Olympic gold medal winners are physiological outliers per definition. But what truly sets these elite athletes apart from others? In this article we dive into the metabolic profile of Grace Brown, who won the female individual time trial in Paris.
The 32.4km course of the individual time trial (ITT) was virtually flat. As Italian’s national time trial champion, Vittoria Guazzini said before the start:
“I think this course reflects the main objective of the time trial, which is to go fast. There are long straights where you can push hard, and a few corners where you can perhaps recover a little.”
Olympic gold winner, Grace Brown covered the 32.4km course in 39:38.24, which requires an average speed of 49 km/h (!). But what physiological traits are necessary to achieve such an astonishing result?
To ride at such a high speed, Brown needs to maintain a high power output. Unfortunately there is no power data available. But we can estimate her power using advanced speed to power calculators.
The exact power number depends mainly on aerodynamics: the more aerodynamic you are, the less power you need for the same speed.
Aerodynamic drag is measured in CdA:
CdA mainly depends on body composition and bike position. Brown’s body length is 168 cm.
A typical time trial CdA ranges between 0.20-0.23. Given her body composition and time trial expertise, it’s fair to assume her CdA is close to the best CdA values. That’s why we assume Grace Brown’s CdA equals 0.21.
As a result, Grace Brown needed an average power of 335W* during the race (49 km/h). To put into perspective, INSCYD athlete Chloe Dygert won silver, pushing 310W (47.2 km/h). French National time trial champion, Juliette Labous became 4th, pushing 277W (47 km/h).
*Calculated using advanced speed to power calculators.
The highest female VO2max in cycling ever reported is 76.0 ml/min/kg (Flavia Oliveira). However, a typical VO2max of an elite female cyclist is more likely to range between 60-70 ml/min/kg.
Since an Olympic gold medal winner is probably at the high end compared to other elite cyclists, it’s fair to assume Brown has a VO2max of 72 ml/min/kg. A significantly lower VO2max seems unlikely, unless her aerodynamic drag is considerably better than our estimate.
The maximal anaerobic power is best quantified using VLamax, which is the anaerobic brother of VO2max.
Contrary to what you might expect, many successful professional time trialists have a reduced ability to produce energy anaerobically. That is because they don’t need to sprint or attack during their time trial.
While VLamax values typically range from 0.2 to 1.0 mmol/l/s, time trialists are likely to have a VLamax close to the VLamax of marathon runners and triathletes: 0.3 mmol/l/s. We assume Grace Brown’s VLamax is 0.28 mmol/l/s.
If the VLamax would be significantly higher, then she would produce (way) more lactate during the time trial. This would lead to an unrealistic high lactate concentration. To compensate for this, she would need to have a higher VO2max.
The anaerobic threshold is the intensity at which the lactate production (red curve in the image below) equals the lactate combustion (blue curve in the image below).
The INSCYD performance software is able to calculate Brown’s threshold, by looking at her maximal lactate production rate (VLamax) of 0.28 mmol/l/s, her VO2max of 72 ml/min/kg and her body composition.
Using these metrics as input, Grace Brown’s anaerobic threshold must equal 328W.
This means she rode the Olympic time trial at 102% of her anaerobic threshold, which makes sense for a 40 minute effort.
But how did Brown’s body respond to this high exercise intensity?
Riding above anaerobic threshold surely doesn’t mean all energy comes from anaerobic energy sources. In fact, the highest energy contribution at 102% of threshold still comes from the aerobic energy system.
The exact energy contribution at 102% of threshold differs vastly per athlete. As you can imagine, this can have a huge impact on time trial performances.
A metabolic profile gives you insight into your energy contribution. The INSCYD aerobic and anaerobic graph, reveals how Brown’s energy contribution looks like, at any given exercise intensity:
During the Olympic time trial in Paris, 91% of the 335W came from the aerobic energy system and 9% came from the anaerobic energy system. This directly affects the energy source (fat vs carbohydrates) used during the race.
