Tuesday, September 30, 2014

Salt deficiency causes cramps -- myth, or fiction?

My goal for last Sunday’s Honolulu Century Ride was to practice my fuel plan for December’s Honolulu Marathon, something I have written about in previous posts. The inspiration came from Matt Fitzgerald; the part about using the bike is mine:
  • You cannot count on the sports drink at an event to have the nutrients you trained with.
  • Carry your own fuel and just take on water at the aide stations.
  • Consuming an entire gel at once can cause stomach upset due to the need for water to digest the carbs.
  • Reduce the carb impact by diluting gel with about 50% water and sipping smaller quantities more frequently, at a rate that equals one gel every 30 - 45 minutes.
  • Using a Fuelbelt 7 oz flask, empty three GU gels into the flask and add water until almost full. Shake well.
Fitzgerald says that he carries two flasks in a marathon and finishes the second one around the twenty mile mark. Well, that’s fine for him because he runs fast. I am looking at over six hours on the run, so I need to work out how to carry more. In the meantime I decided to practice a six hour event using a typical twenty-something ounce water bottle, the kind we normally use on the bike. To mimic the aide stations I would carry a second bottle of plain water and refill at the century ride aide stations, which happen roughly every twelve miles, or one hour apart at a comfortable cruise.

My ride plan was to average 16 MPH. This seemed doable based on several recent forty mile bike rides. I knew it was optimistic for the entire 100 miles, but I like to set high goals and stretch a bit, which is fine as long as I remember that when I fail to achieve them. There are a lot of hills on the route, especially now that it goes along Kahekili Highway, so to average 16 I would need to stay above that as much as possible.

Let’s take a moment and translate this into effort. For a 10K run I would try to stay about 10 beats lower than LTHR, which works out to be mid zone 3. In a triathlon, the first fifteen minutes always end up in the high 4s or low 5s, until my cardiovascular network re-routes the blood flow. I try to hold a perceived effort equivalent of mid zone 3 until my heart rate (HR) comes down to match. And, yes, it takes me a lot more than fifteen minutes to run a 10K. I am slow. For longer distances I aim for mid zone 2 (roughly 70% HRmax), and allow that to rise into 3 on hills. So, for this experiment I wanted to cruise in the mid 2s as much as possible and go as high as 4 on the long hard climbs, particularly Heartbreak Hill; no zone 5. This is harder than I usually ride.

I chose start our riding with Pattie as none of her usual ride group were doing the ride. She did great, made it all the way to Kaiser High School before peeling off to return home. (As it turned out she had a much longer day. I’ll let her tell that story.) At that point I was less than a mile from Heartbreak Hill. I knew I had to get my HR up before I reached the base of the climb or my body would go into shock at the sudden increase in effort. My average HR from the start of Lunalilo Home Road until the high school was 109, barely into zone 1, almost exactly 60% HRmax, what we use in spin class as our recovery rate. I managed to get up to 135 ( low 3Z) at the start of the climb and maxed out at 148 (mid 4Z) at the top. Perfect, and for the first time ever I passed more riders than passed me, by a lot. I was feeling really good. I was really shocked to see how slow everyone else was on the decent -- call me a mad man but I find time wherever I can, and I was flying down that hill.

For this ride I chose not to stop my timer at the aide stations, making more like a race. Remember, I was practicing for the marathon, not to mention future triathlons. I did stop at Sandy Beach because my water bottle was half gone and there was no more Waimanalo aide station. Unfortunately the water station was a thousand miles from the bike parking area and the water tasted like garden hose. Nothing to do but make the best of it.

On the way to Kailua I could not decide how to compensate for the slow initial pace. Should I push the pace to try and get back to my goal of 16, or start now to stay at 16? Should I try to maintain my gel consumption rate, or slow down? I decided to go as fast as traffic would allow, and slow down on gel consumption to match my time, until things evened out. There was no way I could measure my consumption accurately, anyway. I had marks on my bottle that represented a 6 oz flask, and my plan was to consume one flask (3 GU gels) every two hours. With luck, by the time I reached Swanzy Beach Park, the halfway point, my gel mix would be half gone, midway between the second and third tick marks.

Just in case the day got hot I brought along three SaltStick pills. Each one provides  215 g of sodium and  63g of potassium. The weather was cloudy but hot and humid, so in Kailua at the 25 mile point I took one, and planned to take one more at the halfway point.

