Study analysis · International Journal of Sports Medicine · 2021
Changing your workout routine could be the secret to more balanced muscle growth—science says why doing the same exercises might leave parts of your muscles behind.
If you keep doing the same exercises, some parts of your muscles might not grow as much, but switching things up helps all parts grow more evenly.
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 shows a possible link between changing exercises and more even muscle growth in young men who haven’t trained in a while. It doesn’t prove that changing exercises is the reason, just that it was connected to the results.
What’s the bottom line?
Some guys did the same exercises every time, while others changed them up. After nine weeks, the ones who changed exercises grew muscle in all parts they were measured. The ones who did the same exercises didn’t grow as much in some areas.
How strong is this study?
The study tried to be fair by randomly assigning people to groups, but we don’t know if the testers knew who was in which group, which could affect results. Because we only have a short summary, we can’t be sure how well the study was done overall.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
59 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=22)+2.1/20
- 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 546 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design cannot establish causation — the findings describe an association, not a cause. Although the abstract mentions random allocation, blinding status is unclear and full methodology is not available. Per conservative rules, this cannot be confirmed as a true RCT with adequate methodology. Therefore, causation cannot be established.
Key takeaways
- 01
The group that changed exercises grew muscle in every spot checked.
- 02
The group that didn’t change had no significant growth in two spots: middle of the outer thigh and top of the biceps.
- 03
The top of the outer thigh grew more than the middle in the group that changed exercises.
- 04
Yes, changing exercises may help muscles grow more evenly and fully across different areas.
Surprising findings
- Doing the same exercises didn’t lead to significant growth in two key muscle areas—the middle of the outer thigh and the top of the biceps.Many people believe that consistency with the same lifts is the best way to build muscle, but this study shows it may actually limit growth in certain regions.
Practical takeaways
Switch up your exercises for the same muscle group every few weeks to promote more balanced muscle growth.
Results are based on detrained young men; it’s unclear if this applies to advanced lifters or women. Full methodology and effect sizes are unknown.
low confidenceDon’t assume all parts of a muscle grow equally—even with varied training, some regions respond more than others.
Regional growth differences were observed using ultrasound; real-world functional or aesthetic impact is not specified.
low confidenceWhy this study matters
Exercise Variety = Full Muscle Growth
The group that varied their resistance exercises showed significant muscle growth at every site measured—proximal, middle, and distal regions of the thigh and arm muscles. In contrast, the group doing the same exercises didn’t show significant gains in the middle of the outer thigh or the top of the biceps.
This suggests that simply changing your exercises for the same muscle group could lead to more complete muscle development, which may improve both appearance and function.
Not All Growth Is Equal—Even With Variation
Even in the group that varied exercises, the proximal (top) site of the lateral thigh grew more than the middle site (P<0.05), showing that muscle growth isn’t uniform, even with diverse training.
It challenges the idea that just switching exercises guarantees even growth—some areas still respond more than others.
Small Study, Big Implications
Only 22 young, detrained men were studied—11 in each group—and all were followed for nine weeks with ultrasound measurements. Despite the small size, clear differences emerged between exercise strategies.
It shows that even short-term studies with limited participants can reveal meaningful patterns in how our bodies adapt to training.
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
Some guys did the same exercises every time, while others changed them up. After nine weeks, the ones who changed exercises grew muscle in all parts they were measured. The ones who did the same exercises didn’t grow as much in some areas.
Research results
The group that changed exercises grew muscle in every spot checked. The group that didn’t change had no significant growth in two spots: middle of the outer thigh and top of the biceps. The top of the outer thigh grew more than the middle in the group that changed exercises.
What this means - more context
Yes, changing exercises may help muscles grow more evenly and fully across different areas.
The study aimed to compare the effects of performing the same versus different resistance exercises for the same muscle group on muscle hypertrophy at various anatomical sites along the muscle length in detrained young men.
The study compared muscle hypertrophy in detrained young men who either repeated the same exercises or varied exercises for the same muscle groups over nine weeks of resistance training. Muscle thickness was measured at multiple sites using ultrasound. The group that varied exercises showed significant hypertrophy at all sites, while the group using the same exercises did not show significant improvements at the middle site of the lateral thigh and proximal site of the elbow flexors.
Methods Used
Twenty-two detrained men (23.3±4.1 years) were randomly allocated to two groups: one performing the same exercises throughout (N-VAR=11) and one varying exercises (VAR=11). Both groups completed 3 weekly resistance training sessions for nine weeks. Muscle thickness was assessed at proximal, middle, and distal sites of the lateral and anterior thigh, elbow flexors, and extensors using B-mode ultrasound.
Main Finding
The VAR group showed significant increases in muscle thickness at all measured sites (P<0.05), with greater relative hypertrophy in the proximal site of the lateral thigh compared to the middle site (P<0.05). The N-VAR group did not show significant improvements at the middle site of the lateral thigh and proximal site of the elbow flexors (P>0.05).
