by Mark Wolff

As a sports nutritionist, endurance & physiology expert with a deep understanding of how the body responds to energy and hydration requirements during endurance events, especially Comrades Marathon where I have had the opportunity to work with hundreds of amateur and professional athletes over the past decade, I know how crucial nutrition and training is. I have witnessed first-hand how it’s played the biggest role in the collapse and eventual breakdown of even the best of runners when they get it wrong.

Comrades 2018 is now over. One of the largest fields in the history of the race left some elated with their results and others wondering how the wheels fell off so quickly. I decided to write a blog to try to clarify and explain several pitfalls and possibly assist you in understanding where you could have gone wrong or how you can improve for the next year.

Let’s look at the Comrades Marathon route. A down run with plenty of mountains in the first half only to much later dip rapidly downhill to the coastal plain where the race profile is tamer than what was experienced in the first 50km’s.

The first aspect I always look at is pacing in the first half of the race. I was told by one athlete prior to Comrades that in the first half he was going to run quite a bit faster than his goal pace while his legs were fresh and then hang on for the second half. I told him that will never happen. Those awesome seconds he banked in the first half will be minutes if not hours in the second and any experienced Comrades runner knows that the dreaded down needs to be run conservatively in the first half.

Temperature Variance
One thing any down run Comrades runner expects is to freeze at the start and suffer the heat at the end. This year it was cold at the start not as cold as I have felt in previous years but cold enough to lower the sweat rates of the body and as the day progressed the temperature did not climb that high it stayed cool on route with a gentle cool wind blowing most of the day. Probably the lower of temperatures I have experienced on race route in the past ten years. Why is this crucial? Quite simple temperature plays a direct role in how the body will respond to hydration requirements to keep it cool. In hot temperatures there is direct response to heat where heart rate is elevated, and more fluid is lost in the form of sweat to aid the natural cooling system of the body. The hotter it is the higher the heart will perform at a given pace. In cooler conditions the heart rate will be lower, so perceived effort is lower allowing an athlete to sometimes push harder if he is using heart rate as a measure of effort. This is mistake number one and ties directly into the pacing above. I will use a simple example below to demonstrate what I mean.

Below are two running sessions I did with a sub 6hr Comrades runner in the beginning of the year while he was building for the big day.

The Strava segments below are quite straight forward. Both are controlled runs. The one on the left was a 25km run 221m of elevation at an average pace of 4:22. The average heart rate for this run was 163 BPM (Beats Per Minute) as shown in the heart rate chart below.  On the right side is a longer route of 30km with much more elevation and you will notice the pace for the 30km run was faster than that of the 25km run. However, the interesting part is that the slower paced shorter run with less elevation had a much higher average heart rate.  A difference of 8 BPM which is quite significant. Someone said its because you were fitter in the second run, but not, as these were a week apart and fitness doesn’t change that rapidly. The main reason is that the average temperature in the first run was hotter than in the second run. Temperature increase equates to higher heart rate, higher perceived effort which spins into the slower pace.


The above is purely a graphical representation of how at Comrades Marathon if you did feel like you were in control of the pace due to effort you might have gone slightly faster under cooler conditions without realising it as it was cooler on the day.  If this is the case and your muscles were not conditioned for the faster pace over time I can with absolute certainty say the muscles were going to fatigue earlier on and your race would be a sufferfest from that point on. You need to understand how temperature affects the body under stress and adjust pace accordingly this could be one reason for having a bad day out.

Pre-Race Fuelling
I have witnessed the most horrific fuelling strategies on race day and seen how sick people get on the course. The interesting thing is it all starts with the pre-race meal on the morning of the race. Firstly, the meal needs to be tried and tested and many runners suddenly do a switch on race day which can lead to major discomfort later.

