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 :

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.

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

How I Normalized my Blood Pressure via Anaerobic Interval Training

Reproducing the talk that I gave at the Quantified Show & Tell in Boston on how I was able to eventually improve my fitness and blood pressure when I shifted to anaerobic interval training.

SivaRaj_BPFitness

Siva Raj was interested in lowering his blood pressure. With a family history of cardiovascular disease and heart attacks he was worried about slightly elevated blood pressure (pre-hypertension). As someone engaged with understanding and building fitness applications he thought he would be able to lower his blood pressure by staying on track with a regular exercise program that focused on cycling. Interestingly his blood pressure measurement didn’t respond to his constant exercise or weight loss. After reading more research literature about the link between fitness and cardiovascular health Siva decided to change his training to improve his fitness. He decided to incorporate a increased intensity into his routine. After a short period of time he had increases in this fitness and was able to observe the reduction in blood pressure he was looking for. In the video below, filmed at the Boston QS meetup group, Siva explains his methods and talks about how he was able to track his body’s response to different fitness routines.


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.