Table 1.

Determinants, reliability and sensitivity of the different heart rate measures.

	Determinants	Monitoring variable(s)	Typical error, expressed as coefficient of variation	Signal-to-noise ratio*	Smallest worthwhile change*
Resting HR	Cardiac morphology, plasma volume, ANS and baroreflex	Wellness, fitness, readiness to perform	~10%	0.7	~ −2%
Resting vagal-related HRV indices	Genetics, plasma volume, ANS and baroreflex	Wellness, fitness, readiness to perform	Index-dependent, e.g., ~12 (Ln rMSSD) to ~80 (LF/HF)%	0.8	~ +3%
Exercise HR	Fitness, plasma volume	Aerobic fitness	~3%	1.6	~ −1%
Exercise HRV	Intensity-dependent: ANS<VT1, respiration >VT2	In theory, aerobic fitness	Index-dependent, e.g., ~60 (Ln rMSSD) to ~150 (LF/HF)%	N/A	N/A
Post-exercise HRR	Theoretically ANS and genetics but essentially metaboreflex	In theory, wellness, fitness and readiness to perform In practice, more fitness because of its link with relative exercise intensity	Index-dependent, e.g., ~25 (HRR60s) to ~35 (HRRτ)%	1.3	~ +7%
Post-exercise vagal-related HRV indices	ANS and baroreflex, but the metaboreflex has the greater effect	In theory, wellness, fitness and readiness to perform In practice, more fitness because of its link with relative exercise intensity	Index-dependent, e.g., ~16 (Ln rMSSD) to ~65 (LF/HF)%	1.1	~ +4%

HR, heart rate; HRR_{60 s}, HR recovery within 60 s following exercise; HRRτ, time constant of HR recovery derived from monoexponential modeling; HRV, HR variability; N/A, non-available. Typical error: see Acknowledging the Uncertainty of the Measures text for related references. Signal to noise ratio: refers to the magnitude of the change observed in Buchheit et al. (2010a) divided by the typical error reported in Al Haddad et al. (2011). See section Determining the Smallest Worthwhile Change text for the methods used to calculate the smallest worthwhile change.

^*, for positive training adaptations.