Hallo, I'm the REAL Renato Canova, not the moron answering at the beginning of the post. I'm now in Zurich, and was around for some meetings (Stockholm, Heusden) where I could also see some american runner. You are improving in your competitivity, to meet the best runners of the world is the correct way for growing overtaking your current limits. Regarding the question of the post, I try to explain the system that I use for increasing the Threshold.
1) If I want to investigate about the Threshold of an athlete, normally I find a level about 7-8% lower than the pace of 5000m PB (if a specialist of this event), or the same level of the pace of HM (if a good specialist of Marathon and HM). So, the level of AnT is different, according to the different attitude and the different type of training that athletes use.
2) If my problem is to INCREASE the AnT, my behavior must be different according the type of athlete that I want to train.
When I speak about 4x5km, for example, I don't speak about AnT, but about AEROBIC THRESHOLD, that is the Threshold most important for a Marathon runner. My goal is, at first, to increase the AnT of about 3-5% during a period of 4-3 months before the competition, but secondly is to increase the Aerobic Threshold (AT) bringing it very close the level of AnT. When the difference between the 2 thresholds is about 5%, the athlete is resistant enough for beeing prepared for running a good Marathon.
Instead, if I have the goal to increase the AnT of an athlete running, for example, 5000m, the system must be different. I have to use a combined work that has different means : short and continue distance at 95-98% of the race pace (4-6 km, that we call "fast short continue run") ; long intervals at a speed of 2-3% faster than the race pace (for ex., 4 x 2000 rec. 3 min, or 3 x 3000 rec. 3 min, for an amount of about 2 times the length of the race); medium intervals at a speed of 3-5 % faster than the race pace, using very short intervals (f.e., 3 sets of 6 x 500m rec. 45 sec. between tests, 4-5 min between tests). The combined action of these workouts provokes an increment in the level of AnT. You must support all this type of work with a very big volume of full Aerobic run (70-85% of the pace of the race, if you are a specialist of 5000m). Without this, the AnT grows in short time, but the athlete cannot preserve his shape for long time.
Still different the situation for a specialist of 800m. In this case, we must understand if the athlete is a sprinter (Konchellah, Juantorena, Mutua), a full 800m runner (Kipketer, Bungei, Sepeng) or a middle-distance runner (Coe, Cram, Yiampoy). In any case, the phylosophy of training is the same : to use short tests (300-600m) for a total amount of 3-4 km, at the pace of 90-95% of the pace of the race (for an athlete running 1:44, 13.0 pace every 100m, 90% is a pace of 14.3 (600m in 1:25.8) and 95% is a pace of 13.65 (300m in 41.0), increasing step by step number of repetitions, cutting recovery time. In these cases, long run has only the mean of regeneration, and is not important for the final goal.
Good luck to the US runners this night in Zurich (and of course to Shaheen also...)