Acute molecular responses to concurrent resistance and high-intensity interval exercise in untrained skeletal muscle
Question
Does adding acute HIIT after resistance exercise interfere with skeletal muscle molecular responses in untrained men?
Summary
Ten untrained men completed resistance exercise alone and resistance exercise followed by cycling HIIT in a counterbalanced crossover design. Adding HIIT did not show an acute molecular interference effect, but outcomes were muscle signaling and mRNA markers rather than real training gains.
Methodology
- Healthy untrained young men.
- 10 participants.
- Leg extension plus cycle ergometer.
- Work intervals: 10 x 1-min cycling intervals at 90% HRmax after 4 x 8 leg extensions at 70% 1RM.
- Intensity: 70% 1RM and 90% HRmax.
- Single crossover trial.
- Acute.
- Counterbalanced crossover acute exercise study
- mTOR signaling, PGC-1alpha, Proteolytic genes, and Safety were tracked.
Outcomes
Interference
Results did not support an acute molecular interference effect.
PGC-1alpha
PGC-1alpha responses were larger after RE+HIIT.
Total PGC-1alpha increased 8.2-fold at 2 h and 4.5-fold at 6 h in RE+HIIT.
MuRF-1
MuRF-1 was higher after RE+HIIT.
Elevated 4.6-fold at 2 h and 1.6-fold at 6 h in RE+HIIT.
Completion
All participants completed both exercise trials.
10/10 completed.
Insights
- Same-session resistance exercise followed by short cycling HIIT is mechanistically plausible but not proven for long-term outcomes here.
- Do not overstate acute molecular signals as actual hypertrophy or endurance gains.
Limitations
- Very small sample.
- Men only.
- Acute molecular outcomes only.
- No long-term training data.
- Exact HIIT recovery interval was not clear in the the paper.
Safety
- No adverse events were reported.
- Participants were healthy, screened, and supervised; the study included invasive muscle biopsies.