100° Of Blood Sugar (The Absurdities Of Exercise In High Heat and Humidity)

Humidity's Effect On Blood Sugar

It’s been hot here (Oklahoma) and everywhere else. Especially hot for this early in the year. 100° is normal in August, not June. Plus, the humidity been’s flirting with Amazonian levels. Nonetheless, despite the warnings from weather people and health officials, I’ve been out on the trails (not recommending anyone try this out per se, please exercise extreme caution). A justified decision based primarily on an irrational personal desire to be outside, I’ve survived by consuming liters on liters of water out of the Camelbak, keeping Clif Bars in the pocket, searching for shade, and pounding back bananas every 30 minutes. Gotta be careful.

As mentioned earlier, I am not looking to inspire others to try out the whole exercising in triple digits and high humidity concept. The goal is to put forth my observations on safety from the last two weeks of experience on the mountain bike trail (at Lake Draper and Bluff Creek in OKC). After all, these lessons might help someone out there looking to manage sugars during a hot high school baseball game, a Bikram yoga class, or during two-a-day practices.

Heat and Humidity Observations

  • Listening to my body is so important. If I feel my performance sliding, I think blood sugar first before blaming it on the heat or humidity. Those classic low blood sugar signs can be easily disguised by the temperatures. Get that CGM on!
  • My heart rate sprints up to an uncomfortable place much faster than usual, like to a max in 10 minutes on the trail. This makes the first 30 minutes tough.
  • Given the upped heart rate and subsequent increased need for energy (and O2), my blood sugar declines much faster than usual. Yesterday I did my first 4 mile loop (about 25 minutes) at an average intensity but high heart rate, and saw a blood sugar drop from 178 to 55. Boom, just like that, without much insulin on board at all and a temp basal of 25%. On a 65° day, I’d expect my blood sugar to be 130 at the end of that loop.
  • After absorbing the initial low blood sugar drop with a Clif Bar and half a banana over a 15 minute break, my blood sugars stabilized for the next hour of riding.
  • This is a hypothesis but it feels like cortisol and epinephrine help stabilize the sugars but it takes about an hour for them to get into the action. I felt great and didn’t notice the heat near as much about an hour into the ride. The heart rate stabilized and my blood sugar wasn’t 55 (at 130 during the next hour), always a better place to perform.
  • Instead of taking a break every other lap, I opted for the break during each lap. That pause helped calm the heart and let me listen to the body’s experience.

Generally, all the same exercise principles apply, but things are intensified. Going low is still the huge concern here and the heat slims the margin for that error. I like taking a prophylactic approach, entering with a little high blood sugar than normal, limiting active insulin onboard, carrying Clif Shot Blocks, maybe having a snack on board prior, and being over-hydrated. Happy summer everyone and stay safe out there!

**Again, DiabetesDailyGrind is not endorsing exercise in high heat or humidity. These are only Ryan’s observations and not to be interpreted as medical advice.**

6 thoughts on “100° Of Blood Sugar (The Absurdities Of Exercise In High Heat and Humidity)

  1. This sounds about like Indiana. Except, I believe Indiana is a little cooler.

    I referred your blog to the TUDiabetes.org blog page for the week of June 20, 2016.

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