By the time I got to Swanzy I had been on the road four hours. This is spite of going like a bat out of hell at every opportunity. The thing is, I felt great. Plenty of energy, no stomach distress or other negative signs. I was passing people all along the route, often hitting 18-20 MPH.

At that point I called my fuel experiment a success, even though it was not entirely over. I was feeling disappointed at being an hour behind plan and to keep reminding myself that was not important. My only complaints were that the wet roads had made me and my bike filthy, and I was starting to crave solid food. I know I was not low in calorie intake, it was just boredom. Gels are great, for awhile, but after four hours my body was craving a big juicy hamburger. I went to pee, just in case, and there was not much to deliver. I made a note to drink more water.

Around Valley of the Temples on a long slow climb my left hamstring decided it had done enough. One of those cramp onset events that does not quite take you down but forces you to back off and stretch as best you can. It was then that I remembered not taking my second salt pill back at Swanzy, so I took it and as much water as I thought I could tolerate. I had not bothered to stop at Waihee, so now my water supply was getting a tad low. A bit further up the road a couple of friends came along so I tried to stay with them. My hamstring had other plans. I throttled back and cruised to Kailua. 

It was there that I decided to break my fast, only to discover all they had left was bananas. It could have been worse, the potassium was potentially a good thing and easy on my stomach, so I had a handful along with a big slug of blue Gatorade and felt much better. 

With a full bottle of Gatorade on the bike I headed east. Just before the really steep climb out of Enchanted Lakes -- Keolu Drive -- my left hamstring gave up again. I kept going, but I knew I was running out of road, that in a hundred yards I would have to turn right and climb the steepest hill of the ride. I pulled over and spent several minutes stretching out the leg, still on the bike. As I started up the hill a rider ahead went down hard and I could tell that he had the same problem. He got right back up on his bike, went about ten feet and crashed again. Just then I rode past, slowly, and told him I had the same thing. I stopped for a bit more water and a walk around stretch at the park across from Sea Life Park, and again at the aide station in Hawaii Kai. Made it back to Kapiolani Park without any more drama, Eight hours instead of six, but I did not care at that point.

In the aftermath I decided to check my nutrition numbers, thinking that GU gels did not pack enough sodium. I had to do a lot of adjusting to get the values in the same units, which ended up with one cup as the standard amount.

I got these numbers from ProActive Nutrition

Sports Drink 8oz bottle (1 cup)

Brand - Calories - Sodium (g) - Potassium (g)
Cytomax 80 120 15
Gatorade 50 110 30
Gatorade Endurance 50 200 90

The one brand of sports drink that came in really low in sodium was Heed. Gatorade Endurance was on the high end. I asked at the Kailua aide station what we were getting as was told “Gatorade.” So it could have been either one.

A reasonable rate of consumption is one bottle per hour, with a bike bottle running 20-24 oz. That’s three servings of the above amounts.

For my fuel I used GU Mandarin Orange. The numbers for calories, sodium and potassium:

1 gel 100 60 35

3 gels per flask = 300 180 105

Intake rate 1 flask every 2 hours = 150 90 52 per hour

Had I been drinking Gatorade at the normal rate I would have been taking in 150 330 90 per hour.

Conclusion thus far: low sodium intake. But wait. I took three salt pills, the first one in Kailua. The numbers for those:

SaltStick -- 0 215 63

Zero calories but plenty of sodium and potassium. But what about the consumption rate? One pill per hour would just about equal Gatorade, but I only had three with me for the day.

So I started reading up on sodium and cramps. What I found is that despite a ton of conventional wisdom and advice from people I respect that low sodium is a major cause of cramps, the experts disagree. Yes, low sodium can cause cramps, but the entire body is affected and only after other severe symptoms have appeared. This is nothing like what athletes experience when they get a calf or hamstring cramp. The bare, honest truth is that nobody knows what causes exercise induced cramps. (see references below) 

The best guess as to what causes cramps is fatigue, and in light of that the best way to prevent cramps is to workout at the level that causes them, to allow the muscles to learn to operate at the required level of intensity for the required length of time. We usually think of training as being about getting stronger, but there is more to it than that. Our body needs to learn to endure.

This makes sense given my situation. I have done plenty of long runs and bike rides in recent months, but nothing lasting more than a three hours, and those bike rides were not at the intensity I was holding Sunday in the first four hours. So, on that basis I did very well. What I need to do is adjust my ride plan from now until the marathon to add some longer rides. Thank goodness I do not have to survive on gels for those!

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