Exercise Physiology

• Methods of Heat Loss

  • Conduction
  • Convection
  • Radiation
  • Evaporation
• Conduction


  Heat exchanged by 2 objects in contact. As surface area increases, heat loss increases.
• Convection


  Heat exchange by contact with a fluid that is flowing. Heat is carried away from body by air or water currents. The layer of warm air which continually surrounds our body is continually displaced by cold air when air temperature is lower than skin temperature.
• Radiation


  Occurs when heat is transferred from a warmer body to the cooler surroundings without physical contact. Radiation accounts for 60% of heat loss from the body at rest on a cool day.
• Evaporation


  Is the cooling of the body as a result of the vaporisation of sweat. Evaporation of sweat on skin creates cooling effect.
• During exercise, the body's main method of Heat Loss is Evaporation
• Factors that affect the rate of sweating

  • Gender (males more than females)
  • Number of sweat glands
  • Fitness level (higher fitness = higher sweat rate)
  • Body surface area (greater surface area = higher sweat rate)
• Dehydration


  The amount of water leaving the body is greater than the amount being taken in
• Cardiovascular Drift


  An increase in heart rate is smaller than the increase in stroke volume, therefore cardiac output is reduced. As a result, blood flow to skin and muscles decreases, placing extra strain on the body to perform.
• Heat exhaustion


  Dehydration and ineffective circulatory system
• Heat stroke


  Severe dehydration
• Physiological responses to exercising in heat

  • Increase in heart rate and stroke volume allowing body to send blood to the skin, creating a cooling effect via evaporation
  • Decrease in plasma volume
  • Heart rate and stroke volume send blood to the working muscles
  • Decrease in cardiac output, so body must make decision where to send the blood to
• Fluid replacement guidelines


  • Pre-exercise: 600ml 3-4 hours before, 400ml just prior to exercise
  • During exercise: approx. 200ml of water every 15 minutes
  • Post-exercise: for every 1L of sweat loss, consume 1.5L as you will urinate some of this out
• Heat Acclimatisation


  When heat tolerance is improved by repeated exposure to hot environments
• Major adaptations due to Heat Acclimatisation

  • Increase in blood plasma volume- more fluid stored in blood, increases resistance to dehydration
  • Increase sweat rate (sweat glands increase in size)
  • Start sweating at a lower core temperature
• Strategies to help cope with exercising in Heat

  • Hydration - hyperhydrate by consuming 300-400ml just prior on top of 600ml 3-4 hours before
  • Pre-cool body
  • Protection from the sun
• Heat and Humidity Index


  Shows what the temperature actually feels like because of the humidity
• Physiological responses to cold weather

  • Peripheral vasoconstriction - blood flow away from the skin's surface and towards the body's core
  • Shivering, involuntary contraction to help increase heat production
  • Piloerection - hairs on the body stand on end and trap a warm layer of air close to the skin to help keep surface of the skin warm
• Wind Chill chart


  Shows the temperature you actually feel because of the wind and ambient temperature
• Cold acclimatisation is not worth it as there is no evidence to suggest physiological acclimatization takes place, only psychological adaptation
• Strategies to cope with Exercising in the cold

  • Experiment with the length of the warm up
  • Experiment with layered clothing
  • Psychological acclimatisation
  • Ensure adequate fluid replacement as water loss will be increased via the need to humidify dry, cold air before it enters the lungs
• Reduced oxygen pressure at Altitude

  There is a reduction in the pressure of oxygen entering the lungs. This reduces the pressure differential between the alveoli and the capillaries which results in less oxygen.
• Live high train low

  Involves daily intermittent exposure to artificial altitude environment whilst maintaining normal intensities - MOST beneficial as it allows players to maintain their training intensity whilst getting the added benefit of altitude exposure
• Immediate adaptations or responses to being exposed to altitude

  • Increase respiratory rate - hyperventilation to increase amount of oxygen into the lungs
  • Increase tidal volume
• Chronic Adaptations due to Altitude Acclimatisation

  • Increase haematocrit - percentage of red blood cells in blood
  • Increase mitochondria - powerhouse of the cells and the site for ATP production, increases the rate of ATP production
  • Increase aerobic enzymes - increase the rate at which ATP is produced
  • Increase capillaries - allows for greater surface area for diffusion of oxygen at the site of the muscles and the lungs
• Altitude affects Endurance and Power athletes differently

  Endurance athletes negatively affected - less oxygen uptake and lower pulmonary diffusion means a reduced ability of the body to provide oxygen to the muscles via the aerobic pathway. Low humidity at altitude - greater risk of dehydration.

