Why Individual Athlete Profiles Are Essential

Every runner is different.

Sometimes this is clearly visible in external physical characteristics such as anatomy, anthropometry, and the functional properties of muscles, tendons, and joints. The difference between sprinters and marathon runners is usually easy to distinguish, even for an outsider. Yet even within the same category of runners, in this case marathon runners, there are more differences than you might notice at first glance. To see these, you need to look 'under the hood' of the runner, so to speak. Every runner essentially has their own profile.

Two runners with the same marathon personal record can score completely differently at shorter distances, such as the Half Marathon or their 5km. This is because marathon performance depends on multiple physiological variables, including:

• Aerobic Threshold (AeT)
• Critical Speed (CS)
• vVO₂max
• Fatigue resistance

Brief explanation of these 4 'Key Performance Indicators' (KPIs) for the marathon

AeT (Aerobic Threshold)

Marker of low-intensity efficiency and fat oxidation capacity.

CS (Critical Speed)

Functional boundary between being able to sustain a 'steady state' for 30 minutes or not.

vVO₂max (velocity at VO₂max)

Representative of maximum aerobic capacity. In the REN app, we use the 6min 'all out' test as a practical application to estimate vVO₂max.

Fatigue Resistance

Ability to maintain a certain running speed for a long time without significant decline due to peripheral or central fatigue. In other words: the extent to which there is a certain loss of KPIs 1 through 3 after a certain amount of work has been performed. E.g.: your CS is 4'00"/km at the beginning of training, but after a 2h00 long run it 'drops' to 4'10"/km.

Crucial: The relationship between AeT, CS, and vVO₂max differs per athlete

This depends on:

• Training experience
• Muscle fiber type
• Metabolic profile (fat vs. glucose utilization)
• Anaerobic capacity
• Running technique and efficiency

This means that the same marathon time can result from completely different 'KPI-profiles' (key performance indicators).

Practical Example: Three Profiles of 3h00 Marathon Runners (pace: 4'15"/km)

Profile	10km time	AeT	CS	vVO₂max	Fatigue Resistance
A	36:00	4'40/km	3'45/km	3'25/km	Moderate
B	38:00	4'30/km	3'55/km	3'40/km	Good
C	40:00	4'20/km	4'05/km	3'55/km	Excellent

Profile A: The fast 5/10km runner with moderate efficiency
Profile B: The all-rounder with well-balanced thresholds
Profile C: The diesel with extreme endurance capacity

Why These Differences Matter

Training

For long-term performance development, the training strategy must target the weakest element.

• Profile A benefits from better fatigue resistance and needs to invest in making the engine more efficient. Training at AeT and increasing training volume will further develop their 'Aerobic System'.
• Profile C needs to improve vVO₂max or speed to enable further growth.
• Profile B is well-balanced and should use smart periodization to improve all KPIs incrementally.

Strategy for energy intake during exercise

This differs per profile.

• Profile A burns more carbohydrates per km and needs more CHO intake (gels and sports drinks).
• Profile C runs more economically and a lower intake suffices.

Training Intensity

Determine the correct training intensity per KPI, depending on the athlete profile. Profile C can complete their long runs at higher pace. Profile A faces significant risk doing this.

Training Volume

Profile C can tolerate much higher training volumes.

Recovery

Profile A recovers more slowly from the same key sessions for the marathon due to higher 'metabolic stress' and higher carbohydrate consumption. By 'metabolic stress' we mean the stress that arises from the release of metabolites as a result of the high contribution from glycolysis. Additionally, there are elevated concentrations of stress hormones.

How REN Handles This: Training at Three Thresholds

This is why REN works with three separate thresholds: AeT, Critical Speed, and vVO₂max pace. Traditional training methods often use training zones that are all derived from a single measurement point, for example Critical Speed or lactate threshold. The problem is that this loses the individual relationships between these physiological markers.

In Profile A from our example, the AeT is relatively far from the Critical Speed (4'40/km vs 3'45/km - a difference of 55 seconds). If you were to derive his AeT training from his Critical Speed, you risk these 'easy' runs being executed too hard. He would then not be training optimally for fat oxidation and aerobic efficiency, but would unintentionally creep toward an intensity that relies too heavily on his glycolysis.

For Profile C, on the other hand, the AeT is much closer to the Critical Speed (4'20/km vs 4'05/km - only 15 seconds difference). His long runs can therefore be relatively much faster than those of Profile A, without him leaving his optimal training zone.

By determining and training each threshold individually, REN ensures that:

• Your AeT training is truly executed at AeT intensity
• Your CS training actually improves your critical speed
• Your vVO₂max work truly trains your maximum aerobic capacity
• Each training intensity works purposefully on improving the right physiological capacity

This prevents you from systematically training too hard or too easy for the intended goal, simply because your physiological profile deviates from the 'average'.

Conclusion: Don't Just Look at the Output, Dare to Look 'Under the Hood'

Behind every marathon time lies a unique physiological profile. By understanding how AeT, CS, vVO₂max, and fatigue resistance relate to each other, you can:

• Choose the right training emphasis
• Set realistic expectations
• Apply targeted nutrition and pacing strategies
• Avoid blindly training based on what works 'on average'. Work individually instead of following a specific 'method'.