Given the enormous importance of football referees – reflected in the almost universal tendency for die-hard fans to displace frustrations with the team onto their hapless shoulders – it is surprising that sports scientists have paid so little attention to their physical and psychological status and performance.

Now a pair of Brazilian researchers have attempted to redress the balance somewhat with a study of hydration status in six male refs and six assistants (linesmen) during matches of the 2000 Paraná football championship, held in Brazil in their autumn months of March, April and May.

Why study hydration status, you might ask? The answer is that negative effects on performance have been shown with modest degrees of dehydration (2% of body weight). And it is generally accepted that cognitive performance is also impaired when dehydration and hyperthermia are present, which could be particularly relevant to the decision-making aspects of refereeing.

The subjects were weighed without clothes and had blood samples taken before and after each match, after emptying their bladders. The difference in readings before and after a match, plus ad lib water intake at half-time and urinary volume, were used to estimate total body water loss during the match, with the assumption that a body mass loss of 1kg was equivalent to loss of 1 litre of fluid. The blood tests were analysed for changes in plasma volume – the fluid portion of the blood.

The key results were as follows:

• Referees lost 1.22kg of body weight during matches, equivalent to 1.55% of their pre-match weight. Total body water loss averaged 1.60L, equivalent to 2.05% of their pre-match body weight. The difference between the two measurements reflects their half-time fluid intake;
• Linesmen, by contrast, lost only 0.48kg (0.63%) of their body weight and body water loss averaged 0.79L, equivalent to 1.05% of their pre-match body weight;
• The referees showed a reduction in their plasma volume, while the linesmen showed no significant changes in haematological status.

The researchers conclude that referees are moderately dehydrated after a football match, whereas their assistants exhibit only a mild, non-significant degree of dehydration.

‘The physical activity performed by referees is a combination of various types of exercise (walking, jogging, sprinting and reverse running) covering an average distance of 9.3 miles in a match,’ they point out. ‘Our results show that this amount of activity caused significant dehydration which was not redressed by the spontaneous intake of water during the interval.

‘Additional studies are required to find the best form of fluid replacement for football referees (during, before and after a match) to prevent a decrease in their physical and mental performance.’

Br J Sports Med 2003;37:502-506