We report measurements by the T2K experiment of the parameters $theta_{23}$ and $Delta m^{2}_{32}$ governing the disappearance of muon neutrinos and antineutrinos in the three flavor neutrino oscillation model. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, the parameters are measured separately for neutrinos and antineutrinos. Using $7.482 times 10^{20}$ POT in neutrino running mode and $7.471 times 10^{20}$ POT in antineutrino mode, T2K obtained, $sin^{2}(theta_{23})=0.51^{+0.08}_{-0.07}$ and $Delta m^{2}_{32} = 2.53^{+0.15}_{-0.13} times 10^{-3}$eV$^{2}$/c$^{4}$ for neutrinos, and $sin^{2}({overline{theta}}_{23})=0.42^{+0.25}_{-0.07}$ and ${Deltaoverline{m}^2}_{32} = 2.55^{+0.33}_{-0.27} times 10^{-3}$eV$^{2}$/c$^{4}$ for antineutrinos (assuming normal mass ordering). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed.
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