I think Hindu Squats as seen here offer a great complementary exercise for runners or any athlete for that matter who are interested in improving leg strength. This version features a full squat, which may not be recommended for everybody- a half squat version is better for individuals with a history of knee problems.
I can do 50 but they get really taxing near the end. I read about people doing 200-300 and all I can say is that I have lots of work to do before getting to that level.
The best way to build up your number on these is to do them in sets with 1-2 minutes of recovery, at least 3 days per week before running. Once a week I would try for as many as I could do, just as a test. Eventually you should be able to reach 100 in one session (maybe 5 sets of 20 or 4 sets of 25). Make your goal the same as mine: 100 straight Hindu Squats! Combat conditioning guru Matt Furey, who once did 2,000 straight Hindu Squats, says "when you can do 500 straight Hindu Squats, you’re on your way to greatness."