Stress does not necessarily end when the stressful moment ends. A wearable may be able to see the body remain changed long after a hard run or a tense period of work. Stress contributes to the progression of many diseases, yet few methods exist for continuously measuring stress.

This study asked whether cardiovascular signals from a wearable device could serve as markers of stress. The device continuously measured heart rate and heart rate variability, then compared those signals around runs and high-stress work in everyday conditions.

The signals were assessed when participants were motionless. The central idea is like checking a car after driving uphill: instead of judging the strain only during the climb, the device watches how the system behaves afterward. Moderate or vigorous runs kept heart rate higher and heart rate variability lower for hours, while light runs changed them little.

People often lack the knowledge to avoid or properly manage stressful events. The study therefore points to a need for methods that measure the impact and duration of stress in real time. That sets up the practical promise: developing real-time methods to quantify the impact and duration of stressful events could give people better information for managing them.

Certain wearable devices continuously measure cardiovascular signals and create an opportunity to examine the size of stress effects in real time. Heart rate and heart rate variability can change with the body’s stress-related signals, so they may act as stand-ins for stress.

Earlier work had mainly looked for changes after events such as infections and vaccinations over longer periods. The study used continuous monitoring to examine the effects of stressful events in ordinary, free-living conditions. Before interpreting a change as stress, the study found that heart rate and heart rate variability naturally vary across the day.

Their daily pattern also aligns with when a person falls asleep or wakes up. Because these signals naturally follow a daily rhythm, measurements that rely on them may need correction for the time of day. For physical stress, the study compared the signals before and after runs of different intensity.

After moderate or vigorous runs, heart rate stayed elevated for at least several hours, while after light runs it stayed the same or decreased. The stronger runs produced larger increases in heart rate than light runs.

Heart rate variability also stayed lower after moderate and vigorous runs, and vigorous runs produced the larger decreases. The pattern also appeared during high-stress work. Heart rate rose during the stressful work and remained elevated for a short time afterward, then became unchanged or lower.

Heart rate variability tended to be lower during high-stress work and was significantly lower later, after the activity had ended. The results suggest that these wearable signals may mark both physical and psychological stress. Seeing the full time course makes the shift clear: the drop in heart-rate variability persists well beyond the stressful work, with only a modest recovery by the end.

A key finding is that heart rate and heart rate variability follow a daily rhythm linked to when a person falls asleep or wakes up. Across the day, heart rate and its beat-to-beat variation change in different directions. Because these signals naturally follow a daily rhythm, measurements that rely on them may need correction for the time of day.

The study concludes that this daily rhythm can provide a personal baseline. Deviations from that baseline may reveal changes caused by stressful events. The findings provide evidence that stress could be detected passively, outside a clinic, by tracking wearable signals and adjusting them for the time of day.

In everyday life, that could help people notice stressful events, recognize their own body’s response, and improve how they respond to stress. Future research will need to test whether these signals can predict the start of certain diseases.

Heart rate and its beat-to-beat variation can reveal how strongly the body responds to physical or work stress, and how long recovery lasts. That could eventually make stress easier to notice and manage in everyday life.