LT. Lactate Threshold. Tempo. Whatever you choose to call it, it's the type of workout that shows up most often in the early weeks of these six month training cycles, and doing them correctly can be as challenging as saying nice things about Maggie. While it is difficult for competitive athletes to do these properly, it doesn't mean it's an insurmountable task (Maggie, sometimes you tell me to go home and let you finish your workout in peace. That's always what I prefer to do, but I can't leave unless you say I'm free to go. Thanks for that. (See. A nice thing to say. Not insurmountable)).
Okay, back on track. The tendency for a competitive athlete is to find limits, or, rather, push them. A workout, in the mind of an athlete, should take the body to the brink. It should create excess fatigue, it should be exhausting, it should be as hard or nearly as hard as a race or it was a failure. It's the only way to get better. Beat yourself up. Rest. Repeat. LT runs, when run at pace, don't seem to leave the competitive athlete feeling anything other than exhilarated, certainly not exhausted, and it's the tendency of the athlete is to think 'if this pace is good, a little faster pace is better.' While this seems intuitive and accurate, to achieve the true purpose of the lactate threshold run, it's false.
Runners love to run themselves to death during lactate threshold runs, but by doing so you don't fully achieve the purpose and intention of the workout. Don't kill yourself. Run comfortably hard. Run at your threshold.
What is lactate threshold exactly, and why are the LT workouts that litter the training cycle so important to our training? That's an excellent question person I made up for the sake of this article. Gather 'round and I shall tell you....
As your work rate increases, work rate meaning an increase in pace or a climb that puts greater stress on your cardiovascular system, your blood lactate concentration will ever so gradually increase. So long as the pace is mellow enough, the concentration will stay at a manageable, low, and steady level (this is the desirable result of every aerobic recovery run or steady state). There's a point (let's call it, ohhh, I don't know, a threshold) where this lactate blood concentration spikes. Associate this spike with the onslaught of pain and fatigue you'll feel in a race or an interval at paces faster than LT pace. Training right at that or just below that threshold has an element of discomfort (comfortably hard), but you know there's another gear if you needed to use it, and you could run this pace for an hour without falling off.
Lactate Threshold in graph form
Training at your LT pace allows you to adapt, and ultimately become more efficient, thereby allowing greater workloads before reaching this threshold. If your LT pace is 6:30, and you do, let's say, 4-6 up/down miles at this pace or effort, and follow that up the next week with 3 miles at LT and so on, you'll see that your trained LT begins to improve. The workload can increase while the effort level remains the same. In time, 6:20 pace feels like what 6:30 pace used to feel like, and this improved efficiency translates to all other paces. Essentially you've improved your ability to more efficiently intake oxygen, deliver that oxygen to your working muscles, and run at faster paces before the spike in lactate blood concentration. Now your workload must go higher to accomplish a pace that's relative to 10k effort, which is beyond that threshold. As you maximize your threshold during a given cycle, you improve your ability to get more out of paces and races that go beyond LT. Think of your LT as the foundation of your house, which you must put down before you start building the structure (The 19 years of Catholic education wants me to tell you that you can't build a house without a sturdy foundation - don't build your house on sand!). When doing an LT workout, if your workload goes beyond the threshold, even though you're running faster, you're not improving your threshold, which is the intention of the workout.