When Eliud Kipchoge crossed the finish line at the INEOS 1:59 Challenge in Vienna, he not only completed a marathon in under two hours but also shattered a seemingly insurmountable human performance boundary. What made such a feat possible? We’ve delved into the potential physiology behind the 1:59 Challenge, and the findings are astounding…

Eliud Kipchoge crossing the finish line

To cover a distance of 42.195 km in 1:59:40 equates to a speed of 21.2 km/h or, more precisely, 5.88 meters per second (m/s). For most people, achieving half that speed is an ambitious goal, enabling them to complete a marathon under the 4-hour mark.

Superior Running Economy

An average elite athlete requires about 12.5 – 13.0 ml/min/kg of oxygen for every 1 m/s of running speed to generate the energy needed for running at a specific pace. A portion of that energy, however, comes from anaerobic metabolism, which reduces the actual oxygen uptake below the total demand.

But Eliud Kipchoge is no ordinary elite athlete, and the INEOS 1:59 Challenge was far from an average race. That’s why we assume Kipchoge’s energy demand (or oxygen demand) for running 5.88 m/s was lower than in normal situations. Thanks to his superior running economy, we estimate a 0.2 ml/min/kg lower oxygen demand per m/s.

At such a high-end speed a significant part of the energy is needed to overcome aerodynamic drag (visible in the curvilinear shape of the oxygen uptake curve in figure 1). But because Kipchoge was paced throughout the length of the course, it seems fair to assume a reduced aerodynamic drag and — therefore — a reduced energy or oxygen demand for his effort. We can therefore assume that the curvilinear factor of this particular running economy is at least 20% lower, resulting in a 6% lower oxygen demand at 5.88 m/s.

At such top speeds, a significant portion of energy is needed to overcome aerodynamic drag (visible in the oxygen uptake curve’s curvilinear shape in Figure 1). However, since Kipchoge was paced throughout the course, it’s reasonable to assume reduced aerodynamic drag and, consequently, lower energy or oxygen demand for his effort. We can therefore estimate that this particular running economy’s curvilinear factor was at least 20% lower, resulting in a 6% lower oxygen demand at 5.88 m/s.

That’s why we can assume Eliud Kipchoge’s total oxygen demand was not 75.4 ml/min/kg but only 70.0 ml/min/kg (see Figure 1).

Fig.1: Oxygen demand comparison between an average elite runner (navy blue dashed line) and Eliud Kipchoge in the INEOS 1:59 challenge (navy blue solid line). We assumed that, due to the drafting effect, the energy increase required to overcome air resistance as a function of speed is reduced by 20%

Kipchoge's Physique: Exceptional VO2max and VLamax

Elite runners often exhibit a negative correlation between running economy and VO2max, as reported in scientific studies. These athletes typically don’t register a VO2max above 80 ml/min/kg, with values around 75 ml/min/kg being more common among marathon runners.

In our case here, though, we assume a VO2max of at 78.0 ml/min/kg. Eliud Kpichoge is an outstanding athlete and it seems fair enough to consider his VO2max rather at the high end compared to his peers. A VO2max significantly lower than this seems unlikely, unless the running economy is significantly better than we have considered above.

However, we assume a VO2max of 78.0 ml/min/kg for Kipchoge. He is an extraordinary athlete, and it seems fair to consider his VO2max on the higher end compared to his peers. A significantly lower VO2max seems unlikely unless his running economy is considerably better than our estimate.

Highly trained endurance athletes have a reduced ability to produce energy anaerobically through the glycolytic pathway. A high anaerobic—or more precisely, a high glycolytic—energy supply isn’t necessary for endurance events like marathons.

The glycolytic counterpart of VO2max, the VLamax, is a common marker to gauge the glycolytic energy production rate. The VLamax of such athletes typically ranges between 0.2 to 0.4 mmol/l/s of maximum lactate production.

To maintain a speed of 5.88 m/s for two hours, Kipchoge’s VLamax shouldn’t be significantly higher than 0.25 mmol/l/s. A considerably higher VLamax would mean a better-developed glycolytic system, leading to more lactate production.

The marginally higher lactate production itself may not significantly impair performance. However, lactate is a C3 molecule resulting from glucose breakdown. Thus, an increase in lactate production also implies an increase in glucose demand, which does negatively affect performance.

