension (high blood pressure)Systolic and diastolic pressure levels may decrease during both rest and exerciseHelps to reduce resistance to blood flow and reduces strain on the heart, thereby decreasing the risk of heart attack and other cardiovascular conditions
7The arteriovenous oxygen difference, or a-vO2 diff, is the difference in the oxygen content of the blood between the arterial blood and the venous blood. It is an indication of how much oxygen is removed from the blood in capillaries as the blood circulates in the body.
8Increased arterio-venous oxygen difference (a-VO2 diff): Trained individuals are able to absorb more oxygen from their bloodstream into their muscles during exercise performance compared to untrained subjects.This is due to:· Increased muscle myoglobin stores· Increased number and size of mitochondria within their muscles
9As a result of this, the concentration of oxygen within the venous blood is lower Subsequently the arterio-venous oxygen difference is increased during both sub-max and maximal exerciseTherefore, and increased arterio-venous oxygen difference (a-VO2 diff) indicates a greater uptake of oxygen by the muscles with trained individuals
10Increased blood volume and haemoglobin levels: Total blood volume may rise by up to 25% (from 5.25L to 6.6L) for an average adult male with regular and sustained aerobic training.Red blood cells may increase in number and the haemoglobin content and oxygencarrying capacity of the blood may also rise.
11Increased capillarisation of skeletal muscle: The average number of capillaries supplying each muscle fibers is:· 5.9 for trained athletes· 4.4 for untrained athletes
12Changes to blood cholesterol, triglycerides, low- and high-density lipoprotein levels: Results may include a decrease in blood cholesterol levels, triglycerides and low density lipoprotein (LDL).These substances are associated with the development of coronary heart disease.Aerobic training increases the ratio of high-density lipo-protein (HDL) to low-density lipoprotein.High-density lipoprotein is thought to provide a coronary protective effect, lessening the risk of developing coronary heart disease.
16B) RESPIRATORY ADAPTATIONS to aerobic training More efficient and improved lung ventilationAt rest and during sub-maximal exercise, ventilation may be reduced due to improved oxygen extractionHowever, during maximal workloads, ventilation is increased because of increased tidal volume (amount of air breathed in and out in one breath) and respiratory frequency (the number of breaths taken per minute).Pulmonary diffusion (the ability of the blood to extract oxygen from the alveoli) is also enhanced.
17Increased maximum oxygen uptake (VO2 max) Increase in the maximum oxygen uptake (VO2 max) during maximal exerciseImprovement can be between 5–30% following a regular and sustained training program
18This occurs because of adaptations such · Increased cardiac output · Increased red blood cell numbers· Increased a-VO2 difference· Increased muscle capillarisation· Greater oxygen extraction by the muscles as:
19Increased anaerobic or lactate threshold As a result of the adaptations that improve oxygen delivery and utilisation in the muscles, a higher lactate threshold (the point at which oxygen supply cannot keep up with oxygen demand) is developed.
20Advantage:The anaerobic glycolysis (lactic acid) system is not utilised as much until higher exercise intensities are reached.Consequently, lactic acid and hydrogen ion accumulation will be delayed until these higher work-load intensities are attainedThe athlete can “work harder and for longer periods”
21Muscle Tissue Adaptations to Aerobic (Endurance) Training: Chronic aerobic training adaptations within muscular tissue are best produced through continuous training or high-repetition resistance trainingThe following tissue-level changes can be observed within skeletal muscles following extensive endurance training:
22Increased oxygen utilisation: Aerobic training enhances the body’s ability to attract oxygen into the muscle cells andthen utilise it to produce adenosine triphosphate (ATP) for muscle contractionThis process occurs in the following ways:· Increased size and number of mitochondria –
23Mitochondria are the site of ATP synthesis and where glycogen and triglyceride stores are oxidised (Greater oxidisation of fuels to produce ATP)· Increased myoglobin stores – Myoglobin is the substance in the muscle cell that attracts oxygen from the bloodstream into the muscle. (Increase ability to extract oxygen)
24Increased muscular fuel stores: Increase in the muscular storage of glycogen, free fatty acids and triglycerides, along with the oxidative enzymes required to metabolise these fuel stores and produce ATP.
25Increased oxidation of glucose and fats: The muscular adaptations result in an increase in the capacity of muscle fibers to oxidate both glucose and fatsThe capacity of the aerobic system to metabolise these fuels is increasedIncreased oxidation of fats as a fuel source; due to:· Increased storage of triglycerides and free fatty acids· Increased levels of enzymes associated with fat metabolism
26Means that:At any given exercise intensity, a trained individual has to rely less on glycogen, thereby “sparing” glycogen stores (Glycogen sparing)Therefore delaying the time to exhaustion due to glycogen depletion.
27Decreased utilisation of the anaerobic glycolysis (lactic acid) system: The enhanced capacity of the muscles to aerobically metabolise glucose and fats and other muscular level adaptations also means that there is less reliance upon the anaerobic glycolysis system to produce energy for ATP resynthesis until higher exercise intensities are reached.· Allows athletes to work at higher intensities without exceeding lactate threshold.OR· Aerobic training results in an increase in the lactate threshold
28Eg. An athlete must run at a faster pace in order to accumulate the same amount of blood lactic acid as before training
29Muscle- fiber type adaptation: Some research has shown evidence that skeletal muscle switches fiber types from fast twitch to slow twitch as a result of endurance training.Skeletal muscle fibers are classified into three types:Type 1 – Slow-twitch oxidative fibers:· Contain large amounts of myoglobin, and large numbers of mitochondria and blood capillaries.
30Red· Split ATP at a slow rate· Slow contraction velocity· Very resistant to fatigue· High capacity to generate ATP by oxidative metabolic processes.
31Type 2A – Fast-twitch oxidative fibers: · Contain an extremely large amount of myoglobin, and huge numbers of mitochondria and blood capillaries.· Red· Very high capacity for generating ATP by oxidative metabolic processes· Split ATP at a very rapid rate· Fast contraction velocity· Resistant to fatigue
32Type 2B – Fast-twitch glycolytic fibres: · Contain low myoglobin content, relatively few mitochondria and blood capillaries, and large amounts of glycogen· White· Geared to generate ATP by anaerobic metabolic processes· Fatigue easily· Split ATP at a fast rate· Fast contraction velocityIndividual muscles are a mixture of the three types of muscle fibers, but their proportions vary depending on the action of the muscle and the genetic make-up of the individual
33Summary of muscle tissue adaptations to aerobic (endurance) training: