Exercise and the Stress Axis: How Different Workouts Affect Cortisol and DHEA

Exercise is one of the most potent modulators of the body’s stress‑axis hormones, particularly cortisol and dehydroepiandrosterone (DHEA). While both hormones are released from the adrenal cortex in response to physiological stress, their patterns during and after physical activity differ markedly depending on the type, intensity, and duration of the workout, as well as the individual’s training status, age, and sex. Understanding these nuances helps athletes, clinicians, and anyone interested in hormonal balance to design exercise programs that harness the beneficial aspects of the stress response while minimizing the risk of chronic hormonal dysregulation.

The Physiology of the Stress Axis During Exercise

When muscles contract, the hypothalamus receives afferent signals from mechanoreceptors, chemoreceptors, and baroreceptors. In response, it secretes corticotropin‑releasing hormone (CRH), which travels to the anterior pituitary and stimulates the release of adrenocorticotropic hormone (ACTH). ACTH then prompts the adrenal cortex to produce cortisol and DHEA in roughly a 10:1 ratio under basal conditions.

• Cortisol mobilizes energy substrates—glycogenolysis in the liver, lipolysis in adipose tissue, and proteolysis in muscle—ensuring that glucose and free fatty acids are available for working muscles. It also exerts anti‑inflammatory effects, dampening the immune response that can be triggered by tissue micro‑damage during exercise.
• DHEA serves as a precursor for sex steroids (testosterone, estradiol) and possesses neuroprotective, anti‑glucocorticoid, and immunomodulatory properties. Its secretion follows a diurnal rhythm opposite to cortisol’s, peaking in the early afternoon, but acute stressors such as exercise can cause a transient rise.

The net effect of a single bout of exercise is a coordinated surge in both hormones, with the cortisol response typically outpacing DHEA. The ratio of cortisol to DHEA (C/D ratio) is often used as a proxy for the balance between catabolic and anabolic signaling; a lower ratio suggests a more favorable anabolic environment.

Acute Hormonal Responses to Different Exercise Modalities

Key observations:

• Intensity matters more than duration for the magnitude of the cortisol surge. High‑intensity bouts, even when brief, provoke larger acute cortisol spikes than prolonged low‑intensity work.
• DHEA tends to rise proportionally with cortisol, but the relative increase is often larger during resistance‑type stressors, reflecting the hormone’s role in supporting anabolic pathways.
• The C/D ratio is most sensitive to the combination of high intensity and low volume, a pattern typical of power‑oriented training.

Aerobic Endurance Training and Cortisol Dynamics

Acute Effects

During continuous moderate‑to‑high intensity aerobic exercise, cortisol rises steadily as glycogen stores deplete and circulating glucose falls. The rise is mediated by both ACTH and sympathetic activation (epinephrine/norepinephrine). In well‑trained endurance athletes, the cortisol response is blunted compared with sedentary individuals—a phenomenon known as “training adaptation.”

Chronic Adaptations

Repeated endurance training leads to:

1. Reduced basal cortisol in the morning, reflecting improved hypothalamic set‑point.
2. Lower cortisol reactivity to subsequent bouts of the same intensity, indicating enhanced negative feedback sensitivity.
3. Preserved or modestly increased DHEA levels, especially in middle‑aged athletes, supporting a more favorable C/D ratio.

These adaptations are thought to arise from improved mitochondrial efficiency, reduced perceived effort, and enhanced clearance of cortisol metabolites.

Practical Takeaway

For individuals seeking to moderate cortisol exposure while still gaining cardiovascular benefits, steady‑state aerobic sessions at 60–70 % VO₂max for 45–60 minutes, performed 3–4 times per week, provide an optimal balance.

Resistance Training: Impacts on Cortisol and DHEA

Acute Hormonal Surge

Resistance exercise triggers a rapid cortisol increase, peaking 15–30 minutes post‑set, especially when:

• Loads exceed 80 % of 1RM.
• Rest intervals are short (<60 seconds).
• Multiple large‑muscle groups are engaged (e.g., squat, deadlift, bench press).

Simultaneously, DHEA rises, supporting the synthesis of testosterone and other anabolic steroids. The magnitude of the DHEA response correlates with the volume of muscle mass recruited.

Chronic Hormonal Profile

Long‑term resistance training (≥12 weeks) typically results in:

• Lower resting cortisol in the evening, suggesting improved recovery capacity.
• Elevated basal DHEA, particularly in men, which may translate into higher free testosterone levels.
• A reduced C/D ratio, indicating a shift toward an anabolic hormonal milieu.

These changes are most pronounced in novice lifters; seasoned athletes often plateau, requiring program variation (periodization) to sustain hormonal benefits.

Practical Takeaway

A moderate‑intensity, moderate‑volume program (3 sets of 8–12 reps at 70 % 1RM, 2‑minute rest) performed 2–3 times per week is sufficient to elicit favorable cortisol/DHEA adaptations without excessive catabolic stress.

High‑Intensity Interval Training (HIIT) and Hormonal Flux

HIIT combines brief, maximal‑effort bursts with active or passive recovery. The hormonal signature is distinct:

• Cortisol spikes are sharp but short‑lived, often returning to baseline within 60 minutes.
• DHEA rises in parallel, sometimes exceeding the cortisol increase, especially when intervals involve large muscle groups (e.g., sprint cycling, rowing).
• Growth hormone (GH) also surges, interacting with DHEA to promote protein synthesis.

Repeated HIIT sessions (3–4 per week) can lower basal cortisol over time, likely due to improved autonomic balance (increased parasympathetic tone). However, excessive HIIT without adequate recovery can lead to a chronically elevated C/D ratio, a hallmark of overreaching.