A VLamax significantly higher than 0.25 mmol/l/s would necessitate either a considerably higher VO2max and/or a much lower total energy demand (further improved running economy).

The Fuel: Glycogen and Carbohydrates

We assume that Eliud Kipchoge’s body weight was around 52 kg on race day. Since all metrics used here are expressed per kg of body weight, a slightly higher or lower body weight has minimal impact.

Furthermore, we also assumed that he has approximately 43% muscle mass in his body, of which he uses 75% while running. This results in an active muscle mass of approximately 16.8 kg contributing to his locomotion. In highly trained athletes, one kilogram of muscle mass stores around 25g of glycogen. That means Kipchoge began the race with a store of 420g of glycogen in his body.

As it can be seen in the race footage, Kipchoge was constantly given drinks during the race. That suggests he managed a carbohydrate intake of at least approximately 20-40g per hour. Hence, the total carbohydrate availability (stored glycogen plus exogenous supply) sums up to approximately 480g. For a two hour effort, this means that his combustion rate should not exceed 240g of carbohydrates per hour.

As seen in the race footage, Kipchoge was continuously given drinks during the race. This suggests he managed a carbohydrate intake of at least approximately 20-40g per hour. Consequently, the total carbohydrate availability (stored glycogen plus exogenous supply) amounts to approximately 480g. For a two-hour effort, this means his carbohydrate combustion rate shouldn’t exceed 240g per hour.

Learn more about creating fueling and pacing plans using carbohydrate combustion rates via this article: How carbohydrate combustion determines pacing and fueling (whitepaper included!)

Are you fascinated by the exceptional physiology and performance secrets behind Eliud Kipchoge’s record-breaking marathon? Unlock similar insights for your athletes and elevate their performance. Equip yourself with cutting-edge knowledge and stay ahead of the competition. 

Discover the insights that made Kipchoge’s record-breaking performance possible and apply them to elevate your athletes’ performance. Book your free 1:1 consultation with INSCYD’s team of experts in your own language now! Secure your spot before it’s too late, as slots are filling up fast. Don’t miss this unique opportunity to enhance your coaching strategies and stay ahead of the competition. 


In summary, for this case study, we assume:

  • A body weight of 52kg, 16.8 kg of this being active muscle mass

  • A total glucose availability of 480g (stored glycogen plus intake during the run)

  • A reduced energy demand for running, because of an above average running economy and because of the effect of being shielded by other runners

  • A VO2max of 78 ml/min/kg

  • A VLamax of 0.25 mmol/l/s

In the scenario described here, the average speed of 5.88 m/s is equal to a remarkable 97% of the anaerobic threshold (6.01 m/s). Or perhaps even more striking: a utilization of 92% of our virtual Eliud Kipchoge’s VO2max.

The key to this high utilization is the low capacity of his glycolytic system (VLamax). A relatively weak glycolytic systems means that the organism can rely primarily on fatty acids as a fuel at a moderate speed. Significant carbohydrate combustion rates are shifted to higher speed, closer to VO2max. In our case here, at a speed of 5.88 m/s the carbohydrate combustion rate is 221 g/h. As described above, the maximum possible carbohydrate combustion rate was 240g/h without “bonking”.

The key to this high utilization is his low glycolytic system capacity (VLamax). A relatively weak glycolytic system means that the organism can primarily rely on fatty acids as fuel at moderate speeds. Significant carbohydrate combustion rates are shifted to higher speeds, closer to VO2max. In our case here, at a speed of 5.88 m/s, the carbohydrate combustion rate is 221 g/h. As mentioned earlier, the maximum possible carbohydrate combustion rate was 240g/h without “bonking.”

Fig.2: Carbohydrate combustion at 5.88 m/s equals 221 g/h for our virtual Eliud. As calculated in the fuel section, the maximal carbohydrate combustion rate was 240 g/h.


You may argue that this is all theoretical and involves too much guesswork. In fact, we didn’t use any directly measured and validated physiological facts of Kipchoge to confirm the assumptions made here.


If any of the metrics of the real Eliud Kipchoge were significantly different from what we have used here for his virtual avatar, the other metrics would need to compensate for that change and may easily drift into a highly unlikely range.

