Heart rate variability and cortisol responses to acute low- and moderate-intensity exercise in stress-related exhaustion

Q: What are the key findings of this study?

Acute moderate- vs low-intensity cycling reduced post-exercise heart rate variability (lnRMSSD) in stress-related exhaustion patients (p<0.001), who also had lower overall RMSSD than controls (p<0.001).

Q: What is the clinical evidence from this study?

Study design: RCT. Population: Stress-related exhaustion (Exhaustion disorder) (n=59). Intervention: Moderate-intensity cycling exercise vs. Low-intensity cycling exercise (40% of estimated VO2max for 22 minutes) and healthy controls. Primary outcome: Heart rate variability (lnRMSSD) and salivary cortisol responses across pre-exercise, post-exercise, and 30 minutes post-exercise (p=<0.001).

Q: What does this research mean for the field?

Individuals with stress-related exhaustion exhibit altered autonomic regulation following acute exercise, characterized by impaired post-exercise vagal reactivation and greater sensitivity to exercise intensity compared with healthy controls. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

To examine whether autonomic and hypothalamic–pituitary–adrenal axis responses to acute low- and moderate-intensity exercise differ between individuals with stress-related exhaustion and healthy controls.

Jenny Kling; Örjan B. Ekblom; Robert Persson Asplund; David Hallman; Yiwen Jiang; Victoria Blom

doi:10.1007/s00421-026-06467-4

October 25, 2026European Journal of Applied PhysiologyOpen Access

Heart rate variability and cortisol responses to acute low- and moderate-intensity exercise in stress-related exhaustion

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Key result

Moderate- vs low-intensity cycling acutely reduces post-exercise heart rate variability in stress-related exhaustion.

P<0.001
n=59

Why the study?

Exercise is commonly recommended to support stress regulation, but whether autonomic and HPA axis responses to acute exercise differ in individuals with stress-related exhaustion or vary by exercise intensity remained unclear.

Does acute low- versus moderate-intensity cycle ergometer exercise alter heart rate variability and salivary cortisol responses differently in individuals with stress-related exhaustion compared to healthy controls?

Key Points

To examine whether autonomic and hypothalamic–pituitary–adrenal axis responses to acute low- and moderate-intensity exercise differ between individuals with stress-related exhaustion and healthy controls.
In a randomized, counterbalanced crossover trial (NCT06429423), 30 individuals with stress-related exhaustion (93.3% women; age 46.3 ± 5.89) and 29 healthy controls (93.1% women; age 45.5 ± 5.47) completed two 22-min cycling sessions on separate occasions.
Workloads were set to 40% (low intensity) and 55% (moderate intensity) of estimated maximal oxygen uptake (V̇O₂max).
Heart rate variability indices (RMSSD, SD2/SD1, LF/HF) and salivary cortisol were evaluated pre-exercise, post-exercise, and 30 min post-exercise, alongside heart rate variability monitoring during exercise.
Individuals with exhaustion exhibited lower RMSSD overall (Group main effect, p < .001), with post hoc testing revealing significantly lower RMSSD at both post-exercise recovery time points compared with controls (Group × Time interaction, p = .007).
Moderate- versus low-intensity exercise significantly reduced RMSSD (p < .001) and increased SD2/SD1 (p < .001) and LF/HF (p < .001) within the exhaustion group, whereas no intensity differences were observed in controls (p = .433, p = .830, and p = .408, respectively).
Salivary cortisol showed a main effect of Group (p = .044) and a Group × Intensity interaction (p = .028), though no pairwise post hoc comparisons reached statistical significance.

Study Design

Type

RCT (n=59)

Blinding

Open-label

Randomization

Counterbalanced crossover randomization using a computer-generated random order

Multicenter

No

Structured PICO

Does acute low- versus moderate-intensity cycle ergometer exercise alter heart rate variability and salivary cortisol responses differently in individuals with stress-related exhaustion compared to healthy controls?

P

Population

59 adults aged 35-55 years (93.2% female), comprising 30 individuals with non-acute stress-related exhaustion disorder and 29 age- and sex-matched healthy controls, evaluated across two acute exercise sessions separated by at least 1 week.

I

Intervention

Two acute 22-minute cycle ergometer exercise sessions (6-minute warm-up, 15 minutes at target intensity, 1-minute cool-down) performed at low intensity (40% of estimated V̇O₂max) and moderate intensity (55% of estimated V̇O₂max) on separate occasions separated by at least one week.

C

Comparator

Healthy controls (n=29) matched at the group level for age and sex distribution undergoing the identical counterbalanced crossover exercise protocol (comparing 40% vs. 55% estimated V̇O₂max within and between groups).

