Tymewear is an Icelandic company that measures breathing during exercise. It began with a smart shirt and now sells VitalPro, a chest strap used by runners, cyclists and triathletes, including a professional cycling team.

How it works

The band stretches as the ribcage expands, and a soft sensor woven into it reads that stretch, so every breath registers as a change in length. From the size and rate of each breath the app works out how much air moves through the lungs each minute, and the two points where breathing steps up mark the thresholds that separate easy work from hard. Heart rate comes from a single electrical lead in the same strap.

Key considerations

The strap is bought once, though the training plans built on those thresholds renew as a membership.