Not all data carries the same weight. Heart rate remains one of the most critical metrics, but what truly matters are the zones it defines — ranges of effort expressed as percentages of your maximum heart rate. Running steadily in a lower zone strengthens endurance, while higher zones build speed and power. The TAG Heuer Connected Calibre E5 displays these zones in real-time, helping wearers adjust their pace or intensity without guesswork.
Just as significant is heart-rate variability, the subtle change from beat to beat, which offers an early signal of fatigue or stress. Sleep, too, has become measurable in its phases: deep cycles restore the body, while REM stages sharpen the mind. The TAG Heuer Connected Calibre E5 tracks these rhythms alongside indicators such as heart rate variability* and blood oxygen levels*, presenting not just isolated figures but trends that reflect real recovery.
*These features will be available later this winter.