i’m by far no expert but to me it sounds like your just have ADS. your slowing down b/c your aerobic capacity isn’t there to keep your legs going as fast, as long as your legs aren’t getting tired then it could be some muscle endurance as well.

as for training it depends on what your ultimate goal is, if it’s just get in shape/improve fitness just keep at it and it’ll come with time. one thing i’ve learned is the more training with longer sessions the faster the gains, but you have to keep track of your body. the key is can you do a work out and recover by the next day to repeat it? if you can your not over doing it.

Vsquid – welcome!

I second juskojj’s suggestion to do longer sessions. Slow down when you need to, to stay under AeT, but go long. Over time you will be able to run for longer periods of time below AeT. You can also try walk-run combinations that progress, e.g. warm up walking (10 mins), then 1 min run / 1 min walk for 15-30 mins, then cooldown 10 mmins walking. When it feels right, progress to 2 min run / 1 min walk with the same warmup and cooldown, and so on. Strength training will also raise your AeT by reducing the amount of energy you expend with each step.

Hope this helps – keep us posted on how it goes.
Jane