Blazevich and Jenkins (Journal of Sports Sciences 2002) used high-velocity or low velocity protocols on concurrent sprint and plyometric training junior elite sprinters. High-velocity flying 20m: 2.227s before and 2.185s after, low-velocity flying 20m: 2.262s before and 2.207s after. Low velocity group improved by 2.4% and approached statistical significance (which contradicts my belief in velocity specificity). However both groups employed resistances and speed that involved a wide variety of the force-time envelope.
Check out the study – I have a high regard for Blazevich (currently at Brunel University in London). I liked their choice of exercises although closed chain exercises might have yielded better results but may have been impractical given the limitations of commercial equipment. I must add that there is an appropriate piece of equipment gathering dust in the storeroom of the University of Technology Sydney that would have satisfied the closed chain movement specific requirement.