Your body is constantly sending signals about whether you are ready to perform or approaching burnout. However, we often ignore or misinterpret these cues until we become ill or reach a point of exhaustion. When these signals are ignored, we force our bodies to continue functioning when they should instead recover. As a result, the likelihood of injury or reduced productivity increases.
Consider someone who enjoys going to the gym. They may feel completely fine after an intense workout and return the next day without adequate rest. However, they may suddenly develop a severe cold because their body has reached its limit and requires a period of recovery.
Similarly, consider a professional who has had a poor night’s sleep. They may feel “totally fine” the following morning and begin working on a complex project. Nevertheless, they may make unusual or careless mistakes that they would not normally make.
If we can better understand what our bodies are communicating, it becomes easier to determine when to exert maximum effort and when to rest.
A widely accepted metric for interpreting these physiological signals is Heart Rate Variability (HRV).
A Quick Introduction to HRV
HRV refers to the small fluctuations in the time interval between successive heartbeats. For example, if your heart rate is 60 beats per minute, the interval between the first and second beats may be 1.0 seconds, while the next interval may be 1.02 seconds. This slight difference represents heart rate variability.
In general, higher HRV values (based on common metrics such as RMSSD) indicate greater fluctuations in the time intervals between heartbeats. However, comparing absolute numbers with others is less meaningful than tracking your own long-term stability or upward trend. That said, a consistently low HRV relative to your personal baseline may also warrant attention.
To evaluate stability and trends, you must first establish your personal “baseline.” This baseline can be determined by using the same device under similar conditions for approximately 7 to 14 days.
For instance, CUDIS records HRV each night during sleep and presents weekly and monthly averages within the application.
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If your HRV remains stable around a baseline over time, it indicates that your body is well balanced and can transition effectively between states of stress and relaxation.
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Conversely, significant fluctuations in HRV may indicate physical or psychological stress, suggesting a need for recovery.
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An upward trend in HRV generally suggests improvements in recovery and overall health.
Why Is HRV a Trusted Standard?
A 2026 study by Burlacu et al., published in BMC Cardiovascular Disorders, examined military populations and found that HRV effectively reflects stress accumulation, fatigue, and recovery under sustained workloads.
This is because the intervals between heartbeats reflect the dynamic balance between the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). The SNS represents the body’s “fight” response, increasing heart rate to meet external demands. In contrast, the PNS represents the “rest” response, slowing the heart rate to promote relaxation and recovery.
Greater fluctuations in the intervals between heartbeats—reflected in higher HRV, particularly in metrics such as RMSSD—often indicate increased parasympathetic activity, suggesting that the body is in a state of recovery and capable of responding flexibly to changing demands. This capacity to adjust physiological responses according to environmental demands is considered a marker of good health and physical readiness.
Conversely, when the intervals shorten and HRV decreases, it suggests that one system is dominating. This can be normal in specific situations, such as during intense physical exercise or high-pressure tasks, when sympathetic activation enhances focus and performance.
However, persistently low HRV during routine daily activities may indicate that the body is under strain and working harder to recover from factors such as fatigue, stress, dehydration, or illness.
Note: It is worth noting that unusually high or erratic HRV values can, in some cases, be associated with cardiac conditions. Therefore, HRV should be interpreted as part of a broader picture of health, and any persistent abnormalities should be discussed with a healthcare provider.
How to Improve Your HRV
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Regular Cardio: Stick to moderate activities like brisk walking, jogging, or swimming.
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Quality Sleep: Maintain a consistent schedule and get enough rest.
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Stress Management: Practices like meditation, deep breathing, and mindfulness are proven to boost HRV.
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Get Into Nature: Spending time outdoors, especially in green spaces, helps lower cortisol (the stress hormone) and raise HRV.
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Nutrition Management: Cut back on alcohol, especially before bed, and stay hydrated with a balanced diet.
The Value for Regular Exercisers
Regular exercisers use training to create a “recovery gap,” followed by a process of supercompensation that enables them to reach a higher level of fitness. Maintaining consistency depends on keeping this recovery gap within one’s recovery capacity. Conversely, if recovery is insufficient, there is a long-term risk of immune suppression or injury.
HRV can function as a “traffic light” for monitoring recovery, helping individuals adjust their training plans and avoid burnout. A 2024 study by Addleman et al. in Journal of Functional Morphology and Kinesiology highlights that HRV is a valid tool for assessing athletes’ training status and physiological adaptation.
The same applies to ordinary fitness enthusiasts.
Traditional training programmes are often rigid, even though daily readiness for exercise can vary. By measuring HRV in the morning, individuals can objectively evaluate how well their nervous system has recovered. If HRV is above the established baseline, it may indicate readiness for high-intensity or high-volume training. In contrast, a lower HRV value may suggest physiological stress, indicating the need for lighter recovery activity or a complete rest day.
This also suggests that HRV-guided training may still offer advantages over fixed, pre-planned training programmes (Addleman et al., 2024).
The Value for Knowledge Workers
Professionals who regularly face demanding decisions, high-stakes negotiations, and complex data analysis are subject to continuous cognitive demands. These tasks require high-level cognitive abilities, including sustained attention, memory, and executive functioning.
Research indicates that higher HRV—particularly vagally mediated HRV (vmHRV)—is associated with improved executive function, memory, attention, and language performance (Forte et al., 2025). In this context, HRV trends can serve as an indicator of cognitive readiness. When HRV is relatively high, it may be an optimal time to engage in complex negotiations or strategic planning. Conversely, when HRV is low, it may be advisable to postpone major decisions and focus on routine or administrative tasks until adequate recovery has occurred, even if subjective feelings of fatigue are minimal.
How CUDIS Uses HRV
Because HRV is highly sensitive and can fluctuate throughout the day, real-time monitoring may produce inconsistent results. Therefore, CUDIS specifically tracks and records HRV during sleep each night to obtain more stable and reliable data.
CUDIS displays the most recent HRV reading directly on the dashboard. For more detailed insights, users can select the “HRV” section to view weekly and monthly trends, as well as average values.
In addition, HRV serves as a core component of the CUDIS Age ecosystem. It is incorporated into a comprehensive algorithm alongside other key health indicators, such as sleep quality, vitality index, and resting heart rate. By analysing how these multidimensional data points change over time, CUDIS calculates a highly personalised “CUDIS Age” for each user as a composite indicator of overall health trends.
Reference list
Addleman, J. S., Lackey, N. S., DeBlauw, J. A., & Hajduczok, A. G. (2024). Heart rate variability applications in strength and conditioning: A narrative review. Journal of Functional Morphology and Kinesiology, 9(2), Article 93. https://doi.org/10.3390/jfmk9020093
Burlacu, A., Brinza, C., Geman, O., Karppa, M., & Hemanth, D. J. (2026). Heart rate variability as a dual-use digital biomarker: Integrating clinical, AI, and operational perspectives on human performance and resilience. BMC Cardiovascular Disorders, 26(1), Article 87. https://doi.org/10.1186/s12872-026-05543-z
Forte, G., & Casagrande, M. (2025). The intricate brain–heart connection: The relationship between heart rate variability and cognitive functioning. Neuroscience, 565, 369–376. https://doi.org/10.1016/j.neuroscience.2024.12.004
