Can breathing actually measure my fitness level? – Tyme Wear™

Can breathing actually measure my fitness level?

Your fitness is constantly evolving - so should your training.

The importance of individualizing training

Individualizing training to your current fitness level has some major benefits. Studies have shown that it leads to 2.5x greater fitness improvement for the same amount of time spent training. It also significantly reduces the chance of overtraining and injury, and  improves recovery and consistency of training. 

So how does one measure fitness and individualize training to get these benefits? In a lab, this is done by measuring your breathing. A face mask is used to measure the airflow in and out of your lungs and the volume and content of the air is analyzed to assess how much work and how efficiently that work is being performed. 

The reason existing wearable technologies can’t measure fitness level or accurately individualize training, is because they use heart rate to estimate these same lab measurements. The problem is that the heart rate signal doesn’t contain the information needed to measure fitness or individual training targets. The best it can do is estimate them with math formulas that have up to a 29% margin of error. This significant  margin of error  is the reason why individualizing training using accurate measures of current fitness results in 2.5x greater fitness improvement.

Overcoming this 29% margin of error is what Tyme Wear is solving for.  An easy to use wearable that accurately measures someone’s fitness level and identifies their unique training targets to help them improve faster is game changing and that’s exactly what we’ve done.

Our approach is to measure the same output as a performance lab, breathing. A soft sensor embedded in a base layer shirt measures the total volume of air flowing in and out of the lungs. The sensor can withstand over 300 wash and dry cycles, and 1,000’s of wear cycles. 

Tyme Wear’s reliability is a significant improvement in wearable technology. The reliability is paired with accuracy that is on par with high performance lab equipment. Breathing rate is 98.6% as accurate, tidal volume is 85% as accurate, and minute ventilation is 94% as accurate. The key innovation we’ve developed is to use the air flow alone to assess the same markers of fitness that a performance lab measures. These are called the First Ventilatory Threshold (VT1) and the Second Ventilatory Threshold (VT2). Learn more about the Ventilatory Thresholds on our blog here.

Validation of Breathing to detect Ventilatory Thresholds

To validate the accuracy of using breathing to measure individual fitness level, 200 lab tests were performed using a metabolic cart, and were analyzed by detecting VT1 and VT2 using only the Minute Ventilation signal from the metabolic cart while comparing it to the threshold detections obtained using the full contents of the air, oxygen and carbon dioxide. This study found that  VT1 and VT2 had an average difference of 0.8 +/- 7bpm and 0.1 +/- 6bpm, respectively. This represents a 0.6% and 0.06% difference between the two methods. This finding provides strong indication that using breathing alone is a valid method for accurately determining VT1 and VT2. Link to the study.

Chart depicting tidal volume and breathing rate over increasing exercise intensity


Average heart rate at time of detection for ground truth vs ventilation


In Conclusion

To accurately assess your metabolic output and efficiency during exercise, ventilation is the optimal metric to use. Using your current thresholds to inform your training ensures that you are always training at the appropriate intensity. As your fitness changes, you can track those changes with your ventilation signal.

Using ventilation to assess your metabolic output and efficiency can help you prescribe workout intensities for specific training adaptations, such as maximizing fat or lactate consumption. Training at intensities that are appropriate for your current fitness level will improve recovery as well as reduce the chance of overtraining and injury.

Check out this case study from a Tyme Wear user who improved his VT1 power output by 22% in just 4 months by using his individual thresholds as measured by Tyme Wear.

If you want to individualize your training and have questions, we're here to help.

With Tyme Wear you get continuous updates to your training intensities to match your changing fitness level, track your progress, and ensure efficient training

Arnar Larusson

Arnar Larusson is the Co-Founder and CEO of Tyme Wear, a smart shirt that tracks breathing to help athletes measure their unique metabolic thresholds and individualize their training to them. Prior to founding Tyme Wear, Arnar did research at Harvard University where he helped develop the first soft exoskeleton that lowered the metabolic cost of walking. Prior to that, he helped to develop prosthetic limbs for Paralympians at Össur. Arnar is a triathlete, ultra-marathoner, and a former basketball player on Iceland’s youth national team. He holds a degree in Mechanical Engineering from the University of Iceland.