The Skeleton: Structure and Functions

Your skeleton isn't just there to hold you up - it's a complex system with specific parts and functions that are essential for movement. The main bones include the cranium (skull), sternum (breastbone), humerus (upper arm), femur (thigh bone), and tibia (shin bone).

Bones are categorized by their shape and purpose. Long bones (like the femur) translate force from muscles into mechanical leverage, while flat bones (like the cranium) protect internal organs. Short bones provide stability with minimal movement, such as the tarsals in your feet.

Your skeleton serves multiple crucial functions beyond just support. It creates joints where muscles attach via tendons, protects vital organs, produces blood cells in bone marrow, stores minerals, and provides attachment points for muscles.

💡 Think of your skeleton as the framework of a building - it provides structure, protection, and attachment points for everything else that makes your body work!

Joints and Movement

Joints are where two or more bones meet, allowing different types of movement. They're held together by connective tissue, with ligaments connecting bones and stabilizing joints. Cartilage covers bone ends to aid movement, absorb shock, and prevent bone-on-bone friction.

The synovial membrane secretes fluid to lubricate joints, while the joint capsule surrounds and seals synovial joints for stability. Bursae $fluid-filled sacs$ reduce friction between bones and soft tissues, and tendons connect bones to muscles to enable movement.

Different joint types allow various movements. Hinge joints (elbow, knee) move in one plane for flexion and extension. Ball and socket joints (hip, shoulder) provide 360° rotation and movement in all planes. These movements include flexion (decreasing joint angle), extension (increasing joint angle), abduction (away from midline), and adduction (toward midline).

🔍 Next time you move, pay attention to your joints! Try extending your arm (extension) then bending it (flexion) at the elbow - you're experiencing a hinge joint in action.

Muscles and Contraction Types

Muscles work in pairs to create movement since they can pull bones but cannot push them. In these antagonistic muscle pairs, when one muscle contracts as the agonist (prime mover), the other relaxes as the antagonist. Key muscles include the deltoid, biceps, triceps, pectorals, and quadriceps.

During exercise, your muscles contract in different ways. Isometric contractions occur when muscle length stays the same, like when holding a plank. Isotonic contractions involve muscle length changes: concentric contractions happen as muscles shorten (like the upward phase of a bicep curl), while eccentric contractions occur as muscles lengthen under tension (like the downward phase).

The Respiratory System

When you breathe, air travels through your nose/mouth into the trachea, which divides into two bronchi (one to each lung). These split into smaller bronchioles ending at alveoli where gas exchange occurs.

During gaseous exchange, oxygen diffuses from alveoli into the blood, combining with haemoglobin in red blood cells to form oxyhaemoglobin. This oxygenated blood travels to muscles, while carbon dioxide produced in tissues returns to the lungs for removal.

⚡ During intense exercise, your respiratory system works up to 20 times harder than at rest to deliver the extra oxygen your muscles desperately need!

Breathing Mechanics and Measurement

The alveoli are perfectly designed for gas exchange with their moist, thin walls (just one cell thick) and vast surface area. The short diffusion distance between alveoli and surrounding capillaries maximizes oxygen uptake efficiency.

When you inhale, your chest volume increases as the intercostal muscles contract to expand the ribcage, while the diaphragm contracts and moves down. During exercise, additional muscles like the pectorals help pull in more air. When exhaling, the opposite happens - intercostal muscles relax, lowering the ribcage, and the diaphragm relaxes and moves up. During exercise, your abdominals actively pull the ribcage down to force air out more quickly.

A spirometer measures lung volumes, including:

• Tidal volume: normal amount inhaled/exhaled per breath
• Inspiratory reserve volume: additional air that can be inhaled
• Expiratory reserve volume: additional air that can be exhaled
• Residual volume: air remaining in lungs after maximal exhalation

🧠 During exercise, your tidal volume increases dramatically as you take deeper breaths, and your breathing rate can rise from 12-15 breaths per minute at rest to over 40-50 breaths per minute!

The Cardiovascular System

The cardiac cycle is the sequence of events during a heartbeat, consisting of two phases: diastole (chambers relax and fill with blood) and systole (chambers contract and eject blood).

During exercise, your body cleverly redirects blood where it's most needed. This happens through vasodilation (blood vessels to working muscles open wider) and vasoconstriction (blood vessels to less essential systems like digestion narrow). This ensures your hardworking muscles receive the oxygen and nutrients they need.

Your circulatory system consists of different types of blood vessels. Arteries carry oxygenated blood at high pressure from the heart to the body. They have thick walls with elastic fibres and narrow channels (lumen) to maintain high pressure. Veins return deoxygenated blood at low pressure, featuring thinner walls with valves to prevent backflow and wider channels for easier blood flow. Capillaries allow exchange of materials between tissues and blood with their one-cell-thick walls.

