Really tired on easy runs after workouts

Stop jacking off!

In Houston 5 or 6am runs are nice and despite 70s or 80 it feels cool.

why do runners care about pace on easy days ?

To echo others: going slowly on easy runs is fine. The purpose is to get an aerobic effort in without compromising your workouts (ie. recover adequately). I focus on feel; if you have a HRM in your GPS watch, you might aim for around 130 bpm to guide your pace. I am old and experienced, and don't look at HR while I'm running and this is what most of my easy runs are if I go check the data later. Most of the time this type of effort results in runs that are a touch faster than 8' pace. If I'm very tired after a big workout, recovering from illness, it's very hot, or I'm on more technical terrain my runs may be slower. That said, if you are so tired or sore that you cannot run properly, taking a day off or cross-training may be a good idea. For a high school athlete, taking 1 day off a week is pretty common. When I was in HS I used to run 6 days a week since I was doing other sports (no running involved).

If this (feeling like you're struggling to recover) is a chronic thing there probably needs to be a change. It could be that you're doing your workouts a bit too hard - it's important to listen to your coach. The objective of most workouts isn't to run the absolute fastest you possibly could. It's about hitting a certain effort, which is often quite moderate (feels uncomfortable, tired at end, but not head between the knees). Habitually doing workouts too hard digs you in a hole, which means your body isn't able to adapt to sessions you do. This means you might get injured or stagnate.

The other thing to consider is that you might have some medical/nutrition issue. Iron deficiency is very common and can make you feel terribly tired. I have struggled with iron and vitamin D issues before. You can get some blood tests for this type of thing from a family doctor or a walk-in clinic (if you don't have a doctor).

did you just go out one day and hammer that 7x800m workout out of nowhere? if you slowly build up to hard interval days and you have a good amount of base training, you should be fine during your easy days after interval days. just make sure you run your easy recovery runs slowly. if you're still tired the day after the easy recovery run, then you might wanna take the next day off or make sure you get another easy recovery run. it's better to back off on the hard interval days than to push forward and risk burning out. there is no one workout that makes or breaks you. how well you do depends on how well you do throughout the entire season. the next time you do a 7x800, maybe try to aim for 2:30 and see if you're back on track on your recovery days after that.

Never clock the pace of your easy runs.

He's run a 10:19 3200 and 4:41 1600 so of course it makes him feel super tired. He's running 7x800 faster than 5k pace, and nearly at 3k pace.

I often joke that nothing is harder than an easy run. But it took me years to really understand that it's logical. My 10 mile marathon pace tempo workout feels fantastic. The next day a shorter run at a minute per mile slower feels like a slog.

When I was less experienced (younger) that was discouraging. Now I embrace the recovery.

I suspected he was overreaching. Yes, he's capable of doing that workout but he's straining to do it. No wonder he's suffering the next day.

Here is something you seem to be learning: "Easy days" aren't easy. It's because they are recovery days, and they are the days when your body is catching up. Luckily it doesn't matter.

I did the math wrong - it's actually significantly faster (8s/800) than his 3200 pace. Of course he's wiped

I agree with the posters who are saying easy is a feeling not a pace. When I work with athletes on their mental performance, one of the questions I always ask is: how much sleep do you get? Most research says a student-athlete should be getting 8-10 hours of sleep. (I'm not sure your age). The first half of the night is mostly the slow wave cycle where your body produces human growth hormone and repairs muscle and bone. The second half is mostly REM sleep where you repair your thinking, mood, mental energy. Hope this is helpful. Good luck with your recovery :-)

Stop obsessing over pace. Your body's aerobic system doesn't respond to how fast you're running, only how hard your aerobic system is working. Did you get an easy run in that allowed for active recovery? If yes, then it was a good run, even if the run was slower.

Pace only becomes important during the when you're conditioning the neuromuscular system to efficiently recruit muscle fibers. This is what people think of as "speed training." If that's not the goal, then effort is what you should be worried about.