  Power athletes positively affected - less gravity on object, less friction due to thinner air causing less resistance.
• Balanced diet - Nutrition considerations for Endurance vs Power athletes

  • Endurance athlete: 70% carbs, 15% fats, 15% proteins

  Power athlete: 40% carbs, 30% fats, 30% proteins
• Glycaemic Index


  Ranking of carbohydrates on their immediate effect on blood glucose levels
• Examples of Low and High GI Foods

  • Low GI: apples, lentils, kidney beans

  High GI: pure glucose, honey, gel shots
• High GI Foods


  Break down quickly during digestion, have an immediate effect on increasing blood sugar levels, best consumed during and immediately after the event
• Low GI Foods


  Break down slowly during digestion, resulting in a slow release of glucose into the blood stream
• Hitting the Wall


  When muscle glycogen runs out. The stored liver glycogen becomes the primary fuel source, allowing exercise to continue but performance starts to diminish. In the heat, glycogen stores run out faster.
• Methods of Carb Loading

  • 3 day method - consume approx. 7-8g/kg body weight of carbohydrates for 3 days leading up to the competition (700g stored in the muscle and liver), players still can exercise but have significant tapering so don't deplete glycogen stores - marathon runner

  One day method - consume approx. 8-10g/kg body weight of carbohydrate the day before competitions (approx. 700g stored in muscle and liver), supplements may be needed - tennis (team sports)
• Full Nutrition plan


  • Day(s) before: CHO loading combined with exercise taper to top up glycogen supplies, maintain fluid intake to ensure optimal hydration

  Pre-event meal (1-4 hrs before): 1L of fluid to assist with hyperhydration, low GI meal to top up glycogen supplies

  During event: 200ml of fluid every 12 min, 30-60g of high GI CHO per hour

  Immediately after the event (first 30 mins): 1g/kg of body mass of high GI CHO, commence fluid replenishment with the goal to replace 1.5x weight loss

  Next 24 hrs: consume fluid which equates to 1.5x weight loss, consume 7-10g/kg body mass of low to moderate GI CHO, consume protein to assist with muscle repair
• Advantages and Disadvantages of Performance Enhancers

  • Illegal - Stimulants: Advantages - improves awareness and alertness through CNS activity, increase aggression, masks fatigue. Disadvantages - anxiety, restlessness, insomnia

  Illegal - Anabolic Steroids: Advantages - increase the performer's size, strength, power, decrease recovery time. Disadvantages - acne, liver disease, depression

  Legal - Protein Powders: Advantages - increase muscle mass only occurs if the athlete is doing a resistance training program, improve the rate of recovery from training session. Disadvantages - increase risk of osteoporosis, colon cancer, kidney damage
• The body's major 3 Energy Systems

  • ATP-CP: ATP and stored creatine phosphate fuel, >95% intensity, 0-10 secs duration

  Anaerobic glycolysis: carbohydrate fuel source, 80-95% intensity, 10-75 seconds duration

  Aerobic: Carbohydrates and fats fuel, During rest and at sub-maximal intensities <80% HR max, 75 sec > duration
• Periodization


  The planning, well in advance, of training variables to achieve optimal performance at the most crucial times. The design of a training program that involves specific training phases based upon increasing and decreasing (varying) volume or frequency or intensity.
• Difference between Macrocycle, Mesocycle and Microcycle

  • Macrocycles - represents the whole year

  Mesocycles - smaller blocks of time which together form a macrocycle, each mesocycle has a specific goal between 4-12 weeks

  Microcycles - a smaller unit of time between 3-10 days but can be as short as one day. Several microcycles form a mesocycle. A microcycle is often one training week.
• Phases of Training


  • General preparation phase - objective: build a suitable aerobic base and skill level leading into the competition

  Specific preparation phase - objective: develop game specific fitness, skills and strategies

  Pre-competition phase - objective: reach peak match condition

  Competition phase - objective: maintain fitness, dependent on individual situations
• Tapering


  Involves decreasing the volume of training whilst maintaining or increasing intensity an athlete does to allow the body to recover from the stresses placed on them during training. 4-28 days depending on the type of event being tapered for.