Whether a low carb or high carb eater I always advocate a meal of around 1-4grams of carbohydrate intake per a kilogram of body weight around 1-4hrs before an event.  The lower end if you are a lower carb eater and only if you have tried and tested it you can go to the upper end but a higher intake closer to the 4hr mark and lower intake closer to the event. Secondly, we are talking very easily digestible carbohydrates, low in fibre so as not to irritate the bowels. I advocate protein intake as well for long events and would look at a 3:1 or 4:1 carb to protein intake and if you do consume protein then easily digestible lean protein (low to no fat) nothing heavy that would sit and create discomfort. I am not a fan of high fat intake prior to an event, it takes a long time to break down and it can lead to the onset of GI (gastric intestinal) distress during the race. At 2am each year I join the masses in the hotel breakfast room and watch with curious intent at what each person is consuming pre-race. I don’t look at it emotionally I look at it from a performance perspective. Very often I can see by what an athlete consumes whether they will have a bad day or good day out as that can be the first mistake they make on race morning. If you had a rough stomach day think back to what you ate on race morning. It might have been something simple like oats which you might have had before but the question then is which oats did they use? How did the cook it? In water or milk? If milk which milk low or high fat? How long before was it prepared? All these factors can influence a 90km trot. Best is to be prepared.

Race Fuelling
An ultra-marathon is tough. It’s tough on the body and tough on the mind. It’s a long journey which requires optimal fuelling. On Comrades day pace and preference will determine fuel intake. The elite athletes I work with will have liquid feeds on route as their airways need to remain open at all times to allow maximum oxygen uptake to support their efforts. The slower back packers can easily afford to chew or bite on food solids and often walks through water tables allow for this.

The two biggest mistakes in fuelling on race day are over fuelling and nutrient timing.  Let’s look at over fuelling first. Taking in too many carbohydrates during an endurance event can certainly lead to digestive discomfort, but it can also lead to nausea and dizziness. Finally cramping can be triggered by a glucose overload in that it can cause an overly hypertonic environment in the digestive tracts and mitigate optimal fluid uptake from taking place leaving the muscles depleted and in a very unhappy state. How many grams of carbohydrates did you consume per an hour on race day? I feel anything between 30-60grams is more than enough for a runner. Some athletes do go higher and anything on the high end will have to be tested way before race day to see how the digestive system copes with the volume of carbs consumed. It’s not about how many carbs you stick in your mouth but more about what the body is capable of absorbing and processing for use.  How do you prevent over consumption and still maintain a steady flow of energy and remain comfortable? It’s quite simple it’s about nutrient timing and it’s called drip feeding. Split the feeds into smaller more frequent meals over time to allow for the already stressed digestive system to absorb and use the intake without causing any havoc. Over and above that you will be shortening the peaks and troughs of the blood sugar rise and fall, and this will allow for a more balanced energy effect. So, when consuming a gel its better to go with a third to half of a gel every 20-30min as opposed to one gel every 45 minutes. The next statement I am going to make might upset a few runners, but a gel is not a suitable feed for a slow runner over a long period of time. We hardly feed the elite athletes gels on route, they prefer a more balanced approach to fuelling and try to combine the hydration and fuelling together by using various prepared solutions on route which start off more hypertonic in nature when cold and then slowly evolve to isotonic and hypotonic solutions when the temperatures climb later in the event. Options on route are a must as with weather conditions you never know what to expect over time. Comrades marathon isn’t primarily a glycogen fuelled effort but more of a fat tank fuelled effort and so I advocate fuelling accordingly to maximize fat oxidation. If you are not sure about the human fuel tanks used during sports performance, then check out my video on Getting into the Zone where I explain how they work.

Protein Intake
Did you take in protein on the Comrades route? I can promise you if you didn’t then the fatigue would have set in a earlier than an athlete that did take it in. In fact, all the front runner elite athletes we fed on route were mainly fuelled with a protein shake I made up specifically for them, including Bongmusa Mthembu the winner on the day. I used 32Gi Recover 2 scoops to 200ml of fluid with 95mg of caffeine in the form of TrueStart Coffee mixed into it. Why did I do that? Simple I want the runners to get in around 5-6grams of protein minimum per an hour with the carbohydrates in the mix. (check out my video on 32Gi Recover discussing the need for it during an event) Nutrient delivery is optimal, and the intake of protein can lead to the delayed onset of muscle fatigue by delaying muscle protein catabolization as well as keep any hunger at bay. On average an elite athletes will take in around 6-12grams of protein per an hour and around 20 – 50grams of carbohydrates and anywhere from 95-120mg of caffeine. What is interesting about this number is it’s not high at all and yet it’s perfectly suited to the winning performances we see every year. Most slower runners consume way more. The slower amateur athletes I did advise to consume protein on route at least at the 30-40km mark and then 50-60km mark all gave very positive feedback as to how it was a game changer for them on the day and how much they enjoyed the feeling of it. It certainly made a difference on the day.