Practical Takeaway

For those aiming to maximize hormonal “spikes” that favor adaptation, a HIIT protocol of 4–6 × 30‑second all‑out efforts with 2‑minute active recovery, performed 2–3 times weekly, is effective. Ensure at least 48 hours of low‑intensity activity or rest between sessions to prevent cumulative cortisol overload.

Low‑Intensity, Long‑Duration Activity: The Hormonal Balance

Activities such as brisk walking, light cycling, or leisurely swimming at <45 % VO₂max produce minimal perturbations in the HPA axis:

• Cortisol remains near baseline, reflecting low metabolic stress.
• DHEA shows negligible change, preserving the existing C/D ratio.
• Catecholamine response is modest, supporting a calm, restorative state.

These sessions are valuable for active recovery, especially after high‑intensity training blocks, and for individuals with limited tolerance for high cortisol spikes (e.g., those with chronic stress or certain endocrine disorders).

Practical Takeaway

Incorporating 30–60 minutes of low‑intensity movement on non‑training days helps maintain hormonal equilibrium and supports overall recovery without adding catabolic load.

Recovery, Overtraining, and Hormonal Dysregulation

When training volume or intensity exceeds the body’s capacity to recover, the HPA axis can become chronically activated:

• Sustained elevation of cortisol (especially in the evening) interferes with protein synthesis, bone remodeling, and immune function.
• Blunted DHEA response reduces the counter‑regulatory buffer, widening the C/D ratio.
• Symptoms may include persistent fatigue, mood disturbances, decreased performance, and increased susceptibility to infections.

Key markers of overreaching include a C/D ratio that remains >2.5 (relative to baseline) for more than 7–10 days, alongside subjective signs of burnout.

Mitigation Strategies

• Periodize training: Alternate high‑stress weeks with low‑stress weeks (deloads).
• Prioritize sleep and stress‑management (outside the scope of this article, but essential for hormonal recovery).
• Monitor training load using session‑RPE or heart‑rate variability to detect early signs of excessive stress.

Individual Factors: Age, Sex, Training Status, and Genetics

Understanding these modifiers helps tailor programs. For example, post‑menopausal women may benefit from moderate‑intensity resistance work to boost DHEA and offset the age‑related cortisol rise, while older endurance athletes should monitor evening cortisol to avoid sleep‑disruptive spikes.

Practical Guidelines for Optimizing Hormonal Responses Through Exercise

1. Start with a balanced weekly template
• 2–3 moderate‑intensity aerobic sessions (45 min, 60–70 % VO₂max).
• 2–3 resistance sessions (3 sets of 8–12 reps, 70 % 1RM).
• 1 optional HIIT session (4–6 × 30 s all‑out, 2 min recovery) if recovery is adequate.

2. Manipulate intensity to target specific hormonal goals
• Goal: Lower basal cortisol – Emphasize steady‑state aerobic work and ensure adequate low‑intensity recovery days.
• Goal: Raise DHEA / improve C/D ratio – Incorporate heavy‑load resistance training (≥85 % 1RM) and occasional HIIT.

3. Periodize
• Microcycle (1 week) – 3 days moderate, 2 days resistance, 1 day HIIT, 1 rest.
• Mesocycle (4–6 weeks) – Gradually increase load or interval intensity, then deload (reduce volume by 30 % for 1 week).

4. Track subjective and objective markers
• Use a simple training log to note perceived exertion, mood, and recovery quality.
• If available, heart‑rate variability (HRV) can flag autonomic stress before hormonal changes become overt.

5. Adjust for life‑stage and sex
• Women in the luteal phase may reduce high‑intensity volume to avoid excessive cortisol spikes.
• Older adults should prioritize recovery and may benefit from slightly longer rest intervals (90–120 seconds) between sets.

Monitoring Hormonal Changes Without Medical Tests

While laboratory assays provide precise cortisol and DHEA concentrations, practical day‑to‑day monitoring can be achieved through:

• Performance trends – Sudden drops in strength or endurance often precede hormonal imbalance.
• Recovery questionnaires – Tools like the Profile of Mood States (POMS) or the Recovery-Stress Questionnaire (RESTQ‑Sport) capture subjective fatigue linked to cortisol elevation.
• Heart‑rate recovery (HRR) – A slower HRR after a maximal effort suggests heightened sympathetic tone and possible cortisol dominance.
• Salivary cortisol kits – For those comfortable with occasional at‑home testing, a single morning sample can give a snapshot of basal cortisol; pairing it with a post‑exercise sample helps gauge acute response.

By triangulating these indirect measures, individuals can make informed adjustments to training load before hormonal dysregulation becomes clinically significant.

Future Directions and Research Gaps

• Longitudinal DHEA profiling in response to varied training modalities across the lifespan remains limited.
• Interaction with other adrenal hormones (e.g., aldosterone) during exercise is underexplored, yet may influence fluid balance and performance.
• Sex‑specific dose‑response curves for HIIT‑induced cortisol/DHEA changes need refinement, especially in post‑menopausal populations.
• Genomic personalization – Integrating genetic testing (NR3C1, CYP17A1) with exercise prescription could optimize hormonal outcomes, but evidence is still emerging.

Continued interdisciplinary studies combining endocrinology, exercise physiology, and data analytics will sharpen our ability to prescribe “hormone‑friendly” workouts tailored to each individual’s biology.

In summary, exercise is a double‑edged sword for the adrenal stress axis: it can provoke acute cortisol and DHEA surges that drive adaptation, yet chronic mismanagement can tilt the balance toward catabolism. By selecting appropriate modalities, calibrating intensity and volume, respecting recovery, and accounting for personal factors such as age and sex, practitioners can harness the beneficial hormonal effects of physical activity while safeguarding long‑term endocrine health.