💪 Your cardiovascular system adapts brilliantly to exercise demands - during intense activity, your heart can pump up to 5-6 times more blood per minute than when you're resting!

Cardiac Output and Energy Systems

Cardiac output measures how much blood your heart pumps out of the left ventricle in one minute. It's calculated as: Cardiac output = stroke volume (blood pumped per contraction) × heart rate

Your body uses two main energy systems during exercise. Aerobic respiration occurs when there's enough oxygen: Glucose + oxygen → energy + carbon dioxide + water This system powers long-distance running and team sports.

Anaerobic respiration happens without sufficient oxygen: Glucose → energy + lactic acid This powers short, intense activities like sprinting and weightlifting.

After intense anaerobic exercise, your body needs extra oxygen to convert lactic acid into removable waste products like CO₂ and water. This is called EPOC $excess post-exercise oxygen consumption$ or oxygen debt. To recover effectively, you should:

• Take deeper, quicker breaths
• Allow perspiration to lower body temperature
• Perform a good cool-down to help disperse lactic acid

🔥 Understanding your energy systems helps you train smarter! If you're training for a sprint, focus on anaerobic power; for a marathon, prioritize aerobic endurance.

Effects of Exercise and Recovery

Exercise affects your body immediately, shortly after, and in the long term. Immediate effects include increased body temperature (red skin as blood vessels dilate), faster breathing to deliver more oxygen, and increased heart rate to supply working muscles.

Short-term effects (36 hours after) include fatigue from depleted energy stores, light-headedness from dehydration, possible nausea from overexertion, and DOMS (Delayed Onset Muscle Soreness).

Long-term effects develop over months/years of regular exercise and include changes in body shape, increased heart size, lower resting heart rate, and improvements in overall fitness.

The recovery process is crucial for improvement. It involves:

• Rehydration to restore fluids
• Consuming carbohydrates to replenish glucose
• Massage to increase blood flow and prevent DOMS
• Ice baths to reduce inflammation
• An effective cool-down with stretching and light activity

🌟 The magic of fitness happens during recovery, not just during exercise! Your body gets stronger when it repairs itself after a workout, not during the workout itself.

Lever Systems and Movement Mechanics

Your body uses three types of lever systems to create movement:

First-class levers have the fulcrum between the effort and load. Example: lifting your head to look up, where your skull meets your spine (fulcrum), neck muscles provide effort, and your head weight is the load.

Second-class levers have the load between the fulcrum and effort. Example: rising onto tiptoes, with toes as the fulcrum, calf muscles providing effort, and body weight as the load.

Third-class levers have the effort between the fulcrum and load. Example: bicep curl, with elbow as fulcrum, biceps providing effort, and the weight as the load.

A mechanical advantage occurs when the load is closer to the fulcrum than the effort. A mechanical disadvantage exists when the effort is closer to the fulcrum than the load (common in the human body, enabling greater range and speed of movement).

🏋️ Your body is a complex system of levers! Third-class levers (like your elbow) sacrifice force for speed and range of movement, which is why bicep curls feel challenging but allow for quick, wide-ranging movements.

Planes and Axes of Movement

Movement occurs in three planes, each with a corresponding axis:

The sagittal plane divides your body into right and left sides. Movements like flexion and extension (such as doing a front somersault) occur in this plane around the transverse axis, which runs horizontally from side to side.

The frontal plane divides your body into front and back. Movements like abduction and adduction (such as cartwheels) occur in this plane around the sagittal axis, which runs horizontally from front to back.

The transverse plane divides your body into top and bottom parts. Rotational movements (like a figure skating spin) occur in this plane around the longitudinal axis, which runs vertically through your body.

Fitness Testing

Fitness testing helps you understand your current fitness level, develop appropriate training plans, maintain motivation by setting goals, and determine if your training program is working.

However, tests have limitations: they can be too general and not sport-specific, may not include actual movements from your sport, don't account for competitive conditions, and require motivation to complete properly.

📊 Think of fitness tests as your personal progress tracker! They provide quantitative data that can be compared to previous scores or national averages to see exactly where you stand.

Fitness Components and Tests: Part 1

Agility is the ability to change direction quickly and accurately, essential for sports like netball and basketball. The Illinois Agility Test measures this by timing how quickly you can run a specific course with directional changes.

Balance is the ability to maintain your center of mass while stationary or moving. The Stork Test measures this by timing how long you can hold a position with one foot against the inside of your opposite knee while standing on tiptoes.

Cardiovascular endurance is the ability of your heart and lungs to supply oxygen to working muscles for extended periods without fatigue. The Multi-Stage Fitness Test (or bleep test) measures this by having you run between cones 20m apart to increasingly faster beeps until you can no longer keep pace.

🏃‍♀️ Each fitness component contributes to different sporting success. A gymnast needs exceptional balance, while a footballer requires outstanding agility, and a marathon runner depends on superior cardiovascular endurance.