In this episode, I sit down with Arnar Larusson, founder and CEO of Tymewear, to talk about one of the most interesting and still underused metrics in endurance training: ventilation.
Most athletes are accustomed to tracking heart rate, pace, power, and maybe lactate. Tymewear approaches training from a different direction by measuring breathing directly. Its VitalPro chest strap (which I’ve been using in my own training for several months) measures breathing rate, tidal volume, and minute ventilation, allowing athletes to track how much air they’re moving during exercise and use changes in ventilation to identify physiological thresholds (zones) and training intensity.
Arnar and I get into the physiology behind these measurements, why ventilation has traditionally been largely confined to exercise physiology labs, and what becomes possible when athletes can measure it during normal training.
What I like most about the device is that it gives me a physiological signal that complements the metrics I’m already looking at. I can see how my breathing responds as intensity increases and where those responses begin to change.
I’ve found this particularly interesting for Zone 2 and threshold training, where relatively small changes in intensity can move you into a very different physiological domain. It’s also useful when heart rate becomes harder to interpret—for example, during longer sessions or training in the heat.
I think the value of ventilation is in adding another layer of physiological context to the measures I’m already using—and, for someone who enjoys understanding why a workout feels the way it does, it’s a pretty compelling metric.
Episode topics
Why I wanted to discuss ventilation and the VitalPro
Arnar Larusson’s background in engineering, prosthetics, and exosuits
Why breathing is a direct measure of internal workload
Why heart rate is confounded by heat and dehydration
Heat stress, core temperature, and why heart rate drifts
My Zone 2 problem in the Texas heat
Breathing rate, tidal volume, and minute ventilation
Breathing rate as a signal of perceived exertion and fatigue
VT1, VT2, and how they relate to lactate thresholds
Why VT1 and VT2 define training zones
What athletes gain when they train by ventilation instead of heart rate
What changes at the ventilatory thresholds
Why fitter athletes produce less CO₂ at the same workload
Why breathing rate alone is not enough
Whether breathing patterns reveal anything about fatigue
Durability and why prolonged exercise causes physiological drift
Why a rising heart rate is not always a problem
Why ventilation simplifies the durability picture
Why heart rate, pace, and lactate are all proxies
Why lactate can be a noisy marker compared with CO₂-driven ventilation
How professional cycling teams use ventilation in training
Why running needs a better effort metric than pace or heart rate
Can ventilation improve calorie-burn estimates?
What the threshold test actually tells you
How beginners should start using the device
How the VitalPro measures ventilation through chest expansion
Where to find Tymewear and follow the company
If you’re interested in experimenting with Tymewear yourself, I have a listener offer for the Tymewear Training Membership:
Get 67% off your first subscription order for either:
Tymewear Training Membership — 1 Year
Tymewear Training Membership — 2 Year
Get the discount here: https://www.tymewear.com/TWPS
The discount applies to the first subscription order only and is limited to one use per customer.
