With the Tour de France well under way, it is of little surprise that hydration will play a pivotal role in a cyclists success. It is well established that dehydration is the single largest contributor to fatigue when training or racing. The contraction of leg muscles produce the force necessary to pedal and propel a bike forward, yet in doing so, increases the production of internal heat. This being so, internal heat must be dispersed to avoid body temperature exceeding basal metabolism. Although sweating is a crucial mechanism in the process of thermoregulation, the unfoldings of this process lead to an increased loss in fluid and electrolytes. Electrolytes are charged ions that allow water to conduct electricity, stimulating nerve conduction and skeletal muscle contraction. Hence, with increasing fluid loss and a reduction in electrolyte capacity, the body will begin to compensate by decreasing muscle tone, which will subsequently impede performance. For this reason, it is clear that dehydration will impact on cycling performance.
There is evidence to suggest that a 2 percent (1.4 Kg) loss in body weight due to fluid loss can significantly slow performance (Johnston & Timothy, 2010). However, an increase in humidity and/or heat can result in a subsequent increase in fluid loss, well exceeding a 2 percent threshold (Johnston & Timothy, 2010). For this reason, hydrating prior to, and/or rehydrating during an event will limit fluid deficit. To avoid fluid deficits, monitor hydration by screening the colour of your urine (light-yellow is conistent with adequate hydration). If a fluid deficit is apparent, consume 400-600ml of water 2 to 3 hours prior to an event, with an additional 240ml if conditions are hot and humid (Johnston & Timothy, 2010).
Moreover, during an event cyclists should consume fluids at the same rate at which sweat is dispersed. This would require athletes to consume 400 to 800ml of fluid for every hour of exercise or 100 to 200ml every 15 minutes (Johnston & Timothy, 2010). However, one must take into account that fluid needs will vary depending on body size, pace, and weather conditions. For longer rides, a endurance and rehydration formula such as 'Endura' will provide the electrolyte ratio required to relieve muscular cramps and spasms during times of increased physical output.
Johnston, M & Timothy, R. (2010). Sports Nutrition for Road Cycling. Journal of Sports Nutrition & Physical Education, 15, 2, 98-107.