REF-512 · Wilson, Marin, Rhea, Wilson, Loenneke & Anderson, 2012 · Journal of Strength and Conditioning Research, Vol. · Paper
Concurrent Training: A Meta-Analysis Examining Interference of Aerobic and Resistance Exercises
Sample
21 studies, 422 effect sizes (ES). Inclusion: strength-only vs strength + endurance (concurrent), or comparisons of concurrent combinations; at least one outcome of strength, power or hypertrophy; data to compute ES.
Key Findings
| Outcome | Strength only (ES) | Concurrent (ES) | Endurance only (ES) | Statistics |
|---|---|---|---|---|
| Hypertrophy | 1.23 | 0.85 | 0.27 | strength and concurrent both significantly > endurance only |
| Strength | 1.76 | 1.44 | 0.78 | strength and concurrent both significantly > endurance only |
| Power | 0.91 | 0.55 | 0.11 | all three groups significantly different |
Power is the quality where concurrent training was significantly below strength-only (0.55 vs 0.91); for hypertrophy and strength the abstract reports a numerically lower concurrent ES but only the comparison against endurance-only as significant
Modality: resistance training concurrent with running, but not cycling, produced significant decrements in both hypertrophy and strength
Dose: significant negative correlations between endurance-training frequency (r −0.26 to −0.35) and duration (r −0.29 to −0.75) and the ES for hypertrophy, strength and power
Body-fat reduction ES correlated with % maximal heart rate of the endurance work (r −0.60)
Authors' conclusion: interference is a function of the modality, frequency and duration of the endurance training selected
Practical Application
Across 21 studies (422 effect sizes), adding endurance training to strength training lowered the pooled effect for hypertrophy (1.23 → 0.85), strength (1.76 → 1.44) and power (0.91 → 0.55), with power the only outcome where concurrent differed significantly from strength-only; running, but not cycling, as the endurance mode caused significant decrements in both hypertrophy and strength, and longer or more frequent endurance sessions correlated with more interference (r up to −0.75 for duration) — the cost of concurrent training is real, dose-dependent, and in this pooling attached to running more than to cycling.
Masters/hybrid on cycling: combining strength and cycling looked comparatively safe here for hypertrophy and strength.
Masters/hybrid on running: in phases targeting hypertrophy or strength, limit running frequency and session duration — both correlated negatively with the strength-training outcomes.
Explosive/power work is the most sensitive quality in this pooling — protect it from high-volume endurance in the same phase.
For HYROX (which requires running anyway): accept that pure hypertrophy will be a compromise; target muscular endurance.
Note the later meta-analysis REF-330 (Schumann 2022, 43 studies) found no significant moderation by cycling vs running or by frequency — the modality rule from this 2012 pooling is not settled.
Limitations
2012 meta; newer work (REF-330) refines modality/timing and does not reproduce the running-vs-cycling difference
Protocol heterogeneity; "interference" depends on the chosen dependent variable
Does not separate masters as a subgroup — in older adults interference may be more pronounced (AMPK hyperphosphorylation with age; inference, not tested here)
How this entry was checked and changed
Content correction 2026-09-27
"Strength relatively preserved; interference significant for hypertrophy and power" -> pooled ES: hypertrophy 1.23 vs 0.85, strength 1.76 vs 1.44, power 0.91 vs 0.55; power is the outcome where concurrent differed significantly from strength-only.
Running vs cycling -> running (not cycling) caused significant decrements in both hypertrophy AND strength; frequency (r −0.26 to −0.35) and duration (r −0.29 to −0.75) negatively correlated with outcomes. Sample (21 studies, 422 ES) added; contrast with REF-330 noted.
Cross-reference descriptions checked against the cited entries' current content; wrong years, wrong entries and claims the cited entry does not make were corrected.