Nutrition
Nutrition

Training and Performance Nutrition

The physical demands of the sport will dictate the nutritional recommendations

  • Macronutrient requirements will depend on the intensity of the sport
  • Understanding the energy demands of the sports allows for more specific recommendations

ATP  – Adenosine Triphospate

  • Adenosine Triphosphate (ATP) is the energy currency of the cell and is broken down to produce energy
  • There is only a small store of ATP within the muscle that needs to be replaced to support exercise needs
  • ATP gets broken down to Adenosine Diphosphate (ADP) during exercise
  • ATP then needs to be continuously regenerated through different energy systems within the body, mainly phosphocreatine (PCr), carbohydrate/ glycogen and/or fat as a fuel source

  • The energy systems of the body are either aerobic or anaerobic
  • Aerobic energy systems need oxygen to breakdown fuel sources to produce ATP
  • Anaerobic systems can breakdown fuel sources without oxygen
  • Carbohydrates can be broken down either aerobically or anaerobically
  • Fats are broken down aerobically

THE PHOSPHOCREATINE SYSTEM

  • The phosphocreatine molecule is made up of 1 creatine molecule and 1 phosphate molecule
  • Once the bond is broken between the creatine and phosphate The phosphate molecule can be donated to Adenosine Diphosphate to become Adenosine Triphosphate
  • PCr can only provide energy for up to 3-5 seconds of exercise

ANEROBIC METABOLISM

  • Carbohydrate is broken down to carbon dioxide (CO2), water (H2O) and ATP through a series of chemical reactions without oxygen for immediate energy for high intensity exercise lasting up to 90 seconds
  • Both glycogen and blood glucose are used as fuel
  • Lactic acid is a by-product of anerobic glucose metabolism
  • The production of lactic acid is essential for the continued supply of ATP as energy to sustain high intensity exercise

AEROBIC METABOLISM

  • The aerobic energy system involves the breakdown of both carbohydrate and fat into CO2, H2O and ATP
  • Both sets of reactions use oxygen and provide a slower energy release than the anaerobic system

ENERGY CAPACITY OF THE ENERGY SYSTEMS

  • The aerobic energy system has an unlimited capacity to produce ATP compared to the anaerobic system and is the main energy system during sustain/prolonged exercise
  • The contribution of energy from the aerobic or anaerobic energy system depends on the intensity and duration of the exercise, nutrition status and fitness of the individual
  • The more intense the exercise the more the anaerobic energy system will be used
  • The more prolonged the exercise is, the more the aerobic system will be used

Its important to note that all 3 energy systems are switched on during all exercise intensities

  • But one energy system will predominate over the others

CARBOHYDRATE & PERFORMANCE

  • CHO is an essential substrate for almost all metabolic processes
  • CHO is stored as glycogen
  • CHO is increasingly important with greater exercise intensity
  • Can provide more energy per unit of time than fat
  • Depleted within 90 min of intense exercise

Carbohydrate Fuels High Intensity Activity; Sprinting, Jumping, Shooting, Scoring, Tackling, Boxing, Lifting

Glycogen Levels Play a Significant Role in the Athletes’ Ability to Maintain Performance in Sports Lasting Longer than 60min

Carbs Storage

  • There are 3 Main Storage Sites for Carbohydrate:
    • As Glycogen in the Muscle & Liver
    • As Blood Glucose in the Bloodstream
  • The Amount of CHO Stored Depends on:
    • Nutritional Status
    • Training Practices
    • Body Size & composition

Factors effecting Utilisation

  • Intensity
  • Duration
  • Level of Training
  • Initial Muscle Glycogen Stores
  • CHO Supplementation During Exercise

Fuels used during Exercise

  • When fasted, as the intensity increases above 70% VO2max carbohydrate metabolism predominates over fatty acids in the production of energy for the contracting muscle
  • When exercise is performed at a lower intensity in the fasted state fat predominates over carbohydrate, with its highest contribution at roughly 55% of maximum work

Glycogen depletion during Exercise

The higher the intensity of exercise the faster muscle glycogen is depleted

Carbohydrates for Sports Performance

  • Scandinavian scientists studied muscle glycogen metabolism associated with prolonged exercise with the introduction of the needle biopsy in 1960s
  • This research found that both carbohydrate infusion during exercise and carbohydrate diets preceding exercise, improved performance when glycogen concentrations were low or deplete
  • With a high CHO diet, the time to exhaustion was 3 times greater than a diet of only protein and fat

Research has found that players with greater starting glycogen levels performed more high speed runs and walked for almost 50% less time that players with lower levels. (Saltin, 1973)

  • The daily CHO intake guidelines set by the government (50%) cannot be used when working with athletes due to a large individual variance in body composition and activity levels
  • Guidelines should:
    • Be calculated using body mass and activity level
    • Include per kg of bodyweight recommendations
    • Amount should optimise fuelling and recovery to:
      • Restore muscle glycogen
      • Replace energy expended
  • Daily CHO intakes should be recommended based on the activity for that particular day
  • Light activities may include gymnastics or aesthetics training
  • Very high activity may be an endurance athlete training up to 4-5 hours per day

Pre event Intake

  • Aim: Top up muscle and liver glycogen stores
  • Loading is only necessary if event is >90 min
  • Meal timing prior to exercise should be practiced in training to prevent gut issues
  • Based on athlete preference
  • If CHO supplements are provided ensure sources available are safe for consumption
  • Last meal before an event should be low GI if CHO ingestion during an event is restricted

During Event

  • Research has found that if CHO is digested during an event the GI of the meal before is irrelevant
  • If an event is less than 75 minutes there is no need to ingest CHO during the event provided adequate CHO intake prior to the event
  • Carbohydrate mouth rinsing during an event may be beneficial to performance

Carbohydrate Mouthrinse

  • Mouth rinsing a CHO containing drink for 10 seconds may improve performance
  • This may be due to a brain signalling effect
  • Brain receptors are receptive to carbohydrates and not sweetness
  • Mouth rinsing may reduce the Rate of Perceive Exertion (RPE) and allow athletes exercise at a higher intensity
  • Trial in training
  • Rinse for 5-10 Seconds Routinely
  • Improve High Intensity Performance Lasting 30-70 minutes
  • Who to use it with
    • GI Distress
    • Weight Management

Fasted Exercise

  • Muscle contraction during exercise changes the concentration of specific energy sensing proteins that are found within skeletal muscle
  • Low carbohydrate situations increase metabolic stress within the cell and may have a similar effect to fasted training on these proteins
  • Fasted training may increase certain enzymes that promote increased fat oxidation
  • Fasted training may improve training adaptations
  • Research has found no difference between fasted or fed exercise on fat loss when calories are matched

 

Summary

Energy Systems

  • PCr
    • Is the Most Rapidly Available Source of ATP for the Muscle
    • Capacity is Very Limited – Depleted Following 3-5 sec of All Out Exercise
  • Anaerobic System
    • Breaks Downs Carbohydrate without the use of O2 to form ATP with Lactic Acid as a by Product
    • Predominants for 60-90 sec of high intensity exercise
  • Aerobic System
    • Breaks Down Carbohydrate & Fat to Produce ATP with the use of O2
    • Has a Large Capacity for ATP Production (Constant & Never Ending)