Chapter 3 - Bioenergetics of Exercise and Training Flashcards
Bioenergetics
flow of energy in a biological system; conversion of macronutrients into biologically usable forms of energy.
Catabolism
breakdown of large molecules into smaller molecules, associated with the release of energy.
Anabolism
synthesis of larger molecules from smaller molecules; can be accomplished using the energy released from catabolic reactions.
Exergonic reactions
energy-releasing reactions that are generally catabolic.
Endergonic reactions
require energy and include anabolic processes and the contraction of muscle.
Metabolism
total of all the catabolic or exergonic and anabolic or endergonic reactions in a biological system.
Adenosine Triphosphate (ATP)
allows transfer of energy from exergonic to endergonic reactions.
Chemical Structure of ATP
adenosine (adenine+ribose), triphosphate group, and locations of high energy chemical bonds.
Hydrolysis of ATP
The breakdown of 1 ATP molecule to yield energy. Requires 1 H2O molecule.
Breaks the terminal phosphate bond, releases energy, and leaves ADP – an inorganic phosphate (Pi) and a hydrogen ion (H+)
Hydrolysis of ADP
Breaks the terminal phosphate bond, releases energy, and leaves AMP, Pi, and H+
Biological Energy Systems
Phosphagen
Glycolysis
Oxidative
Replenishes ATP in skeletal muscle
Phosphagen System
Body does not store enough ATP for exercise.
ATP needed for basic cellular function.
Uses creatine kinase reaction to maintain concentration of ATP.
Replenishes ATP rapidly.
Law of mass action
Concentrations of reactants or products (or both) in solution will drive the direction of the reactions.
Phosphagen System.
Glycolysis
Breakdown of carbs, either glycogen stored in muscle or glucose delivered in blood, to resynthesizes ATP.
End Result of glycolysis (pyruvate) may proceed in 1 of 2 directions
1) Pyruvate converted to lactate – ATP resynthesis occurs faster but is limited.
2) Pyruvate can be shuttled into mitochondria if sufficient O2 is available (slow glycolysis) – When pyruvate undergoes Krebs, ATP resynthesis is slower, but occurs for longer duration if exercise intensity is low enough (aka aerobic/slow glycolysis).
Glycolysis and the Formation of Lactate
The formation of lactate from pyruvate is catalyzed by the enzyme lactate dehydrogenase.
End result his NOT lactic acid.
Glucose + 2Pi + 2ADP > 2Lactate + 2ATP + H20
Lactate can be transported in the blood to the liver, where it is converted to glucose (Cori Cycle).
Glycolysis Leading to Krebs
Only if sufficient O2 is available.
AKA Slow Glycolysis.
Pyruvate that enters mitochondria is converted to acetyl-CoA by pyruvate dehydrogenase (resulting in loss of CO2)
Acetyl-CoA can then enter Krebs.
NADH molecules enter the electron transport system, where they can also be used to resynthesize ATP.
Glucose + 2Pi + 2ADP + 2NAD+ > 2Pyruavte + 2ATP + 2NADH + 2H20
Energy Yield of Glycolysis
Glycolysis from one molecule of blood glucose yields a net of 2 ATP.
Glycolysis from muscle glycogen yields a net of 3 ATP.
Control of Glycolysis
Stimulated by high concentrations of ADP, Pi, and ammonia and by a slight decrease in pH and AMP.
Inhibited by markedly lower pH, ATP, CP, citrate, and free fatty acids.
Also affected by hexokinase, phosphofructokinase, and pyruvate kinase.
Lactate Threshold (LT) and Onset Blood Lactate (OBLA)
LT: exercise intensity at which blood lactate begins an abrupt increase above baseline concentration. Represents significantly increased reliance on anaerobic mechanisms for energy production (likewise with ventilatory threshold).
OBLA represents second increase in rate of lactate accumulation.
Lactate Threshold (LT)
Exercise intensity or relative intensity at which blood lactate begins an abrupt increase above baseline concentration.
Begins at 50%-60% max 02 uptake in untrained.
