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Signs of Dehydration While Running, Cycling, Or Doing Any Activity

Updated: Mar 21

If you're an athlete, it's important to be aware of the signs of dehydration while running, cycling, or performing any physical activity. Not staying properly hydrated during exercise can reduce your performance, slow down your training gains, and cause you to have a longer recovery time.


While your body is composed of about 60% water, a dehydrated body can still experience adverse effects on your training and performance. Below are some tips to help you stay properly hydrated during your workout.


Dehydrated female cyclist
Dehydrated female cyclist


Drinking to Thirst Adequately Hydrates


One of the key ingredients of proper hydration is to drink before you feel thirsty. While drinking before you feel thirsty is a great way to avoid excessive dehydration, it's not enough to hydrate your body adequately.


During a workout or long ride, you'll need to rehydrate at least 10-20 minutes before you feel thirsty. A good rule of thumb for drinking before you feel thirsty is to drink every 10-20 miles.


Drinking to Thirst Causes Hyponatremia


A low blood salt concentration, also known as hyponatremia, can result in seizures, coma, and even death. The causes of hyponatremia are usually dilution or excessive retention of fluids in the body.


Although exercise-induced hyponatremia was first identified in the mid-1980s, awareness of this condition has increased since the 2005 publication of a study in the world's top medical journal.


Lack of Electrolytes Causes Cramping


It is not clear what causes cramping while running or cycling. In general, a lack of electrolytes is not the major cause. However, electrolyte deficiency can lead to cramping in certain muscle groups.


In fact, electrolyte deficiency has been associated with several health conditions, including diabetes. Also, dehydration can cause cramping, but it is not the only factor.


Lack of Fluid Intake Causes Fatigue


Athletes must replace lost fluids regularly. Dehydrated people can no longer function optimally, causing them to be tired. The signs of dehydration are apparent, such as dark urine and a lack of sweat during physical activity.


Fluids also keep the body cool, which controls heart rate and temperature. Dehydration also affects mental performance. In addition to making you feel thirsty and tired, lack of fluid intake causes you to become more inactive.


Female athletes running in competition on race
Women running race


Lack of Electrolytes Causes Fatigue


When exercising in warm and humid weather, the body is more likely to lose electrolytes through sweat. The heat raises the body's core temperature, leading to increased sweating.


Unfortunately, humidity prevents this sweat from evaporating, losing electrolytes with it. It is essential to replenish electrolytes in the body to stay hydrated and avoid fatigue. To avoid losing electrolytes while exercising, consume plenty of water and sports drinks.


Lack of Electrolytes Causes Sluggishness


This article explains the effects of fluid-electrolyte disturbances on competitive performance, and how to minimize the decrement of performance and the risk of hydration-related illness.


In general, endurance athletes lose 11-13% of their body weight in water, or about 7.8 to 8.5 kg. Although this seems excessive, this reduction in sodium concentration is hardly harmful.


Lack of Fluid Intake Causes Hyponatremia


Among the symptoms of hyponatremia are lack of thirst, confusion and headache. It is often mistaken for dehydration, and some aid stations may not recognize the symptoms as hyponatremia.


Depending on the severity of the condition, you may lose control of your muscles and feel weak. Stopping your exercise immediately is the first step to treating hyponatremia.


Signs of Dehydration Summary


If you're an athlete, it's important to be aware of the signs of dehydration while exercising. Improper hydration or low levels of hydration can reduce your performance and slow down your training gains.


A lack of electrolytes is not the major cause of muscle cramps, but electrolyte deficiency can lead to cramping. Electrolyte deficiency has been associated with several health conditions, including diabetes. Fluids keep the body cool, which controls heart rate and temperature.

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