Training legs at the best of times is quite challenging and demanding for most novices and pros alike!
Because legs being one of the biggest muscle groups in the body have a huge capacity for work!
This sort of training can be daunting at first, yet with practice using good form / technique it can become quite enjoyable as you start seeing those results.
For example doing any type of Squat, can be quite taxing, yet amazingly beneficial to the whole body.
The reason being that lots of major and stabilizing muscles come into play.
Not only do you tend to work the overall body but imagine the calories that are being burnt during a say 45 mins session!
There are so many good articles on the Internet to choose from, here are a few:-