Cardiorespiratory Fitness and Body Composition: Key Concepts for Health and Exercise

Cardiorespiratory fitness (CR fitness)

The ability to perform dynamic exercise involving large muscle groups at moderate to high intensity for prolonged periods.

VO2 Max

Rate of oxygen uptake during maximal exercise, reflects the capacity of the heart, lungs, and blood to deliver oxygen to working muscles, using a metabolic cart.

VO2 Peak

Highest oxygen uptake measured during a test even if plateau is not reached, used when a plateau is not observed, for people with certain medical conditions or medications, when there are safety concerns or submaximal testing limitations.

Absolute VO2

Total oxygen use, directly related to body size, measured in L per min or ml per min.

Relative VO2

Oxygen use per kg bodyweight, more meaningful when comparing fitness, measured in ml per kg per min.

Fat-Free Mass (FFM)

Used to express VO2 relative to body composition, assessing changes in cardiorespiratory fitness independent of mass.

Gross VO2

Total oxygen consumption during an activity including both the oxygen required by resting metabolism and exercise.

Net VO2

Only the consumption of oxygen while exercising, intended to determine the caloric cost of just exercise.

alternative methods for measuring VO2

submaximal and maximal test and field tests, prediciton equations using data from these tests, less money, expertise, and physical demand, better for larger groups

ACSM Metabolic equations

Provide estimates of VO2 for indirect measurement.

Energy expenditure

Measured to help in weight loss and caloric balance calculations.

Body weight and body composition

Important for overall health as maintaining a healthy weight supports long term health and quality of life.

Health risks from too much body fat

Increased risk of cardiovascular, pulmonary, and metabolic disease.

Health risks from too little body fat

Increased risk for cardiac, musculoskeletal, and reproductive disorders, low bone density, and fatigue.

Training intensity

Determined by estimating gross VO2 during exercise testing and program design.

Obesity

Increases risk of cardiovascular, metabolic and musculoskeletal disorders.

Underweight

Risk of malnutrition, weakened immune system, bone loss, reproductive issues, infection risk, poor wound healing.

Responsibilities of fitness professionals

Determine a healthy body weight and guide safe weight management.

Limitations of BMI

Does not measure body composition, cannot differentiate between muscle and fat.

Best practice for BMI

Combine it with DXA or skinfold measurements.

Obesity paradox

Some overweight individuals have better outcomes than normal weight peers due to more fat free mass.

Fitness level predictor

Fitness level is often a stronger predictor of health than BMI alone.

Challenges in weight loss

Overeating and inactivity become habitual behaviors; few maintain consistent energy balance.

Effective strategies for weight loss

Diet, exercise, support, and tools (apps, groups, etc).

Fat storage location

Where fat sits is important for health and disease risk.

Types of body fat

Central fat increases risk of cardiometabolic disease; subcutaneous fat is less harmful.

Visceral fat

Increased risk of cardiovascular disease, diabetes, and metabolic syndrome.

Ectopic fat

Increased cardiometabolic disease risk.

Fat distribution patterns

Android shape (apple) has higher risk of CVD; gynoid shape (pear) is more protective.

Methods to assess fat distribution

Waist circumference and waist to hip ratio are quick and effective measures.

Factors influencing obesity

Personal behaviors, genetics, environment, and socioeconomic factors.

Energy balance

Determines whether a person gains, maintains, or loses weight.

Positive energy balance

Leads to weight gain.

Negative energy balance

Leads to weight loss.

Components of energy intake

Food.

Components of energy output

Metabolism + activity.

Modern lifestyle impact

Decreased physical activity and increased food availability lead to easier weight gain.

Weight change factors

Depends on energy balance, modified by metabolism, behavior, and environment.

Energy stored as body fat

3,500 kcal = 1 lb of fat.

Resting Metabolic Rate (RMR)

Energy used for basic body functions like breathing, circulation, and temperature.

Factors influencing RMR

Age, sex, and fat free mass impact calorie expenditure at rest.

Metabolism and Aging

Metabolism does not naturally slow with age; muscle loss, not age, lowers RMR.

Hormones and Metabolism

Thyroid, growth hormone, epinephrine, and sex hormones affect metabolism.

Exercise and Metabolism

Exercise can boost metabolism by preserving muscle and maintaining activity levels.

Hypertrophy

Fat cells grow larger as they store more triglycerides.

Hyperplasia

New fat cells form when existing ones become too full.

Obesity and Fat Cells

Obese individuals have 40% larger fat cells and a greater number of them.

Fat Cell Development

Hyperplasia occurs during prenatal, infancy, childhood, and adolescence, especially during puberty.

Weight Loss and Fat Cells

Fat cells rarely disappear but can shrink with weight loss.

New Fat Cells in Adults

Adults may develop new fat cells later in life, especially with weight gain.

Genetics and Obesity

Genes influence susceptibility to obesity, but lifestyle choices determine outcomes.

Genetic Influence on Weight

Genes account for 50-90% of weight gain and obesity.

Single Gene and Obesity

Less than 3% of obesity cases are explained by a single gene.

Family Obesity Risk

If both parents are obese, a child has an 80% risk of being obese.

FTO Gene

Increases risk of obesity and slows weight loss.

Exercise and Genetic Predisposition

Exercise can help improve outcomes for those with an obesity-related genetic predisposition.

Obesity Prevalence Increase

Increased prevalence is due to decreased movement, increased processed food, larger portions, and constant availability.

Body Composition Changes with Age

With age, fat increases and muscle decreases.

Muscle Loss with Aging

Men lose about 4 kg of fat-free mass; women gain ~0.5 kg fat/year and lose ~0.1 kg muscle/year.

Preventing Muscle Loss

Resistance training and adequate protein can slow muscle loss and preserve function and strength.

Weight Management Program Steps

Set body weight goals and assess calorie intake and expenditures for clients.

Kilocalorie (kcal)

1 kcal is the heat needed to raise 1 kg of water by 1 degree Celsius.

Total Energy Expenditure (TEE)

RMR accounts for 60-70%, dietary thermogenesis for 8-15%, and physical activity is variable.

Gold Standard for TEE Assessment

Double labeled water is the gold standard; alternatives include indirect calorimetry and prediction equations.

Energy Expenditure Measurement

Expressed through tools like questionnaires, diaries, pedometers, accelerometers, heart rate monitors, and wearables.

MET Definition

1 MET equals 3.5 mL of oxygen consumption and 1 kcal/kg/hr.

Limitations of METs

Does not account for individual differences based on body composition and fitness level.