On July 14, 2012 I raced in my seventh Knee Knackering North Shore Trail Run. It’s almost an annual tradition for me and one of my favourite ultras because the challenging course provides lots of technical trail with almost no flat sections. It involves 8,000′ of climbing and 8.300′ of descending over 30 miles. Woo-hoo!!!
In most years the weather is great though some years it can be hotter and more humid than usual. Such was the case in this year’s race.
All things considered my training had gone fairly well and I felt pretty prepared for the race. The biggest concern was that we had a very cold spring in Vancouver so we never really got to train in the heat and race day conditions were going to be a shock to the system.
I was also asked by a sports supplement company, H2ProHydrate, to test out their product during my training and racing. Basically they provide sodium replacement tablets. However, unlike other sodium drinks they have a medical grade testing procedure that measures your sweat rate so you can calibrate the proper amount of sodium to match it.
They provided some evidence (which you can find on their site) how their product had helped relieving cramping issues with some athletes. But as far as I know the results of their in-house testing hasn’t been published in a peer-reviewed journal.
Anyway I was going to conduct my own experiment of one and see how I responded. And this year’s race conditions were going to be the perfect training lab.
Sodium, Dehydration and Cramping
In a previous article on cramping, I noted that dehydration or electrolyte depletion were not causes but that some sort of nervous system dysfunction was most likely the culprit.
I met the H2Pro reps with an open mind and listened to the thinking behind the product development. Given my previous research into the matter I was skeptical of their claims that sodium deficiency was the cause of muscle cramps but nonetheless I thought what the hell, I might as well try their product and see what happens.
Coincidently at the time I was contacted by H2Pro, I was also reading Dr. Tim Noakes’ (author of the best-selling book The Lore of Running) recently published book, Waterlogged: The Serious Problem of Overhydration in Endurance Sports.
I was familiar with some of Noakes’ previous writing on hydration and this book complied all his latest data as well as his critical evaluation of the science promoted by the sports drink companies. If you’re a semi-serious runner or endurance athlete I highly recommend you give this book a read.
The gist of Noakes’ advice is that dehydration, even up to losing up to 5% of your bodyweight in short term events like marathons or ultramarathons, isn’t really a problem. And cramping isn’t caused by electrolyte or specifically sodium depletion.
Noakes recommends that during endurance events to simply drink according to your thirst. While you may get dehydrated you’ll avoid a more serious condition called exercise-associated hyponatremia (EAH) that could be potentially fatal. EAH is caused by drinking too much fluid and diluting the sodium levels in your blood to extremely low levels.
The book details measurements of top runners who have won races or set world records which showed they had lost up to 4 – 6% of their bodyweight due to dehydration. If the commonly held belief that 2% or more dehydration impaired performance then these runners must be unique. However, Noakes goes on to explain from an evolutionary perspective why humans are designed to operate in events under 24 hours while dehydrated.
Noakes also provides solid evidence that electrolyte status isn’t a cause of cramping. Measurements of thousands of runners and triathletes has shown no difference between crampers and non-crampers in terms of electrolyte status. In fact, some non-crampers had lower levels of sodium and other electrolytes than the crampers.
My Race Preparation and Cramping
Back to my experiment of one, I used the H2Pro tablets in the amounts that matched my sweat rate during training. The recommendations were to use the sodium amount appropriate to your sweat rate and to drink according to thirst. I followed their directions and things were going well until one particular 4-hour run.
The run included a 15 km climb of 3000′ or so and a similar descent. By the 3.5 hour mark we were bushwhacking looking for a new trail and hit some snow. Running for a short section on the snow my adductors (inner thigh muscles) were on the verge of cramping.
This wasn’t an unfamiliar situation for me. In the 2011 Knee Knacker race, there was a lot of snow in the first quarter of the course. Shortly after passing the 1/4 mark, my adductors starting cramping and gave me grief the entire rest of the race. Needless to say that didn’t make my 2011 experience much fun.
My adductor muscles are probably my tightest muscles. This training run was a wake-up call that I should be taking a closer look at preparing them so I didn’t have a repeat of last year’s race.
Having followed the product recommendations, if sodium depletion was a cause of cramping I shouldn’t be experiencing them.
Fast forward to race day and the hot, humid conditions. I had done some mobility and range of motion work on my adductors over the previous four weeks to prepare them for race day and continued to use the H2Pro sodium pills in training and would use them for the race.
I felt my fitness level was good enough to attempt a 6 – 6:15 finishing time. My race plan was not to go too hard in the first half yet I knew I’d probably still have a faster first half than second. But the goal was to minimize the difference between the two.
Even though I was holding my pace in check I still came across the first quarter check point in first place for the men’s 40-49 category. I was surprised by this and didn’t think it would last as there are usually some fast guys in this age group.
But a little while after this point, in almost the same place as the previous year, my adductors began to send signals of being on the point of seizure.
This happened to be near the top of the major descent in the second quarter of the race course. The first arrow in the diagram below indicates the general vicinity.