Let’s see if carbohydrate availability was a limiting factor during the race.
Regardless of your body composition, everyone has enough fat stored in the body to finish a 32.4 km time trial course. But what about the more precious fuel: carbohydrates?
INSCYD can calculate the maximum amount of carbohydrates stored in the body (glycogen), based on an athlete’s body composition. With the estimated body composition of Grace Brown, it’s fair to say she has roughly 360 grams of glycogen available in her muscles.
But what about her carbohydrates utilization during the race?
The amount of carbohydrates burned at 2% above threshold varies greatly from one athlete to another. With a highly individual metabolic profile, you can start to understand which energy source your body uses, depending on the exercise intensity. You can use this to create a nutrition race plan.
Here’s the INSCYD fat and carbohydrate graph of Brown:
When she was riding at 335W, Brown burned 319 grams of carbohydrates per hour. This comes down to 209 grams of carbohydrates in total during the race. Since this doesn’t exceed the carbohydrate availability in the muscles of 364 grams, energy availability was never an issue for Grace Brown.
But what does limit the performance in a 32.4km time trial?
When riding above anaerobic threshold, lactate starts to accumulate. The rate at which lactate accumulates at 102% of threshold intensity, varies significantly for each athlete. Brown was able to maintain this intensity for 40 minutes, while others would “blow up” in no time.
The INSCYD lactate recovery and accumulation graph, shows exactly how fast the body accumulates lactate above threshold. It also shows how quickly an athlete can clear lactate below threshold.
At an Olympic race intensity of 335W, Brown accumulated lactate at a rate of 0.22 mmol/l per minute. With a finish time of 39:38.24, her blood lactate increased by 8.66 mmol/l. Assuming a resting lactate concentration of 1.5 mmol/l, Grace Brown finished with a blood lactate concentration of 10.16 mmol/l.
This is comparable with maximal lactate concentrations from performance tests (source), which can be seen as a confirmation of our assumptions. But what if we are wrong?
You could argue we made too many assumptions to describe the metabolic profile of Grace Brown. Admittedly, we didn’t use any direct measurements.
But what if one of our assumptions is significantly wrong? Say for instance her bike position is not as aerodynamic as we expect. If so, other metrics would need to compensate for that. This quickly leads to highly unlikely values.
For instance: if the aerodynamic drag (CdA) would be 0.23 instead of 0.21, the required power would increase from 335W to 367W. VO2max would need to increase from 72 to 78 ml/min/kg, to maintain the same lactate accumulation rate and therefore max lactate concentration. This quickly leads to unrealistically high VO2max results.
We’ve created the potential physiology behind Brown’s Olympic gold medal in the individual time trial in Paris. Here’s a summary:
Maximal lactate concentration: 10.16 mmol/l
You can create your own metabolic profile of Grace Brown using INSCYD’s virtual performance projection feature. Or better:
Create your own personal metabolic profile of your athletes, to better understand their (future) performance in the next race. You can use this metabolic profile to optimize training and racing.
Coaches and performance labs all over the world use INSCYD to get a clearer picture of the metabolic profile of their athletes. They leverage these insights to elevate their athlete’s performance and coaching/testing business. Get to know the INSCYD software via a free demo.
INSCYD provides a 360° metabolic profile of an athlete:
Clarity on Performance: Accurately measure and track key metabolic markers that limit athletic performance.
Customized Training: Identify the metrics that offer the biggest performance gains and tailor training plans to each athlete’s unique physiology.
Validate Effectiveness: Monitor the physiological adaptations of training programs using clear and actionable data.
Athletes why train with generic plans when you can have a program tailored to your unique physiology? INSCYD is the key to unlocking your full potential. Find your dedicated INSCYD coach or lab here.
Already have a coach? Experience INSCYD in action with your coach and redefine your training approach.
Human Movement Scientist | Content Marketing and Education
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