Originally Posted by isaacnukem
So, what are speed training and interval trainings? I think what I'm doing is the so called distance run because I always just hit a 5 km goal every time I run.
Speed/tempo/tresholds runs are meant to increase your metabolic fitness. As you run, eventually your muscles cannot keep up with the amount acidic by-products your effort generates and they stop contracting (which you feel as fatigue, sometimes combined with pain as the still-active muscles try to compensate for the muscles that are giving out.) The moment your muscles can no longer cope is called the lactic treshold.
If you always do the same mid-level effort 5K run, you get some fitness benefit but you never increase your lactic treshold, which limits your ability to either run faster or longer.
Speed runs make your heart work faster (so you won't last as long as your regular training) which pushes you over the lactic treshold earlier. By pushing into that (uncomfortable but not intolerable) zone at holding for as long as you can, you teach your muscles to become more efficient at processing the by-products which means they keep contracting for a longer period - you've pushed up your lactic treshold and can now run faster/longer as desired.
To help you spend more time in that zone, you can try intervals of speed runs instead of one continuous speed run - every time you peak into the lactic treshold zone, you take a few minutes to recover back to a regular heartbeat (and your muscles get a chance to purge) before you try for another push.
Since it's not the most fun thing you can do while running most recreational runners limit the amount of speedwork but it's good to schedule them regularly because they make a huge difference in how your normal runs feel.
LRC is ridiculous. Didn't realize it was still around.