Study analysis · Stress · 2013
Your 90-minute workout doesn't mess up your stress hormones—here's why that's surprising.
A long, intense workout makes cortisol spike temporarily, but your body still follows its normal daily rhythm—DHEA doesn't even react.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study watched how two stress hormones changed in soccer players after they exercised, but didn't randomly assign who exercised when. So we can say exercise was linked to a spike in one hormone, but we can't say exercise definitely caused it — maybe something else did.
What’s the bottom line?
Scientists checked if a 90-minute intense workout changes the daily rise and fall of two stress-related hormones in soccer players.
How strong is this study?
The study tried hard to measure things at the same times every day, but only had nine people and didn't control for things like sleep or food. That makes it kind of shaky — like trying to guess if ice cream causes happiness by asking three friends. We should be careful trusting big conclusions.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
32 / 100
- Randomizationrandomization unclear
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=9)+0.9/20
- Follow-up+10/10
100 / 100
23 / 100
- P-values+15/15
- Effect sizeno effect size reported
- Confidence intervalsno confidence intervals
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 537 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
This design cannot establish causation — the findings describe an association, not a cause. Study design is not explicitly randomized or controlled; no randomization, blinding, or control group status confirmed in abstract. Therefore, cannot establish causation, only association.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding information were disclosed in the text; study appears independently conducted.
The study lacks any declaration of funding, conflicts of interest, or author affiliations. While the absence of disclosure does not confirm absence of conflict, there is no evidence of bias or industry influence in the provided text.
Key takeaways
- 01
Cortisol spiked at noon after morning workouts and at 4 PM after afternoon workouts, but still dropped normally over the day.
- 02
DHEA didn't change at all.
- 03
The spikes are short-lived and don't disrupt the natural daily rhythm of these hormones, so the body still follows its normal pattern.
Surprising findings
- DHEA showed no acute response to intense aerobic exercise, even as cortisol spiked.DHEA is often assumed to respond to stress alongside cortisol, but this study shows it's completely unreactive—even during prolonged, intense physical stress.
Practical takeaways
Don't worry that a long workout will throw off your stress hormone rhythm for the rest of the day.
This was only tested in 9 recreationally trained soccer players—results may not apply to elite athletes, beginners, or people with hormonal disorders.
low confidenceWhy this study matters
Cortisol spikes—but only briefly
After 90 minutes of intense aerobic exercise, cortisol levels rose significantly at 12:00 h (p < 0.05) after morning workouts and at 16:00 h (p < 0.01) after afternoon workouts. But the overall daily decline pattern remained unchanged.
Most people think intense exercise throws your stress hormones out of whack all day—this shows it’s just a quick spike, not a long-term disruption.
DHEA ignores exercise entirely
Despite cortisol rising sharply after exercise, DHEA showed no acute response at all—its levels stayed flat throughout the 16-hour testing window.
DHEA is often called the 'anti-aging' or 'counter-hormone' to cortisol—so the fact it doesn't budge during intense stress is counterintuitive and rarely discussed.
The rhythm survives the storm
Even with cortisol spikes at noon and 4 PM, the diurnal decline of both cortisol and DHEA over 16 hours remained intact—no disruption to the natural rhythm.
This challenges the fear that one intense workout can 'break' your circadian hormone cycle—your body is more resilient than you think.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists checked if a 90-minute intense workout changes the daily rise and fall of two stress-related hormones in soccer players.
Research results
Cortisol spiked at noon after morning workouts and at 4 PM after afternoon workouts, but still dropped normally over the day. DHEA didn't change at all.
What this means - more context
The spikes are short-lived and don't disrupt the natural daily rhythm of these hormones, so the body still follows its normal pattern.
To determine the effects of 90-minute intense aerobic exercise on diurnal cortisol and DHEA patterns in recreationally trained soccer players.
Intense 90-minute aerobic exercise caused transient increases in salivary cortisol at 12:00 h (morning exercise) and 16:00 h (afternoon exercise), but did not alter the overall diurnal decline pattern of cortisol or DHEA over 16 hours. DHEA showed no acute response to exercise.
Methods Used
Nine recreationally trained soccer players underwent three conditions: no exercise, morning exercise (10:00–11:30 h), and afternoon exercise (14:00–15:30 h). Saliva samples were collected at awakening, 30 min after awakening, and every 2 hours from 08:00 to 22:00 h. Methodology details not available in abstract.
Main Finding
Significant transient increases in salivary cortisol at 12:00 h (p < 0.05) and 16:00 h (p < 0.01) after exercise, with no change in overall diurnal decline of cortisol or DHEA. DHEA showed no significant acute response.
Confidence Level
Limited - based on abstract only, full methodology not available
Study Flags
Red Flags
- •Full text not available - methodology details cannot be verified
- •Sample size of 9 participants may limit generalizability
- •No information on blinding, randomization, or control group details
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Surprising Findings
DHEA showed no acute response to intense aerobic exercise, even as cortisol spiked.