Confidence Level
Limited - based on abstract only, full methodology not available
Study Flags
Red Flags
- •Full text not available - methodology details cannot be verified
- •Effect sizes and confidence intervals not reported in abstract
- •Blinding status and randomization method not specified in abstract
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
Doing the same exercises didn’t lead to significant growth in two key muscle areas—the middle of the outer thigh and the top of the biceps.
Many people believe that consistency with the same lifts is the best way to build muscle, but this study shows it may actually limit growth in certain regions.
Practical Takeaways
Switch up your exercises for the same muscle group every few weeks to promote more balanced muscle growth.
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 546 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This study shows a possible link between changing exercises and more even muscle growth in young men who haven’t trained in a while. It doesn’t prove that changing exercises is the reason, just that it was connected to the results.
Strengths
- Explicit mention of random allocation to groups
- Control group included (N-VAR vs VAR)
- Repeated measurements over 9 weeks with ultrasound assessment
Weaknesses
- Full methodology not available - based on abstract only
- Blinding status is unknown - risk of performance and detection bias cannot be assessed
- Small sample size (n=22) limits statistical power and generalizability
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Some guys did the same exercises every time, while others changed them up. After nine weeks, the ones who changed exercises grew muscle in all parts they were measured. The ones who did the same exercises didn’t grow as much in some areas.
Research results
The group that changed exercises grew muscle in every spot checked. The group that didn’t change had no significant growth in two spots: middle of the outer thigh and top of the biceps. The top of the outer thigh grew more than the middle in the group that changed exercises.
What this means - more context
Yes, changing exercises may help muscles grow more evenly and fully across different areas.
The study aimed to compare the effects of performing the same versus different resistance exercises for the same muscle group on muscle hypertrophy at various anatomical sites along the muscle length in detrained young men.
The study compared muscle hypertrophy in detrained young men who either repeated the same exercises or varied exercises for the same muscle groups over nine weeks of resistance training. Muscle thickness was measured at multiple sites using ultrasound. The group that varied exercises showed significant hypertrophy at all sites, while the group using the same exercises did not show significant improvements at the middle site of the lateral thigh and proximal site of the elbow flexors.
Methods Used
Twenty-two detrained men (23.3±4.1 years) were randomly allocated to two groups: one performing the same exercises throughout (N-VAR=11) and one varying exercises (VAR=11). Both groups completed 3 weekly resistance training sessions for nine weeks. Muscle thickness was assessed at proximal, middle, and distal sites of the lateral and anterior thigh, elbow flexors, and extensors using B-mode ultrasound.
Main Finding
The VAR group showed significant increases in muscle thickness at all measured sites (P<0.05), with greater relative hypertrophy in the proximal site of the lateral thigh compared to the middle site (P<0.05). The N-VAR group did not show significant improvements at the middle site of the lateral thigh and proximal site of the elbow flexors (P>0.05).
Confidence Level
Limited - based on abstract only, full methodology not available
Study Flags
Red Flags
- •Full text not available - methodology details cannot be verified
- •Effect sizes and confidence intervals not reported in abstract
- •Blinding status and randomization method not specified in abstract
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
Doing the same exercises didn’t lead to significant growth in two key muscle areas—the middle of the outer thigh and the top of the biceps.
Many people believe that consistency with the same lifts is the best way to build muscle, but this study shows it may actually limit growth in certain regions.
Practical Takeaways
Switch up your exercises for the same muscle group every few weeks to promote more balanced muscle growth.
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 546 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This study shows a possible link between changing exercises and more even muscle growth in young men who haven’t trained in a while. It doesn’t prove that changing exercises is the reason, just that it was connected to the results.
Strengths
- Explicit mention of random allocation to groups
- Control group included (N-VAR vs VAR)
- Repeated measurements over 9 weeks with ultrasound assessment
Weaknesses
- Full methodology not available - based on abstract only
- Blinding status is unknown - risk of performance and detection bias cannot be assessed
- Small sample size (n=22) limits statistical power and generalizability
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study tried to be fair by randomly assigning people to groups, but we don’t know if the testers knew who was in which group, which could affect results. Because we only have a short summary, we can’t be sure how well the study was done overall.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
59 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=22)+2.1/20
- 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 546 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design cannot establish causation — the findings describe an association, not a cause. Although the abstract mentions random allocation, blinding status is unclear and full methodology is not available. Per conservative rules, this cannot be confirmed as a true RCT with adequate methodology. Therefore, causation cannot be established.
Standing
Who’s using this study?
The videos and claims on this site that lean on this study, and the researchers who wrote it.
1 video from House of Hypertrophy cite this study, drawing 1 claim from it.
- Contradicted
Evidence contradicts this claim.
Evidence
Authored by
9 researchersIf this is your work, this is how we attribute it on Fit Body Science. Bruna Daniella de Vasconcelos Costa is listed as the lead author.
- Universidade Estadual de Londrina
Cited in 16 claims · 3 videos