Aerobic exercise intensity does not affect the anabolic signaling following resistance exercise in endurance athletes.
Level 2 - randomized trial
Individual crossover experimental study in humans.
PubMed 34031501 · doi:10.1038/s41598-021-90274-8
What was done
Eight male cyclists completed three exercise sessions in a crossover design: (1) resistance exercise alone (RES: 6 × 8 squats at 80% 1-RM), (2) resistance exercise plus moderate-intensity cycling (RES + MIC: 40 min at 65% VO2peak), and (3) resistance exercise plus high-intensity interval cycling (RES + HIIC: 40 min with 6 alternating 3-min intervals at 85% and 45% VO2peak). Muscle biopsies were taken at rest and 3 h post-resistance exercise to measure mTOR and AMPK pathway phosphorylation.
What was found
There was a main effect of condition for mTOR S2448 (p = 0.043), with greater phosphorylation in RES + MIC compared to RES (p = 0.033). AMPKα2 T172 also showed a main effect (p = 0.041), with higher response in RES + MIC than in RES + HIIC (p = 0.026) and RES (p = 0.046). No other condition effects were detected for remaining protein kinases (p > 0.05). Exact phosphorylation levels, fold changes, or effect sizes were not reported in the abstract.
Why it matters
The findings challenge the acute molecular interference hypothesis, showing that neither moderate- nor high-intensity endurance cycling impaired acute resistance-induced mTOR signaling in endurance athletes.
Limits
The sample size is very small (n = 8) and restricted entirely to male cyclists. Measurements were taken at only one acute time point (3 h post-exercise), which cannot capture broader signaling kinetics, translation rates, muscle protein synthesis, or chronic training outcomes.
Cited by
- supports Concurrent aerobic and resistance training does not cause an inherent molecular interference effect that blunts muscle adaptations when session quality is maintained.