Blood Glucose Testing After Swimming

Beth McNamara Health Guide
  • The one sport I love to do is swim. I've been swimming for the last three plus decades, and still look forward to getting into the pool several times a week.

    At the urging of a dear friend, I broke out of the pool-mode and tried my first open water event this past May. Much to my surprise, I really liked it.  But my open water adventure did not qualify as hardship duty. The swim was all of one mile in a man made lake and water temperatures measured in the mid-70s.

    Many open water swimmers brave water temperatures in the low 50 degrees to low 60 degrees F and typically do not wear wet suits. Open water swims can be quite long. Take my friend, Patti Bauernfeind, who got me to try open water swimming -- she swam, in a record time of 10 hours 39 minutes, the 22-mile length of Lake Tahoe on August 28. Open water swimmers must account for the factors governed by Mother Nature: weather, tides, altitude, to name a few. Furthermore, swimmers are never allowed to accept outside assistance, which means being touched by someone in their crews or coming in contact with a boat, during the swim for anything, including eating.

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    Another elite open water swimmer is Jen Alexander of Halifax, Nova Scotia, Canada. Jen, who has Type 1 Diabetes, did her first ever open water swim in 1988 while at a diabetes camp. She was the winner of the 2008 "Athlete of the Year" award from the Diabetes Exercise and Sports Association.  

    In 2007, Jen was the first swimmer to complete a double-crossing of the Northumberland Strait. She completed the swim, which was from New Brunswick to Nova Scotia and then back again, in 19 hours, 17 minutes.

    Jen trains out of doors from April to November in Halifax where she says the conditions are "outstanding." The waters in the Northumberland Strait can reach 22 degrees C or 72 degrees F. She does admit that the Atlantic Ocean is "considerably colder." She manages her insulin needs with a water-proof insulin pump that she wears during her swims.
    Putting her many accomplishments aside, the one thing that astounded me about Jen was how she tested her blood glucose level during a swim. Jen explained the complex yet effective process in a recent article done for the U.S. Open Water Swimming Connection:

    "I check my blood sugar every 30 minutes while I swim. Having diabetes and swimming in hypothermia-inducing conditions is actually a bit dangerous.  If your blood sugar drops too low (less than 2.5 mmol/L, or 45mg/dl), you'll actually lose the ability to shiver, and then you can get into trouble, because shivering is a primary way of generating heat.

    "Because I cannot touch my boat when I test, my crew and I have arranged something fairly elaborate process involving a long length of rock-climbing rope, a painter's extension pole, and an easy-to-open waterproof container. My crew will put two Abbott Freestyle Lite meters into the container, and pre-load strips into them. (The fact that the meters are branded "Freestyle" makes me smile! [Note: Freestyle most commonly is associated with the "crawl" style of swimming and typically is used by open water swimmers.]) We use two meters because accidentally touching water to a test strip will make the tests inaccurate. The crew has to turn on the finger flashlight for each meter. They cock the lancing device, and put a dry facecloth into the container as well.

  • "The container is swung/thrown out to me.  I grab the container, and open it up. While treading water, I dry my finger, draw blood, and apply blood to both strips. When the strips have enough blood, the flashlight turns off. Sometimes there is too much sea spray to see clearly into the container, and sometimes the wind blows too loudly to hear the meters beep to signal they have enough blood, so watching the finger flashlight turn off is the only way I know the tests are working. I close up the container, and get swimming again. My crew will pull the container back on the boat.  As I swim, my crew will read the results, determine if they are accurate, and figure out how my blood sugars are trending. Based on my sugars, they will figure out how many grams of carbohydrate to give me. Typically, I take in 15 grams if I want to lower my sugar, 30 grams if I want to preserve it and 40 grams if I'm lower than my target. My crew fills a bottle with the needed number of carbs, signals me to get ready, and then throws the bottle just in front of me. I drink everything, listen for instructions to adjust my insulin, and then get swimming again.

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    "It sounds technical, I know, and it's more complicated than I've described. As I progress through the stages of hypothermia, it gets more and more challenging to draw blood. I actually need to use hospital-grade lancets to get enough blood to test. Also, during long swims in water under 15oC (60oF), I lose grip strength in my hands. (This has nothing to do with diabetes, and is a 'normal' part of hypothermia.)  It makes it hard to manipulate the lancing device. [Note: Without grip strength, it is difficult to twist off the cap of a bottle, let alone press a lancing device to your finger.]

    "If I don't manage my blood sugars, I don't feel well. (Plus, there's the risk of needing helicopter evacuation because I can't shiver myself warm.) I've done exceptionally well at being able to manage my diabetes, though! During one 19+ hour swim, I was able to average 6.2 mmol (112 mg/dl), with no lows, for the best 10 consecutive hours. (I went higher in the late hours of the swim because of the hypothermia.)

    Jen has many swims on her agenda to continue to perfect her BG monitoring systems. She is in the process of booking her second try to swim the English Channel. Her first try, in 2006, was called short due to very rough weather conditions (with waves up to 10 feet high) and the worst expected tides for the next two decades.

    She's promised to keep us posted of where she dives in next.

Published On: September 10, 2009