Accuracy of Revvo in Measuring VO2Max Without Oxygen Masks

Ever since I started working on Revvo a few years ago one of the key questions for me has always been how accurate is the data compared to gold standard measurement of VO2Max using oxygen masks in a lab. And now we have an answer — and it looks like we are getting really close !

vo2max-accuracy

 

In our previous methods we were close for most — but for some we did see an over-estimation. The new method is overall slightly more accurate but also consistently accurate across everyone tested.

TESTING METHOD

19 people tested on Revvo (following our standard process) and also tested in a lab using gold standard Parvomedics metabolic measurement cart that measures their respiratory gases (oxygen, carbon dioxide etc.) to firstly estimate their VO2Max and also estimate their ventilatory thresholds (which corresponds to their lactate threshold).

The sample consisted of men and women, 30-50 years old, with VO2Max levels ranging from <20 to >70 (which is a pretty wide range). This validation sample also included some of the highest (70) and the lowest (18) VO2Max scores from amongst the 600+ tests we’ve done so far which gives us confidence that our methods have the potential to span a very wide range of humans. Our goal is to continue to enlarge the sample and look for diverse populations to test.

The Science Behind Interval Training

This video is a very scientifically grounded yet easily understood review of how short bouts of interval training can achieve dramatic improvements in your fitness level (VO2Max). Great effort by the Australian Broadcasting Corp!

In brief, high intensity interval training increases the mitochondrial density of your muscle cells. These are the energy producing elements of your muscle — more you have, the more oxygen your muscles can uptake to burn glucose as fuel.

Low mitochondrial density not only makes you less fit but also exposes you to a range of health risks.

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 :

Fit at 50 !

I was inspired to write this post by a slew of recent studies showing that midlife fitness (midlife roughly defined as 40-65) makes a big difference to health outcomes and cognitive function for the rest of your life. I’ve certainly experienced this personally – increasing my fitness at 40 helped normalize my blood pressure levels. And I’m probably fitter today than I was in my 20s (talk about wasted youth!).

Here’s a short list of recent studies showing the connection between fitness, age and health issues / benefits. (Fitness, as I’ve explained earlier, is the ability of your body to supply fuel to muscle when you are active):

1/ Fitness measured for 45-62 year olds predicts chances of 10-year survival. (John Hopkins Study)

2/ Higher fitness delays age-associated increase in blood pressure. (USC Study) (Henry Ford Study)

3/ Fit older adults (55-82) did as well as younger adults on cognitive function. Unfit older adults did poorly. (Boston University Medical Center Study)

4/ Higher midlife fitness prevents the brain from shrinking (Boston University School of Medicine Study)

5/ Higher midlife fitness associated with lower risk of certain cancers in men (University of Vermont Study)

The interesting thing about these studies is that you don’t have to be a super-athlete at 50 to stay healthy – the level of fitness expected – 12-13 METs is well within the reach of the average 50-year old male as you’ll see from the charts below.

Fitness-Benchmarks

(Many of these studies have been conducted amongst male cohorts so difficult to be as precise for women — I’m hoping to see more studies on female fitness & health impact in the future).

The other interesting question that it raises – if you can stay as fit as the average 30-year old (which is an achievable goal for most 50-year olds) can you entirely avoid aging related health issues ?


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.

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

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

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

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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.