Intensity-dependent associations of physical activity and cardiorespiratory fitness with hair cortisol concentrations in the context of lifetime air pollution exposure.
Vigorous physical activity was positively associated with hair cortisol concentrations in both self-reported and objectively measured data, highlighting the importance of considering physical activity intensity when interpreting HCC as a biomarker of chronic stress.
Key Findings
Results
Vigorous physical activity was positively associated with hair cortisol concentration when assessed via self-report.
Self-reported vigorous physical activity measured by the Leisure-Time Exercise Questionnaire (LTEQ) was significantly associated with HCC (B = 0.010, p = 0.042).
The sample consisted of 133 adults, 87% women, participating in the Healthy Aging in an Industrial Environment-Programme 4 study (4HAIE).
HCC was quantified from 3-cm hair segments using liquid chromatography-tandem mass spectrometry, reflecting cortisol exposure over approximately 3 months.
Associations were examined using multiple linear regression and hierarchical models.
Results
Vigorous physical activity was positively associated with hair cortisol concentration when assessed via objective wearable monitoring.
Objectively measured vigorous physical activity via 14-day Fitbit monitoring was significantly associated with HCC (B = 0.006, p = 0.044).
Both self-reported and objectively measured vigorous physical activity showed consistent positive associations with HCC.
Physical activity was assessed using two methods: the Leisure-Time Exercise Questionnaire (LTEQ) and 14-day Fitbit monitoring.
Results
Cardiorespiratory fitness (VO2peak) was initially associated with higher HCC, but this association was attenuated after inclusion of vigorous physical activity.
VO2peak showed an initial positive association with HCC (B = 0.019, p = 0.041).
The association between VO2peak and HCC was attenuated when vigorous physical activity was added to the model, suggesting vigorous physical activity may mediate or confound this relationship.
Cardiorespiratory fitness was assessed by peak oxygen uptake (VO2peak).
Results
Moderate physical activity was not significantly associated with hair cortisol concentration.
Neither self-reported nor objectively measured moderate physical activity showed a statistically significant association with HCC.
This finding highlights that the association between physical activity and HCC is intensity-dependent, with only vigorous intensity showing significant associations.
Physical activity intensity differentiation was a key design feature of the study, assessing both moderate and vigorous categories separately.
Results
Lifetime ambient air pollution exposure was not significantly associated with hair cortisol concentration.
Lifetime exposure to particulate matter (PM2.5 and PM10) and nitrogen dioxide (NO2) was estimated from residential histories and historical air pollution models.
None of the air pollution measures (PM2.5, PM10, NO2) were significantly associated with HCC.
The study population came from an industrial environment context (the 4HAIE study), which was selected in part because of potential air pollution exposure relevance.
Air pollution exposure was included in hierarchical regression models alongside physical activity and fitness variables.
Methods
The study sample was predominantly female and drawn from a subsample of an existing cohort study focused on healthy aging in an industrial environment.
The sample consisted of N = 133 adults, of whom 87% were women.
Participants were drawn from the Healthy Aging in an Industrial Environment-Programme 4 study (4HAIE).
HCC reflected cortisol exposure over approximately 3 months via 3-cm hair segments analyzed by liquid chromatography-tandem mass spectrometry.
The high proportion of women is a notable sample characteristic that may limit generalizability.
What This Means
This research suggests that the intensity of physical activity matters when it comes to understanding how exercise relates to a biological marker of long-term stress called hair cortisol concentration (HCC). HCC is measured from hair samples and reflects the body's average cortisol (a stress hormone) levels over roughly three months. The study found that people who engaged in more vigorous physical activity — whether they self-reported it or it was tracked by a Fitbit device — tended to have higher hair cortisol levels. In contrast, moderate physical activity showed no significant relationship with hair cortisol. This was true in a sample of 133 adults (87% women) living in an industrial region of the Czech Republic.
The study also found that better cardiorespiratory fitness (measured by peak oxygen uptake, or VO2peak) appeared related to higher hair cortisol at first, but this relationship largely disappeared once vigorous physical activity was taken into account. This suggests that it may be the vigorous exercise itself — rather than fitness level per se — driving the cortisol signal. Importantly, long-term exposure to air pollutants like fine particulate matter and nitrogen dioxide, estimated from participants' residential histories and historical pollution data, was not significantly related to hair cortisol levels.
This research suggests that scientists and clinicians interpreting hair cortisol as a marker of chronic psychological stress should consider whether a person does a lot of vigorous exercise, since exercise itself can elevate cortisol levels and may be mistaken for stress-related cortisol elevation. The findings add nuance to a field where evidence has previously been mixed, potentially because earlier studies did not consistently separate moderate from vigorous physical activity.
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Cibulcova V, Elavsky S, Cipryan L, Jackowska M, Dostal T, Jirik V, et al.. (2026). Intensity-dependent associations of physical activity and cardiorespiratory fitness with hair cortisol concentrations in the context of lifetime air pollution exposure.. Stress (Amsterdam, Netherlands). https://doi.org/10.1080/10253890.2026.2721526