Begins at 70%-80% max 02 uptake in trained.
Onset Blood Lactate (OBLA)
Second increase in rate of lactate accumulation.
Occurs at higher relative intensities.
Occurs when concentration of blood lactate reaches 4 mmol/L.
Oxidative (Aerobic) System
Primary sources of ATP at rest and during low-intensity exercise.
Uses Primarily carbs and fats as substrates.
Glucose and Glycogen Oxidation
Metabolism of blood glucose and muscle glycogen begins with glycolysis and leads to Krebs (Reminder: if O2 is present in sufficient quantities, the end product of glycolysis, pyruvate, is NOT converted to lactate but is transported to the mitochondria, where it’s taken up and enters Krebs).
NADH and FADH2 molecules transports H+ atoms two ETC, where ATP is produced from ADP.
Fat Oxidation
Triglycerides stored in fat cells can be broken down by hormone-sensitive lipase.
This releases FFA from fat cells into the blood, where they can circulate and enter muscle fibers.
Some FFA come from intramuscular fibers.
FFAs enters mitochondria, are broken down, and form acetyl-CoA and hydrogen protons.
Protein Oxidation
Protein is NOT a significant source of energy for most activities.
Protein is broken down into amino acids, and the amino acids are converted into glucose (gluconeogenesis), pyruvate, or various Krebs cycles inter-mediates to produce ATP.
Amino acids contribution to producing ATP estimated to be minimal during short-term exercise, but 3-18% during prolonged activity.
Control of the Oxidative (Aerobic) System
The ETC and Isocitrate dehydrogenase are stimulated by ADP and inhibited by ATP.
Rate of Krebs cycle is reduced if NADH+ and FAD2+ are not available in sufficient quantities to accept hydrogen.
The ETC is stimulated by ADP and inhibited by ATP.
Energy Production and Capacity
In general, there’s an inverse relationship between a given energy system’s max rate of ATP production (i.e. ATP produced per unit of time) and the total amount of ATP it’s capable of producing over a varying exercise duration.
Exercise Duration and Intensity of Primary Energy System Used
Phosphagen: 0-6s, extremely high intensity
Phos. & Fast Glycolysis: 6-30s, very high intensity.
Fast Gly.: 30s-2min, high intensity.
Fast Gly. & Oxidative (Slow Glycolysis): 2-3min, moderate intensity
Oxidative: >3min, low intensity.
Energy System Rank of Rate of ATP Production and ATP Capacity (Production/Capacity)
(Production/Capacity) 1 =fastest/greatest, 5=slowest/least Phosphagen: 1/5 Fast Gly.: 2/4 Slow Gly.: 3/3 Oxidation of CHO: 4/2 Oxidation of Fats/Proteins: 5/1 Extent to which each energy system contributes ATP production depends primarily on the intensity of muscular activity and secondarily on duration. One systems will NEVER provide all of the ATP.
Substrate Depletion and Repletion - Phosphagens
CP can decrease markedly (50%-70%) during first stage of extremely high-intensity exercise (5-30s) and can almost be eliminated as a result of very intense exercise to exhaustion.
ATP may decrease only slightly or may decrease up to 50-60% of preexercise levels.
Post-exercise Phos. repletion can occur in a relatively short period; complete resynthesis of ATP appears to our within 3-5 min, and complete CP resynthesis occurs within 8 min.
Substrate Depletion and Repletion - Glycogen
Rate of glycogen depletion is related to exercise intensity.
At relative intensities of exercise above 60% of max O2 uptake, muscle glycogen (MG) becomes an increasingly important energy substrate; the entire glycogen content of some muscle cells can become depleted during exercise.
Repletion of MG during recovery is related to post exercise CHO ingestion. Optimal oof 0.7g-3.0g CHO/kgBW ingested every 2 hours post exercise.
