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.

Screen Shot 2017-10-27 at 2.17.31 PM

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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VO2Max

What We Learnt from 750 Fitness Tests!

TL;DR

Weight is a very poor proxy for fitness (even though culturally we think fitness = “being in shape”). Increasing activity improves fitness but does not lead to lower weight. Fitness declines with age, but this is not a given. Improving recovery is an ‘easy’ win for everyone.

THE FULL ANALYSIS

Revvo is the first exercise bike to measure an individual’s fitness profile : Aerobic Fitness/VO2Max, Recovery and Endurance/Threshold. And right from the earliest test, we’ve captured information on the individual’s demographics and current weight, activity levels (mainly because it was required pre-screening information).

1. Test Fitness

While we’re definitely not the first to aim to understand how these different variables correlate, the fact that we are measuring a wider range of variables on the same individuals with a pretty high degree of accuracy and consistency should hopefully provide some additional insight. Details on the test methodology can be found here: Revvo: Science.

1. We tested people across a wide range of fitness levels

While our sample is not a fully representative one (we do not have many at the lowest and highest ends of the fitness spectrum), it does represent a broad spectrum of fitness levels – both in terms of VO2Max and Recovery.

VO2MaxRecovery

Interestingly, Recovery is skewed lower than the VO2Max results and this is something that we’ve anecdotally observed in quite a few “fit” individuals. Recovery is partly an indicator of lifestyle – stress, lack of sleep will show up here. So if you’re looking to enhance performance or general wellness, check your heart rate recovery status — sleeping better and reducing stress might give you immediate results.

2. If you’re already fit, focus on recovery

In fact this opportunity to improve Recovery becomes more obvious when you cross-analyze VO2Max and Recovery data. In general, there is a positive correlation between the two i.e. higher the VO2Max, higher the expected Recovery. However this is a weak correlation as you’ll see from the plot.

Vo2Max Vs. Recovery.png

I’ve often seen people with relatively poor VO2Max scores who’re doing fine from a health perspective since their heart rate recovery is good and also fit people with poor recovery that indicates underlying health issues (perhaps genetics the culprit here rather than lifestyle). Fit people also often have poor recovery due to excessive training loads i.e. if you ran an ultra-marathon over the weekend, it will take a few days for recovery to return to normal levels.

3. You could be fat & fit or thin & unfit

We often conflate weight and fitness – but these are two semi-independent variables. We’re seeing lots of people who are relatively heavy but score pretty well on VO2Max (despite the fact that weight is the denominator in VO2Max calculations). And on the other hand many who have perfect BMI but with suffer from aerobic fitness.

VO2Max Vs. Weight.png

Above 250lbs however, its rare to find someone who’s really fit. But below 200lbs there’s a huge variation in fitness levels – if we only analyzed that population there would be very little correlation between fitness and body weight. So just because some looks thin doesn’t mean they are fit and vice versa.

Recovery versus body weight shows the exact same pattern.

Recovery Vs. Weight

4. Being active improves fitness, but doesn’t impact body weight

We’ve now seen a ton of data confirming that activity, on its own, doesn’t seem to make much difference to body weight. And our analysis supports that conclusion.

There’s practically zero correlation between how active people say they are and how much they weigh and a slight negative correlation when you contrast BMI vs. Activity. Yet we keep telling people that they should exercise more to lose weight, setting them up for failure!

Body Weight Vs. Activity

BMI Vs. Activity Level

Why does increasing activity levels not help with weight loss? Vox did a fantastic summary of the available evidence in this video and article.

The real benefit of activity is an improvement in fitness – and this is what our analysis reveals as well. Higher activity levels correlate pretty well with higher levels of fitness.

And aerobic fitness (VO2Max), as I’ve explained before, is not just an indicator of athletic potential but also the single best overall indicator of health. The primary purpose of exercise is to improve the functioning of your heart and muscle. Weight loss, if it happens, is a spin-off benefit.

Therefore if you want to assess if exercise is yielding results, track your fitness level, not your body weight.

VO2Max Vs. Activity

This is not of course not a perfect correlation as different types of activities have different effects: walking for an hour will not improve VO2Max as much as 10 minutes of high intensity interval training. And genetics also effects how well activity translates into an improvement. Which is why, even for people at the same level of activity, there is such a wide variation in fitness levels.

