My experience has been the following: LSD running definitely leads to speed improvement, but it is a slow steady improvement. I'm inclined to think that if your fastest 5K was 30 minutes and it was taxing then an 11 min pace for the half might be aggressive this round, but definitely possible for your second, but you've also got plenty of time to build up and it depends a lot on the terrain and environment. Hotter = slower, hills = slower. I would think about taking one of your slow/steady runs and mix it up a little. Do some speed work in the middle (fartleks) or try the first half at an easy pace and then try for conservative negative splits for the last miles. Though, I wouldn't try this on your longest long run of the week. The other thing that lead to big improvements for me was running with people. You chat and laugh, they run faster than you and you keep up and don't notice the struggle as badly.

When I run a half I break the run into segments, basically a slow easy start then building speed towards the end. The limiting factor being when I start building speed. My first one my goal was to keep enough gas in the tank that when I hit the 9 mile mark I could start to push harder. My second half I moved that back to the 6 mile mark. Subsequent races I've used that model. Easy 7 plus a 10K.

First, great job at working towards a half! I do not like most running plans out there, because they focus too much on quantity. 3 slow runs and 1 short but faster run means you will never see much of an improvement. You need to do interval and tempo work. I would recommend looking up Fartleks. Personally, I have zero slow and steady training days. If I am just training to get ready for a race, I run 3 times per week; interval, tempo, and long run. The goal of my intervals is to push myself to a speed that is significantly faster than my race for short distances, then repeat this...or I do pyramids or ladders. Or I just do Fartleks. For tempo, I am running at a pace to push my lactate threshold. For my long run, I am running at a comfortable pace that is slower than race pace, with a focus on form, breathing, and fueling. Now, with all of that said...most people who are runners like to run. So 3 days a week is torture, because they want to be out there running 7 days a week if they could. So, in that case, I will usually add a speed work day as well. This is usually longer distance repeats at a faster pace. For example, I might do a 6 mile run where I do a 3x1 mile repeats with half mile jog in-between, where I am going at about 10%-15% faster than race pace. With 15 weeks, if you even just add some speedwork, you could see some decent improvement. Good luck! And if you have Pinterest, there are always tons of free training plans being posted...find ones that have speed work and/or intervals in the training plan.

You can't pull speed up from the top by running faster.. Better to push it up from the bottom buy running more.

Miles per week? That's the real question and answer.

Once you are running a fairly consistent schedule with a gradual ramp up, you'll likely see it on the shorter distances first with the longer distance becoming easier and gradually faster (though it really depends upon where your fitness level is when you start).

Using a 1-mile test as a basis, I started out being able to run a mile in 11:40 (not exactly conversational but not huffing and puffing either). That was holding a steady heart rate of about 165-170 bpm. At a sub-maximal output, I could run that mile in about 9:45 and a higher heart rate. But I could not sustain that pace for the 5K distance.

About 6 weeks after I first started running on a 26-week plan to marathon distance, I could run the 5K distance in 33:40 (10:50/mile) on a flat course (and I do mean flat). Sixteen weeks in, my 1-mile pace was down to ~8:15 and my 5K completion time was 28:03 (9:01/mile) on a not so flat course.

You may see gradual progress or great breakthroughs in speed. Part of that comes with the buildup in mileage. Part comes from a moderate stressor to the running system with time for recovery. Finding the correct balance is the trick though the 80/20 approach seems to help quite a bit in the ratio of easy to hard runs.

I haven't run a half marathon recently (won't until fall) and it'll be interesting to see how much speed I've picked up by that time. But I recently ran a 5K while on vacation and I didn't really run that hard because I knew in my age group I would just get toasted. Missed my PR by a mere 10 seconds (25:42) and it would have been interesting to see what I could have done had I really pushed myself. But I was recovering from sore hip flexors and took the longer view of enjoying the run and NOT hurting myself.

Good luck and enjoy your training.

I've been running for 5-6 years, and I would not see too much improvement in 15 weeks. I mean maybe 10 seconds per mile max. In the beginning, maybe closer to 30 seconds per mile. It's a long process