Most of my runs include hills, and I do hill reps once a week, most weeks. They do help build up strength and endurance.

I live in a flat town, so finding hills would mean a drive for me. I still try to do hill work once a week though as quite often races have some hills, so I just use the treadmill for my sessions.

Ultimately its a good idea to train on the terrain you plan to race on, hills do build strength but ultimately if all your work is on hills you're going to be using different muscles to what are primarily required on the flat - for this reason great fell runners dont always make great road runners, and vice versa. That said most of my runs have some hills in, and a hill session once a week can only be a positive...just be wary of putting too much strain on your calfs and achilles by doing excessive hill work too soon....you can get a good workout with less impact from speed work on hills, but in my mind nothing beats track intervals for form and pace translation in flat races....all depends what you are training for.

I live on what could loosley be called a hill so all my runs have an element of hill running in them...but it depends what type of session i'm doing as to how fast i run it.

normally I do one hilly run a week. when training i did hill reps, hill undulations, long hilly run plus flat runs and track, but not all in the same week. I tend to use a 2 week training programme.I don't really think that you need to include hills in all your runs. If you want to do a steady or tempo run or intervals then flat is good.It's always better to train for the race you are going to run but if you just want to be ready to enter any race that takes your fancy then an allsorts approach is good.

Is it good practice to include a hill on each training session?Shouldspeed work include ascent work also to improve all over form and potential race pace?