The correlation between Recovery and Activity is not as strong – and this makes sense. Lifestyle factors (sleep, stress etc.) often have a bigger effect on improving Recovery than increasing activity per se. And of course being too active can negatively impact Recovery. Recovery is intrinsically a more complex variable.

Recovery Vs. Activity

5. Fitness can – but need not – decline with age

At a general population level, VO2Max is reckoned to decline ~1% per year as we age and our analyses confirms the broad trend. However within that trend, there is huge variation: we’ve seen so many young people who are less fit than their grandparents and so many older individuals who’s fitness level has been an inspiration to me personally.

So your fitness is in your hands (or legs!).

VO2Max Vs. Age

Recovery seems to be even less correlated with declining age.

Recovery Vs. Age

 

Uncategorized

How to Measure Your Fitness Level

Last week I attended the first ever Quantified Self Expo in San Francisco – which had a ton of interesting products and sessions on various topics covering areas of self-measurement. I was there demoing Revvo and also gave a talk titled “How to Measure Your Fitness Level”, which I thought would be useful for a wider group to review. Below are my slides :

Uncategorized

How I Ignored Conventional Wisdom To Achieve My Fitness Goals

Yes its the time of the year when a remarkably large number of people resolve to do something they will predictably give up within a few weeks of starting i.e. trying to get fit. And until recently I was part of this pattern — resolving countless times to get fit yet giving up within a few weeks of starting an exercise program. Something however changed the year before & for the last ~2 years I’ve actually managed to stay at it for long enough to now genuinely claim that I am indeed fit.

The biggest challenge with getting fit – as we all know – is to actually stick with it through thick & thin – rain, snow and heat – long days & sleepless nights (thanks to my 2-year old!). And to achieve this I had to completely ignore conventional wisdom on the subject (as reflected in countless articles – for example, see here & here).

1/ Find Something You Like Doing

Conventional wisdom suggests you should find an activity you like doing and do just that if you want to get fit. I LOVE cycling along the Erie Canal (which is a few minutes walk from where I live) — I can cycle for hours. Yet I managed to do this just twice in the whole of last year!

It’s not difficult to explain why — I need to dedicate a significant chunk of time for the activity, the weather needs to be decent and my kids cannot ask to join me (which they inevitably do & I find difficult to refuse and in which case all we end up doing is a short & gentle trip where my heart rate goes up only because my 8-yr old keeps trying his best to jump into the canal).

Also the reason why I like the long canal biking trips so much is their rarity .. if I was doing this daily (say this was my commute), I’m pretty sure I’m not going to like it quite that much.

So forget trying to do the thing you like … instead focus on finding something that you can actually do on a daily basis.

2/  Find a Friend 

When I was 27 (that feels like a looong time ago!), I had a friend living in the apartment below who would wake me up at 5.30 so both of us could go for a run. And on days that he was being lazy I would pay him back! Even after nights of partying until 2 am I still managed to get out for a run early the next morning, thanks to him.

Things change when you have kids — your friends don’t control your schedule, your kids do. And that’s true for your friends too. Its still possible occasionally to co-ordinate our schedules so we can all get together for activity. However its incredibly rare to be able to do this on a daily basis.

So ignore conventional wisdom & find an activity you are happy to do on your own. Think of this as your time, free of work, kids, family & social commitments.

3/ Set a Weight Loss Goal

This is the conventional wisdom that in my opinion is the most dangerous & counter-productive. Yet how could you argue against setting a weight loss goal ? The reason – weight loss does not really happen via exercise alone. Many studies have shown that the average person loses very little weight solely through exercise. And some of course even gain weight (because we want to reward ourselves for that long ‘hard’ run we just finished!).

And so if you do set a weight loss goal, you’ll probably end up giving up on exercise because you won’t see results.

The real reason why you should exercise is so that you can stay fit. Fitness, as I pointed out in an earlier post, is not about your weight. Its about how effective your body is in providing & utilizing oxygen to fuel your physical activity. And is perhaps the single best indicator of your overall health.