Running Form and Cramping
Unlike the previous year, I couldn’t blame running on snow as the cause for my adductors to cramp. But I wasn’t about to let cramps start again this early in the race as I was until this point, right on target pace.
The hints of cramping began near the top of the downhill. As I ran I noticed that I had really increased my stride length as the downhill section began. I consciously shortened my stride length and landed with a more flexed knee position. This proved to be the saving grace as all signs of cramping disappeared…for now.
By the time I came to the halfway point (middle of the graph above, the lowest point after the long descent) I was now in second place in the men’s 40-49 category. My buddy Scott Riddell, a terrific downhill runner, had caught me on the downhill but I was still on target for my goal time and crossed mid-point of the race in 2:55:06.
The second half was a much different story. The temperature continued to climb and my pace slowed dramatically. But it wasn’t solely due to the weather. In the third quarter of the race, as indicated by the second large arrow in the elevation profile, my cramping issues amped up big time.
There was a specific pattern to the cramping. It primarily occurred in my adductors, though a few times my hamstrings cramped as well, and it would take place during abrupt changes in the slope of the trail. For example, if I had just finished a section of running downhill and then began going uphill my inner thighs would cramp. Same thing going the other way (uphill to downhill).
I had continued to use the H2Pro tablets as recommended but this had no effect on the cramps. In addition I was drinking plain water and Coke at every aid station. Not too much but enough to satisfy my thirst. I wasn’t taking in as many calories as I had planned but tried to keep eating what food I could. Potatoes, watermelon and bites of energy bars provided my calories.
The cramps would last anywhere from 30 seconds to several minutes during which I’d have to slow down and walk or sometimes stop until the cramp lessened or went away. In addition to the physical pain this was also draining mentally so I’m sure that was a major factor in my pace slowing.
By the time I crossed the last major checkpoint at the 3/4 mark in the Seymour LCR I wasn’t sure what my placing was and I didn’t really care. I knew my goal of finishing between a 6 and 6:15 was shot but was hoping to still make it in under 6:30.
About 20 minutes after passing the Seymour LCR aid station I caught up to my buddy Scott. He was having cramping issues as well and could only walk at this point. I wished him well and hoped he’d be able to run again soon but I kept going.
During this last quarter of the race the cramps would still come and go but I could maintain running for longer stretches as the terrain wasn’t quite as undulating as the previous section. I did have some major cramping after finishing the last major climb and beginning the last, long descent as indicated by the last arrow in the elevation map.
Normally in the last 3 – 5 km of the race I can speed up again and have a relatively strong finish but this year I couldn’t muster enough energy for a strong finishing “kick”. I could only maintain a hobbling running gait even on the downhill sections which are usually my strong point.
Coming down the final half-mile into Panorama Park I knew finishing in under 6:30 was going to be very, very close. I spotted my wife with our 2-year old daughter a couple of hundred metres before the finish line. I picked up my daughter and ran carrying her to cross the line in 6:29:23!
I was surprised to later find out that was good enough for 3rd in the men’s 40-49 age group. In most years the third place time is much faster.
But it seems many racers found the conditions tough this year as the median finishing time was the second slowest in race history, the finishing rate was the second lowest as well and far fewer Personal Bests were set than in most years.
Post Race Analysis
Speaking to a number of other runners, they experienced similar cramping issues to mine. They would cramp severely when there were abrupt changes in the slope of the trail and the runners were forced to switch from uphill to downhill running or vice versa.
If cramping were simply the cause of dehydration then the change in terrain shouldn’t have had such a correlation to the onset of cramps. However, if cramping was in fact due to some dysfunction in the nervous system then the abrupt change in running gait to match the conditions of the trail would provide a reasonable explanation.
Golgi Tendon Organs (GTO’s) are receptors found in muscle cells that sense the strength of muscle contractions and cause the muscles to relax when that contraction becomes too strong. According to the nervous system dysfunction theory, GTO function is inhibited while the actions of muscle spindles (another type of receptor in muscles that causes muscles to contract) is increased.
GTO function is also further limited when muscles are contracted in a shortened position. During running when you lift your leg, the adductor muscles shorten. If you have tight adductors like I do this “inner range”, where the muscles feel like they’re already shortened, is increased.
So in my experiment of one, I believe it is this malfunction in the nervous system, due to fatigue and the tightness of my muscles that caused the cramping.
If cramps were solely due to dehydration then I wouldn’t expect the cramping to be so isolated to my adductors and partly my hamstrings. I would expect there to be major cramping in my quads, calves and hip flexors.
Likewise if electrolyte depletion was the cause. And this year I was using a sports drink that supposedly provided the exact amount of sodium I needed so I shouldn’t have been sodium depleted.
The take away for me is that I need to continue to work on the flexibility of my adductors. But this means more than just stretching. They need to be able to go through a decent range of motion while under load as this is how they work in the real world.
In the end, I believe Noakes is correct in his hypothesis. Cramps don’t happen because of dehydration or electrolyte imbalance (at least not exercise induced cramps). Cramps occur due to a dysfunction in the nervous system. Following a training program to properly adapt and prepare for the race conditions is needed to prevent cramps.
