I was actually looking into the meaning of the word run-up after seeing this question. Well after seeing Michael's comment actually, but yeah.
When I Googled the word, I got the following result:
the period preceding a notable event. "a programme aimed at lowering unemployment in the run-up to the next election"
an act of running briefly to gain momentum before performing a jump in athletics, bowling in cricket, etc. "high jumper Steve Smith will use his shortened five-stride run-up"
...and many more.
Now I fairly understood which meaning of run-up was intended in that question. However, the second entry shows this sentence where the phrase "high jumper" is used. Now I looked into the what the word jumper means here, but could not deduce my observations. Jumper has following entries in the Sports category meanings on Google:
a person or animal that jumps. "the horse should be a better jumper this season"
Basketball - another term for jump shot.
Now I really can't understand which meaning is intended in this context. Steve Smith doesn't jump while batting, I mean that's kind of weird. He isn't playing Basketball either.
Is it referring to the motion of him coming forward to hit the ball, like players do when they hit a six (they come considerably away from the stumps to hit the ball)? Also I would appreciate if someone gave me the word for the above described motion (coming forward to hit the ball in cricket), I believe it has a term.