This 2018 UK human study detailed epigenetic muscle memory:
“We aimed to investigate an epigenetic memory of earlier hypertrophy in adult human skeletal muscle using a within measures design, by undertaking:
- Resistance exercise induced muscle growth (loading) [3 days a week for 7 weeks], followed by;
- Cessation of resistance exercise, to return muscle back towards baseline levels (unloading) [7 weeks], and;
- A subsequent later period of resistance exercise induced muscle hypertrophy (reloading) [3 days a week for 7 weeks].”
The findings were:
“Frequency of genome-wide hypomethylation is the largest after reloading induced hypertrophy where lean muscle mass is enhanced.
Hypomethylation is maintained from earlier load induced hypertrophy even during unloading where muscle mass returns back towards baseline, and is inversely associated with gene expression.
A single bout of acute resistance exercise evokes hypomethylation of genes that have enhanced gene expression in later reload induced hypertrophy.”
The study provided another example of how our bodies remember. It began with only eight male 27.6 ± 2.4 year-old subjects, though, and one of them dropped out.
See the discussion of a 2017 Netherlands human study in Are Underpowered Studies Ever Justified? with comments on studies with few subjects, such as:
“The problem occurs when people do small quantitative studies, but draw conclusions nonetheless, simply adding a disclaimer to the discussion (which they don’t put in the abstract, or the press release)..”
“Underpowered studies may only be useful to check if the experiment works out wrt understanding instructions, do the programs run, etc, but not as much for testing and estimating effects.”
“The problem with underpowered studies is that all estimates can vary erratically between samples. Combined with the desire of many researchers (and universities’ press offices) to find sensational patterns, this means that evidence from underpowered studies is ‘asymmetrically’ likely to be considered more conclusive. As in, something that seems really cool will probably be considered more conclusive than something that’s disappointing. Highly powered studies don’t afford this flexibility.”
https://www.nature.com/articles/s41598-018-20287-3 “Human Skeletal Muscle Possesses an Epigenetic Memory of Hypertrophy”