  Classical rotating closed string are folded strings. At the folding points
the scalar curvature associated with the induced metric diverges. As a
consequence one cannot properly quantize the fluctuations around the classical
solution since there is no complete set of normalizable eigenmodes. Furthermore
in the non-critical effective string action of Polchinski and Strominger, there
is a divergence associated with the folds. We overcome this obstacle by putting
a massive particle at each folding point which can be used as a regulator.
Using this method we compute the spectrum of quantum fluctuations around the
rotating string and the intercept of the leading Regge trajectory. The results
we find are that the intercepts are $a=1$ and $a=2$ for the open and closed
string respectively, independent of the target space dimension. We argue that
in generic theories with an effective string description, one can expect
corrections from finite masses associated with either the endpoints of an open
string or the folding points on a closed string. We compute explicitly the
corrections in the presence of these masses.
