Exercise Metabolism and Energy Expenditure Overview

Exercise Physiology

Study of physiological responses to exercise.

Laboratory Testing

Evaluates athletic potential and conditioning effectiveness.

Skeletal Muscle Fiber Type

Indicates potential athletic success via biopsy.

Anaerobic Power

Power produced without oxygen during high-intensity efforts.

ATP-PC System

Energy system for short, explosive activities.

Glycolysis

Breakdown of glucose for energy production.

Aerobic Metabolism

Energy production using oxygen for prolonged activities.

Energy Pathways

Systems providing energy during physical activities.

Maximal Effort

Highest intensity exertion over a brief duration.

Specificity in Testing

Tests should match muscle groups used in sport.

Ultra Short-Term Tests

Assess ATP-PC system capacity under 10 seconds.

Short-Term Tests

Evaluate overall anaerobic capacity for 30-60 seconds.

Explosive Anaerobic Power Tests

Standing broad jump and vertical jump assessments.

Percent Contribution of Energy Systems

Shows energy source usage over time during exercise.

Transition Periods

Time when energy systems shift during activity.

Maximal Anaerobic Power

Peak energy output from anaerobic pathways.

Duration and Intensity

Key factors influencing energy system contributions.

Feedback for Athletes

Information on strengths and weaknesses in sports.

Physiological Factors

Biological elements influencing athletic performance.

Psychological Factors

Mental aspects affecting athletic success.

Barker et al. (2011)

Reference for testing elite young athletes.

Energy System Interaction

All systems work together for exercise performance.

Direct Calorimetry

Measures heat production to assess energy expenditure.

Substrate Metabolism Efficiency

40% energy converted to ATP, 60% to heat.

Calorimeter

Device measuring heat from metabolic processes.

Indirect Calorimetry

Estimates energy expenditure via O2 and CO2 measurements.

VO2

Volume of O2 consumed per minute.

VCO2

Volume of CO2 produced per minute.

Haldane Transformation

Calculates inspired air volume from expired air volume.

Respiratory Exchange Ratio (RER)

Ratio of CO2 production to O2 consumption.

RER for Fat

R = 0.70 for palmitic acid oxidation.

RER for Carbohydrate

R = 1.00 for glucose oxidation.

Basal Metabolic Rate (BMR)

Energy expenditure at rest in supine position.

Resting Metabolic Rate (RMR)

Similar to BMR; easier to measure.

Metabolic Rate

Rate of energy use by the body.

Energy Expenditure at Rest

RER ~0.80, VO2 ~0.25 L•min-1.

Total Daily Metabolic Activity

Includes all daily activities; 1,800 to 3,000 kcal.

Competitive Athlete Energy Needs

Can reach up to 10,000 kcal/day.

VO2 Drift

Upward VO2 increase at constant power outputs.

Type II Fibers

Less efficient muscle fibers recruited at high intensity.

Heat Production

Increases with energy production during metabolism.

Caloric Equivalent

Caloric value derived from O2 consumption.

Exercise Equipment Heat

Adds extra heat, affecting calorimetry accuracy.

Sweat Measurement Error

Sweat can skew calorimetry results.

VO2max

Maximum oxygen uptake during intense exercise.

Aerobic fitness

Best measured by VO2max performance.

Endurance performance

Not solely predicted by VO2max.

Training plateau

VO2max plateaus after 8-12 weeks.

Higher competition percentage

More training allows higher VO2max usage.

VO2max units

Expressed in liters per minute (L·min-1).

Normalized VO2max

Measured in ml O2·kg-1·min-1.

Body size comparison

Normalized VO2max allows fairer comparisons.

Untrained young men

Typical VO2max: 44 to 50 ml O2·kg-1·min-1.

Untrained young women

Typical VO2max: 38 to 42 ml O2·kg-1·min-1.

Sex difference

Due to lower fat-free mass and hemoglobin.

Anaerobic effort

Involves excess post-exercise O2 consumption (EPOC).

Lactate threshold

Point where lactate accumulates in the blood.

ATP at rest

Almost 100% produced by aerobic metabolism.

Resting blood lactate

Levels are low, typically <1.0 mmol·L-1.

Resting O2 consumption

0.25 L·min-1 or 3.5 ml·kg-1·min-1.

Energy expenditure increase

May rise 15-25 times during heavy exercise.

ATP production during exercise

Can increase 200 times over resting levels.

Homeostasis

Steady internal environment during rest.

Oxygen uptake lag

Delay in oxygen consumption at exercise onset.

Steady state VO2

Achieved within 1-4 minutes of exercise.

ATP supply-demand balance

ATP production meets ATP requirements during exercise.

Initial ATP production

Primarily through anaerobic pathways.

ATP-PC system

Immediate energy source for short bursts of activity.

Glycolysis

Anaerobic pathway for ATP production.

Bioenergetic pathways

Metabolic routes providing energy during exercise.

ATP production

Rate of ATP synthesis increases with exercise intensity.

Rest-to-exercise transition

Shift from low to high energy demand activities.

O2 consumption

Measurement indicating aerobic metabolism efficiency.

Skeletal muscle changes

Adaptations in muscle metabolism at exercise onset.

7 mph running

Speed requiring increased ATP for muscle contraction.

Instantaneous ATP increase

Rapid rise in ATP to prevent exercise interruption.

Treadmill exercise

Controlled environment for studying exercise metabolism.

Aerobic metabolism

Energy production using oxygen during prolonged activity.

Oxygen Deficit

Lag in oxygen uptake at exercise onset.

Anaerobic Energy Expenditure

O2 demand exceeds O2 consumed early in exercise.

Oxygen Debt

Repayment for O2 deficit post-exercise.

Excess Post-exercise O2 Consumption (EPOC)

O2 consumed exceeds O2 demand during recovery.

ATP-PC System

Energy system for immediate ATP production.

Glycolysis

Anaerobic pathway producing ATP from glucose.

Steady-state VO2

Constant oxygen uptake during submaximal exercise.

Upward Drift in VO2

Gradual increase in oxygen uptake over time.

Rapid Component of EPOC

Quick replenishment of ATP and oxygen stores.

Slow Component of EPOC

Prolonged recovery involving elevated metabolic rate.

Gluconeogenesis

Conversion of lactate to glucose post-exercise.

Factors Contributing to EPOC

Includes heart rate, temperature, and hormones.

Metabolic Responses to Exercise

Changes in energy systems based on intensity.

High-energy Phosphates

Stored energy sources in muscles for quick ATP.

O2 Required

Amount of oxygen needed for exercise intensity.

O2 Consumed

Actual oxygen uptake during physical activity.

Anaerobic Pathways

Energy production without oxygen, primarily during intense exercise.

Prolonged Exercise

Exercise lasting longer than 10 minutes.

Moderate Exercise

Sustained activity at a manageable intensity.

Heavy Exercise

Intense activity requiring significant energy expenditure.

EPOC Terminology

Reflects only ~20% O2 consumption for repayment.

Exercise Recovery

Period following exercise where physiological processes stabilize.