When people look at HRV, they usually focus on one thing:
Is it high or low?
But one of the most important — and most overlooked — patterns is how stable HRV is over time.
A consistently low HRV can reflect a system under steady load. Large swings up and down often signal something more disruptive: nervous system instability.
Your body can adapt to consistent stress. It struggles with unpredictable stress.
Stable Suppression vs. System Instability
A consistently lower HRV may mean:
• Ongoing training or life stress
• The system is working hard but predictably
• Recovery may be limited, but regulation is intact
Large HRV swings often mean:
• The nervous system is overreacting to stress
• Recovery is inconsistent from day to day
• The body is struggling to maintain balance
Instability requires more energy to manage than steady load.
Why Big HRV Swings Happen
Large fluctuations often come from inconsistent or compounding stressors:
• Irregular sleep schedules
• Emotional stress spikes
• Alcohol
• Illness or immune stress
• Big changes in training load
• Travel or schedule disruption
These cause the system to bounce between overactivation and forced recovery, instead of staying regulated.
Why Instability Slows Progress
When HRV swings wildly:
• Performance becomes unpredictable
• Recovery timing becomes unclear
• Fatigue accumulates unevenly
• The nervous system spends more energy regulating than adapting
Instead of building capacity, the system keeps trying to restore balance.
Why This Feels Confusing
People often say:
“My HRV was high yesterday and crashed today — what happened?”
Often nothing dramatic happened. The system is just struggling to stabilize under total stress load.
High variability can make it hard to tell whether training is productive or excessive.
What To Do If HRV Is Unstable
The goal is not to eliminate stress — it’s to make stress more predictable and recoverable.
Helpful strategies include:
• Keeping sleep and wake times consistent
• Reducing sudden spikes in training volume or intensity
• Limiting alcohol during heavy training periods
• Adding more low-intensity aerobic work
• Creating daily recovery routines (walks, sunlight, breathwork)
Consistency helps the nervous system regulate more efficiently.
The Big Takeaway
HRV isn’t just about how high the number is — it’s about how stable your system is over time.
A steady but slightly suppressed HRV often reflects manageable stress. Large swings usually signal a system that’s struggling to regulate under unpredictable load.
Recovery capacity improves when stress is consistent enough for the body to adapt — not when the nervous system is constantly trying to catch up.