Recovery Science — Stress, HRV & Adaptation

HRV is the variation in time between heartbeats. Counter-intuitively, a more variable heart rate indicates better recovery and fitness — it means your autonomic nervous system is responsive. LOW HRV: High stress, poor recovery, illness, overtraining, alcohol last night. Your body is in sympathetic dominance ('fight or flight'). HIGH HRV: Well-recovered, low stress, good sleep quality. Parasympathetic dominance ('rest and digest'). HOW TO MEASURE: Whoop, Oura Ring, Garmin, Apple Watch (via HRV4Training app with chest strap for accuracy). Measure first thing in the morning before getting up — post-sleep HRV reflects overnight recovery. HRV BASELINE: Trend is more important than absolute number. Your HRV is personal. A reading 20% below your 7-day baseline is a signal to reduce training load or address stressors.

STRESS + REST = ADAPTATION. Remove either variable and adaptation stops. TYPES OF STRESS THAT AFFECT RECOVERY: • Physical: exercise, illness, surgery, heat/cold • Cognitive: high decision load, sustained focus, stress • Emotional: conflict, anxiety, grief • Chemical: alcohol, caffeine, poor nutrition • Environmental: noise, light, temperature All stress uses the same recovery resources. A brutal work week and a brutal training week both demand the same recovery capacity. Most people budget physical stress without accounting for cognitive and emotional stress. RECOVERY ACCELERATORS: • Sleep (primary) • Nutrition (protein timing, anti-inflammatory foods) • Cold exposure (10-15 min at 15°C — reduces inflammation) • Heat exposure (sauna at 80-100°C — HSP upregulation, cardiovascular) • Social connection (parasympathetic activation)