There are a couple of ways to handle this issue. First lets say your run cycle is from frame 1 to 120. On Frame 120, before making any changes past 120, make sure to make a key frame for each channel that has any movement from 1-120. Make a exact copy of frame 120 then paste it into 121. What this does is locks down the spline curves so anything after 121 does not affect the frames 1-120. The other way is to use layers. So you have the run from 1-120. Make a copy of frame 120 and go to the next layer and paste in the 120 frame into 120 and use the next layer to make the guy jump the wall. Use Replace on the layers. What this does is make each movement separate but will transition between layers with no jump if you make the start and stop exact copies and use the replace on the layers.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13