In the last few years, there has been a large amount of debate concerning hydration during endurance exercise. Although it is possible and potentially dangerous to over-drink, for the majority of riders tackling sportives and long training rides, dehydration through under-drinking and the associated performance losses are more of a concern.
How does dehydration affect performance?
Sweating is a highly individual bodily function, with most people 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.
The importance of 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.
The colour and volume of your urine is one of the most accurate signs of your hydration level. Dark coloured urine can indicate that you’re dehydrated and need to drink more (1). Always note that some foods and vitamins can change the colour of your urine, even when you’re in a hydrated state. Follows these pre-hydration tips the night before and the morning of your event:
- drink at least 2 litres of fluid per day
- drink at least 500ml of an electrolyte solution with breakfast
- 1-2 hours before exercise: 500ml
- 30 mins before exercise: 250ml
Hydrate while riding
Thirst is a response to ensure that we maintain a constant fluid balance. However, it has been suggested that thirst is a poor indicator of hydration and when an athlete is thirsty, they are already dehydrated. As a general rule, aim not to lose any more than 2-3% of your body mass (1,4,5). They best way to work this out is to weigh yourself before and after training rides, in a range of temperatures and plan accordingly. Follow these tips:
- Weigh yourself before and after your training rides to estimate your sweat rate
- Take on fluid little and often during rides
- Make sure your fluid contains electrolytes
- As a general rule of thumb, take a sip from your bottle every 10-15 minutes and aim to consume 500 ml per hour depending on conditions and individual needs.
- If you tend to forget about drinking, set an alarm on your watch or bike computer to remind you.
Rehydration post ride
Aim to replace 150% of the fluid lost through sweat (1), within 1-4 hours post-exercise. Don’t forget that this fluid can be incorporated with a post-exercise REGO Rapid Recovery shake.
SiS GO Hydro?
SiS GO 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, SiS GO Hydro meets your sodium requirements in an appropriate amount (0.7 grams per L) and concentration (30 mmol/L) (6).
- 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.
- 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.
- Stachenfeld, N. S. (2014). Sodium Ingestion, Thirst and Drinking During Endurance Exercise. Sports Science Exchange, 27(122), 1-5.
- Arnaoutis, G., Kavouras, S. A., Angelopoulou, A., Skoulariki, C., Bismpikou, S., Mourtakos, S., & Sidossis, L. S. (2015). Fluid balance during training in elite young athletes of different sports. Journal of strength and conditioning research/National Strength & Conditioning Association, 29(12), 3447–3452.
- Bardis, C. N., Kavouras, S. A., Arnaoutis, G., Panagiotakos, D. B., & Sidossis, L. S. (2013). Mild dehydration and cycling performance during 5-kilometer hill climbing. Journal of Athletic Training, 48(6), 741-747.
- Coyle, E. F. (2004). Fluid and fuel intake during exercise. Journal of Sports Sciences, 22(1), 39-55.