The physiological effects of prolonged exercise – a decrease in performance after two hours, even in well-trained subjects – are well understood by sports scientists. Much less is known, though, about its effects on cognitive (mental) performance.

This is an evidence vacuum a team of French researchers set out to fill with a study of eight endurance-trained cyclists. The athletes were subjected to two tests of cognitive performance – the ‘critical flicker fusion’ test and a map recognition task – before, every 20 minutes during, and immediately after three hours of cycling at 60% VO2max.

This cycling task was carried out under two separate experimental conditions:

• with fluid ingestion (400ml of mineral water immediately before and 200ml every 20 minutes during the cycle task);
• with no fluid ingestion.

A control group carried out the same cognitive tasks without exercise or fluid.

Key findings were as follows:

• A significant decrease in CFF performance was observed after 120 minutes of exercise when compared with the first 20 minutes, irrespective of hydration status;
• A significant improvement in map recognition ability was recorded between 80 and 120 minutes, but performance declined after 120 minutes;
• No changes in cognitive (mental) performance were observed in the control group.

‘These results provide some evidence for exercise-induced facilitation of cognitive (mental) function,’ conclude the researchers. ‘However, this positive effect disappears during prolonged exercise.’

Int J Sports Med 2005; 26:27-33

Isabel Walker