REF-1540 · Mortensen et al., 2007 · Journal of Applied Physiology · Paper · PubMed

Did twice every second day beat daily on the PGC-1 family?

In 7 young men, one leg each way for 10 wk: no significant difference in PGC-1α, PGC-1β or PRC mRNA. Read beside Hansen 2005. Markers, knee extension only.

Main caveat: Read from the abstract. No fold changes, no p values, and glycogen state not stated.
limited, mixed evidenceMeasured on non-athletes and recreational people

Seven young healthy men trained one leg once daily and the other twice daily every second day for 10 weeks, with total training equal between legs. Before and after training, mRNA of the three PGC-1 family members was measured in response to 3 h of exercise. The legs did not differ significantly.

Training lowered PGC-1β in both legs; PGC-1α went up in the once-daily leg without reaching significance; PRC did not change. Acute exercise raised PGC-1α and PRC, but not PGC-1β, before and after training. In a separate comparison of three muscles, only PGC-1β levels differed, inversely with the share of type I fibres.

Our reading: from the group that started the claim, a direct result that the pattern of training did not show up in this gene family.

Protocol

What it isolates: the pattern of training (a double with a rest day against daily) at equal total training, with low glycogen part of the pattern if it followed REF-1539 (inference; this abstract does not mention glycogen). The abstract describes the outcome as one family of genes only.
Relation to Hansen 2005 ([REF-1539]): four of six authors, the hospital department, 10-week length, one-leg knee extension and n = 7 match. Whether these are the same seven men is not stated in the abstract (inference: likely; read as one laboratory's programme and do not count as independent replication).
Who: young healthy men, n = 7; for the muscle comparison, n = 7 (triceps, soleus, vastus lateralis).
Acute test: 3 h of exercise before and after the 10 weeks, mRNA as the outcome. Glycogen state in the test is not given in the abstract.
Funding and interests: PubMed: Research Support, Non-U.S. Gov't; sponsor and conflicts not readable in the abstract record.

Key Results

MeasureOnce-daily legTwice every second day legBetween legs
PGC-1α mRNA, trainingrose, not significantno significant change reportedno significant difference
PGC-1β mRNA, trainingfellfellno significant difference
PRC mRNA, trainingno changeno changeno significant difference
Acute exercise, PGC-1α and PRCroseroseno significant difference
Acute exercise, PGC-1βno changeno changeno significant difference
No clear difference, not "the same". The abstract concludes that regulation does not depend on the protocol. With 7 men and no equivalence test, the data show only that no difference was detected.
Muscle comparison: only PGC-1β level differed among muscles, correlating inversely with type I share. This does not bear on doubles.
No fold changes or p values are printed in the abstract.

Mechanisms

Measured: mRNA of three transcriptional coactivators.
Authors' interpretation: the PGC-1 family's response did not depend on the training protocol; training itself lowered PGC-1β mRNA, the title finding.
Inference: if these are Hansen's men, this suggests enzymes and time to exhaustion moved there without a PGC-1 mRNA difference here. That is a suggestion from two papers, not one test. The 3-h test was a single bout before and after training, not a reading around the second session, so it does not test whether a second session briefly raises PGC-1α.
Not measured, or not in the abstract: protein, enzymes, mitochondrial content, performance, women.

Practical Application

Did twice every second day beat daily on the PGC-1 family? In 7 young men, one leg each way for 10 wk: no significant difference in PGC-1α, PGC-1β or PRC mRNA. Read beside Hansen 2005. Markers, knee extension only.
Good for: a counterweight when PGC-1α is the reason offered for stacking sessions: in this design, with 7 men, no significant difference in the chronic response was detected between patterns.
Good for: reading REF-1539 honestly: results there on enzymes and exhaustion time did not need a PGC-1 family difference here, if this is the same programme (inference).
Not good for: concluding doubles do not matter. A marker in a small muscle group settles nothing on performance.
Not good for: the acute signal around a close second session; see REF-1536 and REF-1548.

Limitations

Read from the abstract. No fold changes, no p values, and glycogen state not stated.
n = 7, one small muscle group.
Markers only. mRNA is not protein, enzyme or performance.
Not independent of [REF-1539] (likely, by inference).
Men only.
How this entry was checked and changed
Why this level

(from the abstract) — within-subject n = 7 (rubric B: crossover <15), one step lower: the outcome is a marker, not performance. Subscription article; no copy in PubMed Central or Europe PMC