legs weights or not?

When training for running longer distances such as 5km+, are leg weights neccessary or should you just focus on the running side of things?

By legs weights I mean leg curls, squats, etc to build the muscle and develop endurance.

Yes, you should do those things, so you develop more muscle to protect the Joints, and also the resistance training would boost Bone density and connective tissue condition.

However, owing to the style of training you do for long distances, don't expect Shotputters thighs, as you'll be doing a lot of Cardio, which will to come extent hamper or limit muscle growth potential.

Though such development could still be had.

You should defiantly do these exercises they are so helpful with running and help prevent injuries. Do every exercise at a low weight but I repetition before running if you do it on the same day.

Pay attention to your diet with the long distances and the strength training. You may need to tweak your carbs and proteins and thus your fats so you don't retard growth and strength/indurance increases you are aiming for.

xcrunner suggested low weights but to achieve the goals that Boss Man is discussing you should move towards the heavier weights and lower reps. Heavier lifting increases hormone production in the body better than light lifting does.

In regards to when you strength train, 2-3x per week is good. I would recommend it on your light run or no run days but some people choose different ways.

cheers