nutritional supplements, team sports

Caffeine is known to enhance endurance performance and there is growing evidence that it also works for short-term intense efforts. Now a ground-breaking New Zealand study suggests that caffeine gives a substantial boost to several aspects of high-intensity team sports.

The researchers set out to investigate the effects of caffeine in a performance test that simulated the various demands of a rugby union game. Nine competitive male rugby players ingested either caffeine (6mg per kg of body mass) or placebo (dextrose) 70 minutes before performing a rugby test. One week later they performed the same test after taking the other substance – ie caffeine if they had had placebo first time, and vice versa.

Each rugby test consisted of seven circuits in each of two 40-minute halves, with a 10-minute half-time rest. Each circuit included stations for measurement of sprint time (two straight-line and three agility sprints), power generation in two consecutive drives, and accuracy for passing balls rapidly.

The results – for all variables except second drive power – were so positive that even the researchers were surprised. The effects of caffeine on mean performance over all 14 circuits were:

• Sprint speeds – performance enhanced for all five sprints, ranging from 0.5% for 20m sprint speed to 2.9% for tackle sprint speed;
• First drive power – 5% improvement;
• Second drive power – 1.2% reduction;
• Passing accuracy – 9.6% improvement.

The researchers comment: ‘The largest and possibly most exciting new finding with caffeine was a 10% improvement in the ability to pass balls accurately while pressurised to pass rapidly (simulating game conditions).

‘With the sprint tasks, an astounding finding was that in the very last circuit the subjects were able to restore sprint times relative to that of the first circuit (or even improve the time).’

Although the mechanisms behind caffeine’s apparent ergogenic effects are still not understood, the researchers believe it works on the central nervous system to reduce fatigue and permit a higher level of motor drive and motor skills throughout games.

Med Sci Sports Exerc, vol 37, no 11, pp 1998-2005