Exercise/Sports Physiology

Learning Objectives Definitions- Aerobic vs. anaerobic Isometric vs. Isotonic Acute response vs. exercise training Sk muscle- ATP synthesis pathway Aerobic exercise training Anaerobic exercise training

Motor and Autonomic control CVS- B.P; HR; CO; VR; Flow redistribution; training. RS- Ventillation; Oxygen extraction; EPOC; Training

Exercise Classification

Energy System Time Course Adenosine triphosphate–creatine phosphate system;phosphagen sys : 8 – 10 s Glycogen Lactic acid system: 0.5- 2.5 min Oxidative phosphorylation: hrs When athletes run at speeds typical for the marathon race, their endurance (as measured by the time that they can sustain the race until complete exhaustion) is approximately the following: Minutes High-carbohydrate diet 240 Mixed diet 120 High-fat diet 85

C) Glycogen-lactic acid system D) Phosphocreatine system E) Stored ATP Which of the following sources can produce the greatest amount of ATP per minute over a short period of time? A) Aerobic system B) Phosphagen system C) Glycogen-lactic acid system D) Phosphocreatine system E) Stored ATP B) Over a short period of time the phosphagen system can produce 4 moles of ATP/min. The phosphagen system comprises the ATP and phosphocreatine system combined. However, when a person runs a long distance race, such as a 10-km race, the phosphagen system can supply energy for 8 to 10 sec only. The glycogen-lactic acid system supplies energy can produce 2.5 moles of ATP per minute. Therefore, the aerobic system, which consists of metabolism of glucose, fats, and amino acids, can produce 1 mole of ATP/min.

A) One on a high-fat diet B) One on a high-carbohydrate diet Which of the following athletes is able to exercise the longest before exhaustion occurs? A) One on a high-fat diet B) One on a high-carbohydrate diet C) One on a mixed carbohydrate–fat diet D) One on a high-protein diet E) One on a mixed protein–fat diet B) An athlete on a high-carbohydrate diet will store nearly twice as much glycogen in the muscles compared to an athlete on a mixed carbohydrate–fat diet. This glycogen is converted to lactic acid and supplies four ATP molecules for each molecule of glucose. It also forms ATP 2.5 times as fast as oxidative metabolism in the mitochondria. This extra energy from glycogen significantly increases the time an athlete can exercise.

A) Adenosine triphosphate (ATP) B) Anaerobic glycolysis Most of the energy for strenuous exercise that lasts for more than 5 to 10 seconds but less than 1 to 2 minutes comes from which of the following sources? A) Adenosine triphosphate (ATP) B) Anaerobic glycolysis C) Oxidation of carbohydrates D) Oxidation of lactic acid E) Conversion of lactic acid into pyruvic acid B) Most of the extra energy required for strenuous activity that lasts for more than 5 to 10 sec but less than 1 to 2 min is derived from anaerobic glycolysis. Release of energy by glycolysis occurs much more rapidly than oxidative release of energy, which is much too slow to supply the needs of the muscle in the first few minutes of exercise. ATP and phosphocreatine already present in the cells are rapidly depleted in less than 5 to 10 sec. After the muscle contraction is over, oxidative metabolism is used to reconvert much of the accumulated lactic acid into glucose; the remainder becomes pyruvic acid, which is degraded and oxidized in the citric acid cycle. TMP12 860–861

Effect of diet on the rate of muscle glycogen replenishment after prolonged exercise.

Effect of duration of exercise as well as type of diet on relative percentages of carbohydrate or fat used for energy by muscles:

Aerobic exercise training Anaerobic exercise training 1. Energy stores: increase in myocyte gly-cogen stores. 2. Metabolism: increases mitochondrial size and numbers and increase in myoglobin content 1. Hypertrophy: increase in the cross-sectional area of type IIa and IIx muscle fibers by adding new myofibrils to the myocytes. 2.Neural recruitment: 3. Metabolism and energy stores:

Effects of training on muscle mass and performance.

Motor and autonomic control

Peripheral Nervous System Alpha-Motor neurons: Motor units: Muscle sensors: Mus spindle, Golgi tendon organs, Mus afferents Cardiovascular receptors

Central nervous system Somatic: The premotor cortex, supplemental motor cortex, and basal ganglia aid in motor program development. This motor program is then executed by the primary motor cortex and signaled via the corticospinal tract. The cerebellum coordinates leg and foot move-ments d

2. Autonomic: Autonomic systems are required to redistribute flow. This is accomplished via sympathetic feedforward and feedback pathways

3. Senses: Vision plays a major role in pro-viding information about potential obstacles and the nature of the terrain. Hearing plays a lesser role, but it does help provide clues about the location of other riders, gearing, and under-the-tire terrain. The vestibular system provides information regarding linear acceleration (otolith organs) and head position when scanning the path ahead and looking for items on either side of the path.

