In February, a puck-shaped protrusion was spotted under the jersey of a Visma–Lease a Bike rider.
Eagle-eyed cycling-tech fans quickly identified it as a Tymewear VitalPro strap – a device that combines a heart-rate monitor with a breathing sensor.
The interest in the new technology isn’t limited to cycling either, with everyone from the Norwegian Olympic Committee to NBA teams getting in on the action, and according to its founder, Arnar Larusson, it’s set to revolutionise performance wearables.
But what are breathing sensors, and will they become a crucial addition to the amateur athlete’s training toolbox?
Or will they be consigned to the drawer with all of the other ‘must-buy’ wearables, such as the continuous glucose monitor?
What does it measure?
The Tymewear device is comprised of a chest strap, a heart-rate monitor and a very sensitive strain gauge.
“The sensor measures the expansion and contraction of the chest cavity,” explains Larusson.
“We measure that displacement, and that allows us to measure breathing rate, which is the peaks of that expansion and contraction, but it also gives us a reference for the tidal volume.”
Although not a direct measure of tidal volume (the amount of air that moves in or out of the lungs with each respiratory cycle), the device can show with 95% accuracy how much oxygen and carbon dioxide are going into and out of the lungs without the use of a mask.
Larusson adds that tidal volume is a key measurement because, “what’s going in and out of the lungs is what’s going in and out of the muscles throughout the body”.
By multiplying breathing rate and tidal volume, you also get ‘minute ventilation’ – the total volume of air inhaled and exhaled out of the lungs in 60 seconds – which is a marker of how effectively the respiratory system is responding to the metabolic demands that are placed upon it.
“By understanding [this], we can get a really good idea of the internal workload of the body. How quickly or how much air is going in, and how that’s changing over time, tells us how efficiently you’re producing that workload,” adds Larusson.
Breathing basics
Adding these three additional data fields to your head unit or post-ride analysis is all well and good, but it’s how you can interpret the information that could unlock additional physiological improvements.
To understand why, though, it’s important to delve into the role of breathing during exercise.
At lower intensities, endurance activities such as cycling rely predominantly on the aerobic energy system.
This is where oxygen that’s inhaled is transported via red blood cells to each muscle cell and used in the mitochondria to break down stores of carbohydrates, fats and proteins to produce ATP – the energy that powers cells.
Carbon dioxide and water are byproducts of this process, which the body gets rid of through exhaling and urination.
“Your brain tells your muscles to produce a certain power output or effort.
“The muscles have to provide the energy to produce or maintain that power, and then you have to provide the substrates to create that – so fats and carbohydrates with the aerobic side with oxygen,” explains sports physiologist Dr Jonathan Baker, founder of Palmares and data scientist for Alpecin-Deceuninck.
“You need more oxygen at higher power outputs, and that means you have to breathe more.”
Oxygen isn’t solely relied on at lower intensities, though, and is used right up to VO2 max – your maximum aerobic capacity. Along the way, you pass two ventilatory thresholds (VT) where there’s a shift in energy creation.
The first, VT1, signals when you transition from a primarily aerobic to a mixed aerobic and anaerobic source, while VT2 is the point at which anaerobic metabolism becomes the dominant energy source.
Although not exactly the same, these are closely linked to the lactate thresholds you’d get from lactate testing.
Importance of thresholds
Knowing these thresholds can give you a much more personalised approach to training.
Rather than completing an FTP test and using a generic formula to generate your training zones, your ventilatory thresholds enable you to see your unique response to different workout intensities.
With the right training, it’s possible to improve your output at each threshold, thereby increasing your metabolic efficiency and how hard or long you can ride aerobically before you have to start tapping into other energy sources.
“If these are true ventilator thresholds, and it feels like they are, you get these physiology training zones – moderate, heavy, severe – which are very distinct in terms of how the body responds to them,” says Baker.
He adds that the breathing sensor enables you to have three zones that fit the simple polarised 80/20 training model and “nail down where those transitions are”.
But he cautions that “when you start slicing into different chunks – which you can and probably should – you have to then use other things as well, like heart rate, lactate, power, etc, just to make sure you’re achieving what you want.”
Larusson adds that a ventilatory assessment can also reveal inefficiencies – for example, reaching VT1 at 50% of VO2 Max, rather than 75%.
“By targeting them, we get better. The body builds that capability, and eventually those inefficiencies become more and more efficient, and you shift that whole curve.”
Training-specific tool
While Larusson says most of the Tymewear VitalPro strap’s value comes during training, it has also been spotted in professional races.
So is its use during competition likely to make or break someone’s chances of winning?
“There are really interesting things around breathing, and especially breathing rate, that can tell you if someone has cooked themselves,” he says.
“If you can show that at that limit, they cook themselves, then in theory, you could try to avoid that in a race.
“But if the breakaway is going, you’re not going to hang around like, ‘Oh, my number’s saying I can’t go, so I’m not going to go’. That’s not how a race works.
“From a racing standpoint, it’s probably most interesting retrospectively, when you’re trying to understand an athlete’s workload.
“If you’re [a coach] setting up the training for the week after a race, you want to know what effect that race had on them.
“With heart rate, it’ll pretty much go up to whatever percentage of max it’ll go to and then kind of simmer there.
“But with breathing, we can see the full range of that energy expenditure and how intense it was.
“It gives us a metric to understand how much work was done and [a coach] can use that in the recovery to build them back up appropriately without overdoing it.”
Increased accessibility
Traditionally, getting this data requires heading to a lab and conducting tests using a metabolic cart.
Widely regarded as the gold standard of physiological testing, it involves strapping yourself into a VO2 gas analyser’s face mask and conducting a ramp test on a stationary bike or treadmill.
The cost makes these tests prohibitively expensive, and amateurs might only ever do one once – which is great for setting training zones, but not if you need to update them after some targeted training.
Although the Tymewear breathing sensor isn’t claimed to be 100% accurate compared to a metabolic cart, Baker’s own testing with a beta device suggests it provides accurate numbers and could open up ventilatory thresholds to the masses.
“You’re getting a little bit of the lab thing in the real world – a VO2 gas analyzer is £40,000 or so; these things are a couple of hundred,” he says.
Not a silver bullet
Baker warns that a breathing sensor isn’t going to replace your power meter and heart-rate monitor, though.
“All of these things are tools. We need to use them in combination. I often triangulate things to understand what’s happening.
“How you use that number in a productive way is also probably the challenge, and the education on these things is really important.”
Larusson says Tymewear is getting as close as anyone ever has to a metabolic cart’s accuracy outside of lab settings.
“We’re starting to shine a light into a part of a physiology training intensity that hasn’t been possible outdoors or in the natural athlete environment,” he says.
While Baker wouldn’t go that far, he agrees it’s an interesting development.
“Ventilation is the one thing that I don’t test regularly, but now we can. Now it’s a strap, we can measure a new aspect of ‘physiology’ in real-time, through each and every ride. Over time, that’ll create an interesting dataset.”