Here are some examples:

1. Less aerodynamic advantage?

Let’s assume that Kipchoge’s pacemakers did not reduce his aerodynamic drag efficiently. In this case, his oxygen demand would increase to 74.2 ml/min/kg. At a speed of 5.88 m/s, his carbohydrate combustion rate would have jumped from 221g/h to 302 g/h. As described above, this is clearly above his limit, which is likely in a range of 240g/h. Without the drafting effect, the speed at the same assumed carbohydrate combustion rate of 221g/h would have dropped from 5.88 m/s to 5.64 m/s, resulting in a finish time of 2:04:41 instead of 1:59:40.

It turns out that the reduction of the air resistance Eliud experienced may be the key element to breaking 2 hours. A 10% reduction in aerodynamic drag results in a reduction of oxygen cost of approximately 2.2 ml/min/kg. The drafting may have provided an advantage of approximately 5 minutes.

2. A lower VO2max?

Let’s assume his VO2max was only 75 ml/min/kg instead of the assumed 78 ml/min/kg. In this case, the carbohydrate combustion at 5.88 m/s would have jumped to 270 g/h, again making it unlikely that he would be able to sustain this speed because the combustion rate would be well above the maximum glucose availability.

Only if his energy demand is decreased further (better running economy) would a VO2max value significantly below 78 ml/min/kg become possible. The assumed reduction in air resistance by only 20% is a rather conservative estimate. If the V-formation of his pacemakers provided a bigger aerodynamic advantage than assumed here, it would actually open up the opportunity for an even faster marathon time, because VO2max values significantly higher than 75 should be within reach. Hence, if combined with a similar great running economy, this could result in faster times.

Figure 3: Carbohydrate combustion rate with a VO2max of 78 ml/min/kg (solid line) vs. carbohydrate combustion with a VO2max lowered to 75 ml/min/kg (dashed line). At the average race speed, the combustion rate increases from a most likely sustainable rate of 221g/h to 270 g/h.

3. A higher VLamax?

The assumed glycolytic lactate production of a maximum of 0.25 mmol/l/s is on the low end of what has been measured in highly trained endurance athletes. A higher VLamax of 0.3 or even 0.35 mmol/l/s seems unlikely: Such a high VLamax would have increased the carbohydrate combustion from 221 g/h to 272 g/h. If Kipchoge were able to take in 90 g/h of carbohydrates, such a high combustion rate of glucose might be possible, but such high carbohydrate rates seem unlikely in running.

Create your own RESULTS

We’ve delved into the potential physiology behind Eliud Kipchoge’s 1:59 Marathon at the INEOS 1:59 Challenge, and the findings are astounding. Here’s a summary of the key factors that contributed to his groundbreaking performance:

  • Superior Running Economy: Kipchoge’s exceptional running economy allowed him to maintain a lower oxygen demand per m/s, contributing to his ability to sustain a high pace throughout the marathon.
  • Exceptional VO2max and VLamax: Kipchoge’s estimated VO2max of 78 ml/min/kg and VLamax of 0.25 mmol/l/s further demonstrate his unique physiological profile as an elite athlete.
  • Efficient Fueling Strategy: Kipchoge’s well-executed fueling strategy, which included both stored glycogen and carbohydrate intake during the race, allowed him to maintain a sustainable carbohydrate combustion rate.

Eliud Kipchoge’s incredible performance has shown us the potential of human physiology and the power of science in pushing the boundaries of what’s possible. Now is the time for you as sport coach and lab to leverage these insights and elevate their athletes’ performance to new heights.

Secure your free 1:1 consultation with INSCYD’s team of experts in your own language. Act now, as slots are filling up fast! Don’t let your athletes miss out on the opportunity to benefit from the expertise that helped Eliud Kipchoge make history. Book your consultation today and embrace the future of sports coaching. Time is running out, so secure your spot before it’s too late!

Do you want to create your own virtual Kipchoge? Or do you want to see what parameters would need to change in your athletes to reach their goal? Use our virtual performance projection feature.

Or create your own pacing and fueling plan, using the carbohydrate combustion graph. Here’s how (whitepaper included)!

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