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How does dehydration affect performance?

Sweating is a highly individual bodily function, with most individuals losing around 500-1000ml of fluid (through sweating) per hour of exercise depending on the exact environmental conditions(1). Although the production of sweat is a beneficial response as it is our body’s main way of losing heat and keeping our body temperature regulated, if such fluid losses are not replaced at an appropriate rate, dehydration occurs and performance can be impaired. Indeed, dehydration can alter the function of our most important organs such as the brain, heart and muscles, as well as bone density. In a dehydrated state, our body temperature rises, heart rate increases, we deplete carbohydrate stores quicker and we perceive exercise to be more intense(2). In essence, we have to work much harder just to perform at the same speed or power output. If left unchecked, the negative physiological effects of dehydration can interact such that fatigue can rapidly occur.

What are electrolytes?

The composition of sweat is largely made of water (from the watery component of the blood known as plasma) and important substances known as electrolytes. Electrolytes are minerals that carry an electrical charge (e.g. sodium, potassium, magnesium, chloride and calcium) and have crucial roles to maintain normal cell function such as the transportation of substances into and out of cells. Sodium is the most important electrolyte, as it helps to stimulate thirst, improve fluid palatability and promote fluid absorption and retention(3). The concentration of sodium in our bloodstream is normally tightly regulated within a concentration of 135-145 mmol/L. When the blood sodium level drops below the range, this is known as hyponatremia(2). Sodium loss, like sweat loss is very individual, with some athletes losing more sodium than others.

Only rehydrating with plain water can dilute plasma sodium levels to lower concentrations thereby further compounding the negative effects of dehydration. As such, the general consensus from leading scientists(2) is that electrolyte-containing (especially sodium) solutions are superior to plain water for ensuring adequate hydration before, during and after endurance exercise.

What is Hydro?

Hydro represents a scientifically based formulation that is designed to ensure you are effectively hydrated to produce your best performance. As an effervescent tablet that readily dissolves in plain water, it represents a highly practical approach (simply drop one tablet in your 500 ml water bottle) to ensure that all of your electrolyte and fluid requirements are met. Importantly, Hydro meets your sodium requirements in an appropriate amount (0.6 grams per L) and concentration (26 mmol/L)(4).

How can Hydro help improve performance?

With an athlete’s hydration, weight and strength so integrally linked to performance, electrolytes play a major role in endurance nutrition. It is difficult to provide precise fluid recommendations for athletes given that hydration requirements are dependent on exercise intensity, duration and ambient temperature as well as individual characteristics such as training status, age and gender etc. Firstly, it is crucial that athletes commence exercise in an adequately hydrated state so that subsequent performance is not impaired. In this regard, consuming 5-10ml per kg of body mass in the 2-4 hours prior to exercise is recommended, ensuring that urine is pale in colour(2).
During exercise itself, the main aim is to prevent losing more than 2-3% of your body mass through sweating(2). To figure this out, try weighing yourself before and after your training sessions, consider the weight of the fluid and food that you have taken on (1000ml = 1kg) and the difference is generally what you have lost through sweating. For most people, drinking around 500ml of hour, or drinking to thirst will suffice.

In terms of recovery, for every 1 kg lost during exercise, you should consume 1.5 L of fluid in the post-exercise period so as to promote adequate re-hydration(5). Your REGO Rapid Recovery shake will also count towards this amount, but try to include an Hydro to promote optimal hydration.


  1. Casa, D. J., DeMartini, J. K., Bergeron, M. F., Csillan, D., Eichner, E. R., Lopez, R. M., & Yeargin, S. W. (2015). National Athletic Trainers’ Association position statement: exertional heat illnesses. Journal of athletic training, 50(9), 986-1000.
  2. Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Medicine and Science in Sports and Exercise, 48(3), 543.
  3. Stachenfeld, N. S. (2014). Sodium Ingestion, Thirst and Drinking During Endurance Exercise. Sports Science Exchange, 27(122), 1-5.
  4. Coyle, E. F. (2004). Fluid and fuel intake during exercise. Journal of Sports Sciences, 22(1), 39-55.
  5. Baker, L. B., & Jeukendrup, A. E. (2014). Optimal composition of fluid‐replacement beverages. Comprehensive Physiology, (4), 575-620
Written By

Ted Munson (Performance Nutritionist)

Ted is a Performance Nutritionist here at Science in Sport.