DHEA is often assumed to respond to stress alongside cortisol, but this study shows it's completely unreactive—even during prolonged, intense physical stress.
Practical Takeaways
Don't worry that a long workout will throw off your stress hormone rhythm for the rest of the day.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 537 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Human Cross-Sectional
Subject
Lower probability
on the GRADE evidence scale
This study watched how two stress hormones changed in soccer players after they exercised, but didn't randomly assign who exercised when. So we can say exercise was linked to a spike in one hormone, but we can't say exercise definitely caused it — maybe something else did.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Repeated measures design across multiple conditions (rest, morning exercise, afternoon exercise)
- Clear timing of saliva sampling over a 16-hour period
- Statistical analysis reported with p-values for observed changes
Weaknesses
- Full methodology not available - based on abstract only
- No confirmation of randomization, blinding, or control group
- Very small sample size (n=9)
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists checked if a 90-minute intense workout changes the daily rise and fall of two stress-related hormones in soccer players.
Research results
Cortisol spiked at noon after morning workouts and at 4 PM after afternoon workouts, but still dropped normally over the day. DHEA didn't change at all.
What this means - more context
The spikes are short-lived and don't disrupt the natural daily rhythm of these hormones, so the body still follows its normal pattern.
To determine the effects of 90-minute intense aerobic exercise on diurnal cortisol and DHEA patterns in recreationally trained soccer players.
Intense 90-minute aerobic exercise caused transient increases in salivary cortisol at 12:00 h (morning exercise) and 16:00 h (afternoon exercise), but did not alter the overall diurnal decline pattern of cortisol or DHEA over 16 hours. DHEA showed no acute response to exercise.
Methods Used
Nine recreationally trained soccer players underwent three conditions: no exercise, morning exercise (10:00–11:30 h), and afternoon exercise (14:00–15:30 h). Saliva samples were collected at awakening, 30 min after awakening, and every 2 hours from 08:00 to 22:00 h. Methodology details not available in abstract.
Main Finding
Significant transient increases in salivary cortisol at 12:00 h (p < 0.05) and 16:00 h (p < 0.01) after exercise, with no change in overall diurnal decline of cortisol or DHEA. DHEA showed no significant acute response.
Confidence Level
Limited - based on abstract only, full methodology not available
Study Flags
Red Flags
- •Full text not available - methodology details cannot be verified
- •Sample size of 9 participants may limit generalizability
- •No information on blinding, randomization, or control group details
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Surprising Findings
DHEA showed no acute response to intense aerobic exercise, even as cortisol spiked.
DHEA is often assumed to respond to stress alongside cortisol, but this study shows it's completely unreactive—even during prolonged, intense physical stress.
Practical Takeaways
Don't worry that a long workout will throw off your stress hormone rhythm for the rest of the day.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 537 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Human Cross-Sectional
Subject
Lower probability
on the GRADE evidence scale
This study watched how two stress hormones changed in soccer players after they exercised, but didn't randomly assign who exercised when. So we can say exercise was linked to a spike in one hormone, but we can't say exercise definitely caused it — maybe something else did.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Repeated measures design across multiple conditions (rest, morning exercise, afternoon exercise)
- Clear timing of saliva sampling over a 16-hour period
- Statistical analysis reported with p-values for observed changes
Weaknesses
- Full methodology not available - based on abstract only
- No confirmation of randomization, blinding, or control group
- Very small sample size (n=9)
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study tried hard to measure things at the same times every day, but only had nine people and didn't control for things like sleep or food. That makes it kind of shaky — like trying to guess if ice cream causes happiness by asking three friends. We should be careful trusting big conclusions.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
32 / 100
- Randomizationrandomization unclear
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=9)+0.9/20
- Follow-up+10/10
100 / 100
23 / 100
- P-values+15/15
- Effect sizeno effect size reported
- Confidence intervalsno confidence intervals
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 537 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
This design cannot establish causation — the findings describe an association, not a cause. Study design is not explicitly randomized or controlled; no randomization, blinding, or control group status confirmed in abstract. Therefore, cannot establish causation, only association.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding information were disclosed in the text; study appears independently conducted.
The study lacks any declaration of funding, conflicts of interest, or author affiliations. While the absence of disclosure does not confirm absence of conflict, there is no evidence of bias or industry influence in the provided text.
Standing
Who’s using this study?
The videos and claims on this site that lean on this study, and the researchers who wrote it.
2 videos from 2 different creators cite this study, drawing 2 claims from it.
- Contradicted
Evidence contradicts this claim.
Evidence
- Very strong evidence
Randomized or controlled trials support this claim, alongside consistent supporting evidence.
Evidence
Authored by
7 researchersIf this is your work, this is how we attribute it on Fit Body Science. Zakaria Labsy is listed as the lead author.
- Laboratoire d'Énergétique Moléculaire et Macroscopique, Combustion
Cited in 2 claims