Bioenergetic Limiting Factors in Exercise Performance - LIGHT (Marathon)
1= least probable limiting factor, 5= most probable limiting factor
ATP and CP Muscle Glycogen Liver Glycogen Fat Stores Lower pH
ATP and CP: 1 Muscle Glycogen: 5 Liver Glycogen: 4-5 Fat Stores: 2-3 Lower pH: 1
Bioenergetic Limiting Factors in Exercise Performance - MODERATE (1500m run)
1= least probable limiting factor, 5= most probable limiting factor
ATP and CP Muscle Glycogen Liver Glycogen Fat Stores Lower pH
ATP and CP: 1-2 Muscle Glycogen: 3 Liver Glycogen: 2 Fat Stores: 1-2 Lower pH: 2-3
Bioenergetic Limiting Factors in Exercise Performance - HEAVY (400m run)
1= least probable limiting factor, 5= most probable limiting factor
ATP and CP Muscle Glycogen Liver Glycogen Fat Stores Lower pH
ATP and CP: 3 Muscle Glycogen: 3 Liver Glycogen: 1 Fat Stores: 1 Lower pH: 4-5
Bioenergetic Limiting Factors in Exercise Performance - VERY INTENSE (Discus)
1= least probable limiting factor, 5= most probable limiting factor
ATP and CP Muscle Glycogen Liver Glycogen Fat Stores Lower pH
ATP and CP: 2-3 Muscle Glycogen: 1 Liver Glycogen: 1 Fat Stores: 1 Lower pH: 1
Bioenergetic Limiting Factors in Exercise Performance - VERY INTENSE (Repeated snatch exercise at 60% 1RM)
1= least probable limiting factor, 5= most probable limiting factor
ATP and CP Muscle Glycogen Liver Glycogen Fat Stores Lower pH
ATP and CP: 4-5 Muscle Glycogen: 4-5 Liver Glycogen: 1-2 Fat Stores: 1-2 Lower pH: 4-5
O2 Uptake and the Aerobic and Anaerobic Contributions to Exercise
Excess Postexercise Oxygen Consumption (EPOC)
-Factors Responsible-
Replenishment of O2 in blood and muscle.
ATP/CP resynthesis
Increased body temp., circulation, and ventilation.
Increased rate of triglyceride-fatty acid cycling.
Increased protein turnover.
Changes in energy efficiency during recovery.
Excess Postexercise Oxygen Consumption (EPOC).
O2 uptake above resting values used to restore body to preexercise condition.
Also called post exercise uptake, O2 debt, of recovery O2.
Metabolic Specificity of Training
Use of appropriate exercise intensities and rest intervals allows for the “selection” of specific energy systems during training and results in more efficient and productive regimens for specific athlete events with various metabolic demands.
Includes: Interval Training, HIIT, and Combination Training.
Interval Training
A method of training that emphasizes bioenergetic adaptations for a more effect energy transfer within the metabolic pathways by using predetermined intervals of exercise and rest periods.
More training can be accomplished at higher intensities.
Difficult to establish definitive guidelines for choosing specific WORK:REST ratios
Interval Training WORK:REST ratios and Primary Energy Systems Stressed
Phosphagen (1:12 - 1:20), 5-10s – 90-100% max power
Fast Glycolysis (1:3 - 1:5), 15-30s – 75-90% max power
Fast Glycolysis/Oxidative (Slow Glycolysis) (1:3 - 1:4), 1-3 min. – 30-75% max power.
Oxidative (1:1 - 1:3), >3 min. – 20-30% max power
High Intensity Interval Training (HIIT)
Involves brief repeated bouts of high-intensity exercise with intermittent recovery periods.
HIIT Variables to Manipulate
Intensity of active phase. Duration of active phase. Intensity of the recovery phase. Duration of recovery phase. Number active/recovery phases in each set. Rest time between sets, numbers of sets. Recovery intensity between set. Mode of exercise for HIIT.
Combination Training
Adds aerobic endurance training to the training of anaerobic athletes in order to enhance recovery (because recovery relies primarily on aerobic mechanisms).
Combinations Training Impact on Anaerobic Training.
May reduce anaerobic performance capabilities, particularly high-strength, high-power performance.
Can reduce the gain in muscle girth, maximum strength, and speed- and power-related performance.
May be counterproductive in most strength and power sport.
