REF-1548 · Cochran et al., 2010 · Journal of Applied Physiology · Paper · PubMed

What does the fuel between two interval sessions 3 h apart change?

In 10 men, placebo raised p38 after the second session; AMPK and PGC-1α mRNA showed no clear difference. Both arms doubled. Markers only.

Main caveat: Read from the abstract. No dose, no glycogen values, no p values.
thin evidenceMeasured on a mixed group

Ten men did two trials in random order, each with a morning and an afternoon session of 5 × 4 min cycling at about 90-95% of heart-rate reserve, 3 h apart. Between sessions they took a high-carbohydrate drink or a placebo with no energy.

Phosphocreatine and ATP were similar after the morning but fell further in the afternoon on placebo. p38 and AMPK phosphorylation rose about 4-fold and 2-fold in the morning, with no difference by condition. After the afternoon session p38 was higher on placebo; AMPK did not differ.

PGC-1α mRNA rose about 8-fold in the recovery after the morning and remained up during the afternoon, with no difference by condition. Our reading: one of the few direct readings around a second same-day interval session; the second session began with PGC-1α mRNA already raised, and fuel changed p38 but not the PGC-1α readout.

Protocol

What it isolates: the fuel between two sessions. Both arms did the double at a fixed 3-h gap, so the double, the gap and the order are constant. There is no single-session arm, so what the second bout adds to a day with one bout is not measured.
Who: 10 men; training status not given in the abstract.
Sessions: AM and PM, each 5 × 4 min cycling at about 90-95% of heart-rate reserve, 3 h of recovery between.
Fuel: a high-carbohydrate drink (HI-HI) or a placebo with no energy (HI-LO) before the PM session. The dose is not given in the abstract.
Measures: vastus lateralis biopsies: phosphocreatine, ATP, p38 and AMPK phosphorylation, PGC-1α and COXIV mRNA.
Funding and interests: PubMed: Research Support, Non-U.S. Gov't; sponsor and conflicts not readable in the abstract record.

Key Results

MeasureHigh-carbohydrate drinkPlaceboBetween conditions
Phosphocreatine and ATP after AMsimilarsimilarnot different
Phosphocreatine and ATP during PMsmaller falllarger fallgreater fall on placebo
p38 phosphorylation during AMabout 4-foldabout 4-foldno difference
AMPK phosphorylation during AMabout 2-foldabout 2-foldno difference
p38 phosphorylation after PMlowerhigherhigher on placebo
AMPK phosphorylation after PMnot differentnot differentno difference
PGC-1α mRNA, recovery from AM and during PMabout 8-fold, stayed raisedabout 8-fold, stayed raisedno difference
COXIV mRNA, 3 h after AMraisedraisedno difference
No clear difference, not "the same": n = 10, and the abstract reports no equivalence test.
Not given: the carbohydrate dose, glycogen values and p values.

Mechanisms

Measured: muscle energy stores, two kinases and two mRNAs across two interval sessions.
Authors' interpretation: p38 may be sensitive to nutrients and could be involved in the adaptations reported after training with restricted carbohydrate, but this needs confirming. It is a proposal, not shown here.
Inference: since PGC-1α mRNA was already high when the second session started, a raised reading after a close second session cannot be credited to that session alone. The abstract offers no separate contribution, and no single-session arm exists to give one.
Not measured, or not in the abstract: adaptation, performance, second-session power, women.

Practical Application

What does the fuel between two interval sessions 3 h apart change? In 10 men, placebo raised p38 after the second session; AMPK and PGC-1α mRNA showed no clear difference. Both arms doubled. Markers only.
Good for: one direct reading of a same-day second interval session: the gene signal from the first was still present when the second began.
Good for: noting the cost in the second session on placebo: energy stores fell further (a marker, not power).
Not good for: deciding whether to double. There is no one-session comparison.
Not good for: advice to skip carbohydrate between sessions. It shows a kinase difference, not an adaptation; the training version of this question is REF-1549.
Not from this paper: the base's guidance on fuelling a close next session is in SYNTH-85.

Limitations

Read from the abstract. No dose, no glycogen values, no p values.
Acute markers, one day, n = 10.
No single-session arm.
Training status not stated; men only.
Fuel drink before PM only; intake during the first session and the day before is not in the abstract.
How this entry was checked and changed
Why this level

(from the abstract) — mechanistic laboratory study with no performance outcome (rubric C+). Subscription article; no copy in PubMed Central or Europe PMC