Bioenergetics of Exercise Reading Essentials of S C 73

Bioenergetics of Exercise Reading: Essentials of S&C 73 -91 Christopher T. Ray, Ph. D. , ATC, CSCS

Extra Credit Opportunity #1

Housekeeping n Schedule – Assessments with partners n Next Wed & Fri – Sign in 9: 00 -9: 05; Assessments 9: 00– 9: 35 Plan accordingly n Equipment = Calipers, S&R Box, VERTEC, Tape Measurer, cones, masking tape, courts, indoor track & weight room. Questions?

What? n What does Exercise Rx mean to you? n What do mean when I say “Be Evidence Based”

Why Did Usain Bolt not Run the 400 meters? n WR 100 meters = 9. 69 WR 200 meters = 19. 30 n WR 400 meters = 43. 18; 43. 75 = Gold n *45. 29

Table 5. 3 Effect of Event Duration on Primary Energy System Used Duration of event Intensity of event Primary energy system(s) 0 -6 s Very intense Phosphagen 6 -30 s Intense Phosphagen and fast glycolysis 30 s-2 min Heavy Fast glycolysis 2 -3 min Moderate Fast glycolysis and oxidative system > 3 min Light Oxidative system

Practice n n n Sport Assessment Training Regime (Int. , Duration, Rest)

Calculations n 200 meter PR = 20; Training 75% 90%; Recovery = 1: 3 -1: 5 – 20 X 1. 10 = 22 X 5 = 110 sec. – 20 X 1. 25 = 25 X 3 = 75 sec.

“Wolff’s Law” n n The body adapts to the stress placed upon it. law according to which biologic systems such as hard and soft tissues become distorted in direct correlation to the amount of stress imposed upon them.

Bio-energetics is dynamic

Basic Training Principles 1. 2. 3. 4. 5. 6. The Principle of Individuality The Principle of Specificity The Principle of Progressive Overload The Principle of Hard / Easy The Principle of Periodization The Principle of Disuse

Basic Training Principles 1. The Principle of Individuality Different people respond to the same training in different ways. Heredity plays a major role in determining how quickly and to what degree the athlete adapts to a training program. For these reasons any training program “must take into account the specific needs and abilities of the individuals for whom it is designed. ”

Basic Training Principles 2. The Principle of Specificity To maximize the benefits, training must be specifically matched to the type of activity the athlete use to be engaged in. (endurance vs strength and power training). By this principle the training program must stress the physiological systems that are critical for optimal athlete’s performance, in order to achieve specific adaptations for specific sports.

Basic Training Principles 3. The Principle of Progressive Overload and Progressive Training are the foundation of all training programs. A well-designed Training Program must involve working the muscles, respiratory and cardiovascular systems harder than normal (overload); as the body adapts, Training progresses to a higher work level (progressive training)

Basic Training Principles 4. The Principle of Hard / Soft Bill Bowerman (former U. S. Olympic track coach and founder of NIKE) developed a training strategy for his distance running that became known as ‘ The principle of hard / soft’. According to this principle, one or two days of hard training should be followed by one day of soft training, allowing the fully recover of body and mind and prevent the athlete’s overtraining.

Basic Training Principles 5. The Principle of Periodization is the gradual cycling of specificity, intensity and volume of training to achieve peak levels of fitness for competition.

Basic Training Principles 6. The Principle of Disuse “ Use it or loose it” According to this principle, training benefits are lost if training is either discontinued or reduced too abruptly. To avoid this, all training programs must include a maintenance program.

