Sports Performance, VO2Max

What we learnt from 750 fitness tests (2): Power, Endurance and VO2Max

[In Part 1 of this analysis of over 750 fitness tests conducted on Revvo, we looked at how metrics of overall fitness (VO2Max, Recovery) correlated with activity, weight and other demographic indicators.]

In this second part, we’re taking a deep dive into some of the performance metrics we collect on Revvo, to better understand how they correlate with each other.

MAX POWER (ANAEROBIC CAPACITY)

Max power is the maximum cycling output, measured in watts that an individual can produce on average over 30 seconds (called a Wingate protocol) and is considered one of the best ways to measure anaerobic capacity / output. I think of this as “sprint power”.

Revvo measures max power by guiding the individual step by step through a ~15 minute fitness test where the target increases progressively until the person reaches exhaustion. (Click here to see how the test works).

Max power was pretty well distributed across the 750+ tests and centered around 300-400w – with men producing on average ~100 watts more than women. Gender differences in max power persisted even after correcting for weight (men produced 5.1 watts / kg on average versus women who produced 4.4 watts/kg) and might reflect underlying differences in fitness levels and body composition.

 

 

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VO2Max and Max Power

VO2Max had a strong positive correlation with max power – both in absolute terms and particularly when adjusted for weight (max power in watts / body weight in kg). Higher aerobic capacity could therefore create a strong foundation to help maximize anaerobic output.

 

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Its also well established that high intensity (anaerobic) interval training is very effective at improving VO2Max. Tabata et al studied the effects of moderate intensity endurance and higher intensity interval training on both VO2Max and anaerobic capacity. The study found that high intensity interval training increased both metrics significantly, whereas moderate intensity endurance training only increased VO2Max (to a lesser degree).

So while VO2Max could improve without increase in anaerobic capacity, it seems likely to improve more when anaerobic capacity is also simultaneously targeted/increased.

Weight and Max Power

Does body weight make a difference to your max power output? Other things being equal, the heavier you are the more power you should be able to produce on a cycle due to sheer gravitational effect. And that’s what the data shows – max power in absolute terms increases with body weight.

 

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However, max power per unit of body weight declines with increase in weight — i.e. heavier you are, less the power produced per unit of your body weight. And max power / kg is a better indicator of performance on the road, particularly when going uphill.

Recovery and Max Power

Could your state of recovery affect your max power output? Turns out it does – doubling your recovery (e.g. from ~5%, which is low to about 10%, which is good), increases max power by around 0.25w/kg – which can make all the difference in a competitive sprint.

Max Power X Recovery

THRESHOLD (ENDURANCE)

Revvo detects the lactate threshold by analyzing the heart rate response to different levels of stress as the individual progresses through an intermittent ramped cycling test.

Lactic acid is produced as a by-product when muscles use glucose as fuel, creating the familiar sensation of “burn”The lactate threshold is the highest intensity at which you can tolerate the amount of lactic acid being produced and can therefore sustain. As a result, the threshold has a ~90% correlation with endurance performance.

Web graphics 3 ThresholdAt intensities above the threshold, there is excess lactic acid produced, slowing you down when you cannot tolerate the “burn” anymore.

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Based on the threshold watts per kilo of body weight, cyclists are typically classified into the following 9 categories. Where Pro are typically national champions and elite are world class.

 

 

The distribution of the Revvo sample is below — with a good spread from Cat 3 (experienced cyclists) to novices.

Threshold Distribution

Threshold and VO2Max

How does VO2Max impact the lactate threshold — in theory the two are semi-independent. High VO2Max is a necessary but not sufficient condition for endurance performance.

And the results confirm that — there is a positive but weak correlation between VO2Max and threshold in absolute terms. The correlation does strengthen when we consider threshold watts / kg but this is still not as high as that between VO2Max and Max Power.

 

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The implication from a training perspective is to focus on the factor that is relatively weak — improving that will deliver the biggest bang for your effort. And to polarize training (mid of high intensity interval training and moderate intensity endurance training) so that is able to target these two systems more directly and effectively.

