If you can only run once a week because of the shin splints you should stop until they are better before you end up with stress fractures, which take even longer to heal.

If you can run once a week without pain you should be able to work toward two and then three runs a week. I don't see how you can be seeing much benefit from running once a week no matter which type workout you choose. Usually, higher intensity runs are better than less intensity when time is limited, but given your injury running toward lactate threshold levels seems like nothing more than begging for a more serious injury. If you can tolerate running, it would probably be wise to slow down a bit while building up muscle endurance around the shins for tolerating the force of landing.

Good luck with the splints, they are tough to get over.

It sounds like you should be building a base and not worrying too much about lactate threshold or speed at this point.

Try doing eliptical or bike for awhile to let your shins heal and then get back out on slow easy runs to build a base. Keep it slow, listen to your body.

Your goal should be building the number of miles you can do in a week, not how fast you can do them. Once your legs get stronger then you can progress into some speed worrk and interval training.

Good luck with the PT and healing.

Thanks for your concern!! But after the very first time I got shin splints years ago and didn't know what they were and kept running, only to be able to not walk properly for a week.. I now know how to listen to my body, and if i'm sore in the shins I don't run. (I'm constantly called weak for it by my running buddy, but I just tell him to get stuffed!)
If I DO run more than once a week, that's when I get them.
The problem is, i've tried taking time off from running..
I've tried different lengths of time ranging from 2-12 weeks and nothing works!
I had a physio appointment tonight, and need to do more stretching and strengthening exercises, as well as try and run for the same distance, but break it up over 2-3 runs, which although i've tried before, hopefully combined with everything else will work.
Yet another new pairs of shoes are also on the list of things to do!
I'm already cycling, as I have a 210km "Around the Bay in a Day" ride in 5.5 weeks!!
And I can only manage to get to the gym 1-2 times per week which i'm using to do my Strength and Core workouts. So I'm reliant on being able to run in my lunch break at work..
I don't think i'm the only one who would say I wish there were more hours in the day!

Well after several visits to the physio, lots of stretching, strengthening and running more often for less distance/time, I seem to be on the way to recovery!
I've been running 3 times a week, and without even trying am improving due to the consitancy.
Did a 7.5km fun run on Sunday and was really happy with the time! 33m 13s, 11th fastest female and 2nd in my age group(20-24)!
Am sore after that, and also had a massage after which i think has caused some pain too, but did a walk/jog yesterday and am going again later this week.
Here's to being able to run this consitantly for a lot longer to come!

First of all get well and get rid of the pains, then start out slow and short. You will likely have to run by yourself. Sounds like your friends are workin' ya pretty hard. Looks like, based on what you have told us, you are not ready for that intensity and distance. Well, the body seems to not be ready. Start slow w short runs of say 2-4mi max and remember frequency is key; more as opposed to long, with low heart rates (<70%HRmax) That is key to get yourself up to better fitness. You have to develop a stronger foundation (base), as Cayman says. Then after about 3-4 mo turn up the volume. Good luck with it; my 2 cents.