When HRV becomes an indicator of your body’s recovery capacity, it may become one of the primary metrics you check each morning.
It is unexpected to see HRV drops instead of rising after you have what seems like enough sleep. Even you take a week off from training, your HRV is still under the baseline. This can be confusing.
However, several factors are that quietly influencing your HRV without you noticing.
CUDIS Blog will outline five daily-life factors offering insights to help you better understand your HRV in this article.
Factor 1: Physiological Factors
HRV does not start at the same baseline for everyone.
A study published in Applied Psychophysiology and Biofeedback, including individuals aged 10 to 89, found that HRV tends to decrease with age (Ortega et al., 2023).
In addition, a Sleep Medicine study of 888 adults found age and sex effects on HRV: middle-aged men had lower HRV than younger men, while women showed higher LF (β=0.52) and HF (β=0.54) (Gonzales et al., 2023).
HF is often used as an indicator of parasympathetic activity, although it is also influenced by breathing. Neither LF nor HF maps directly to total HRV, although higher HF often indicates greater HRV.
In other words, HRV is inherently shaped by age, sex, and other physiological characteristics.
Mechanistically, HRV reflects the flexibility of the Autonomic Nervous System (ANS). The Sympathetic Nervous System (SNS) pushes the body into action, while the Parasympathetic Nervous System (PNS) brings it back to a state of rest.
It is like this: some people are born with a more stable foundation, while others need to cultivate it more carefully.
So rather than comparing your HRV with others, just look at how you do against your own long-term average.
Factor 2: Stress and Psychological Load
If physiological characteristics is the car chasis, stress is quiet foot on the gas pedal.
A study published in Stress and Health used Ecological Momentary Assessment (EMA) to examine the relationship between psychological stress and HRV.
It showed HRV dropped when people reported higher stress, appearing within a 10-minute window. Conversely, lower HRV in the preceding hour predicted higher perceived stress afterward (Kim et al., 2024).
From a physiological perspective, stress activates the sympathetic nervous system, putting the body into a “fight-or-flight” state.
Rising heart rate, alertness and blood pressure – these are all designed to help you cope with challenges.
The problem is that the stress of today comes from messages, emails, meetings, and deadlines rather than physical treats.
Your body can respond in a similar way whether chased by a lion or facing your boss. It may treat both situations as threats.
As a result, sustained mental tension lowers HRV even in well-rested, untrined people.
Factor 3: Sleep Quality and Duration
Sleep is a major driver of recovery.
A study in Sleep Medicine found a positive correlation between sleep duration and the HF. Longer sleep raises HF power; among women over 40, those who slept fewer than 7 hours showed significantly lower RMSSD and HF power than those who slept enough (Gonzales et al., 2023).
RMSSD is commonly used to estimate parasympathetic activity; lower RMSSD means less beat-to-beat variation and therefore lower HRV.
The reason is straightforward: sleep is a key window during which the parasympathetic system often becomes more dominant and supports recovery.
Poor or fragmented sleep reduces recovery time, which can help explain low HRV even after eight hours in bed.
The issue may not only be how long you sleep, but how well you actually sleep.
Factor 4: Alcohol Intake
Alcohol is widely regarded as a sleep aid. But for HRV, it acts as a sedative rather than promoting physiological recovery.
A PLOS Digital Health study analyzed 20,968 participants (over 5.1 million person-days) and found each extra drink reduced nighttime HRV by about 3.8 ms in women and 3.3 ms in men (Grosicki et al., 2026).
Why does this happen?
Because alcohol:
1. Disrupts sleep pattern
2. Raises nighttime heart rate
3. Delays autonomic nervous system recovery
4. Increases awakenings and sleep fragmentation
So while you may feel like you’re sleeping soundly after drinking, your body may actually be working overtime throughout the night.
Factor 5: Exercise Patterns
Long-term exercise tends to improve HRV, but short-term sessions – especially when intense or late in the day – can temporarily lower it.
A study in Scientific Reports found that HRV decreases as exercise duration and intensity increase, with intensity having a greater impact than duration (Brockmann & Hunt, 2023).
Another study in Nature Communications, which tracked 14,689 participants over a year, found that later and more intense evening exercise was associated with lower HRV and higher nighttime resting heart rate (Leota et al., 2025).
Because exercise is a deliberate physiological stressor that raises sympathetic activity, intense or late workouts can temporarily suppress HRV.
Training briefly disturbs the body’s recovered state and the body adapts during recovery. So a short-term drop in HRV is not a bad thing.
The real red flag is when you train too hard for too long and can not keep up with recovery, and when your HRV keeps dropping below your normal level. At that point, it is no longer a training stimulus—it may indicate accumulated fatigue or insufficient recovery.
Practical Takeaways
1. Create your own HRV baseline (CUDIS app)
a)Measure daily for 2-4 weeks
b)Use your personal long-term average as baseline
c)Compare future readings to that baseline
2. Pay more attention to your sleep & stress (CUDIS app) and check whether you have
a)Insufficient sleep
b)Frequent awakenings
c)Excessive stress
3. Try to finish high-intensity evening workouts earlier:
At least four hours before sleep onset after high-intensity evening workouts
4. HRV is a guide, not a rule:
People who monitor HRV look at trends and adjust intensity or recovery accordingly.
Note:
HRV is influenced by many factors, not just the five covered in this article. It is also affected by breathing rate, measurement timing, body position, and many other factors.
Reference list
Brockmann, L., & Hunt, K. J. (2023). Heart rate variability changes with respect to time and exercise intensity during heart-rate-controlled steady-state treadmill running. Scientific Reports, 13, 8515. https://doi.org/10.1038/s41598-023-35717-0
Gonzales, J. U., Elavsky, S., Cipryan, L., Jandačková, V., Burda, M., & Jandačka, D. (2023). Influence of sleep duration and sex on age-related differences in heart rate variability: Findings from program 4 of the HAIE study. Sleep Medicine, 106, 69–77. https://doi.org/10.1016/j.sleep.2023.03.029
Grosicki, G. J., Robinson, A. T., Joyner, M. J., Carter, J. R., von Hippel, W., Presby, D. M., et al. (2026). Real-world effects of alcohol on heart rate, sleep, and physical activity by age and sex. PLOS Digital Health, 5(3), e0001284. https://doi.org/10.1371/journal.pdig.0001284
Kim, J., Foo, J. C., Murata, T., & Togo, F. (2024). Reduced heart rate variability is related to fluctuations in psychological stress levels in daily life. Stress and Health, 40(5), e3447. https://doi.org/10.1002/smi.3447
Leota, J., Presby, D. M., Le, F., Czeisler, M., Mascaro, L., Capodilupo, E. R., Wiley, J. F., Drummond, S. P. A., Rajaratnam, S. M. W., & Facer-Childs, E. R. (2025). Dose-response relationship between evening exercise and sleep. Nature Communications, 16(1), 3297. https://doi.org/10.1038/s41467-025-58271-x
Ortega, E., Chan, Y. X., & Ng, S. C. C. (2023). The pulse of Singapore: Short-term HRV norms. Applied Psychophysiology and Biofeedback, 49(1), 55–61. https://doi.org/10.1007/s10484-023-09603-4
