Hydration plans and strategies can be a nightmare for players, trainers and coaches. Changes in the environment, game conditions and even the opponent will require changes to your hydration strategy. Current hydration literature suggests that a body weight decrement of 1-2% per exercise session is acceptable. However a decrement of >2% body weight can lead to adverse health and performance outcomes including decreased reaction time, motor control, time to fatigue, ratings of exertion, power output and in some cases repeated effort tasks (e.g. weight lifting). While a decrement of >2% body weight is dangerous, over hydrating is equally dangerous. Superimposing fluid intake can lead to hyponatremia (electrolyte imbalance) and will adversely affect performance. Hyponatremia occurs when there is a dilution of serum sodium < 135mmol/L. The optimal hydration strategy begins with calculating your individual sweat rate. Your sweat rate tells you how much fluid you have lost, and therefore how much fluid you need to consume per hour of exercise. The amount an athlete sweats is quite easy to calculate, however collecting the data requires a serious commitment from the athlete. Sweat rate = (Pre Exercise Weight – Post Exercise Weight) + (Fluid Intake – Urine output) / Length of Exercise (h) Save time by using this Sweat Rate Calculator. While the sweat rate will change from testing to game days, it does provide a objective measure and baseline for tailoring your hydration strategy and identifying athletes that will lose more fluid and need closer monitoring. The rate at which athletes consume fluids should be at the athletes discretion. Current research that drinking to thirst is the safest and optimal drinking strategy to prevent dehydration without risk of hyponatremia. This allows the athlete autonomy over their fluid intake. As a field measurement athletes should assess their hydration status via urine colour and thirst perception. If athletes have the ability to check urine measures and blood biomarkers this will enhance a sports scientists ability to capture an athletes hydration status. Justin Holland Justin Holland is currently under undertaking his PhD at the University of Queensland examining the effects of Individualised Sodium replacement on cognitive and physical performance in elite motorsport drivers. Justin is an Accredited Exercise Physiologist (AEP, ESSAM) and level 1 Strength and Conditioning Coach (ASCA). Justin is happy to discuss hydration strategies and plans with teams and athletes. You can connect with Justin via LinkedIn.