The technique is an adapted version of the powerful gene editing tool called Crispr. While the original version of Crispr snips DNA in precise locations to delete faulty genes or over-write flaws in the genetic code, the modified form “turns up the volume” on selected genes.
and
In the new version a Crispr-style guide is still used, but instead of cutting the genome at the site of interest, the Cas9 enzyme latches onto it. The new package also includes a third element: a molecule that homes in on the Cas9 and switches on whatever gene it is attached to.
and
The team showed that mice, with a version of muscular dystophy, a fatal muscle wasting disorder, recovered muscle growth and strength. The illness is caused by a mutation in the gene that produces dystrophin, a protein found in muscle fibres. However, rather than trying to replace this gene with a healthy version, the team boosted the activity of a second gene that produces a protein called utrophin that is very similar to dystrophin and can compensate for its absence.
Of course, once you can activate genes at will, you can also boost a perfectly healthy human in areas where he/she is weak or inept.
Genetic engineering for skill enablement, that is.