Muscle Metabolism and Physiological Responses to Exercise
Muscle Metabolism and Energy Systems
Glycolysis
Glycolysis is the breakdown of glucose to pyruvate under anaerobic conditions.
Energy Systems in High-Intensity, Short-Duration Exercise (10-15 seconds)
The dominant energy system in high-intensity, short-duration exercise is the phosphocreatine system, where phosphocreatine is used to rapidly form ATP.
Creatine kinase activity is stimulated by high levels of ADP.
Muscle Adaptations
Adaptations to exercise occur in both structural and neurological factors.
Motor Units
A motor unit consists of a single motor neuron that innervates multiple muscle fibers of the same type.
Sarcomere Length-Tension Relationship
Sarcomeres generate maximum force at an optimal length. Intermediate-length sarcomeres do not produce maximal force.
Glycolytic Pathway Location
The glycolytic pathway occurs in the cytosol.
Type IIa Muscle Fibers
Type IIa muscle fibers have mixed oxidative-glycolytic properties, are fast-twitch, and relatively fatigue resistant.
Cellular Energy Source
ATP is the primary source of cellular energy.
Energy Systems in 5-10 Second Exercise
The phosphagen system is the primary energy source for exercises lasting 5-10 seconds.
Muscle Tissue Modifications from Training
Specific muscle training can induce modifications in muscle tissue, such as increased capillarization in endurance exercise.
Stretch-Shortening Cycle
The stretch-shortening cycle is the basis of plyometric exercise.
Muscle Receptors
Muscle spindles are receptors within the muscle that are stimulated by stretch.
Acute Responses to Exercise
Acute responses to exercise involve immediate physiological changes.
Motion Control by the Nervous System
The nervous system controls motion through anticipation and feedback mechanisms.
Platform Jumping
Countermovement jumps utilize the accumulation of elastic energy in the muscles.
Sarcomere H-Band
The H-band of the sarcomere contains only myosin filaments.
Muscle Contraction Classification
Muscle contractions are classified as static (isometric) or dynamic (isotonic).
Phosphocreatine and ATP Synthesis
Phosphocreatine serves as a source of phosphoryl groups for the rapid synthesis of ATP from ADP.
Cardiac and Respiratory Physiology
Inotropism and Cardiac Output
Increased inotropism (force of contraction) enhances cardiac output.
Hemoglobin-Oxygen Dissociation Curve
Increased temperature shifts the hemoglobin-oxygen dissociation curve to the right.
Cardiac Output Calculation
Cardiac output is calculated as heart rate multiplied by stroke volume (CO = HR x SV).
Resting Tidal Volume
Normal resting tidal volume is approximately 500ml.
Inspired Gas Composition
Inspired air is approximately 79% nitrogen and 21% oxygen.
Venous Oxygen Partial Pressure
Venous PO2 is approximately 40 mmHg.
Cardiac Output During Exercise
Cardiac output continues to increase during maximal exercise due to a rise in heart rate.
Valsalva Maneuver
The Valsalva maneuver involves increasing intrathoracic pressure, which can increase blood pressure.
Cardiac Hypertrophy
Concentric cardiac hypertrophy is associated with weight training.
Blood Viscosity and Hematocrit
Blood density and viscosity increase with increasing hematocrit.
Fick’s Law
Fick’s Law is used to calculate VO2.
Normal Blood Pressure
The upper limit of normal blood pressure is 140/90 mmHg.
Poiseuille’s Law
According to Poiseuille’s Law, if the radius of a vessel decreases by half, resistance increases 16 times.
Hemoglobin and CO2 Affinity
Hemoglobin’s affinity for CO2 increases when it is not bound to oxygen.
Hemoglobin-Oxygen Dissociation Curve and CO2
A PCO2 of 20 mmHg shifts the hemoglobin-oxygen dissociation curve to the right.
Hypoventilation
Hypoventilation can lead to an increase in anatomical dead space.
Metabolic Equivalent (MET)
One MET is equal to 3.5 ml/min/kg of oxygen consumption.
VO2 Max
VO2max is measured using established protocols, including continuous ramp tests, and can be assessed in both laboratory and field settings. It can be measured as the ratio of ventilation (VE) to oxygen consumption (VO2), and is related to heart rate (HR).
Alveolar PO2
Alveolar PO2 is approximately 100 mmHg.
Diaphragm During Inspiration
The diaphragm contracts during inspiration.
Environmental Pollution
Carbon monoxide (CO) is harmful due to its high affinity for hemoglobin.
Hypercapnia
Hypercapnia is an increase in CO2 levels.
Veins
Veins carry blood towards the heart.
Heart Rate During Exercise
Heart rate increases during exercise due to increased oxygen demand.
Gas Exchange During Exercise
Gas exchange during exercise occurs in the capillaries.
pH Changes During Exercise
Decreased pH during exercise can be caused by increased muscle fatigue and shifts in the respiratory center response curve.
Oxygen Saturation in Skeletal Muscle
Oxygen saturation is generally higher in skeletal muscle.
Oxygen Transport During Exercise
Oxygen is primarily transported bound to hemoglobin during exercise.
ADP and Phosphocreatine Coupling
The coupling of ADP and phosphocreatine is essential for ATP formation.
Energy Systems in High-Intensity, Longer-Duration Exercise (30-35 seconds)
High-intensity exercise lasting 30-35 seconds involves both the phosphagen system and the participation of phosphocreatine in ATP formation.
Gluconeogenesis
Gluconeogenesis in the liver can synthesize glucose from amino acids, glycerol, and lactate.
Marathon Running
Marathon running involves both glycolytic and aerobic systems.
Phosphocreatine Role
Phosphocreatine is primarily involved in short-duration, high-intensity activities.
ATP Synthesis Location
ATP synthesis takes place in the mitochondria.
Phosphocreatine Decrease During Exercise
Phosphocreatine decrease during exercise helps maintain stable ATP levels.
Wingate Test
The Wingate test measures power and can estimate VO2max.
Muscle Hyperplasia
Hyperplasia in skeletal muscle can potentially double the number of fibers.
Muscle Triad
A muscle triad consists of a T-tubule and two terminal cisternae of the sarcoplasmic reticulum.
Blood Pressure During Exercise
Blood pressure can increase significantly during exercise, potentially reaching 240 mmHg systolic.