Body Beast Build Legs. Toughest workout!
I did a Tough Mudder (12 mile mud/obstacle run) last October and couldn't get over any of the walls by myself (actually had to walk around some of them because even with assistance I couldn't get over them) and my whole body (especially my legs) were so sore for a week afterwards.
I've been doing Body Beast for almost a month now. I did my second Tough Mudder this past Sunday. I was able to get over all the walls without help! It was a super hilly course and we had to go up what I kept calling a "mountain" (which DH kept reminding me was just a super steep hill) and people kept having to stop and rest or crawl up it (hands on the ground). I walked right up it with ease. I kept saying "thank you Body Beast, thank you Body Beast!"
It's now a couple of days later and I'm not sore at all.