I am figuring out how to structure my double days and right now I have 2 mile easy runs in the afternoon of easy days. Should I change them to 3+ miles and make the morning run shorter or keep it at a 2mi in the afternoon?
Afternoon runs are mostly to get a good shake out and get some bonus mileage with it. They are not supposed to increase your aerobic capacity the same way your morning run will. I would keep your morning runs longer, and do your other run as a shakeout.
All runs are worth. Maybe just do 2 miles + strides/some core. If you want ears ago i have a funny routine with double 5 miles on six day a week and one day off. So maybe do that on your doubles day
Beneficial -yes. Experiment to see what works best. Consider situations where you're tired or busy - 2 miles is an easy run that doesn't take much time.
The research is old now, but Dr. Kenneth Cooper found that aerobic benefits were achieved after 12 minutes so as long as you are running 12 or more minutes you are getting some aerobic benefit.
Even a shorter slow run will provide benefits by improving circulation to help pump out waste materials from the muscle cells and speed repair for the next workout.
Say your resting HR is 45 or so. You go on a 2-3 mile run averaging 145-155 bpm. It takes a couple minutes to get back down under 100 after the run, but then your HR takes it’s sweet time to get back down into the 40s. Even when you’re done running, your heart is still straining and will adapt to be more efficient in the future. Having your body do this twice a day is much more beneficial than once.
Personally I wouldn't do one that short, unless all of my runs were only 2-3 miles due to just getting into running. If you're running some 4-6 mile runs, I wouldn't add a 2 mile run. I'd instead run my runs 5-7 miles in distance. I typically only start adding in doubles when my main daily run is over an hour, then I might drop it down to 45 minutes and 30 minutes to get the extra running in instead of running 75 minutes all at one whack. Not because of any training benefits, I doubt it really matters that much, but because of practicality. Running 2 miles doesn't really seem worth it, I'd rather add it on to another run until the other runs are too long.
Personally I wouldn't do one that short, unless all of my runs were only 2-3 miles due to just getting into running. If you're running some 4-6 mile runs, I wouldn't add a 2 mile run. I'd instead run my runs 5-7 miles in distance. I typically only start adding in doubles when my main daily run is over an hour, then I might drop it down to 45 minutes and 30 minutes to get the extra running in instead of running 75 minutes all at one whack. Not because of any training benefits, I doubt it really matters that much, but because of practicality. Running 2 miles doesn't really seem worth it, I'd rather add it on to another run until the other runs are too long.
2 miles in the morning was what Jim Spivey did in college, apparently because that's what he could fit in. 4 miles might have been better, but 2 is a lot more beneficial than 0.
Afternoon runs are mostly to get a good shake out and get some bonus mileage with it. They are not supposed to increase your aerobic capacity the same way your morning run will. I would keep your morning runs longer, and do your other run as a shakeout.
What is so special about morning to increase aerobic capacity vs. the afternoon?
When I first got into running I only ran 5K each time and I gained fitness from that, so 3 miles works. When I broke 20 minutes I did 5 miles 3 times a week. So IMO 3-5 miles is ideal for a second run.
Yes. If you've ever not ran for a long time, you'll see that just 2 mile runs makes a world of difference. All training has diminishing returns at some point though.
The research is old now, but Dr. Kenneth Cooper found that aerobic benefits were achieved after 12 minutes so as long as you are running 12 or more minutes you are getting some aerobic benefit.
Are you referring to the maximal treadmill exercise test used in the military? Its looks like basic test of current fitness similar to a "How many sit-ups or pushups you can do in 2 minutes. Run as fast as you can for 12 min is essentially a VO2 max test. I don't think this relates to the OP's situation.