Current Concepts in Sports Nutrition - Australian Sports Commission

DURING EXERCISE
Commercially available sports drinks (4–8 per cent carbohydrate, 10–25mmol/L
sodium) promote effective rehydration during exercise and simultaneously deliver
an additional source of fuel for the muscle and brain. The inclusion of sodium and
flavouring in sports drinks has been shown to improve voluntary fluid intake, making
it easier for athletes to achieve fluid intake goals. Water can be a suitable choice in
lower-intensity exercise or exercise lasting less than 60 minutes.
Carbohydrate
Many studies have shown that consumption of carbohydrate during prolonged (>60–90
minutes) exercise enhances endurance and performance. More recently, carbohydrate
intake has also been shown to benefit performance during shorter (~60 minutes) events
and ‘stop and go’ intermittent sports such as tennis and soccer. The performance
benefit may occur due to sparing of muscle glycogen stores, the prevention of low
blood-glucose levels (hypoglycaemia) or effects on the central nervous system that
are not well explained as yet. The benefits can translate into faster race times, a delay
in the onset of fatigue towards the end of the event, ability to cover more ground at
faster speeds in the last half or quarter of a game, and better maintenance of skills and
concentration right to the final siren.
The optimal rate of carbohydrate ingestion during exercise is unknown. However, in
events lasting longer than 60 minutes, athletes are encouraged to consume carbohydrate
at a rate of 30–60g per hour. Experimentation in training or less important events may
allow the athlete to finetune this plan for their specific needs and opportunities. It makes
sense for refuelling during the event to start well before fatigue is experienced and before
a fluid deficit can build to a level where gastric emptying is reduced.
The effects of consuming fluid and carbohydrate during exercise are additive.
A variety of options exist for carbohydrate intake, however sports drinks offer a
convenient strategy for meeting fluid and carbohydrate needs simultaneously. If other
carbohydrate choices are used, care should be taken to consume adequate amounts
of fluid.