Body Composition Methods Quiz

Body Composition Methods

• Underwater weighing: Measures body density via water displacement; leaner individuals sink more easily. Based on Archimedes' principle.
• BodPod: Measures body volume via air displacement, calculated via Boyle's Law. Most practical and comfortable, efficient time wise.
• DEXA (Dual Energy X-ray Absorptiometry): Uses X-rays to measure fat, lean mass, and bone density. Considered the gold standard.
• Skinfolds: Measures subcutaneous fat thickness using calipers. Error rate is 3-5%. Important to consider factors like reduced subcutaneous fat in older adults and increased visceral fat in diabetes cases.

Skinfolds

• Error rate of 3-5%
• Older populations typically have less subcutaneous fat than younger adults, while those with diabetes often have more visceral fat.

BMI (Body Mass Index)

• Weight-to-height ratio used as a general health indicator.
• Calculation: [Weight (kg) / Height (m^2)]
• Normal range for adults is 18-25. Provides a basic health metric but does not account for body fat distribution.

Waist-to-Hip Ratio

• Measures circumference of waist and hips.
• High ratios are indicative of increased visceral fat and potential obesity.
• Average ratio: Women - 0.80, Men - 0.90.

BIA (Bioelectrical Impedance Analysis)

• Uses electrical currents to estimate body water and fat-free mass.
• Fat tissue resists currents more than lean tissue.
• Can be used to estimate hydration levels; lower body fat percentage corresponds with higher hydration.

Adipose Cells

• Hypertrophy: Fat cells grow larger to store excess lipids. A key contributor to obesity.
• Hyperplasia: Fat cells increase in number. This also contributes to obesity, but this is more associated with developmental stages.

Impact of Exercise on Diet

• Consistent exercise, increases muscle, increases hunger initially, but a decrease in fat leads to decrease in hunger through decrease in leptin (hormone related to hunger).
• Leptin signals when you are full. Leptin resistance can lead to decreased sensitivity to body signals leading to uncontrolled hunger.
• Exercise can improve appetite regulation, leading to better control of hunger.
• After one day of working out, there is no impact on appetite regulation.

Basal Metabolic Rate (BMR)

• Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR) measure the energy needed to sustain vital functions; measures the amount of calories needed to maintain basic functions in a resting state.
• Males tend to have higher BMRs than females.
• Resistance training and muscle mass increase RMR; caloric restrictions reduce it.

Impact of Diet and Exercise on RMR

• Short-term: Exercise boosts metabolism; extra calories burned are from activity itself and recovery (EPOC).
• Long-term: Exercise and diet can increase resting metabolic rates (RMRs). Metabolism and RMR will decrease with caloric restrictions. Resistance training increases RMR due to increased muscle mass.

Effects of Diet and Exercise Training on Body Composition and Weight

• Stricter diets with less caloric intake lead to muscle gain without significant fat loss.
• Calorie needs should be high enough to maintain basic bodily functions.

Impact of Exercise on the Thermic Effect of a Meal

• The thermic effect of nutrients is increased with meals before or after exercise.

Resistance Training and RMR/BMR

• Resistance training promotes increased lean muscle mass.
• This subsequently raises RMR as more metabolically active tissue increases overall energy expenditure.

Thermogenesis

• Thermogenesis (EAT and NEAT) contribute to daily energy expenditure. A process that requires energy.
• Thermal effect of feeding (TEF) is the amount of energy required for digestion, absorption, and synthesis of protein, fat, and carbohydrates.

Sliding Filament Theory

• Muscle contractions involve the sliding of actin (thin) filaments over myosin (thick) filaments to create concentric or eccentric contractions.

Muscle Fiber Types

• Type I (Slow Oxidative): Fatigue-resistant fibers, primarily used for endurance activities.
• Type IIA (Fast Oxidative Glycolytic): Intermediate fibers, used for moderate-intensity activities.
• Type IIX (Fast Glycolytic): Fast-twitch fibers, primarily used for short, explosive actions.

Muscle Contractions

• Isometric: Constant force, no movement. Examples: planks, holding a weight.
• Isotonic: Constant force, with movement. Examples: bicep curls, squats.
• Isokinetic: Constant speed of movement. Examples: machines that control speed.

Parallel Elastic Component

• Connective tissues within muscle fibers provide passive resistance during stretching.
• Also contributes to elasticity and stability of muscle fibers.

Mechanical Factors influencing Muscle Contractions

• Eccentric contractions use less energy than concentric contractions; fewer fibers are activated and require less ATP.

Role of Calcium

• Essential for muscle contraction and relaxation.

Delayed-onset Muscle Soreness (DOMS)

• Pain and stiffness occurring 24-48 hours after intense exercise.
• Typically more prominent after eccentric contractions.
• High mechanical forces during contractions can lead to structural damage, degradation of proteins, inflammation, and fluid accumulation in the muscle.

Neuromuscular Adaptations to Resistance Training

• Important adaptations such as increases in strength, endurance, CSA (cross sectional area)and power occur as a result of resistance training.
• This is primarily due to increases in motor unit recruitment, and firing rates, that are important in a variety of activities and to enhance functionality and control of muscles during activities.

Hypertrophy

• Mechanisms: Motor unit recruitment, mechanical stress (tension resulting from resistance training), and stretch (eccentric contractions) contribute to muscle growth.
• Resistance training benefits multiple fiber types (i.e. increasing fiber size, and length).

Nervous System Branches

• The central nervous system (CNS) consists of the brain and spinal cord, integrating commands.
• The peripheral nervous system (PNS) sends and receives signals from the CNS to muscles, organs, and skin, for various functions. It contains the somatic and autonomic nervous systems.
  • Somatic: voluntary control of skeletal muscles,
  • Autonomic: involuntary control of organs (i.e. heart). The autonomic nervous system contains the sympathetic (fight or flight) and parasympathetic (rest and digest) divisions.

Myotatic Stretch Reflex

• Protects against overstretching, by signaling muscle contraction in response to rapid stretching.

Muscle Spindles

• Detect muscle length and velocity changes.
• Initiate the myotatic reflex, for muscle control.

Golgi Tendon Organ (GTO)

• Monitors tension in tendons, causing relaxation of the muscle when tension becomes excessive.

Types of Stretching

• Static: Maintain a stretch for a set amount of time.
• Dynamic: Controlled movements to prepare muscles for activity.
• PNF: Combines stretching with muscle contractions to increase flexibility.

Test your knowledge on various body composition methods and principles, including underwater weighing and BMI calculations. This quiz covers essential concepts related to body density, fat cells, and the impact of exercise on fat and hunger.