i agree with something like speed. your times basically reflect having one gear. windsprints/strides might work. so might cross-training at a sport where you run or jump, soccer, basketball.
for an adult your times aren't bad. "lack speed" is exaggerated, like relative to elite HS or college runners. 5-something isn't bad. it's just that 400m is kind of a tipoff you just kind of groove at a pace.
This might be kind of out there, but could it be that you lack flexibility? Seems like your 5k is substantially better than your 400, so odds are you either simply lack speed or lack flexibility/mobility, possibly in the hips or hamstrings
If you can run sub 6 but not sub 70, then you are not sprinting, or even running with a kick. Most likely you're running exactly the same way you run a mile but trying harder. That doesn't work.
The secret is you must increase your cadence. Watch the elites with no kick and see how they just keep plugging along while everyone else leaves them behind with a massive increase in turnover. You probably take about 3 steps per second like most distance runners. In a sprint, you should get as close to 4 as you can. Real sprinters all go above. 800 elites go about 3.5.
This is simple if you swing a yo yo around your head and think about how fast the yo yo is going. When you run, your feet have to be going as fast as the ground when they hit it. That determines how quickly they have to go back and forth through the gait cycle. Just like making the yo yo faster means it does more rpm's, so it is with the gait cycle.
you need to run close to 60 flat. You have a very long way to go, and an aerobic-focused long series of 200s won't get you there.
Never listen to distance runners about speed. Find a sprinter's website and follow its advice. You need high turnover and that means changing how you move, like retooling a golf swing. Lots of work on technique and strength, not effort, not endurance.
Seems to me like a lack of mobility or flexibility or just poor running form .I think its a physical issue that you just need to fix .Then increase your milage abit while focusing on more variety. I think you should get a decent coach if you don't have one will help you fix it.
you need to run close to 60 flat. You have a very long way to go, and an aerobic-focused long series of 200s won't get you there.
Never listen to distance runners about speed. Find a sprinter's website and follow its advice. You need high turnover and that means changing how you move, like retooling a golf swing. Lots of work on technique and strength, not effort, not endurance.
It's true there's a fundamental difference between sprinting and MD/distance form. Distance runners don't change technique when they "sprint", they just push off harder. Sprinting is all front side - hammer your foot down hard and get it back up as quickly as humanly possible to do it again. No long pushing off movement.
Your 400 is the weakest by far and 10K the strongest. That doesn't automatically mean you lack speed though - doing some 100s and flying 60s will tell you what your actual speed is like. 400 is speed endurance, and imo already tipping towards endurance. It's a hard distance to run to your max capability and you may be able to go faster right now with a little technique practice. 63 would be in line with your mile/5K.
You haven't said what distance you're targeting though - do you want to improve your 400 or 10K?