Your body is almost 60% water, but despite the importance of water for health, it’s easy to forget to drink it. It happens to everyone! You get busy and forget to grab a glass of water. Research shows many people walk around in a mildly dehydrated state without knowing it, but your kidneys, blood vessels, and brain feel the strain.
Even mild dehydration can cause fatigue, lack of motivation, mood changes, and a mild headache. When enough blood flow doesn’t reach your kidneys, your kidneys are stressed too. Mild dehydration can even affect how tough your workouts feel and how you perform. Let’s look at the negative effects dehydration can have on your workout performance and your body.
Your Heart Has to Work Harder
When you have less fluid in your blood vessels due to dehydration, your heart must beat faster and work harder to deliver blood to your muscles and tissues. For a healthy person, this won’t have serious health consequences, but if you have undiagnosed heart disease, it’s extra stress your heart doesn’t need.
If you take a diuretic for hypertension or a heart condition, it’s even more important to drink enough water. Not doing so reduces blood flow to your kidneys. A study in Annals of Nutrition and Metabolism raises the question of whether proper hydration lowers the risk of chronic kidney disease.
Studies also show that even mild dehydration (around 2%) worsens endothelial function, how your blood vessels contract and expand in response to stimuli. With even mild dehydration, your blood vessels stiffen and behave somewhat like the blood vessels of a smoker. Your blood pressure rises, and the risk of a blood clot forming in your vessels goes up too.
How much is 2% dehydration? Most people barely feel thirsty with this degree of fluid loss. That’s why it’s important to drink even if you don’t feel thirsty.
Your Workout Will Feel Harder
If you’re struggling to get through a workout, ask yourself how well you hydrated beforehand. As your blood vessels and tissues lose fluid, your body temperature rises. With a rise in body temperature, the rate of perceived exertion, how hard you feel like you’re working, increases. So, you feel like you’re working harder than normal. It’s not a stretch to say you can make your workouts feel easier and more enjoyable by hydrating well beforehand. Entering a workout in a dehydrated state will make that workout feel more demanding and you’ll feel less motivated too.
Your Workout Performance Will Suffer
Studies show mild dehydration, at a level of 2 to 3% of total weight, impairs aerobic and anaerobic exercise performance. The effects even persist after rehydration for up to 24 hours. So, dehydration during one workout could affect performance on a subsequent workout, even if you rehydrated properly.
Why does dehydration affect performance? One reason is your heart must work harder when there’s less fluid in your blood vessels. Plus, dehydration makes it harder to regulate body temperature, and a higher body temperature impairs performance. As muscles heat up, they, too, undergo stress that affects their function. Research shows that muscle fibers A higher body temperature also speeds up carbohydrate metabolism, thereby reducing muscle glycogen reserves. If you’re sweating and losing electrolytes, it can affect nerve and muscle function.
Your Recovery Will Be Slower
When you’re dehydrated, your heart rate recovery after a workout will be delayed, meaning your heart rate stays elevated longer after your workout is over. Plus, dehydration can affect muscle protein synthesis and delay muscle repair. So, dehydration can even affect muscle repair and hypertrophy.
The effects of dehydration on your heart, blood vessels, and brain will cause you to feel more fatigued than you normally would after a workout. Hydration has a major impact on mood too. If you want to recover quickly and feel mentally sharper after a workout, stay hydrated.
The Bottom Line
Even a small loss of water can have a significant effect on your workout. That’s why it’s important to follow the guidelines for staying well hydrated:
Drink at least 16 ounces of fluid 30 minutes before a workout.
While exercising, drink an additional 8 ounces of fluid every 20 minutes.
How much should you hydrate after a workout? Weigh yourself before your workout and write down your weight. After your workout, reweigh yourself and subtract the second value from the first. For every pound you’re down, drink 16 ounces of water to replenish lost fluid stores. Monitor your urine color after a workout too. It should be almost clear to pale yellow if you’re drinking enough fluid.
If you’re exercising for longer than 90 minutes, switch to an electrolyte-rich beverage like a sports drink or coconut water with an added pinch of salt. Drinking pure water when you’re losing lots of sodium through sweat can lead to a sodium deficiency that can be life-threatening. Sometimes, this happens to marathon runners.
Hydrate well! It matters for your health and performance.
References:
- “DEHYDRATION AND EXERCISE-INDUCED MUSCLE DAMAGE ….” .gssiweb.org/sports-science-exchange/article/dehydration-and-exercise-induced-muscle-damage-implications-for-recovery.
- Barley OR, Chapman DW, Blazevich AJ, Abbiss CR. Acute Dehydration Impairs Endurance Without Modulating Neuromuscular Function. Front Physiol. 2018 Nov 2;9:1562. doi: 10.3389/fphys.2018.01562. PMID: 30450056; PMCID: PMC6224374.
- Barley OR, Chapman DW, Blazevich AJ, Abbiss CR. Acute Dehydration Impairs Endurance Without Modulating Neuromuscular Function. Frontiers in Physiology. 2018 ;9:1562. DOI: 10.3389/fphys.2018.01562. PMID: 30450056; PMCID: PMC6224374.
- Gatorade Sports Science Institute. “DEHYDRATION AND EXERCISE-INDUCED MUSCLE DAMAGE: IMPLICATIONS FOR RECOVERY”
- Chan J, Knutsen SF, Blix GG, Lee JW, Fraser GE. Water, other fluids, and fatal coronary heart disease: the Adventist Health Study. Am J Epidemiol. 2002 May 1;155(9):827-33. doi: 10.1093/aje/155.9.827. PMID: 11978586.
- “Endothelium – an overview | ScienceDirect Topics.” .sciencedirect.com/topics/agricultural-and-biological-sciences/endothelium.
- Tremblay JC, Ainslie PN, Turner R, Gatterer H, Schlittler M, Woyke S, Regli IB, Strapazzon G, Rauch S, Siebenmann C. Endothelial function and shear stress in hypobaric hypoxia: time course and impact of plasma volume expansion in men. Am J Physiol Heart Circ Physiol. 2020 Nov 1;319(5):H980-H994. doi: 10.1152/ajpheart.00597.2020. Epub 2020 Sep 4. PMID: 32886005.
- Roncal-Jimenez C, Lanaspa MA, Jensen T, Sanchez-Lozada LG, Johnson RJ. Mechanisms by Which Dehydration May Lead to Chronic Kidney Disease. Ann Nutr Metab. 2015;66 Suppl 3:10-3. doi: 10.1159/000381239. Epub 2015 Jun 18. PMID: 26088040.
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