Excuse me, but reading what many runners think about long run is, for me, very funny.
One question : if you want to run a Marathon at 3:19 pace (about 2:20 final time), do you think that running 30k at 4:00 pace can have some connection ?
If you want running 10000m in 30:00, do you think that the main workouts are 400m on track, and long run must be only easy regeneration ?
The first man changing this old mentality was one Australian, Ron Clarke, that in 1964-68 was the first athlete running (not every day, of course, but once every week) for 15-20km very close 3:00 per km. He was able to destroy the World Record of 10000m moving, completely alone, from 28:15 to 27:39 without any rabbit.
If you want to beat your PB, you must run LONG and FAST. Running fast intervals and slow long run is not enough. Running always fast lon run and never fast intervals is not enough. Training is a combination of different speeds, and, more slow is the speed, longer is the duration. If we want to see what really happens in our body, we can see that, for very little difference of speed (for example, from 3:00 per km to 3:10 per km) the level of lactate is very different. The type of work has different targets, the time that you use for building the same enzymatic situation is different, the quantity of fibres interested in our run is different. Running at 3:00 or at 3:20 or at 3:40 are different type of training. So, we must put, in our training, ALL these speeds. I give you an example, for an athlete having a PB of 15:00 in 5000m :
100% of speed = 3:00 per km (this speed is good for some interval till 2000m, using a general volume of 8-10 km like 1000 / 2000 / 1000 / 2000 / 1000 / 2000 with 3:00 recovery, in 3:00 / 6:00, for example). The goal is to increase the ability in removing lactate from muscular fibres. This training has a direct influence in raising the Anaerbic Threshold.
105% of speed (3:00 less 9.0 = 2:51) is SPECIFIC SPEED ENDURANCE. The goal is to increase the ability in accumulating lactate. We can develop a global volume of 5 km, using intervals between 500m and 1km (2 x 1000 in 2:50, rec. 3:00, plus 6 x 500 in 1:25 rec. 1:00, for example)
110% of speed (3:00 less 18.0 = 2:42) is HIGH SPEED ENDURANCE. The goal is to increase the ability in producing lactate. We can use this speed for a global volume of 3000 / 3500m, using intervals from 400m to 600m, example 400 / 600 / 400 / 600 / 400 / 600 / 400 in 64.0 / 1:36 with 1:30 of recovery.
Speed faster than 110 % (for example, 200m in 27.0, 400m under 60.0, 1000m under 2:40) : have a MECHANICAL goal, and/or can work for increasing the LACTIC POWER. We can use only few repetitions with very long recovery.
When we go slower than the pace of the race, we can have the following situations :
95% (3:09 per km) : the goal is to increase AEROBIC POWER. We can use long intervals (for ex, 3 x 3000 in 9:27 + 1000m fast at the end, with 3:00 recovery) for a global volume of 10-15 km, but also LONG CONTINUE RUN for 6-7 km in 18:54 / 22:03. The ability in EXTENDING this speed can give a better base for the workouts FASTER than the 100% speed, helping in raising your Threshold.
90% (3:18 per km) : the goal is to increase the support for the AEROBIC POWER. You use this ONLY with continue run, starting from 10km for looking for extending your endurance till 20km. Running 10k in training in 33:00 for an athlete of 15:00 in 5km is very easy, but he cannot run in short time in 31:00 if doesn't become able to extend his long run till 20k in 66:00.
85% (3:27 per km) : the goal is to increase AEROBIC ENDURANCE, that is connected, more or less, with the AEROBIC THRESHOLD. You can start with 15-18 km, for going till 30km. THIS HAS NOTHING TO DO WITH MARATHON.
In another thread, I explained that Shaheen runs, once per month, a long FAST RUN of 37-39 km at 3:15 - 3:10 pace at 2300m of altitude, also in full season. In training, nothing is negative. THE ONLY QUALITY THAT YOU LOSE IS THAT ONE YOU DON'T TRAIN. So, you don't lose speed if you go for long run, but if you don't go for speed. At the same time, you don't lose endurance because you train your speed, but because you don't go for fast long run.
The development of training is not to replace some type of workouts with some other, but to ADD something that you didn't use before. Training is the ability in stimulating your body in different directions. So, one stimula can be with more intensity, another with more duration at the same speed. We have to mix everything together, respecting a correct proportion between the different workouts.
Regarding long run and speed, I want to give you an example : Paula Radcliffe tried, for many years, to become faster in the last lap, working on her speed. In 5 or 6 years, she moved her PB in 3000m from 8:31 to 8:28, practically always the same situation. When finally, tired to be no. 4 in every race, she decided to move to full marathon, her first race after winning her first marathon in London in 2:18, less than 2 months later, was a 3000m. Final results : 8:22, improving her best of 6.0 !
Personally, I had a similar situation in 2000m, with my Italian athlete Maura Viceconte. We worked very hard for beating the Italian Record in Marathon. She ran, winning, Vienna in 2:23:47 (NR) in May. After this, she was able to increase her PB in 5000m from 15:45 to 15:18, and to beat the NR of 10000m running 31:05.54, improving her PB of 1 min from the past.
At the end of every discussion, the question is :
What I ask to my training ? I want to try to reach my best potential results, or I want to be fresh every day, running only for my health and my fun ? In the first case you must use long and fast run, with a correct modulation. In the second case, run slowly and enjoy your life, but don't speak about good results in athletics.