Does lifting leg weights help running?

Way too many factors there to think that taking lifting out of the equation was why you raced poorly. Lack of running is probably the biggest factor, get out and run.

Lifting will help for a few reasons:

Less injury prone

Recover faster when injured

Cover more ground with each stride

Better fuel transportation into muscles

Maintain muscle mass

Bone density

Neuromuscular benefits, among many others benefits

But it's likely a combo of all that you listed. In a scientific test, you change ONE variable between two groups and compare them. There's no way we'll know for sure the cause(s) of your "lack of power." Also, you'll be better off with compound exercises like back squats or deal lifts rather than isolating muscles groups (e.g., quad ext, leg curl). Fine for working out muscle imbalances or basic strength tho.

Most of us don't "pack on a few extra pounds" that easily after only a few days of cross training in the place of running. It sounds to me that your mileage and consistency has declined over the past few weeks. You did not have a substantial enough base nor the speed work to feel fresh and fast for your race. So the lack of lifting may have played a role, but the more substantial aspect to racing is your actual time spent running, which is probably not all there. Get some core work in and back on the grind of training.

Get back to lifting weights first, but approach strength training more intelligently.

Day 1 (Explosive Day):

Squats - 10 x 65% max, 8 x 75%, 6 x 85%

Pull-Ups between squats. Full recovery.

Day 2 (Core Day):

Core Workout: Plank, Side Planks, Supermans, and Torso Rotations

Day 3 (Injury Prevention Day):

Lungs - 2 sets of 10 ~ 65%

Single-Leg Deadlifts - 2 sets of 10 ~ 65%

Leg abductions (focusing on smaller glute muscle)

Day 4 (Core Day):

Repeat Day 2

Day 5: rest

Repeat.

My PT gave me this after a serious injury and has done wonders. Longest day takes 30 minutes. It isn't an "end all be all" and obviounsly isn't periodized. Add this to your routine now. Increase your milage slowly.

theres is no reason to do leg curls or extensions if youre a runner, maybe once a month, if you want to get faster, better form then do squats, jump squats, plyometrics, lunges-this will imrpove your running times guranteed

no one you know wrote:

I stopped lifting leg weights a few months back. No particular reason, just a lack of time/motivation. I was doing leg extensions (quads), hamstring curls, and heel raisers (calves). I "raced" yesterday to one of my worst times in recent history, just didn't have any power in my legs. There were other factors at work too though, i.e. a lack of actual running (recent icy conditions; been cross-training on an elliptical instead) and a few extra pounds around the middle. I know I need to lose the gut and run more. Do I need to add the weights back in as well?