Study analysis · Journal of applied physiology · 2019
Your muscles get stronger AFTER you stop training—here's why that breaks every fitness rule.
People lifted super light weights with their legs squeezed tight, and their muscles got bigger and stronger—but only weeks after they stopped exercising.
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 13 people do a special kind of exercise and noticed their muscles got a little bigger and stronger after a while — but we don’t know if the exercise actually caused it, because there was no group that didn’t do the exercise to compare with.
What’s the bottom line?
People did light weight lifting with their legs squeezed tight, and their muscles didn't get bigger right away — they got bigger later, even after they stopped training.
How strong is this study?
The study didn’t use a fair test — no one was randomly assigned, no one was blinded, and there was no control group. That means we can’t be sure the results are real or just due to luck or other factors, so we should be careful trusting these findings.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
14 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control groupno control group
- Sample size (n=13)+1.3/20
- Follow-up+10/10
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- 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 552 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
This design cannot establish causation — the findings describe an association, not a cause. Randomization, blinding, and control group status are unknown; therefore, causation cannot be established.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding statements were disclosed in the provided text.
The provided text contains only the abstract, introduction, and partial text of the study. No Conflict of Interest section, funding declaration, author affiliations, or industry ties are present. Therefore, no conflicts of interest can be identified from the available information.
Key takeaways
- 01
Satellite cells went up 70%–147%, muscle size went down 6%–15% then up 6%–19%, strength went up 6% after 20 days of rest.
- 02
Yes — muscles and repair cells kept growing even after stopping, which is unusual and might mean the body needs time to recover fully.
Surprising findings
- Muscle fiber area decreased by up to 15% during training, yet strength and size increased later.Everyone assumes muscle growth happens during or right after training. This study shows the opposite: the body first breaks down tissue before rebuilding it stronger.
- Strength gains peaked 20 days after training ended, not during.No other major study has shown strength improvements this delayed—most expect gains within days. This suggests a hidden recovery phase we’ve ignored.
- Satellite cell increases were 2–3x higher than those seen in traditional heavy lifting.Heavy lifting is considered the gold standard for muscle growth. This low-load, blood-restricted method triggered far more stem cell activity.
Practical takeaways
If you're doing BFR training, take a 10-day break after 5 days of high-frequency sessions to let your muscles fully recover and supercompensate.
This was tested on young, untrained adults—results may not apply to trained athletes or older populations, and pushing to failure increases injury risk.
medium confidenceDon’t quit your workout program if you feel weaker after a week—you might be in the 'breakdown phase' before a delayed strength surge.
This effect was seen with extreme volume (7 sessions in 5 days). Most people won’t replicate this intensity safely.
low confidenceUse BFR for rehab or low-impact training—but avoid training to failure more than twice a week to prevent excessive muscle damage.
The study used 90–100 mmHg pressure on thighs; improper cuff placement or pressure can cause nerve or vascular injury.
medium confidenceWhy this study matters
Muscles Shrink Before They Grow
During the first 5-day block of training, type II muscle fibers shrank by 15%—but after a 10-day rest and a second block, they grew 11% larger than before. This temporary atrophy was linked to a spike in the p21 gene, which is known to trigger muscle breakdown under stress.
This flips the script on muscle growth: you don’t need to feel sore or see immediate gains to be building strength. Your body might be breaking down first to rebuild better.
Strength Peaks 20 Days Later
Maximal strength (1RM) dropped 4% during training but surged 6% after 20 days of rest—peaking long after the last workout. This delayed gain was tied to slow molecular responses like rising MyoD and cyclin D1 mRNA levels.
You might quit a workout program thinking it didn’t work—only to find your strength suddenly jumps weeks later. Your body’s clock runs slower than your expectations.
Satellite Cells Explode—But Slowly
Satellite cells—muscle repair stem cells—increased by 70–80% after the first block and jumped 80–147% after the second, peaking 10 days post-training. Type II fibers saw a 147% surge, the highest ever recorded in a human BFR study.
This proves your body doesn’t just repair muscle—it rebuilds it with more cellular machinery than heavy lifting ever does, but it takes weeks to kick in.
The p21 Gene: The Hidden Saboteur
The p21 gene spiked 4-fold right after training and stayed elevated for days. Researchers found it correlated directly with muscle fiber shrinkage—suggesting it’s not just a repair signal, but a trigger for temporary atrophy.
This could be why some people lose strength at first when starting BFR—your body isn’t failing, it’s preparing for a comeback.
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
People did light weight lifting with their legs squeezed tight, and their muscles didn't get bigger right away — they got bigger later, even after they stopped training.
Research results
Satellite cells went up 70%–147%, muscle size went down 6%–15% then up 6%–19%, strength went up 6% after 20 days of rest.
What this means - more context
Yes — muscles and repair cells kept growing even after stopping, which is unusual and might mean the body needs time to recover fully.
To investigate muscle hypertrophy, strength, and myonuclear and satellite cell responses to high-frequency blood flow-restricted resistance exercise (BFRRE)
Thirteen young adults performed two 5-day blocks of 7 BFRRE sessions (20% 1RM, 90–100 mmHg restriction) with a 10-day rest in between. Satellite cell and myonuclear numbers increased significantly, muscle fiber area initially decreased then increased, and strength peaked after 20 days of detraining. Molecular markers showed delayed upregulation post-intervention.
