Exercise physiology

• Exercise physiology


  Study of the body's response to physical activity. These responses include changes of the metabolism and in physiology of different areas of the body like the heart, lungs and muscles and structural changes in cells
• What happens to our body when we exercise?

  
• Responses to exercise


  • Cardiovascular response
  • Hormonal response
  • Acute changes: increase heart rate and respiratory rate
  • Long term effects: Metabolic changes
  • Changes at a cellular level
  • Increases flexibility
  • Increasing concentration
  • Increase mobility
  • Increase cardiovascular health
  • Increase bone mineral density
  • Increasing mood
  • Increase muscle capillary perfusion
  • Increase mitochondria level

  
• Why is it useful for us to know what happens to the body during exercise?


  • The use of exercise to further understand how the body functions
  • The use of that knowledge to develop activities and programs that establish, maintain and promote physical exercise

  
• Do you know how and why veterinary physiotherapists use exercise in rehabilitation of injury recovery of disease?
• Uses of exercise by veterinary physiotherapists


  • Strengthening
  • Rehab
  • Prehab
• Equine exercise physiology


  • Test maximal performance of the heart, lungs and skeletal system
  • To support training program development
  • To assess risk of disease of injury
• Tests completed with equine athletes


  • Cardiovascular function tests- limitations to the supply of oxygen anywhere along the pathway from intake to conversion of energy can limit the animals athletic performance
  • Maximal oxygen uptake- VO2 max. Key measure of aerobic contribution to energy production. It is measured by measuring cardiac outpt, maximal heart rate and return to resting heart rate

  
• Effects of training on the systems


  • Cardio respiratory response to training- when this is likely to occur? When a plateau is seen? when is the horse at its peak? It can also give an indication of the effects of different types of training programmes
  • Skeletal muscle adaptations to training- such as ratio of type 1 to type 2 muscle fibres, increase in capillary size
  • Increase in the enzymes responsible for changing oxygen into energy
  • Increased mitochondrial volume
  • Changes on glycogen loading
• Principles of exercise physiology and training


  • Strength training (causes hypertrophy through an increase of myofibril size and the number of fast- and slow twitch fibres. The recruitment pathways of muscle fibres become more effective and greater force development of the trained muscles
  • Speed (cardiac adaptations lead to increased cardiac output while exercising, and a higher VO2 max after exercise)
  • Endurance (cross-sectional area of slow twitch fibres increases slightly in response to aerobic work. The fast-twitch fibres develop a higher density of capillaries, permitting a greater blood flow with increased delivery of nutrients

  
• What is exercise physiology?


  Exercise is physical activity that is planned, structured and repetitive for the purpose of conditioning any part of the body. Exercise is used to improve health, maintain fitness and its important as a mean of physical rehabilitation

  
• Types of exercises

  • Range of motion- need to maintain as much movement as possible of the joints, stretching, flexibility
  • Strengthing exercises- resistance to muscle to improve overall strength
  • Cardiovascular exercises- improve cardiovascular system and fitness
  • Anaerobic exercise- increases heart rate, after 30 seconds, short distance running
  • Aerobic exercises- after 30s after exercise has occurred. Prior to 30s, anaerobic is used and is exercise without oxygen, long distance

  
• Aerobic exercises

  • Gym class
  • Long distance running
• Anaerobic exercises

  • HIIT classes, depends on the intensity and length

  
• Benefits of exercise


  • Reduce weight
  • Improve physiological
  • Improve Strength
  • Cardiovascular fitness
• Physical training


  The systemic use of exercise to promote bodily fitness and strength
• Principles of training


  • Progression- gradually improve intensity and cardiovascular and cardiovascular intensity. Increase 10% every 10 days
  • Regularity- regular training is important as will lose the improvements. Should be training 3-5 days a week
  • Overload- in order to progress, the body needs to be put under additional stress beyond what is normal
  • Variety- change it up to stop boredom
  • Recovery- rest period between physical activity. Usually 24-48 hours after work
  • Balance- rest and recovery and training
  • Specificity- what is the end goal? Make them relevant

  
• Different training methods


  • Interval training- develops strength, speed and muscular endurance
  • Weight training- builds muscle strength. Animals find it difficult or have a poor technique. If there are compensations, will be difficult. Techniques need to be perfect
  • Continuous training- develops cardiovascular fitness, 20 mins
  • Plyometric training- develops power. Plyball in dogs, showjumping in horses, muscle lengthens and rapidly shortens- need to be careful in athletes who aren't used to this
  • Range of motion- develops flexibility, important in all athletes and animals
• Muscle fatigue


  Decline in muscle performance. Temporary and reversible
• Disuse muscle atrophy

  A decrease in the size of muscles in the body. Disuse atrophy occurs when a muscle is no longer as active as usual
• Causes of muscle atrophy


