We calculate the effective g factor ($g^*$) in the υ=1 quantum Hall system based on a skyrmion-antiskyrmion pair excitation, and compare the result with that obtained from a quasihole-quasiparticle excitation. Using the Hartree-Fock approach on the Haldane's sphere geometry, we find that $g^*$ is significantly lowered due to the Coulomb interaction between reversed spins. Since our excitation gap is still overestimated, our calculated value of 2.55 at 7.7 T is suggested to be an upper limit for $g^*$. Our results are used to explain the temperature dependence of electron spin polarization observed by optically pumped nuclear magnetic resonance measurements.
