Alcohol lowers HRV-derived overnight recovery in a dose-dependent way starting from small intakes, and being physically active does not protect against it
Key Findings
HRV-derived overnight recovery fell by 9.3, 24.0 and 39.2 percentage units at low (≤0.25 g/kg), moderate (>0.25–0.75) and high (>0.75 g/kg) alcohol intake.
4098 Finnish employees (55.81% women, mean age 45.1 years) with beat-to-beat recordings on nights with and without alcohol; outcomes from the first 3 hours of sleep.
Intake groups: low ≤0.25 g/kg, moderate >0.25–0.75 g/kg, high >0.75 g/kg of pure alcohol.
HRV-derived physiological recovery state fell on average by 9.3, 24.0 and 39.2 percentage units with low, moderate and high intake.
The within-person effect was present at low intake too (all P < .001).
The suppression was similar in men and women and in physically active and sedentary people; it was stronger in younger people and in those with a lower baseline sleeping heart rate.
Practical Application
A low morning HRV or raised resting heart rate after drinking is the alcohol, not a training-load signal: do not cut or reshape the plan on that reading alone, and say why.
Fitness does not blunt it — a low resting heart rate went with a larger effect, not a smaller one.
One drink is enough to show up; read the following morning's numbers with that flag before anything else.
Limitations
Observational, self-reported dose, drinking time not controlled.
The outcome is a proprietary HRV-derived recovery index, not raw RMSSD; raw heart rate and RMSSD changes are not in the abstract (abstract only was read).
Only the first 3 hours of sleep were analysed.