  • Increased age
  • Following age
  • In a disease process
  • Following trauma to nerve supply
  • Systemic illness
  • Prolonged illness
  • Poor nutrition
• Physiological changes in muscle atrophy


  • A decreased cross-sectional area of muscle fibres, concomitant reduced whole muscle volume and mass, but no decrease in number of fibres
  • Age related- age related muscle fibre atrophy which is accompanied by a reduction in number of muscle fibres
  • Results in reduced protein content, reduced force production, increased fatiguability and decreased insulin sensitivity in both
  • Decreased capillary density of both fibre type
• Overuse injury


  Any type of muscle or joint injury, such as tendinitis or a stress fracture, that's caused by repetitive trauma. Typically stems from training errors or technique errors
• Repetitive strain injury (RSI)


  Typically a soft tissue injury characterised by an inflammation of the muscles, nerves, ligaments or tendons. Micro tears can occur then culminate in a breakdown of ligament, tendon
• Why do our muscles get fatigued?


  1. The muscles ability to respond to signals from the brain

  2. Signals travel from the brain to the muscles in a fraction of a second via long, thin cells called motor neurons. Motor neuron and the muscle cells are separated by a tiny gap, and the exchange of particles across this gap enables the contraction

  3. In response to a signal from the brain, the motor neuron releases acetylcholine, which triggers pores on the muscle cell membrane to open. Sodium flows in and potassium flows out. The flux of these charged particles is a crucial step for muscle contraction. The change in charge creates an electrical signal called an action potential that spreads through the muscle cell, stimulating the release of calcium that's stored inside it. This flood of calcium causes the muscles to contract by enabling proteins buried in the muscle fibres to lock together and ratchet towards each other, pulling the muscle tight

  4. The energy used to power the contraction comes from a molecule called ATP. ATP also helps pump the ions back across the membrane afterward, resetting the balance of sodium and potassium on either side. This whole process repeats every time a muscle contracts

  5. With each contraction, energy in the form of ATP gets used up, waste products like lactic acid are generated and some ions drift away from the muscles cell membrane, leaving a smaller and smaller group behind

  6. Eventually over the course of repeated contractions there may not be sufficient concentrations of potassium, sodium or calcium ions immediately available near the muscle cell membrane to reset the system properly

  7. So even if the brain sends a signal, the muscle cell can't generate the action potential necessary to contract

  8. With a little time, they will flow back to the areas where they are needed, Sometimes with the help of active sodium and potassium pumps

  9. So if you pause and rest, muscle fatigue will subside as these ions replenish throughout the muscle. The more you exercise, the longer it takes for the muscles to fatigue= the stronger you are, the fewer times this cycle of nerve signal from the brain to contraction in the muscle has to be repeated

  10. As physical fitness improves, you can exercise longer at the same intensity. Many muscles grow with exercise, and larger muscles also have bigger stores of ATP and a higher capacity to clear waste, pushing fatigue even further into the future

  
• Myofibrils


  Contractile units that make up each muscle fibre. They are building blocks of muscles
• Sarcomeres


  The smallest functional unit of skeletal muscle. Composed of 2 protein elements- actin and myosin
• Actin


  Thin filament
• Myosin


  Thick filament
• Interaction between actin and myosin

  How muscles contract and shorten. The number of myosin cross bridges formed between actin and myosin determines amount of force
• Types of muscle fibres

  • Slow twitch type 1- contract slowly, good blood supply- smaller and develop less force than fast twitch
  • Fast twitch 2a- fast contraction- aerobic and anaerobic- white fibres- less reliant on oxygen and therefore fatigue Quicker- suited to heavy weight and 400m sprint
  • Fast twitch 2b- contract very rapidly, forcible muscle contraction, fatigue quickly, white fibres- only use anaerobic- speed, strength, power, heavy lifting, powerlifting

  
• Concentric muscle contraction

  Causes muscles to shorten, thereby generating force
• Eccentric muscle contraction


  Causes muscles to lengthen in response to a greater opposing force
• Isometric muscle contraction


  A muscular contraction in which the length of the muscle doesn't change. Little to no movement

  
• Roles of skeletal muscle during movement


  • Agonist- the muscle(s) that provides the major force to complete the environment
  • Antagonist- the muscles that oppose the agonist
  • Synergist- the muscle(s) that stabilises a joint around which a movement is occurring
  • Fixator- the muscle(s) that stabilises the origin of the agonist and the joint that the origin spans in order to help the agonist function most effectively

  
• What muscle(s) contract concentrically to flex the elbow in the forelimb during cranial flight phase of walk?
• What muscle(s) contract eccentrically during this same movement?
• What muscle(s) contract concentrically to flex the stifle during cranial flight phase of gait of the hindlimb?

  
• What muscle(s) contract eccentrically during same movement?
• Are there any isometric muscle contractions occurring during walk?