How much speedwork per week is necessary?

Do this if you want a faster 5k.

Drop the long run and get your easy miles down to sub 7 minute pace. Your one workout should not be longer than 800 meters per repeat. When you get into season, add one to two more workouts in your schedule. Only go "easy" on your normal runs when you're really tired. This is a tried and true method for runners who don't respond to volume or slow mileage.

Sham's advice could work depending on your resistance to cumulative fatigue and/or ability to recognize when an easy run is needed. Also Look into training Periodization. It could lead to greater long term performance.

Arthur Lydiard created a schedule for people like you, i.e., people who mostly raced on the roads and wanted to be in good shape to race regularly rather than peak for a big effort once or twice a year:

Road (non-race week)
Monday: repetitions 3 × 1,600 meters or 6 × 800 meters
Tuesday: aerobic running 90 minutes
Wednesday: time trial 3 miles
Thursday: aerobic running 90 minutes
Friday: fast relaxed striding 6-10 × 100 meters
Saturday: time trial 3 miles
Sunday: aerobic running 90 minutes or more
Road (race week)
Monday: wind-sprints 10-16 × 100 meters
Tuesday: easy fartlek 30-60 minutes
Wednesday: time trial 1 mile
Thursday: fast relaxed striding 4-6 ×100 meters
Friday: jog 30 minutes
Saturday: race
Sunday: aerobic running 90 minutes or more
This is just something to give you a starting point for your thinking. The mileage probably comes out to something in the 50s, so a bit more than you want to do. And I suspect a lot of people may find three 90 minute runs in a week a bit much but you could shorten them. Again, it's just something to show a little structure.

I think you gotta look at things a little differently. 1-2 workouts/week is plenty. But not every workout should be categorized as "speed work." It's incredible to not do more than 3-4 miles of work & then race as well as you've done at 10k & higher. It's not about cramming in faster running -- it's about training different systems. I'm impressed that the 10k is strong compared to the 5k & that the half is decent. You'll get stronger by doing tempo runs & threshold intervals -- higher volume than what you've been doing but with short rest. Those PRs are also strong on 4 days of running/week. Increase mileage if you want to get better. Build workout volume & mix in tempo/threshold sessions.

Depends on what you're training for. For a mid d runner during base phase you're going be throwing in strides, short hill sprints and 200s/300s a lot more often than let's say a marathoner who would be fine just throwing in a few strides twice a week(even the last few weeks when they're peaking). And for what you call speed, which is more like vo2 max or Lt workouts (not sure how fast you're running the mile repeats), but that's more of what I call strength workouts as opposed to speed work. And depends on the phase of training. But those kind of workouts only need to be done once or twice a week(or none at all during early base training or returning from injury).

I think you should run at least 5 times a week. Preferably 6. No need to increase mileage or do more workouts. Just spread out a little. Right running only 4 days is leaving money on the table.

Do this, works always. One maxVO2 interval and one Lactate threshold interval per week. Works always and all runners improve this way. Good luck! - Magic Man- 🧙‍♂️🇸🇪👍

HRE mentioned the race week/non race week of Lydiard's. He created this for people who wanted to race often, year around, but it is not going to get you too-too much faster. Maybe a little faster.

If you want to drop your PBs, Lydiard's regular program is the way to do it. Come to a peak period twice per year, spring and fall.

In this case you change the meaning of so-called speed work to strides, easy sprints, weekly fartlek the real way, by feel. This is "speed" as in muscular stimulation and neuromuscular stimulus.

The anaerobic work is the hard and fast stuff, like hard 200s, for example.

The LT, sub-LT and V02Max work have their place throughout, but basically, you want to periodize like this:

12+ weeks of a base phase (no short race, not harsh workouts)
3-6 weeks of a hill phase
4-6 weeks of an anearobic phase
2 week consolidation
1-2 week taper
Race your butt off until performances start to lag.

But you should search out the finer details in a Lydiard schedule and remember not to be married to the day-to-day schedule (because only you know if you are recovered for the next run, whatever it may look like), but keep the principles in-tact.

Your base phase should come up from 40-45 mpw to more, depending on how time you have and how well you recover etc.....work with what you have...manage your expectations on that.

