The new studies follows close on the heels of those involving professional footballers which show that some players lose as much as 10 grammes of salt in a 90-minute training session at a time when advice from the Food Standards Agency is to cut back to six grammes a day.

It was concern over those findings that led the Salt Manufacturers Association to commission sports scientists at Loughborough University to test members of the UIK's leading women's cycling team, FBUK.

The losses of water and electrolytes such as sodium were monitored throughout a 90-minute training session. Although the temperature was a mild 15 degrees Celsius (59 degrees Fahrenheit), the cyclists still lost up to three grammes of salt. In hotter temperatures, they would have lost far more. 

The constant flow of air rapidly evaporates perspiration, which can dehydrate cyclists and deplete vital sodium levels in their bodies. Poor performance and cramps can follow, but a greater risk comes from hyponatraemia. This potentially life-threatening condition, which has affected several marathon runners, is caused by drinking excessive amounts of liquid. This dilutes the levels of salt in the blood. 

Helen Wyman of Team FBUK is the current UK Number 1 ranked female rider. She says: "Our team is very aware of the ill effects of consuming too little salt. Many of us experience cramps, which we are convinced is connected to our sodium intake. I believe that the importance of replacing sodium lost through sweat is not given as much attention as it should. Anyone who exercises needs to be careful, but particularly a professional athlete like me. Not only could my performance be severely affected, but my health could be at risk."

The team's coach, Stefan Wyman, added: "Riding at the highest level can place demands of more than 30 hours training per week. If some members of our team lost three grammes of salt in a moderate 90-minute session, just think what they would lose in a four-hour uphill cycle on a hot day. I want my team to be safe and to do the best they can. Their nutrition is a major part of this."

Professor Ron Maughan leads the team of sports scientists at Loughborough University which was commissioned by the Salt Manufacturers' Association to conduct the research. "Due to the temperature and the fact that this was not a hard training session, the sodium losses in this instance were not in the dangerous category," he says. "However, I have undertaken similar trials on professional footballers who lost up to 10 grammes of salt in a single training session while exercising in the heat.

"Sweating is a highly individual issue. In these trials, some riders lost twice as much sodium as others. It is absolutely clear that the government's blanket advice is not appropriate and could indeed be harmful."

Professor Maughan estimates that one in six people are particularly "salty sweaters" - in other words, they sweat profusely and some lose a lot of sodium when they do so. This may make them more vulnerable to muscle cramps. The best way to avoid hyponatraemia is to plan ahead. His tips include using a sports drink containing sodium during events where high sweat losses are expected, and eating salty foods after training and  competition when salt losses are high.

The issue is a concern to other sports personalities. At Wimbledon, the American tennis player Robert Kendrick called for salt during his match with Rafael Nadal. He added it to his water bottle and drank from it as he fought to stave off the effects of sodium lost through sweating. A female runner died during the 2002 Boston marathon of hyponatraemia - low blood sodium levels caused by drinking too much water, which resulted in swelling of the brain. Others studies suggest that some 10 percent of marathon runners have the same condition, although most cases are mild and do not require hospitalisation.