Development of Individual Hydration Strategies for Athletes

Abstract

Athletes are encouraged to begin exercise well hydrated and to consume sufficient amounts of appropriate fluids during exercise to limit water and salt deficits. Available evidence suggests that many athletes begin exercise already dehydrated to some degree, and although most fail to drink enough to match sweat losses, some drink too much and a few develop hyponatremia. Some simple advice can help athletes assess their hydration status and develop a personalized hydration strategy that takes account of exercise, environment, and individual needs. Preexercise hydration status can be assessed from urine frequency and volume, with additional information from urine color, specific gravity, or osmolality. Change in hydration during exercise can be estimated from the change in body mass that occurs during a bout of exercise. Sweat rate can be estimated if fluid intake and urinary losses are also measured. Sweat salt losses can be determined by collection and analysis of sweat samples, but athletes losing large amounts of salt are likely to be aware of the taste of salt in sweat and the development of salt crusts on skin and clothing where sweat has evaporated. An appropriate drinking strategy will take account of preexercise hydration status and of fluid, electrolyte, and substrate needs before, during, and after a period of exercise. Strategies will vary greatly between individuals and will also be influenced by environmental conditions, competition regulations, and other factors.

Half-Marathon and Full-Marathon Runners' Hydration Practices and Perceptions

“…13,14 However, only 5 (4 of these from the High group) of 276 runners (2%) reported measuring changes in body weight. Runners tend to greatly underestimate their actual sweat losses.…”

“…When fluid may not be readily available (as opposed to during a race with hydration stations), a key aspect of hydration is pre-exercise hydration status. 5,13,14 Urine color was the most reported method (20 runners) used to assess hydration status. This simple technique correlates highly with urine specific gravity and urine osmolality 26 and is a practice supported by the National Athletic Trainers Association.…”

“…created an original questionnaire constructed of items influenced by topics and content from recent reviews and position stands addressing fluid and nutritional concern for performance and prevention of heat-related illnesses. 5,6,[13][14][15][16] The survey items were reviewed for readability and content by the co-investigators, who included people with research experience in nutrition and performance, environmental physiology, and thermoregulation. The review panel also consisted of experienced runners and a registered dietitian.…”

Textile sensors to measure sweat pH and sweat-rate during exercise

“…As a wearable system this is challenging due to complex circuitry, measurement times [11] and the effects of movement and electrode placement [12]. to In the field, the most practical way for athletes to monitor their sweat loss is to measure changes in body weight pre-and postexercise [13]. Therefore it is clear that a method is needed to collect and analyse sweat in an unobtrusive way in normal settings, at home, in the gym or on the track to provide realtime analysis of sweat activity.…”

Nutrition for sports performance: issues and opportunities

“…This is not helpful to performance and may in extreme cases lead to hyponatraemia, which is occasionally fatal (32) . Even in apparently homogeneous populations exercising at similar intensities in the same environment, there is a large individual variability in both sweat rate and sweat composition, and so some individual prescription is necessary, and the composition of drinks to be taken during exercise should be chosen to suit individual circumstances (33) . Prescription of fixed rates of fluid intake is generally not helpful.…”