Ideally you should measure and track your fitness (which until now has required a visit to an exercise science lab). Or track a proxy – such as your average heart rate for the same activity level, or your average pace / finish time for a fixed distance you run or bike. And particularly if you’ve been sedentary for a while, you’ll see improvement within a few days / weeks of starting an exercise program.

So what are my personal suggestions to help you meet your fitness goals?

1/ Set a Fitness Goal

2/ Find a Short Workout Effective at Improving Fitness

3/ Integrate that into your Daily Life

My workout is indoor cycling (at home), at high intensity, for 10 minutes daily — I can do this rain or shine, sleepy or otherwise. It may not be quite as much fun as cycling on the canal but it does not require that I change my lifestyle, plus I can watch music on youtube as I bike. I track changes in my fitness each time I workout so I know how much meaningful progress I’m making. I am change the intensity as I make progress so I don’t plateau. (Full Disclosure : I’m building a smart exercise bike called Revvo that does all this).

I do this pretty much the same time everyday — its now literally like brushing my teeth or taking a shower so it doesn’t require an enormous amount of willpower to get me going. It’s just a habit and that’s how it should be.

Happy 2015!


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

Interval Training

Could 10 Minutes of Exercise Make You Fit ?

Study after study shows that we are in denial about a number of things – our weight and our calorie intake both of which we generally tend to under-estimate. But nothing comes close to the amount by which we over-estimate how active we are.

In a 2011 study published in the American Journal of Preventative Medicine, US adults self-reported close to 60 minutes of daily activity everyday (this includes exercise and also other casual activity such as gardening, household chores or walking to the pantry to pick up a chocolate!). However when activity levels were actually measured using an accelerometer turns out we are active for an average of just 9 minutes daily!

Guidelines provided by the American Council of Sports Medicine and endorsed by other leading health organizations suggest 150 minutes / week of moderate intensity activity (i.e. brisk walking or jogging) – which only 9% of US adults actually achieved. This level of activity is considered necessary to maintain / improve fitness.

So how do we resolve this problem ? A team of exercise physiologists from McMaster University, led by Gillen JB looked to see if we could improve our fitness by exercising for just 10 minutes, 3 times a week (Martin Gibala, a co-author to the study is a pioneer in interval training). After completing a 2-minute warm-up, study participants cycled all out for 20 seconds, followed by 2 minutes of recovery where they cycled at a gentle place. This was repeated 2 more times during that session and then finished off with a 3 minute cool down for a total time commitment of 10 minutes per session.

The results were astonishing – within 6 weeks both men & women saw a significant increase in their cardio-respiratory fitness by ~12%.

journal.pone.0111489.g005

Gillen JB, Percival ME, Skelly LE, Martin BJ, Tan RB, et al. (2014) Three Minutes of All-Out Intermittent Exercise per Week Increases Skeletal Muscle Oxidative Capacity and Improves Cardiometabolic Health. PLoS ONE 9(11): e111489. doi:10.1371/journal.pone.0111489

In addition, they also saw important health benefits – mean arterial pressure (which correlates with blood pressure) decreased by 7%. Insulin sensitivity (important for those with pre-diabetes & diabetes) also improved amongst both groups. 24-hour glucose levels however only dropped amongst men (& not amongst women, which warrants further study).

journal.pone.0111489.t002

This is not the first study to show significant benefits for interval training over continuous exercise – a meta-analysis published in the British Journal of Sports Medicine by Weston et al showed 2x improvement in fitness through interval training compared to moderate intensity continuous exercise. Another review by W Kent in the same publication indicated a 15% increase in fitness within 6 weeks of interval training.

What’s unique in this study is the relatively low time commitment required to achieve this remarkable improvement in fitness and health – a level of commitment that almost everyone should be able to make (with of course brief moments of intense effort). In other words there are no more excuses for not getting fit!


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

Definitions, Guidelines

How Fit Should You Be ?

Most of us would say being fit is a good thing – but exactly how fit do we need to be ? The answer – like most things in life – tends to be ‘it depends’. If your goal is to improve your athletic performance then definitely more is better (well trained world class athletes tend to have 2-3x higher fitness than the average untrained person).

