Staying Hydrated Helps Heart Rate Recover Faster

We hear a lot about the importance of hydration, but recently scientists looked at the impact of hydration on the autonomic nervous system and discovered a critical reason for water’s importance.

When we exercise – especially when we do cardio for extended periods – the increased metabolism results in a thermic effect. In fact, mechanical inefficiency in the conversion of energy in the actual work performed is pretty high, with the rest of the energy wasted as heat. Think about it like a light bulb. When you touch a light bulb it’s hot, right? This might seem trivial, but it’s hot because when you put all that energy into producing light you get a lot of wasted energy, too. And when energy is wasted you get heat. Incidentally more efficient bulbs aren’t as hot as you may have noticed, but I digress.

(I know this is all basic stuff, but bear with me because the simplest stuff really is the best, right? Just like focusing on the fundamentals in your sport makes you a great athlete, focusing on the basics in science makes you a better academic.)

All this heat results in a loss of water. Why is that exactly? Looking at atmospheric pressure, relative humidity, and the evaporation point of water, it just so happens that this amazing fluid is the perfect thing to leave your body and evaporate readily into the air most of the time. And when water changes states from liquid to gas it takes energy with it. So, all that wasted energy that was supposed to work your muscles floats away harmlessly into the air.

Now it’s known that this dehydration can lead to a decrement in performance and even your health. What’s amazing is that a recent article in the Journal of the International Society of Sports Nutrition studying the effects of an isotonic solution (think: sports drink) on the autonomic nervous system (ANS) during exercise represented the first study of its kind. Your ANS, by the way, controls all kinds of things, including digestion, sex, hormones, fight or flight, your organs and most of your body’s unconscious processes.

In this study of the ANS athletes exercised for 90 minutes, and some of them drank Gatorade before and after their workout and some didn’t. Despite a scientifically insignificant improvement in performance, the extra hydration didn’t make a lot of difference during the workout. It helped the athlete’s maintain their bodyweight by maintaining hydration status, but otherwise didn’t have a huge impact. Where the benefit came was after the workout. The athletes drinking the Gatorade had a more rapid recovery in several of their indices that influence the ANS, specifically cardiac modulation – meaning, their heart rate recovered faster.

As a coach, I have long believed that recovery is the name of the game. If you can recover faster, you can do more exercise sooner and that equates to better results every time. More rapid recovery of the part of your nervous system that controls your internal organs is a critical avenue for improved performance. And all you have to do is stay hydrated. Simple and very effective.

This isn’t an ad for Gatorade, either. I think water alone will work just about as well, and there are better sports drinks out there, but the point is critical: Don’t forget to bring your water bottle with you.


1. Isadora Moreno, et. al. “Effects of an isotonic beverage on autonomic regulation during and after exercise,” Journal of the International Society of Sports Nutrition 2013, 10:2

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