Macronutrients

Carbohydrates

  • For typical person - accounts for approx. 55% of dietary intake

  • For endurance athletes - can increase to 70% of dietary intake

Role of carbs

  • Produces energy for ATP production

  • Can be broken down to produce ATP fast - meaning they are preferred energy source for high workouts

  • However, the amount of energy produced per 1 gram of carbohydrate is low

 

Carbs - Glucose - Glycogen

  • We eat carbs - they are digested and broken down into their simpler unit Glucose

  • Once in the form of glucose, there are two main fates

  1. Glucose circulates the blood - providing fuel for the brain and immediate body function

  2. Glucose can then be converted to glycogen and stored in the liver and muscles

 

Classifying carbs

  • Carbs can be classified depending on their Glycaemic index (GI)

  • GI relates specifically to how quickly the carbohydrate is broken down and enters the blood stream

  • Rates carbs on a scale from 0-100  (0 low - 100 high)

 

  • High GI - carbs broken down very quick, rapid release of glucose to bloodstream

  • Low GI - carb broken down slow, resulting in slow sustained release of glucose into bloodstream.

 

Fats

  • Typical person - approx. 30% of dietary intake

  • Athletes generally consume slightly less than 10-20% of dietary intake

 

Role of fats

  • Are a plentiful source of energy - high 'yield' - amount of energy produced is lots

  • Fats breakdown to produce ATP slow, so are better for mid intensity exercises

  • Insulates body and protects vital organs

  • Helps produce hormones

 

Free fatty acids - triglycerides

  • We eat fats, however they exist in the body as either:
    - free fatty acids + triglycerides

 

Protein

  • Typical person - approx. 15% of dietary intake

  • For strength athlete - can increase to 30%

Role of protein

  • Growth and repair of muscle and connective tissue

  • Helps produce Red blood cells, hormones and antibodies

  • Protein only used for energy production in extreme cases

 

Athlete dietary considerations v typical person

  • Depending on the type of sport being played or event, diet needs to be modified e.g.

  • Endurance athlete: more total energy and carbs(preferred fuel source when exercising) can increase to 60-70% of dietary intake

  • Bodybuilders/power athletes: more total energy and protein (to produce  high force and speed efforts which increased muscle mass is beneficial for). Increased protein and carbs consumed

Energy systems and fuel sources

 how much each of these fuels are used by each system depends on:

  • Intensity of the exercise

  • Duration of the exercise

  • Fitness of athlete

 

At rest and low intensity

  • Aerobic system predominant - fuelled by both fats and glycogen

  • Fats are used as they breakdown slower and during low intensity exercise there is no need for ATP to be produced at quick rates

Increasing intensity

  • Oxygen cant be supplied to muscle cells quick enough to meet required energy, therefore lactic acid system predominant

  • Glucose main fuel source

At high intensity

  • Lactic acid system predominant system, produces energy quickly and fuelled by glucose can only produce ATP for limited amount of time due to fatiguing by product (lactic build-up)

  • Athletes exercising for longer than two minutes will switch to aerobic system

At maximum intensity

  • The ATP-CP system will be predominant( up to 8 seconds) as it produces energy the quickest, it is fuelled by stored ATP and creatine phosphate

  • If effort is max and goes for longer than 8 seconds, lactic acid system will become predominant, fuelled by glucose

 

OFF season v IN season nutrition

 

IN-season

  • Characterised by higher volume and high intensity physical activity due to

  • Higher % of carbs - high intensity training uses glycogen stores as a fuel source, therefore, carbs are essential

  • Higher % of protein - more muscle breakdown, protein is required to repair and rebuild muscle

  • Lower % of fats - fat is slow to breakdown and inefficient

 

Off-season

  • Characterised by less physical activity at lower intensities, nutritional considerations include

  • Lower %  of carbs

  • Lower % of protein