Using analysis of covariance , early physical therapy showed improvement relative to usual care in disability after @ months ( mean ODI score : early physical therapy group , @ -LSB- @ % CI , @ to @ -RSB- at baseline to @ -LSB- @ % CI , @ to @ -RSB- at @ months ; usual care group , @ -LSB- @ % CI , @ to @ -RSB- at baseline to @ -LSB- @ % CI , @ to @ -RSB- at @ months ; between-group difference , -@ -LSB- @ % CI , -@ to -@ -RSB- , P = @ ) .