Human Energy Systems and Body Composition Insights

Total body calories

Sum of energy stored in the body.

Energy sources

ATP, PCr, carbohydrates, fats, proteins.

Serum glucose

20 grams available in the bloodstream.

Muscle glycogen

1,500 grams stored in muscle tissue.

Serum-free fatty acids

7 grams available for energy use.

Adipose tissue triglycerides

80,000 grams stored for energy.

Humans store chem energy in different forms to answer various needs

Sprinting to safety (need rapid energy production)

Deprivation periods (need high storage capacity)

Energy system predominance

One system dominates based on activity type.

ATP-PCr System

Immediate energy source for muscle contraction.

Role of ATP

Essential for muscle contraction and energy release.

PCr function

Rapidly replenishes ATP during high-intensity work.

Glycolysis

Process that helps replace ATP quickly.

Glycogen

Storage form of glucose in muscles.

Energy system blend

Most exercises use a combination of systems.

Mitochondria

Cell organelles that produce ATP using oxygen.

Glycolysis

Breakdown of glucose for energy production.

Lactic Acid

By-product of anaerobic metabolism during insufficient ATP.

O2 System

Produces ATP from various energy sources.

Total Daily Energy Expenditure

Total calories burned in a day.

Resting Energy Expenditure

Calories burned at rest, includes BEE and activity.

Thermic Effect of Physical Activity

Energy expenditure from physical activity, roughly 400 cal.

Thermic Effect of Food

Energy used for digestion, roughly 200 cal.

Basal Energy Expenditure

Calories burned at complete rest, roughly 1,400 cal.

Basal Metabolic Rate (BMR)

Energy for autonomic functions while awake.

Resting Metabolic Rate (RMR)

BMR plus energy from prior activity.

Resting Energy Expenditure (REE)

RMR extrapolated over 24 hours.

Thermic Effect of Food (TEF)

Metabolic increase after eating, highest 2 hours post-meal.

Postprandial

Period after eating when TEF is highest.

Carbohydrate TEF

5-10% of meal energy content.

Protein TEF

20-30% of meal energy content.

Fat TEF

0-5% of meal energy content.

Estimating REE Formula

1 kcal x kg body weight x hour.

Genetic Factors

Age, gender, body size affect REE.

Sarcopenia

Age-related loss of muscle mass affecting metabolism.

Body Composition

Muscle increases REE; fat decreases REE.

Environmental Factors

Cold, heat, altitude affect metabolic rate.

Caffeine

Stimulant that can increase REE by 10-12%.

Nicotine

Stimulates metabolism, increasing REE.

Exercise

Key factor that significantly increases metabolic rate.

Krebs Cycle

Series of reactions producing energy in mitochondria.

Electron Transport Chain

Final stage of ATP production in mitochondria.

Energy Expenditure at Rest

Energy used for basic bodily functions.

EPOC

Increased caloric cost post-exercise consumption.

RMR

Resting Metabolic Rate, elevated after intense exercise.

% increase in RMR

Typically ranges from 4-16% after exercise.

Duration of elevated RMR

Can last up to 48 hours post-exercise.

Extra kcals/day

Varies from 30-120 kcals after exercise.

Energy sources at rest

Primarily fat (60%) and carbs (40%) utilized.

Oxygen energy system

Dominant energy system during rest and low activity.

Resting Oxygen Consumption

3.5 mL oxygen/kg/min at rest.

Oxygen Volume Conversion

1 L oxygen equals 1000 mL oxygen.

Caloric Value of Oxygen

1 L oxygen provides 5 kcals.

Oxygen Consumption Calculation

3.5 mL oxygen x 70 kg equals 245 mL/min.

Liters per Minute Conversion

245 mL/min equals 0.245 L/min.

Caloric Burn Rate

0.245 L/min x 5 kcal equals 1.225 kcal/min.

White Adipose Tissue

Primary fat storage site in adult humans.

Brown Adipose Tissue

Heat-producing and metabolically active fat.

Adipose Tissue Function

Previously viewed as passive energy storage.

Visceral Fat

Endocrine fat secreting adipokines.

Adipokines

Hormones secreted by adipocytes influencing metabolism.

Chronic Inflammation

Obesity linked to low-grade chronic inflammation.

Leptin

Regulates appetite through hypothalamus; increases with obesity.

Leptin Resistance

Obesity leads to impaired leptin signaling.

Adiponectin

Increases insulin sensitivity; decreases with obesity.

Tumor Necrosis Factor alpha (TNF-a)

Pro-inflammatory; decreases insulin sensitivity.

Interleukin-6 (IL-6)

Pro-inflammatory cytokine; affects insulin signaling.

Plasminogen Activator Inhibitor (PAI-1)

Inhibits blood clot dissolution; increased in obesity.

Insulin Role

Facilitates glucose uptake from blood into cells.

Thyroid Gland Function

Releases T3 and T4 hormones; regulated by TSH.

Hypothyroidism Symptoms

Low T3 causes lethargy and sedentary behavior.

Hyperthyroidism Symptoms

High T3 leads to fatigue and increased appetite.

Graves Disease

Autoimmune disorder causing thyroid overactivity.

Negative Feedback Loop

Increased T3 and T4 inhibit TSH release.

Body Composition Assessment

Measures fat and fat-free mass proportions.

Overweight Definition

Deviation from ideal body weight relative to height.

Chronic Disease Risks

Obesity linked to CAD, diabetes, and cancer.

Nonessential Fat

Fat not required for basic physiological functions.

Essential Fat

Minimum fat needed for health: 8-12% women, 3-5% men.

Recommended Body Fat

Optimal fat levels: 20-35% women, 8-22% men.

Visceral Fat

Fat between muscles and organs, increases cardiovascular risk.

Subcutaneous Fat

Fat located under the skin, not directly linked to health risks.

Lean Tissue

Muscle and organ mass, crucial for overall health.

Sarcopenia

Age-related loss of muscle mass and function.

Body Mass Index (BMI)

Weight (kg) divided by height (m²); <18.5 underweight.

Circumference Measurements

Physical measurements to assess body shape and size.

Waist-to-Hip Ratio (WHR)

Waist circumference divided by hip circumference.

Body Composition Norms

Guidelines for healthy body fat percentages.

Measurement Techniques

Methods to assess body composition: direct and indirect.

Direct Measurement

Dissection and analysis of cadaver tissues.

Indirect Measurement

Estimates body composition using props and calculations.

Anthropometry

Physical measurement techniques for human body assessment.

Skinfold Measurements

Technique to estimate body fat using skinfold thickness.

Epidemiological Studies

Research analyzing health trends in populations.

Health Risk Indicators

Metrics like WHR to assess obesity-related risks.

Bone Mass and Density

Key predictors of osteoporotic fractures.

Chronic Malnourishment

Condition resulting from excessively low body fat.

ADL (Activities of Daily Living)

Basic self-care tasks affected by muscle strength.

Cost and Equipment Availability

Factors influencing body composition measurement methods.

Portable Equipment

Less complex tools for field body composition assessments.

Physiological Dysfunction

Health issues arising from low body fat or lean mass.