Sentence:  <WSD>Bumshoving</WSD> ¶ ... It will occur if you fail to hold your core whilst driving with the legs, leading to your arse going backwards faster than the blade handle, and thus the angle you're rocked over to increasing. 
Meaning of the word marked with <WSD> tags:  Giving way of the hips during the drive phase.[http://arcrsa.blogspot.ca/2008/06/correcting-errors-analysis-of-movement.html]