Hydration to me is the more crucial aspect of Comrades Marathon in that you have sufficient fuel in your natural fuel tanks in the form of glycogen and fat to get you to the finish line and hydration will play an even more important role on the day. It is not possible to replenish all the fluid lost in the form of sweat during exercise, but we aim for an 80% replenishment. To do this water consumed on its own will not achieve this as it has a slower absorption rate than a mineral or isotonic carbohydrate drink. When I feed elite athletes, I do not allow pure water consumption unless it’s with some sort of a carbohydrate or mineral rich product which will help pull the fluid out of the digestive tracts into the system. I prefer a hypotonic drink as a means of hydration as it is designed to maximize fluid absorption. Drinking water on its own will sit in the stomach and take its time to get out if there is nothing assisting it. This can lead not just to stomach discomfort and a washing machine effect with fluid sloshing around inside, but it can also place strain on the kidneys and could ultimately be a trigger of hyponatremia (overhydration) which can lead to illness and in severe cases death. In our case we use 32Gi Hydrate for seconding which is a pure electrolyte solution with a decent sodium content to ensure rapid fluid absorption. (Check out my blog on Hydration to get more in-depth understanding)

Did you take in caffeine on race day? It can be in any form and many forget that even coke contains caffeine. So the low down on caffeine is such. Firstly it needs to be tried and tested, it is acidic and if you don’t tolerate it well it can cause digestive issues. Secondly caffeine is one of those stimulants that once consumed will metabolize over an approximate time of 60 minutes meaning that once you get the rise you will get the fall. If you start taking it in you need to keep taking it in prior to the 60 minute life, otherwise you will hit a downer. When taking in caffeine understand once you start you need to keep going. Some runners will take much later in the race when they need it and there are those that take all the way through. If you did consume caffeine early on but did not continue with it you might have felt the dreaded crash.

Every year on Comrades route nausea and cramps takes its toll on the masses of runners that haven’t practised proper fuelling strategies and have just read the packaging directions on a product. The problem is the packaging on a product does not know you are running a 90km run over so many hours and so it is of prime importance to ensure you have planned, tried and tested your fuelling strategies under various conditions before you get to race day to ensure you don’t land up in the pitfalls of the many that do.

If Comrades was a good day out for you that’s great and maybe you had everything properly planned or you did fall victim to some of the issues on race day and managed to overcome them. Possibly you can do much better next year with a better prepared and properly planned strategy to tackle the up run. If you were one of those that had a miserable day out I can pretty much bet, you were under prepared from a training and or nutrition perspective and this is your opportunity to think very carefully about how you can better tackle an ultra-event the next time you do.

In the meantime well done to all the finishers, recover well and yes this does require proper nutrition as well 😉. Get proper rest and begin an active recovery program when ready and make sure you plan better for next time.

All the best


Mark Wolff is a certified sports nutritionist and an endurance nutrition and physiology expert with over 20 years experience. An endurance multi-sport athlete with a triathlon, mountain biking and weight lifting background, he works extensively with professional and amateur athletes in a variety of sports disciplines as well as those just wanting to change their lifestyles. He firmly believes that a person can only reach their full potential when their health and nutrition is down packed. Mark’s focus on nutrition and physiology is not just on training and racing, but he places major emphasis on recovery, immune system health, emotional stability, stress management and performance. Mark is co-founder of 32Gi a sports nutrition company, focused mainly on health and endurance nutrition.



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1 comment

Luzuko Ntissa June 13, 2018 - 12:04 pm

Very comprehensive breakdown and interesting too.Could this strategy be applicable while one is still training?I am struggling with my weight.In my 9 Comrades I have 2 Bill Rowans,2012 and 2014,but since then I am not getting back to those performances.I think I need your assistance.


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