Opportunity to get back on my good side #1 n Pick a sport – What are the components – Where does it fit on the bioenergetics spectrum? How would you train athletes in this sport? n How would you Assess them? n

Introduction - Energy n Ability to do work – Bioenergetics n Flow of energy in a biological system – Catabolism n Breakdown of larger molecules into smaller molecules (glucose to pyruvate) – Anabolism n Synthesis of larger molecules from smaller molecules (polypeptide from AA residuals)

Introduction – Exergonic reactions n n Energy-releasing reaction; generally catabolic reaction Ex. Blood glucose during catabolism = release of energy – Endergonic reactions n n Energy-consuming reaction; generally anabolic reaction Ex. Protein synthesis – Metabolism n Total of all the catabolic/exergonic and anabolic/endergonic reactions in a system

Introduction – ATP n Adenosine triphosphate; intermediate molecule that allows the transfer of energy from exergonic to endergonic reactions – Smallest usable form of energy

Biological Energy Systems – Three energy systems used to replenish ATP n Phosphagen – Occurs in the sarcoplasm – An anaerobic energy system n Glycolytic – Occurs in the sarcoplasm – An anaerobic energy system n Oxidative – Occurs in the mitochondria – An aerobic energy system

Biological Energy Systems n n n Phosphagen system (anaerobic), occurs without oxygen. Glycolysis (Fast & Slow) is the breakdown of carbohydrates, either glycogen stored in the muscle or delivered in the blood to produce ATP. Oxidative system is the primary source of ATP at rest and low-intensity, it uses primarily carbohydrates and fats as substrates. All three energy systems are active at a given time; the extent to which each is used depends on the intensity of the activity and its duration.

Biological Energy Systems n All energy systems are active at any given time – The extent of their contribution: n Primary – Intensity, power output, work rate n Secondary – Duration

Phosphagen System – Primary functions n Provide ATP for high intensity activities (e. g. , sprinting, weight training) n For 0 -6 seconds up to 20 -30 seconds of activity n Active at the start of all exercise – Regardless of intensity!

Summary of Phosphagen System – Summary: n Rapid ATP resynthesis rate n Efficient system (due to the few number of involved reactions) – Creatine kinase reaction – Myokinase reaction n BUT a low capacity of total ATP produced

Glycolytic System – Primary functions n Carbohydrate (CHO) (i. e. , blood glucose and muscle glycogen) break down to produce ATP in the sarcoplasm of a muscle cell – Provides energy primarily for moderate to high intensity activities – For 30 seconds up to 2 -3 minutes of activity – Hypoxic (anaerobic) cellular environment

Glycolytic System n Fate of pyruvate – High rate of energy demand – Insufficient O 2 present – Fast glycolysis (pyruvate to lactate) – Example: 1200 meter sprint run n Low rate of energy demand – Sufficient O 2 present – Slow glycolysis (pyruvate [with NADH] is sent to the Krebs Cycle in the mitochondria) – Example: 30 minute stair climbing workout

Summary of Fast Glycolysis n n n Fast glycolysis occurs during reduced oxygen availability and the end product is lactic acid. Lactic acid accumulation in tissue is the result of an imbalance of production & utilization. As lactic acid accumulates, there is an increase in the concentration of H++ ions inhibit glycolytic reactions. H++ ions interfere with E-C coupling by inhibiting Ca from binding with troponin. The decrease in p. H also inhibits enzymatic activity.

Lactic Acid and Lactate n n n Lactic acid is converted to its salt, lactate, by buffering systems in the muscle and blood. Lactate is not fatigue producing, it is often used as an energy system in Type I and cardiac muscle. Lactate is used in gluconeogensis, the formation of glucose from lactate and non-carbohydrate sources during extended exercise and recovery. Concentrations of lactate in blood and muscle: – At rest, 0. 5 – 2. 2 mmol/L – At high intensity exercise 20 – 25 mmol/L Peak blood lactate concentrations occur approximately 5 minutes after the cessation of exercise. Blood lactate accumulation is greater following highintensity intermittent exercise, than lower intensity continuous exercise.

Oxidative System - Primary function – Provide ATP for low intensity activities (e. g. , long distance running, cycling, swimming) – For longer than 3 minutes of activity – Substrates n CHO n Fats n Proteins – Reactions occur in the mitochondria n “Power house” of the muscle cell

Oxidative (Aerobic) System Requires molecular oxygen Provides ATP at rest and during low-intensity activities Uses primarily carbohydrates and fats as substrates At rest, 70% of ATP is from fats & 30% carbs. As exercise intensity increases there is a shift from fats to carbohydrates as substrates. At high intensity, almost 100% of ATP is from carbs. During prolonged, submaximal steady state work, there is a gradual from carbs back to fats & proteins.