CARDIOVASCULAR SYSTEM

Arterial Pressure

Cardiac Output Heart Rate Stroke Volume Venous return

Flow redistribution

Cardiac adaptation to long term training Aerobic Anaerobic Volume-induced cardiac hyper trophy. This type of hypertrophy increases both the LV chamber diameter and LV wall mass and likely is caused by the high venous return and preload accompanying exercise. This adap tation increases resting EDV and SV. Anaerobic exercise training, which involves repeatedly forcing the LV to eject against an elevated MAP, stimulates a LV hypertrophy. Such hypertrophy is charac-terized by an increase in LV wall thickness but a decrease in lumen diameter.

Vascular adaptation to long term training Training increases the ability of skeletal and cardiac muscle to vasodilate, probably through increased nitric oxide pro-duction. Over time, angiogenesis increases capillary density and, thereby, decreases the distance for diffusional exchange of O2 and nutrients between blood and myocytes.

(A) Arteriovenous O2 difference (B) Heart rate (C) Cardiac output Which of the following parameters is decreased during moderate exercise? (A) Arteriovenous O2 difference (B) Heart rate (C) Cardiac output (D) Pulse pressure (E) Total peripheral resistance (TPR) E

Q. During exercise, total peripheral resistance (TPR) decreases because of the effect of (A) the sympathetic nervous system on splanchnic arterioles (B) the parasympathetic nervous system on skeletal muscle arterioles (C) local metabolites on skeletal muscle arterioles (D) local metabolites on cerebral arterioles (E) histamine on skeletal muscle arterioles. C

Q. During exercise, there is an increase in a person’s a Q. During exercise, there is an increase in a person’s a. Stroke volume b. Diastolic pressure c. Venous compliance d. Pulmonary arterial resistance e. Total peripheral resistance A

Olympic athletes who run marathons or perform cross country skiing have much higher maximum cardiac outputs than non-athletes. Which of the following statements about the hearts of these athletes compared to non-athletes is most accurate? A) Stroke volume in the Olympic athletes is about 5% greater at rest B) Percentage increase in heart rate during maximal exercise is much greater in the Olympic athletes C) Maximum cardiac output is only 3% to 4% greater in the Olympic athletes D) Resting heart rate in the Olympic athletes is significantly higher B) When comparing Olympic athletes and nonathletes, we find that there are several differences in the responses of the heart. Stroke volume is much higher at rest in the Olympic athlete and heart rate is much lower. The heart rate can increase approximately 270% in the Olympic athlete during maximal exercise, which is a much greater percentage than occurs in a non-athlete. In addition, the maximal increase in cardiac output is approximately 30% greater in the Olympic athlete.

a

e

Respiratory System

Ventilation At the beginning of exercise, there is an immediate increase in ventilation, mediated primarily by central respi-ratory control centers. Then, via peripheral feedback from muscles and chemoreceptors (via PaCO2), ventilation increases linearly throughout low-to-moderate exercise. During heavy exercise, ventilation increas-es to a greater extent because of added anaerobic generation of H, which further stimulates peripheral chemoreceptors

Oxygen extraction Muscles consume O2 at increased rates when exercised, which de-creases PO2 locally and enhances the magnitude of the gradient driving O2 diffusion from the atmosphere to the musculature. This phenomenon manifests as a widening of the arteriovenous (a-v) O2 difference, from 5 mL O2/dL at rest to 15 mL O2/dL during maxi-mal aerobic exercise (Figure 39.11). O2 delivery to the active tissues is facilitated by a decrease in hemoglobin (Hb)-O2 binding afnity, which increases ofoading. The rightward shift in the O2- dissociation curve occurs due to increased CO2 and H production and rising lo-cal temperatures (

Excess postexercise oxygen consumption

Training Ventilation: Maximal alveolar ventilation and VE both increase. Arteriovenous oxygen difference increase: decreased diffusional distance between blood and myocytes due to increased capillary density, and increased blood flow ,Hb also increases . 1. Ventilation: Maximal alveolar ventilation and VE both increase with aerobic exercise training. This likely occurs via aerobic training adaptations in the respiratory muscles that increase fatigue re-sistance.

3. Oxygen uptake: The increase in CO, alveolar ventilation, and a-v O2 difference combine to increase maximal O2 uptake during training.

Which of the following statements about respiration in exercise is most accurate? A) Maximum oxygen consumption of a male marathon runner is less than that of an untrained average male B) Maximum oxygen consumption can be increased about 100% by training C) Maximum oxygen diffusing capacity of a male marathon runner is much greater than that of an untrained average male D) Blood levels of oxygen and carbon dioxide are abnormal during exercise C) During exercise the maximum oxygen consumption of a male marathon runner is much greater than that of an untrained average male. However, athletic training increases the maximum oxygen consumption by only about 10%. Therefore, the maximum oxygen consumption in marathon runners is probably partly genetically determined. These runners also have a large increase in maximum oxygen diffusing capacity, and their blood levels of oxygen and carbon dioxide remain relatively normal during exercise.