• Allison Koch, MS, RD, CSSD, LDN

Staying Hydrated During The Summer Heat: Tips For Pre, Post And During Exercise

When the temps start to heat up, my mind always turns to hydration. It can literally make or break your workout. In fact, it can be a major contributing factor to a race day DNF (did not finish) or PR (personal record) – whether it be from over-or under-hydrating.


Monitoring your Hydration Status: Making sure you are sufficiently hydrated will also get you to the finish line feeling good. Your goal with hydrating during a long run in particular is to start and finish adequately hydrated. How will you know you did a good job? There are a couple of ways.


First, you could weigh yourself before and after your run. If you have lost weight, up your intake a bit next time. Weight loss of just 2% has been associated with decreases in performance and negative health implications. If you have gained weight – slow your roll! Weight gain may indicate excessive hydration which can lead to a life-threatening complication called hyponatremia or ‘low blood sodium.’ This results from having too little sodium in your bloodstream as a result from either unsuccessfully replacing the sodium lost in your sweat and/or overdoing it on the water stops. It’s much rarer than dehydration but the consequences are more severe including bloating, nausea and in extreme cases brain seizure or even death. Those most at risk are smaller athletes and those running a slower marathon pace (in the 5+ hour range).


Another way to check your hydration status besides weighing yourself is to use the “pee test” – it’s gross but true – if the color of your urine is clear yellow – not too dark but also not too light – then you are likely adequately hydrated. You should also be visiting the bathroom at least every 2 to 4 hours. Any less and you may need to up your intake throughout the day as well as during your workout.


So how much do you need?


Daily Needs: Maybe you’ve heard you need to drink at least 8 cups of water per day. Or perhaps you’ve heard the recommendation that you should aim for at least half of your body weight in ounces (e.g., 150 lb person would need 75 ounces or about 9 cups of water/day).


Neither suggestion is incorrect, and both are good rules of thumb, but the truth is everyone is different. I try to always have a water bottle handy that I’m sipping from and monitor my trips to the bathroom as well as the way I’m feeling to determine if I should have more. Signs and symptoms you may be dehydrated in general include an obvious one – being thirsty – but also some signs that may be less obvious like dry mouth, chapped lips or dry skin, you have a headache, bad breath, and even muscle spasms or general fatigue.


Pre-Workout or Long Run: This is very specific to the individual and how much they sweat – but in general, I recommend aiming for 1.5-2 cups (12-16 oz) of water or sports drink at least 2 hours in advance of a long run or big workout. You can drink about 1 more cup (8 oz) 15-20 min before. Sip don’t chug to allow time to absorb/digest it. If you chug it down, you’ll likely find yourself peeing it all out shortly after or worse, a couple miles into your run.


During Exercise: I recommend about a 1/2-3/4 cup (4-6 oz) every 15-20 minutes. That is equivalent to a couple of gulps every 15-20 minutes. If it is hot (over 75 degrees) or you are an excessive sweater you may benefit from more than this, so it is important to practice now and find that sweet hydration spot for you. Also, the bigger you are, the more you’ll need and vice versa. The best way to know exactly how much is to practice seeing what you can tolerate and that feels best for you.


What about Sports Drinks? The carbohydrate in most sports drinks helps to increase the water we actually absorb. They also typically contain added electrolytes (sodium/potassium) which are lost in the sweat – so it’s important we replace those as well. I generally recommend the addition of a sports drink with electrolytes for anyone working out for longer than 1 hour and/or during exercise in the heat. I suggest alternating between water and sports drink and if taking any solid nutrition - like gels, gummies, etc. - to take those with water only to not overload your stomach.


Following Exercise: Drink roughly 2.5 to 3 cups (20 to 24 ounces) of water for every pound of weight you lose during the workout. If you have had a particularly long or sweaty run, you might benefit from a sports drink that contains some sodium and other electrolytes to help restore balance. The presence of sodium helps the body retain the ingested fluids. Don’t fret if this seems like a lot – you can get some of your water from the foods you eat. Things like watermelon, cucumbers, milk, oranges, apples, and lettuce contain mostly water and are also great at helping you hydrate.


Still unsure you are hydrating right? Let me know! In the meantime, here’s a fun pic of me at the finish line of the 2016 Nashville Rock ‘n Roll Half Marathon re-hydrating it up. It was a steamy, stormy day and hydration definitely played a factor in everyone’s performance.




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