Does adding cardio reduce muscle growth or strength?
Across 43 studies, adding aerobic training on top of an identical strength training programme did not compromise muscle hypertrophy or maximal strength development. Explosive strength gains may be attenuated, and that attenuation was more pronounced in the studies where the aerobic and strength work were done in the same session than where sessions were separated by at least 3 h.
Schumann M (2022) · Sports Medicine (Auckland, N.Z.) · PMID 34757594
It does not say cardio is free of any cost. Explosive strength was attenuated (- 0.28, p = 0.007, CI excluding zero), so "cardio doesn't affect anything" is an overclaim. The null covers muscle hypertrophy and maximal strength only.
It does not establish that the same-session effect is causal. The abstract reports a p-value within the same-session subgroup (p = 0.043) and a non-significant one for sessions separated by at least 3 h (p > 0.05). Those are two within-subgroup results, not a formal test of the difference between the two arrangements. Treat "separate your cardio from your lifting" as a reasonable inference from a subgroup pattern, not a proven mechanism.
It does not say more cardio is always costless. The comparison was a strength programme with versus without added aerobic work, so it speaks to whether adding aerobic training subtracts from lifting adaptations — not to what happens at very high endurance volumes, or in athletes already at their recovery ceiling. Training status in this analysis topped out at "active"; highly trained and elite athletes were not analysed as a distinct group.
It does not settle maximal strength at the subgroup level. A separate 2024 meta-analysis in the same journal (Huiberts et al., PMID 37847373, 59 studies, 1346 participants) reported blunted lower-body strength adaptations in males but not females (male: - 0.43, group difference P = 0.03). A card claiming "maximal strength is completely unaffected, for everyone" could be knocked down with one link. Whole-muscle hypertrophy is the outcome that no whole-muscle meta-analysis contests, and it should carry the claim; Huiberts reported that data on muscle hypertrophy were insufficient to draw any conclusions.
It does not say the muscle is unaffected at every level of measurement. A meta-analysis on muscle fibre hypertrophy (Lundberg et al., PMID 35476184) found a small negative effect at the fibre level, most visible for type I fibres when the aerobic training was running rather than cycling, even though whole-muscle hypertrophy was unaffected. That paper is not independent corroboration of this one: it shares the identical PROSPERO registration (CRD42020203777) and identical search dates, and Schumann is an author on it. It is a protocol sibling.
It does not establish that the pooled studies were randomised. The abstract and the PubMed publication types establish controlled, supervised interventions with a matched comparison arm — nothing more. Do not write "randomised" on the card.
It does not address fat loss, body composition, sport performance, injury, or nutrition. And its literature search closed on 15 March 2021, so nothing published after early 2021 is in it.
Every figure below is shown with the sentence it was taken from, so you can check it against the paper rather than trusting us.
- 43studies
Number of studies pooled in the meta-analysis
A total of 43 studies were included.
- - 0.01standardised mean difference
Effect of adding aerobic training on muscle hypertrophy — effectively nil. This is the third SMD in the sentence, mapped by the trailing 'respectively'.
The estimated standardised mean differences (SMD) based on the random-effects model were - 0.06 (95% confidence interval [CI] - 0.20 to 0.09; p = 0.446), - 0.28 (95% CI - 0.48 to - 0.08; p = 0.007), and - 0.01 (95% CI - 0.16 to 0.18; p = 0.919) for maximal strength, explosive strength, and muscle hypertrophy, respectively.
- 0.919p-value
Significance for the hypertrophy effect — not significant
The estimated standardised mean differences (SMD) based on the random-effects model were - 0.06 (95% confidence interval [CI] - 0.20 to 0.09; p = 0.446), - 0.28 (95% CI - 0.48 to - 0.08; p = 0.007), and - 0.01 (95% CI - 0.16 to 0.18; p = 0.919) for maximal strength, explosive strength, and muscle hypertrophy, respectively.
- - 0.06standardised mean difference
Effect of adding aerobic training on maximal strength gains — essentially zero and not statistically significant. First SMD in the sentence, mapped by the trailing 'respectively'.
The estimated standardised mean differences (SMD) based on the random-effects model were - 0.06 (95% confidence interval [CI] - 0.20 to 0.09; p = 0.446), - 0.28 (95% CI - 0.48 to - 0.08; p = 0.007), and - 0.01 (95% CI - 0.16 to 0.18; p = 0.919) for maximal strength, explosive strength, and muscle hypertrophy, respectively.