O

Outcome

Autonomic nervous system regulation assessed via heart rate variability (HRV: RMSSD, SD2/SD1, and LF/HF ratio) measured pre-exercise, during exercise, immediately post-exercise, and 30 minutes post-exercise, and hypothalamic–pituitary–adrenal (HPA) axis response assessed via salivary cortisol measured pre-exercise, immediately post-exercise, and 30 minutes post-exercise.surrogate

Main Result

p-value: p=<0.001

Individuals with stress-related exhaustion demonstrate blunted post-exercise vagal recovery (lower RMSSD) and greater autonomic sensitivity to moderate- versus low-intensity exercise compared to healthy controls, indicating that exercise intensity and post-exercise recovery are important considerations when prescribing physical activity in this population.

Limitations

Sample size was powered for fatigue rather than physiological outcomes (HRV and cortisol)
Blinding of participants and researchers was not feasible
Cardiorespiratory fitness (VO2max) was estimated using a submaximal cycle ergometer test rather than measured directly
Predominantly female sample (93.2% women), limiting generalizability to men
Higher antidepressant use and lower baseline cardiorespiratory fitness in the exhaustion group compared with controls
Blinding was not feasible
Cardiorespiratory fitness (V̇O₂max) was estimated using a submaximal cycle ergometer test rather than a maximal test
Study was retrospectively registered at ClinicalTrials.gov

Implication

Moderate-intensity exercise warrants caution in stress-related exhaustion due to blunted vagal recovery; extends general-population autonomic findings to this group.

Abstract

Purpose Exercise is commonly recommended to support stress regulation and mental health, yet it remains unclear whether these benefits translate to conditions characterized by prolonged stress and fatigue. The aims were to examine whether autonomic and hypothalamic–pituitary–adrenal (HPA) axis responses to a single exercise bout differ between individuals with stress-related exhaustion and healthy controls, and whether responses vary by exercise intensity. Methods In a randomized, counterbalanced crossover design, 30 individuals with stress-related exhaustion (93.3% women; age 46.3 ± 5.89) and 29 healthy controls with a comparable age and sex distribution (93.1% women; age 45.5 ± 5.47) completed two 22-min cycling sessions at workloads corresponding to 40% (low intensity) and 55% (moderate intensity) of estimated maximal oxygen uptake (V̇O₂max) on separate occasions. Heart rate variability (HRV; RMSSD, SD2/SD1, LF/HF) and salivary cortisol were assessed pre-exercise, post-exercise, and 30 min post-exercise, with HRV also assessed during exercise. Results Compared with controls, individuals with stress-related exhaustion showed lower RMSSD overall, with the most apparent between-group differences observed during the post-exercise period. Within the exhaustion group, moderate- compared with low-intensity exercise was associated with lower RMSSD and higher SD2/SD1 and LF/HF, whereas no intensity effects were observed in controls. No between-group differences were observed in HRV during exercise. Cortisol analyses suggested overall group-related differences, without clear differences across time points. Conclusions These findings suggest altered physiological stress-system regulation in stress-related exhaustion and highlight the post-exercise period and exercise intensity as important considerations when tailoring exercise recommendations for this population. The study was retrospectively registered on 05/30/2024 at Clinical Trials.gov, with trial registration number NCT06429423.

Discussion

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Cite This Study

Kling et al. (2026) conducted an RCT in Stress-related exhaustion (Exhaustion disorder) (n=59). Moderate-intensity cycling exercise vs. Low-intensity cycling exercise (40% of estimated VO2max for 22 minutes) and healthy controls was evaluated on Heart rate variability (lnRMSSD) and salivary cortisol responses across pre-exercise, post-exercise, and 30 minutes post-exercise (p=<0.001). Acute moderate- vs low-intensity cycling reduced post-exercise heart rate variability (lnRMSSD) in stress-related exhaustion patients (p<0.001), who also had lower overall RMSSD than controls (p<0.001).

synapsesocial.com/papers/6adf5612953ea0d7a3d1dbe2 https://doi.org/10.1007/s00421-026-06467-4

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Heart rate variability and cortisol responses to acute low- and moderate-intensity exercise in stress-related exhaustion

Key Points

Study Design

Structured PICO

Main Result

Limitations

Implication

Abstract

Discussion

Cite This Study

Heart rate variability and cortisol responses to acute low- and moderate-intensity exercise in stress-related exhaustion

Key Points

Study Design

Structured PICO

Main Result

Limitations

Implication

Abstract

Discussion

Cite This Study

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