Summary of Oxidative System – Adaptations to training n Increased muscle mitochondrial content n More effective sparing of CHO for use by the central nervous system n Blunted drop in intracellular p. H during a longterm aerobic endurance event

Substrate Depletion and Repletion – Energy substrates used to produce ATP – Phosphagen – Glycogen – Glucose – Lactate – Free fatty acids – Amino acids

Substrate Depletion and Repletion – Phosphagen and ATP n Depletion – Creatine phosphate (CP) stores can decrease 5070% in the first 5 -30 seconds – CP stores are virtually eliminated as a result of high intensity exercise – ATP stores do not decrease more than 60% even with very intense exercise

Substrate Depletion and Repletion – Phosphagen and ATP n Repletion – Post-exercise resynthesis of ATP can occur within 3 -5 minutes – Post-exercise resynthesis of CP may require up to 8 minutes – Most post-exercise CP resynthesis is accomplished through oxidative energy pathways

n Oxidative system yields 38 ATP from 1 glucose molecule.

Energy Production and Capacity – Rate and capacity of the three energy systems to supply ATP n Inverse relationship n Rate (how fast ATP can be created) n Capacity (how much ATP can be created)

Table 5. 4 Rankings of Rate and Capacity of ATP Production System Rate of ATP production Capacity of ATP production Phosphagen 1 5 Fast glycolysis 2 4 Slow glycolysis 3 3 Oxidation of carbs 4 2 Oxidation of fats and proteins 5 1 1 = fastest/greatest; 5 = slowest/least

Energy Production and Capacity

The 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 athletic events with various metabolic demands.

Substrate Depletion and Repletion n ATP and creatine phosphate, glucose, glycogen, lactate, FFA and amino acids can be selectively depleted.

Phosphagen Depletion & Repletion n n n Phosphagens are more rapidly depleted with high intensity exercise than aerobic exercise. Creatine Phosphate decreases 50 -70% during high intensity exercise and can be almost eliminated by exercise to exhaustion Muscle ATP concentrations do not decrease by more than 60% of initial value even during intense exercise. Intramuscular ATP is spared by the depletion of creatine phosphate from the myosine kinase reaction. Post exercise repletion of phosphagen with: – Resynthesis of ATP in 3 – 5 min – Complete creatine phosphate resynthesis in 8 min Resistance training can result in an increase in the resting concentration of phosphagens.

Glycogen Depletion & Repletion are available for exercise, approx. 300 Limited stores of glycogen n n n 400 g in total body muscle and 70 -100 g in the liver. Anaerobic training can increase glycogen stores. Muscle glycogen is more important than liver during moderate – intense exercise. Liver glycogen is more important in low intensity exercise and its contribution increases with duration. Repletion of muscle glycogen during recovery is related to post exercise carbohydrate consumption. Repletion is optimal if 0. 7 – 3. 0 g of carbs/kg is ingested every 2 hrs. Muscle glycogen may be completely replenished within 24 hrs with sufficient carbs in diet.

n n Glycogen depletion can be a limiting factor both for: – Long duration, low intensity exercise – Repeated very high – intensity exercise Lactic acid and tissue H++ ion concentration can be limiting factors for resistance training, sprinting and other anaerobic activities.

Low-Intensity, Steady-State Exercise Metabolism n n n EPOC = Excess postexercise oxygen uptake At the start of exercise, some of the energy is provided by anaerobic metabolism. The anaerobic contribution to the total energy cost is termed Oxygen Deficit. Post-exercise oxygen uptake remains elevated according to intensity and duration and is termed Oxygen Debt.

High-Intensity, Non-Steady-State Exercise Metabolism