Optimizing Intersession Reliability of Heart Rate Variability-The Effects of Artifact Correction and Breathing Type.
Level 3 - non-randomized controlled study
Prospective repeated-measures test-retest reliability study
PubMed 33105371 · doi:10.1519/JSC.0000000000002258
What was done
Resting heart rate variability (HRV) was measured across 2 separate days in 41 participants (age: 19.9 ± 1.2 years; 28 females, 13 males) using Polar Team monitors. Within each session, participants completed 10 minutes of spontaneous breathing and 10 minutes of controlled breathing in randomized order. Kubios HRV software analyzed 180-second epochs using "low" or "strong" artifact removal. Intersession relative reliability was evaluated using intraclass correlation coefficients (ICC2,1) and absolute reliability using mean-normalized SEM%.
What was found
Time-domain and nonlinear HRV parameters showed poor to good intersession agreement (ICC = 0.34–0.68; SEM% = 11.0–39.0) with "low" artifact removal regardless of breathing condition. Frequency-domain parameters demonstrated fair agreement during controlled breathing (ICC = 0.40–0.45; SEM% = 26.0–70.0) but poor agreement during spontaneous breathing (ICC = 0.07–0.13; SEM% = 32.0–81.0). Minimal differences in ICCs were observed between "low" and "strong" artifact removal.
Why it matters
Time-domain and nonlinear HRV indices provide more stable day-to-day tracking than frequency-domain measures during spontaneous breathing. Intersession differences below 30% largely reflect normal daily variation rather than true physiological changes.
Limits
The sample was limited to 41 young, healthy individuals (mean age ~20 years), restricting generalizability to older or clinical populations. Data were collected over only two sessions using one specific monitor and software pipeline.
Cited by
- supports Even under strictly controlled laboratory conditions controlling time of day, diet, and breathing depth and rate, day-to-day heart rate variability shows a plus or minus 25% variation.