Diaphragm monitoring relies on the measurement of trans diaphragmatic pressure (Pdi) during cervical magnetic stimulation (CMS). Specifically, twitch Pdi (Pdi tw ) is measured using esophageal and gastric probes. Such probes are invasive and require a high level of expertise, and non-invasive methods to assess diaphragm function are necessary. Here we test how maximal diaphragm tissue velocity (Vdi max ) is related to stimulation intensity and Pdi tw , during CMS. Ultrafast ultrasound of the diaphragm was performed in 13 healthy subjects at various intensity levels. We show that Vdi max is strongly related to stimulation intensity and Pdi tw , in all participants. Within-day reliability for Vdi max was strong and similar to that of Pdi tw . Our findings open prospects for the non-invasive monitoring of Pdi tw in clinical populations. Indeed, the relative changes in Pdi tw over time may be monitored by assessing the relative changes in Vdi max .