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OCTOBER 8, 2018 · BY CHRISSIE WELLINGTON AND ANDY KIRKLAND Considering athlete weight in relation to performance is important when planning and executing training. But, where is the line between an increase in performance and encouraging an athlete to adopt unhealthy behaviors? Being a coach isn’t an easy job. We often work with highly-motivated people living complex lives. It’s our job to help them achieve their potential and actualize their dreams. While planning and prescribing training plans is a large part of what endurance coaches do, ultimately, we are influencing the behavior of athletes to help enhance performance. However, like many relationships, things can sometimes go wrong. A few poorly-chosen words, poor communication, or lack of understanding of the needs of the other person can lead to acrimony, or worse. “Ideal racing weight” is an important subject because the mass of an athlete affects performance. While it can be a sensitive topic for a coach to address, i...

EY TERMS The amount of water and electrolytes (primarily sodium, Na+) lost as a consequence of thermoregulatory sweating during exercise can vary considerably within and among athletes. The reported range in sweating rate and sweat Na+ concentration ([Na+]) is ~0.5 to 2.0 L/h and ~10- 90 mmol/L, respectively. Sources of intra/interindividual variability in sweating rate and sweat [Na+] during exercise include exercise intensity, environmental conditions, heat acclimation status, aerobic capacity, genetic predisposition, body size/composition, protective equipment, sex, diet and hydration status. Sweat testing can be conducted to estimate individual sweating rates and sweat Na+ losses to help guide personalized fluid and electrolyte replacement recommendations. However, unstandardized methodological practices and challenging field conditions can produce inconsistent/inaccurate sweat testing results. Based on study findings to date, as well as some practical considerations, curren...

KEY POINTS In humans, thirst tends to be alleviated before complete rehydration is achieved. When sweating rates are high and  ad libitum  fluid consumption is not sufficient to replace sweat losses, a cumulative loss in body water results. Body mass losses of 2% or greater take time to accumulate. Dehydration of > 2% body mass and greater is associated with impaired thermoregulatory function, elevated cardiovascular strain, and in many conditions impaired aerobic exercise performance (e.g., warmer, longer, more intense). Circumstances where planned drinking is optimal include: longer duration activities > 90 min, particularly in the heat; higher intensity exercise with high sweat rates; exercise where performance is a concern; when carbohydrate intake of 1 g/min is desired. Circumstances where drink to thirst may be sufficient include: short duration exercise < 60 to 90 min; exercise in cooler conditions; lower intensity exercise. NEVER  drink so much t...