Are the two 3 mile time trials all out?

I don't know why this is getting downvoted; it's the closest thing to a correct answer there is.

To expand on it, I'd suggest trying to bump up to running 5 days a week at least (unless you're already cross training on the other days).

These days should consist of a long run (no more than a third of your weekly total mileage), a Vo2 Max workout (5k of volume should be enough), and a Lactate Threshold tempo/intervals (6-8k of volume).

The other 2 days should be easy. Stick to your 8:00 miles, and completely disregard what Sham_69 suggested. The way to improve speed is with quality speedwork, not by tiring yourself out with "greyzone" running.

Other things to note:

1. Make sure you do strides before your workouts (5 x 80m @ roughly 90% full speed - no straining, take off easy and gradually build your speed up)

2. Space out your workout days. For example: I follow this system and I do a Long Run on Monday, an LT workout on Wednesday and Vo2 Max intervals on Saturday.

3. Don't hammer your workouts. You will get far more benefit from hitting the right zones than simply smashing yourself. In Vo2 workouts, you should always finish knowing that you could've done another rep; and in LT workouts, you should finish feeling very comfortable.

4. Ideally you'd build up to running 6 days a week, with an additional easy days added in. But don't build up too quickly. Run 5 days a week for at least 8 weeks before building to 6 days.

Good luck.

Fast pace but no big finish.

Idk how anyone is supposed to do 3 time trials in 1.5 weeks (2 3 mile time trials in 4 days?), with other workouts mixed in (including some back to back stuff), and then expect to race. Keep it simple OP -- more miles + train different systems.

Speed Kills

Again, it's a template. If someone finds three time trials and a race over a two week span too demanding they'd adjust, maybe bag a time trial, etc. The same goes for the three 90 minute runs. For most people doing those runs would accomplish what you suggest, run more miles. But some people will struggle to do that many runs of such a length in a week too much so maybe they do a 90, a 75, and a 60. The OP only runs four days a week so he really couldn't just go ahead and adopt this schedule, he'd have to figure what to leave out.

It has been a long time since I read Lydiard but aren't those time trials more like 90% effort. They are more of a hard tempo run..

I would argue that a 4 day week is something like

Long run. Try to get up to 90 mins

Tempo/threshold things like 5*5min at HM pace or like 6 miles at MP. Through in a couple mile warm up/cool down and your good. Maybe a couple 200@1500 or hill sprints when you are handling this workout.

CV/Vo2 workout. I would alternate something like 6*1000@10k pace with 12*400@5k pace. I find vo2 every week is too close to the edge for me... Drop this for a race.

What ever easy runs you want to fit in.

Alternatively replace the tempo workout with running the last 20 mins of the long run at HM/mp pace...

Obviously the easiest way to drop 30s off would be to run 1 more day and do another 7 miles. That might not be possible. Time wise it might be easier to try and add 10-20mins to the existing runs...

I'll add my two cents as someone who has been running and racing for over 50 years now. HRE's Lydiard approach and Coach Wizard's much more abbreviated recommendation are largely the same thing. I ran times similar to yours in my 40s (mid to high 17s) on about the same mileage. I had a coach who was a bit more VO2 max oriented than Lydiard, but not by much. My son, who is more talented than I am, is now in his 40s and running mid-16 5Ks on similar training. Talent factors into the results of training as well. From being a student of training methods and a lot of experimentation, I would say that optimal training for 5k at the volume you are doing boils down to as much threshold work as you can handle plus one VO2 max workout or race per week. I was partial to rotating through 12x400, 6x800, 3xmile, 400, 800,1200, mile, 1200, 800, 400 ladder workouts for VO2 max. I had good results following Lydiard's schedule after my coach retired. If you are interested in racing distances 10k and up this program has too much VO2 max and not enough threshold, but that's another discussion. Experiment a little to find what works for you that you like doing.

Coach Wizard says this should be done all year round. Lydiard approach involves more of periodisation, building towards a peak.

The Race Week-non Race Week schedule was really meant to be a year round approach. There's not much periodization though after you'd done it for a while Arthur would likely have suggested doing a base phase.

I don’t think you are really going to move forward until you are ready to run more than four times per week.