Any movement that is largely composed of extension would elongate or stretch the SFN. Conversely, general flexion movements (e.g., being seated and hunched over a computer) will shorten the SFN. Given that modern society is flexion dominant, SFN tightness or hypomobility is common. To gain better extension or if a client desires to exercise the extensors (i.e., gluteus muscles, spinal extensors, etc.), stretching the SFN is advised.
SNF Stretch: Superman