Why Consistency Matters
HRV is highly sensitive to conditions. Your reading can vary by 20-30% based on time of day, body position, recent food, and mental state. To track meaningful trends, you need consistent measurement conditions.
When to Measure
First thing in the morning, immediately upon waking. Before checking your phone, before getting out of bed, before coffee. This captures your baseline nervous system state before daily stressors accumulate.
Set your phone and sensor on your nightstand so they're ready when you wake.
Body Position
Choose one position and stick with it:
Lying supine (on your back): Most common and comfortable. Arms at sides, relaxed breathing.
Seated upright: Acceptable alternative. Feet flat, hands on thighs, spine straight but not rigid.
Mixing positions will introduce noise into your trend data.
Breathing
Breathe naturally—don't try to control or slow your breath during the reading. Controlled breathing changes your HRV significantly. You want to capture your natural state, not an optimized one.
Some apps include guided breathing as a separate coherence exercise. That's fine, but do it after your baseline reading.
Reading Duration
Most apps recommend 1-3 minutes. Longer isn't necessarily better—you want enough data for statistical reliability without introducing position drift or mental wandering.
2-2.5 minutes is the sweet spot for most people.
Factors That Affect Readings
Be aware of these and consider logging them:
- Alcohol the night before (significant HRV suppression)
- Poor sleep or late bedtime
- Intense workout the previous day
- Illness or fighting something off
- Stress from work or personal issues
- Travel and time zone changes
- Menstrual cycle (for women)
Many apps let you tag these factors to see correlations over time.