- 0.446p-value
Significance for the maximal strength effect — not significant
The estimated standardised mean differences (SMD) based on the random-effects model were - 0.06 (95% confidence interval [CI] - 0.20 to 0.09; p = 0.446), - 0.28 (95% CI - 0.48 to - 0.08; p = 0.007), and - 0.01 (95% CI - 0.16 to 0.18; p = 0.919) for maximal strength, explosive strength, and muscle hypertrophy, respectively.
- - 0.28standardised mean difference
Effect of adding aerobic training on explosive strength — a small attenuation relative to strength training alone, with a CI excluding zero. This is a between-group difference in gains, NOT a within-group decline. Second SMD in the sentence, mapped by the trailing 'respectively'.
The estimated standardised mean differences (SMD) based on the random-effects model were - 0.06 (95% confidence interval [CI] - 0.20 to 0.09; p = 0.446), - 0.28 (95% CI - 0.48 to - 0.08; p = 0.007), and - 0.01 (95% CI - 0.16 to 0.18; p = 0.919) for maximal strength, explosive strength, and muscle hypertrophy, respectively.
- 0.007p-value
Significance for the explosive strength attenuation — statistically significant
The estimated standardised mean differences (SMD) based on the random-effects model were - 0.06 (95% confidence interval [CI] - 0.20 to 0.09; p = 0.446), - 0.28 (95% CI - 0.48 to - 0.08; p = 0.007), and - 0.01 (95% CI - 0.16 to 0.18; p = 0.919) for maximal strength, explosive strength, and muscle hypertrophy, respectively.
- 0.043p-value
Significance of the explosive-strength attenuation within the same-session subgroup. This is a within-subgroup p-value, NOT a test of the difference between same-session and separated arrangements — do not present it as an interaction test.
Attenuation of explosive strength was more pronounced when concurrent training was performed within the same session (p = 0.043) than when sessions were separated by at least 3 h (p > 0.05).
- 3hours
Separation between aerobic and strength sessions in the subgroup where the explosive-strength attenuation was not statistically significant
Attenuation of explosive strength was more pronounced when concurrent training was performed within the same session (p = 0.043) than when sessions were separated by at least 3 h (p > 0.05).
- 4weeks
Minimum training intervention length for a study to be included
healthy adults of any sex and age; Intervention: supervised concurrent aerobic and strength training for at least 4 weeks; Comparison: identical strength training prescription, with no aerobic training; Outcome: maximal strength, explosive strength, and muscle hypertrophy.
- 59studies
Size of the separate 2024 meta-analysis that partially contests the maximal-strength null. DIFFERENT PAPER — Huiberts et al., PMID 37847373. Must be attributed to that paper wherever it appears.
In total, 59 studies with 1346 participants were included.
- 1346participants
Pooled participant count of the contesting 2024 meta-analysis. DIFFERENT PAPER — Huiberts et al., PMID 37847373. This figure must never be attached to the Schumann claim, whose abstract reports no participant total.
In total, 59 studies with 1346 participants were included.
- - 0.43standardised mean difference
Blunted lower-body strength adaptation in males found by the contesting 2024 meta-analysis; no such effect in females. DIFFERENT PAPER — Huiberts et al., PMID 37847373. This is the number that makes an unqualified 'cardio never hurts your strength' headline unsafe.
Concurrent training showed blunted lower-body strength adaptations in males, but not in females (male: - 0.43, 95% confidence interval [- 0.64 to - 0.22], female: 0.08 [- 0.34 to 0.49], group difference: P = 0.03).
- 0.03p-value
Significance of the male-versus-female group difference in lower-body strength adaptation. DIFFERENT PAPER — Huiberts et al., PMID 37847373.
Concurrent training showed blunted lower-body strength adaptations in males, but not in females (male: - 0.43, 95% confidence interval [- 0.64 to - 0.22], female: 0.08 [- 0.34 to 0.49], group difference: P = 0.03).
Healthy adults of any sex and age. The comparison is a supervised concurrent aerobic-and-strength programme of at least 4 weeks against an identical strength training prescription with no aerobic training added. Moderators reported as non-significant in the Results were type of aerobic training (cycling vs. running), frequency of concurrent training (> 5 vs. < 5 weekly sessions), training status (untrained vs. active), and mean age (< 40 vs. > 40 years); the Objective also names training modality, training type and exercise order as subgroups examined. Note that "active" is the upper bound of the training-status subgroup, so highly trained or elite athletes were not analysed as a distinct group. The abstract reports no pooled participant count.
Schumann M, et al. (2022)Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function: An Updated Systematic Review and Meta-Analysis.
Sports Medicine (Auckland, N.Z.) · PMID 34757594
Meta-analysis · 43 studies
Who funded itAuthors declare no conflicts of interest.
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