Association of skeletal muscle and serum metabolites with maximum power output gains in response to continuous endurance or high-intensity interval training programs: The TIMES study - A randomized controlled trial

Castro A, Duft RG, Ferreira MLV, Andrade ALL, Gáspari AF, Silva LM, Oliveira-Nunes SG, Cavaglieri CR, Ghosh S, Bouchard C, Chacon-Mikahil MPT

Question

Which baseline serum and skeletal muscle metabolites are associated with gains in maximum power output after continuous endurance training or HIIT?

Summary

The TIMES study randomized sedentary young men to 8 weeks of supervised cycling HIIT, continuous endurance training, or control. HIIT and endurance training produced similar improvements in maximal power output, while control declined slightly. The main focus was metabolomics: baseline serum and muscle metabolites were associated with who improved more, but these associations are exploratory and not ready for workout prescription.

Methodology

Seventy healthy sedentary young Caucasian men included in the metabolomics/completer analysis.
70 participants.
Cycle ergometer.
Work intervals: 5 x 4 min at 90% HRR.
Recovery: 3 min active recovery at 50% HRR in weeks 1-4 and 60% HRR in weeks 5-8.
Intensity: 90% HRR work intervals, cadence 70-80 rpm.
40 min.
3 days/week for weeks 1-4, then 4 days/week for weeks 5-8.
8 weeks.
Randomized controlled trial with supervised cycling endurance training, HIIT, and control groups, plus baseline metabolomic association analyses.
Maximum power output, Baseline metabolite associations, Heart-rate maximum, and Adherence were tracked.

Outcomes

Maximum power output

HIIT and endurance training similarly improved maximum power output compared with control.

ET +49.0 +/- 15.3 W (+21.4 +/- 8.0%); HIIT +56.6 +/- 17.2 W (+24.3 +/- 8.5%); control -10.0 +/- 9.3 W; p<0.01 vs pre and control.

Improved

Metabolite associations

Different baseline serum and muscle metabolites were associated with response to ET and HIIT, with shared pathway themes involving amino acid and carbohydrate metabolism.

HIIT-associated examples included serum lysine, phenylalanine, creatine, and muscle glycolate; ET-associated examples included serum glycerol and several muscle amino acid-related metabolites.

Mixed

Heart-rate maximum

HRmax did not change after training.

No clear change

Adherence

Completers attended more than 90% of prescribed sessions.

>90% session attendance among completers.

Improved

Insights

A supervised 5 x 4 min cycling HIIT protocol can improve maximal power output in sedentary young men.
Continuous cycling produced similar performance gains, so this paper should not be used for HIIT superiority claims.
Metabolomics findings are useful background for response variability, not current app personalization.

Limitations

Young Caucasian men only.
Short 8-week duration.
Metabolite associations were exploratory.
Targeted metabolomics limited coverage.
No clinical or long-term adherence outcomes.

Safety

Participants were medically screened with ECG.
No adverse event signal was reported in the extracted NXML.
High-intensity protocol was supervised.