Methods Used
Thirteen young adults (24±2 yr, 9 men) completed two 5-day blocks of 7 unilateral knee extension sessions at 20% 1RM with partial blood flow restriction (90–100 mmHg) to volitional failure. Muscle biopsies and imaging (ultrasonography, MRI) were taken before, during, 3 days, and 10 days after training. Strength was measured via 1RM knee extension.
Main Finding
Satellite cell numbers increased 70%–80% in type I/II fibers after first block, then 80%–147% after second block. Muscle fiber area decreased 6%–15% in first block, then increased 6%–19% after second block. Maximal strength increased 6%±6% after 20 days of detraining. Myonuclei increased 30%–31%. All adaptations peaked 10–20 days post-training.
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 is very small (n=13) with no control group mentioned
- •Blinding, randomization, and follow-up protocols not specified
Surprising Findings
Muscle fiber area decreased by up to 15% during training, yet strength and size increased later.
Everyone assumes muscle growth happens during or right after training. This study shows the opposite: the body first breaks down tissue before rebuilding it stronger.
Practical Takeaways
If you're doing BFR training, take a 10-day break after 5 days of high-frequency sessions to let your muscles fully recover and supercompensate.
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 552 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This study watched 13 people do a special kind of exercise and noticed their muscles got a little bigger and stronger after a while — but we don’t know if the exercise actually caused it, because there was no group that didn’t do the exercise to compare with.
No conflicts of interest were detected in this study. No score impact.
Weaknesses
- Full methodology not available - based on abstract only
- Randomization status unknown — cannot be classified as RCT
- Blinding status unknown
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
People did light weight lifting with their legs squeezed tight, and their muscles didn't get bigger right away — they got bigger later, even after they stopped training.
Research results
Satellite cells went up 70%–147%, muscle size went down 6%–15% then up 6%–19%, strength went up 6% after 20 days of rest.
What this means - more context
Yes — muscles and repair cells kept growing even after stopping, which is unusual and might mean the body needs time to recover fully.
To investigate muscle hypertrophy, strength, and myonuclear and satellite cell responses to high-frequency blood flow-restricted resistance exercise (BFRRE)
Thirteen young adults performed two 5-day blocks of 7 BFRRE sessions (20% 1RM, 90–100 mmHg restriction) with a 10-day rest in between. Satellite cell and myonuclear numbers increased significantly, muscle fiber area initially decreased then increased, and strength peaked after 20 days of detraining. Molecular markers showed delayed upregulation post-intervention.
Methods Used
Thirteen young adults (24±2 yr, 9 men) completed two 5-day blocks of 7 unilateral knee extension sessions at 20% 1RM with partial blood flow restriction (90–100 mmHg) to volitional failure. Muscle biopsies and imaging (ultrasonography, MRI) were taken before, during, 3 days, and 10 days after training. Strength was measured via 1RM knee extension.
Main Finding
Satellite cell numbers increased 70%–80% in type I/II fibers after first block, then 80%–147% after second block. Muscle fiber area decreased 6%–15% in first block, then increased 6%–19% after second block. Maximal strength increased 6%±6% after 20 days of detraining. Myonuclei increased 30%–31%. All adaptations peaked 10–20 days post-training.
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 is very small (n=13) with no control group mentioned
- •Blinding, randomization, and follow-up protocols not specified
Surprising Findings
Muscle fiber area decreased by up to 15% during training, yet strength and size increased later.
Everyone assumes muscle growth happens during or right after training. This study shows the opposite: the body first breaks down tissue before rebuilding it stronger.
Practical Takeaways
If you're doing BFR training, take a 10-day break after 5 days of high-frequency sessions to let your muscles fully recover and supercompensate.
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 552 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This study watched 13 people do a special kind of exercise and noticed their muscles got a little bigger and stronger after a while — but we don’t know if the exercise actually caused it, because there was no group that didn’t do the exercise to compare with.
No conflicts of interest were detected in this study. No score impact.
Weaknesses
- Full methodology not available - based on abstract only
- Randomization status unknown — cannot be classified as RCT
- Blinding status unknown
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study didn’t use a fair test — no one was randomly assigned, no one was blinded, and there was no control group. That means we can’t be sure the results are real or just due to luck or other factors, so we should be careful trusting these findings.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
14 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control groupno control group
- Sample size (n=13)+1.3/20
- Follow-up+10/10
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- 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 552 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
This design cannot establish causation — the findings describe an association, not a cause. Randomization, blinding, and control group status are unknown; therefore, causation cannot be established.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding statements were disclosed in the provided text.
The provided text contains only the abstract, introduction, and partial text of the study. No Conflict of Interest section, funding declaration, author affiliations, or industry ties are present. Therefore, no conflicts of interest can be identified from the available information.
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 House of Hypertrophy cite this study, drawing 2 claims from it.
- Very strong evidence
Randomized or controlled trials support this claim, alongside consistent supporting evidence.
Evidence
- Conflicting evidence
Evidence points in both directions — no clear conclusion yet.
Evidence
Authored by
10 researchersIf this is your work, this is how we attribute it on Fit Body Science. Thomas Bjørnsen is listed as the lead author.