However if you’re someone like me who does not want to compete in the Olympics (!) but does want to stay healthy, then is there a fitness level you could target? What is a healthy fitness level … lets see if science can give us an answer.

Fitness = Maximum Oxygen Uptake

Untitled

As I had defined in an earlier post, fitness or more precisely cardio-respiratory fitness is the ability of the body to supply oxygen to muscles during times of increased physical activity. Fitness is typically expressed as VO2Max, i.e. the maximum oxygen your body can uptake during structured exercise. And usually estimated by measuring oxygen uptake while progressively increasing running or biking speed until the person reaches maximum oxygen uptake (commonly called a “stress test” or maximal test). Athletes typically have higher VO2Max numbers (Norwegian cyclist & junior world champion Oskar Svendson has one of the highest reported fitness numbers / VO2Max of 97.5 ml/kg/min). VO2Max is typically expressed in units of ml/kg/min which basically translates to the maximum ml of oxygen per kg of body weight the body can utilize in a minute. Of course higher VO2Max by itself doesn’t guarantee a better race outcome – motivation, training status, efficiency and a host of other factors matter. But having lower fitness certainly makes it more important to work on the rest.

11 METs = Healthy Fitness Level 

METs-chart-(intensity)_03

From a health perspective, fitness is usually expressed as METs (Metabolic Equivalents) – a more clinically meaningful metric – both to understand how healthy the person is as well as to determine how much exercise intensity the person can cope with.  Essentially 1 MET =~3.5 VO2 units, which basically is the amount of oxygen you need to sit & watch TV! METs also provide an easy way to compare the relative intensity of different activities (the chart on the left is adapted from lists created by the CDC & ACSM).  The intensities are directly comparable – so sex is therefore almost 5 times as intense as watching TV. And your fitness needs to be at least 6 METs for you to be able to have sex, safely!

This gets even more relevant when you look at people with different fitness levels and their health outcomes. One of the seminal studies that looked at the relationship between fitness, cardio-vascular health & all-cause mortality was conducted by a group led by Saturo Kodama. They combined data from 33 different studies that covered 100,000+ subjects and segmented people into different levels of fitness.

METs-chart-(fitness)_03

In categorical analyses, individuals with low CRF (<7.9 METs in MAC) had a substantially higher risk of all-cause mortality and CHD/CVD compared with those with intermediate and high CRF (7.9-10.8 and ≥10.9 METs in MAC, respectively) … These analyses suggest that a minimal CRF of 7.9 METs may be important for significant prevention of all-cause mortality and CHD/CVD

Those with fitness of less than 7.9 METs had a 40% higher risk of mortality than those with intermediate fitness (7.9 – 10.8 METs) and 70% higher risk than those with high fitness (10.9+ METs).  And every 1 MET increase in fitness tends to result in ~15% improvement in cardiovascular health. Based on the Kodama findings & other studies, I would categorize fitness into five zones (chart on the right). So increasing fitness beyond 7.9 METs yields dramatic improvement in health outcomes. And a fitness level of 11 METs or higher would be considered healthy.


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.

Aging

How to Measure Your Age!

How long you’ve lived is clearly one way to measure age — but if aging is about the gradual decline of body function and eventual mortality then perhaps there is another contender for the best way to measure age – your  fitness. And unlike your calendar age, you can actually change your fitness. In my last two posts I talked about my personal experience reducing blood pressure by improving fitness and the massive published data validating the link between fitness and aging induced blood pressure.

Now a group of Norwegian researchers from HUNT University have published a study looking at ~38K men & women who they followed-up for a mean duration of 24 years to demonstrate that fitness was a very good predictor of mortality at all age levels and perhaps the best predictor for those less than 60 years of age. Every 1 MET increase in fitness resulted in 15% lower risk of all-cause mortality amongst men and 8% lower risk amongst women.  In this particular example fitness was estimated using demographic + activity data (which gives a rough indicator but is not that accurate).  The accompanying NYT article has more detail on the study and related research.

The group also created a really cool online calculator — you can plug in your data and get an estimate of your fitness, compare it to age cohorts. Worth trying out!

From the study, here’s what your fitness should look like on average, if you’re aging well:

Fitness-Benchmarks