  Wave functions and energy eigenvalues of the path integral Hamiltonian are
studied in Lorentz frame moving with velocity $v$. The instantaneous
interaction produced by the Wilson loop is shown to be reduced by an overall
factor $\sqrt{1-(\frac{v}{c})^2}$. As a result one obtains the boosted energy
eigenvalues in the Lorentz covariant form $E= \sqrt{\veP^2+M^2_0}$, where $M_0$
is the c.m. energy, and this form is tested for two free particles and for the
Coulomb and linear interaction.Using Lorentz contracted wave functions of the
bound states one obtains the scaled parton wave functions and valence quark
distributions for large $P$. Matrix elements containing wave functions moving
with different velocities strongly decrease with growing relative momentum,
e.g. for the time-like formfactors one obtains $F_h(Q_0)\sim
(\frac{M_h}{Q_0})^{2 n_h} $ with $n_h = 1$ and 2 for mesons and baryons, as in
the "quark counting rule".
