“…QT interval, P-wave duration). Where high resolution inner heartbeat information is not required, light-weight wearable heartbeat interval (or R-R) recorders have facilitated simple non-intrusive high frequency and accurate collection of HR data (Buchheit, Simon, Viola, Doutreleau, Piquard, & Gabrielle, 2004;Serrano et al, 2008). Agreement analyses for commercially available heartbeat interval recorders and traditional ECG recorders typically find a high degree of concordance between both types of systems across a range of samples and metrics of cardiac chronotropy (Gamelin, Berthoin, & Bosquet, 2006;Heilman & Porges, 2007;Nunan, Jakovljevic, Donovan, Hodges, Sandercock, & Brodie, 2008).…”