Lower back pain and running

I'd love some advice please. Fifteen yrs ago I suffered a herniated (slipped) disc in my lower back. Lots of sciatica and back pain followed, but thanks to physio and gym I finally got to a stage to begin running again 2 years ago. My back pain has got less and less, and I've been reassured that the odd twinge is muscular, not disc-related, more 'memory pain' from the original injury than anything more. 

The problem is I've recently stepped up my training a little, and am now enduring quite a lot of lower back pain and some sciatica. It goes away if I have a total rest day but then returns. I run on dirt tracks in parks a lot, and do 4-5 runs pw: 1 lsr, 1 tempo/speedwork, and 2-3 reasonably easy runs. I also stretch for at least 15 mins after each run, using exercises physio gave me for this purpose.

I have recently stepped up my weekly lsr from 6 to 8 miles, and my 2-3 easies from 3 to 5 miles. As I write, I wonder if I have overdone things, too much too soon. If so, I'd love some advice about how to go about cutting back without making things too easy for myself. I have looked at Hal Higdon's training plans, but can't find one that totally fits my schedule and am a bit confused about what to do. I do pilates and yoga classes so have reasonably strong core. Very frustrated and disheartened. Any advice welcome. Thank you.

Maybe ask a physio or chiropractor for some advice?

I found I had some sciatica problems caused by weak glutes, that really interrupted my running. Although you have a strong core, have you done any specific glute strengthening work?

Thanks! What you say about glutes is interesting. I find that my right glute is often very tight, so I've been focusing on loosening it by stretching (it is the right side of my back and my right leg where I've been experiencing pain). For strengthening, I do 20 squats per day and use that pilates position, the bridge. Any other suggestions really welcome though. I've got an osteo appointment this afternoon, she's v. good. Unfortunately my physio is on maternity leave and they are difficult to find round here. 

Can you independently glute squeeze? I'd bet it's a glute problem. Dysfunction there will refer to lumbar spine. Standing on one leg activating your core muscles and squeezing glutes is the way to go. Global exercises like squats won't help as squats are a leg exercise.

That's a great exercise, thanks! I'm really pleased too because the osteo said she doesn't think running caused it - my sacroiliac joint was disfunctioning, which I'm a bit prone to it turns out because of having one leg shorter than the other (I'm so used to that I forgot to note it in my OP). She sorted it and now feel much better. She thinks it may be to do with something entirely unrelated to running - dashing to the car with a load of heavy shopping and tripping up last week! She's told me to get back to pilates classes, so I've booked myself a session for tomorrow afternoon with a physio pilates trainer she's recommended. And I'm allowed to start running again tomorrow. 

That's great news. Have you found pilates beneficial for running generally? I'm thinking of trying a class.

I'd really recommend it (just back from an hour one-to-one and really feel like my core has worked!) Definitely sorted out my back problems, which prob isn't relevant to you, but more generally it is a brilliant way of building a strong core, and a class will definitely help you to stretch and strengthen hips, glutes, abs, back muscles, hips and hamstrings. Physio who works with our local uni told me that he'd seen massive decrease in injuries among the runners in their athletics team when he started sending them to pilates classes. My tip would be to book a one-to-one with a pilates tutor who is a trained physio if at all possible, as they can advise on weak spots and suitable classes. But I know that kind of thing doesn't come cheap. 

I might look up a class at least and see how that goes before investing too much £££. I was actually looking forward to the social aspect of a class as well, as only been living in the area for 7 months and still don't really know anyone outside work.