  O'Hara's energies, introduced by Jun O'Hara, were proposed to answer the
question of what is the canonical shape in a given knot type, and were
configured so that the less the energy value of a knot is, the "better" its
shape is. The existence and regularity of minimizers has been well studied. In
this article, we calculate the first and second variational formulae of the
$(\alpha,p)$-O'Hara energies and show absolute integrability, uniform
boundedness, and continuity properties. Although several authors have already
considered the variational formulae of the $(\alpha,1)$-O'Hara energies, their
techniques do not seem to be applicable to the case $p>1$. We obtain the
variational formulae in a novel manner by extracting a certain function from
the energy density. All of the $(\alpha,p)$-energies are made from this
function, and by analyzing it, we obtain not only the variational formulae but
also estimates in several function spaces.