Threshold and Weight

The relationship between threshold and weight is very similar to that between max power and body weight. In absolute terms threshold output increases with body weight but threshold watts/kg declines fairly significantly as weight increases. A 25lb. increase in body weight is the equivalent of dropping one category in terms of threshold output.

 

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Threshold and Recovery

Low recovery clearly dampens threshold output, very similar in magnitude to the effect on max power.

Threshold X Recovery (2).png

MAX POWER AND THRESHOLD

Cycling is a sport that requires both endurance and power (to take on hills) – elite cyclists need to develop both capabilities. So not a surprise that there is a pretty high correlation between the two.

Threshold X Max Power

SUMMARY

Traditionally, studies on performance metrics have been conducted largely amongst population of well trained athletes and as such its hard to see much divergence in these metrics across populations that have been training for long periods of time.

The Revvo sample on the other hand reflects a much broader range of individuals and therefore we are able to see how these metrics perform in less trained individuals / closer to their natural state.

From the perspective of an amateur endurance athlete in particular, it seems very likely that different individuals (even with similar performance levels) may have very different physiological make-ups. And understanding the underlying physiological make-up would allow you to customize the training program — so you’re targeting the area of greatest personal opportunity for improvement.

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Definitions

What is Fitness ?

I was inspired to create this blog by a recent Show & Tell I did at Quantified Self Boston – sharing data on how I normalized my blood pressure by measuring & improving my fitness. And it seems pretty clear to me that while most people talk about wanting to be fit, very few have actually measured their fitness (or even realize that this is measurable!).

So I decided to pull together some of the resources I was familiar with into one place so that others interested in understanding, measuring, tracking and improving their fitness would find it easier.

We often use fitness in the context of “looking fit” (and I’m guilty of this as much as anyone else). However fitness is not about how much you weight – in fact you can be both fat & fit (though of course if you’ve been sedentary for a while you’re likely to put on weight & lose fitness).

Fitness is also not about how active you are – being active can of course help you stay fit or even improve your fitness but this is by no means a given. The impact on your fitness varies considerably by the type of activity / training you engage in and we will touch upon this in later posts.

Fitness often also tends to imply or suggest muscle strength & endurance. Undoubtedly this important and is often described as “functional fitness”. However for the purposes of this blog and in the interests of creating a common understanding of the term I’m going to separate fitness from muscle strength.

So What is Fitness?

In scientific terms, fitness is shorthand for “cardio-respiratory fitness” – i.e. the ability of the body to supply oxygen to muscles when they become active. (See Wikipedia for a more detailed definition). Another word for this is aerobic capacity. As your fitness improves your arteries & capillaries expand so that your heart can pump more blood (each time it beats) and supply that to the muscles to fuel activity. So in simple terms, the fitter you are – the faster you could run or cycle (though there are other factors that influence your performance including motivation, efficiency etc.).

But the really interesting evidence about fitness relates to its effect on overall health & wellbeing – according to a recent policy statement published by the American Heart Association (Kaminsky et al, The Importance of Cardio-Respiratory Fitness, 2013), fitness:

… appears to be one of the most important correlates of overall health status and a potent predictor of an individual’s future risk of CVD. Besides being perhaps the strongest predictor for CVD and total mortality, CRF (i.e. cardio-respiratory fitness) is also strongly associated with other important health and functional outcomes, including depression and dementia, and their related mortality risks, as well as mortality rates attributable to various cancers, especially of the breast and colon/digestive tract.

In simple terms – you want to stay healthy the one metric you should measure & look to improve would be your fitness.

Over the next few posts I hope to add more information on various ways in which you could measure fitness, various hacks to improve fitness and what science is telling us about the effects of fitness on different health conditions. Alongside I hope to share my own personal data / experience (including from the Show & Tell as well as other information) and I would welcome others who are interested in doing the same.


Disclaimer: The content on this blog (and linked websites) is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this blog or linked websites. Reliance on any information provided on this blog is solely at your own risk.