At no point am i suggesting that you cheat on this achievement since there is no way to do it.
The fastest way to do it is obviously workout. BUT, if you are going for the achievement SPECIFICALLY
then you want to start on Mossa Fight #1: Fight Sequence 5, Round 2 and 3.
Rounds 2 and 3 are jumping rounds that are 24 seconds long each. 48 seconds total. When the round ends simply press start and return to Round 2.
I averaged 43 jumps total each set.
It took me 5-6 rounds/average 250-260 jumps total to move it 1%... Yes, 1%
The first time it moved 1% i got 240 jumps, so jumping higher obviously moves it faster but it will tire you out since i PUT all my effort in jumping as high as possible as fast as possible.
What I did was simply jumped and swung my arms up and down for the momentum. The kinect will count your score so I am assuming that helps out to since you cannot simply slack on it.
With my calculations it will take you 24,000 jumps for this achievement, luckily i am at 95% for this achievement at this time so my calculations are correct since i started counting at 90%.
Meaning it will take you 240,000 jumps for Peak Performance (100km)
So, again, if you just want to work out your legs for LEG DAY, do this method.
Once you finish it you will have the LEGS of STEEL!!!!!
Best of luck.
*This method works for me and I am 5'9" and my kinect did not give me issues. So the numbers will probably vary on that and how your kinect picks you up.