Electrolyte Testing - Magnus Jonsson | Runner's World

Magnus Jonsson

After a long break from racing Ironman it’s time to get back. My goal is to explore if it’s possible to become faster at 50 than I was at 30 - when i finished 74th overall in Hawaii. I will use every possible advantage I can get with new technology, training methods and experience – everything except doping and drafting which I hate with a passion – now as then. http://www.magnusjonssontri.com Instagram: magnusj66



Electrolyte Testing

11 dec 2017
av: Magnus Jonsson

In my race nutrition plan I have always calculated to get 250-300kcal of energy per hour. Typically; that means carrying a bottle of my own mix on the bike (15 Isostar gels, a few boosters  with BCAA and some water mixed in to make it easier to drink). For the run, I carry 6-8 gels with me and that’s pretty much it. I take the provided sports drink every second bottle / cup at aid stations and usually trust the organizers to provide a quality isotonic drink that contains the necessary electrolytes. Unfortunately; I have realized that this can’t be taken for granted anymore.

I have done plenty of Ironman races in what most people would call extreme hot condition, not extreme cold as I would NEVER expose myself to racing in cold conditions if I had a choice to avoid it (anything <+25C° in the water or air is just not for me).

When I saw the Ironman Lanzarote photos I remember thinking – “that’s a lot of salt on my sleeves”. I guess the arms were the only area that did not get drenched by water at every aid station so my loss of salt was clearly visible.

As you have probably understood, I really love the heat and have never had any (...) problems racing in +30C°, sure - I have ended up in the medical tent hooked up to a few pints of IV after seven or eight races – but for me that has been part of the race; you cross the finish line, get an IV, the medal a finishers t-shirt and then ride your bike back to the hotel. But, I never liked the IV part so at the last race Ironman Los Cabos I was extremely happy and proud that I didn’t get an IV - even if I was cramping and was sick as a dog after the finish.

In retrospect; I realize that there might be some room for improvement with regards to my race nutrition plan. I have never really reflected on the importance of electrolytes and the effects it can have if you are depleted of it as I never experienced any problems during the event – until this past race. As I started to read up on the effects the lack of electrolytes can have, I realized that I likely have reduced my possibilities to race fast, but also could have ended up in a much worse situation than getting an IV. Apparently, you can end up in a condition called hyponatremia that occurs when the level of sodium in your blood is abnormally low. When you are in this condition the body can’t absorb water and there have been cases where the resulting “over-hydration” that happens when the body can’t absorb water has caused deaths. Ops….

Once I got back to Sweden I talked with Johan Hasselmark at Aktivitus and he recommended that I should come in and do a sweat test where they would see how much electrolytes I loose and from that be able to suggest a hydration / supplement plan for my long training days and for racing. I’m not interested in just buying stuff and without understanding what my individual needs are so it sounded like a great idea. I really don’t like to take too much or too little electrolytes in relation to what I loose.

Micke Hanell - set up for testing.

I booked a time and was met up by Micke Hanell at Aktivitus. He is using a system from Precision hydration who are on the leading edge with regards to analyzing your sweat and prescribing the right amount/concentration of electrolytes that you should take.


Micke hooked me up to a system that stimulates the lower arm to get just enough sweat into the collector and enable analysis of the water/salt mix.

I was surprised to see the results that I was on the very high side. Apparently, I have the second highest value that Micke has ever seen and he has done hundreds of tests. I guess that means; a) it’s a miracle that I have been able to race Ironman distance races in hot conditions without supplementing electrolytes b) I will see significant improvements to my racing once I start to add electrolytes during the race.


Next day I got a personalized plan for what I should take before and during hard training and racing and I look forward to getting back into the heat and race again and see if the additional electrolytes will make a difference – I am certain it will.


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