The number of muons in the high-energy region of the continuum in the reaction $K^{+}\to {\pi }^0+{\mu }^{+}+\nu$ has been measured. The portion of the spectrum explored extended from 107.1 to 126.4 MeV. We measured the longitudinal polarization of the muons in the same energy interval by observing the spatial anisotropy of the $e^{+}$ from muon decay. The rate of decay with a muon in this energy interval was found to be 0.054±0.008 of the total $K^{+}$ decay rate in the mode $K^{+}\to {\pi }^0+e^{+}+\nu$. The polarization of the muons was found to be +0.61±0.39. These results are consistent with an analysis made assuming constant form factors, pure vector coupling, and equal muon and electron weak-coupling strength. A real or imaginary vector form-factor ratio, $\xi =\frac{f_{-}}{f_{+}}$, is consistent with the data. If $\xi$ is real, the most probable solution is $+0.2<\xi <+1.4\mathrm{}$. As a calibration experiment, we measured the polarization of muons from $K^{+}\to {\mu }^{+}+\nu$. We found it to be -0.94±0.21.

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