To explore the mechanisms of speech articulation, which is one of the most sophisticated human motor skills controlled by the central nervous system, we investigate the force generation dynamics of the human speech articulator muscles [lips: orbicularis oris superior (OOS) and inferior (OOI)]. Short pulse electrical stimulation (300 µs) with approximately three or four times the sensation threshold intensity of each subject induced the muscle response. The responses of these muscles were modeled as second-order dynamics with a time delay, and the model parameters [natural frequency (NF), damping ratio (DR), and time delay (TD)] were identified using a nonlinear least mean squares method. The lips [orbicularis oris superior (NF: 6.1 Hz, DR: 0.71, TD: 14.5 ms), orbicularis oris inferior (NF: 6.1 Hz, DR: 0.68, TD: 15.6 ms)] showed roughly similar characteristics in eight subjects. The dynamics in the tongue (generated by combined muscles) also showed similar characteristics (NF: 6.1 Hz, DR: 0.68, TD: 17.4 ms) in two subjects. The NF was higher and the DR lower than for the arms [triceps long head, NF: 4.25 Hz, DR: 1.05, TD: 23.8 ms], indicating that articulatory organs adapt for more rapid movement. In contrast, slower response dynamics was estimated when muscle force data by voluntarily contraction task was used for force generation dynamics modeling. We discuss methodological problems in estimating muscle dynamics when different kinds of muscle contraction methods are used.