Think of it this way, as one incrementally increases velocity and samples blood plasma lactate accordingly, one notices that lactate rises at first and then falls to resting values until at some point it doesn't anymore. This is the aerobic threshold. Let's say your normal resting lactate is 1.2 mmols. You run along at 10:00 per mile and your lactate after 3 minutes is 1.8 mmols but by 6 minutes it levels back down to 1.2 mmmols. Clearance caught up to and surpassed production so the lactate dropped after awhile to normal resting values. This happens over and over as pace is increased. At some particular speed (velocity) it doesn't drop back to a resting level. This point, where it doesn't drop to resting levels, is the aerobic threshold, and it occurs at roughly 2 mmols for most distance runners. The actual value can vary, but the intensity level among trained runners is the same (in the upper 70% range relative to VO2 max). Unfit people have lower aerobic threshold values; around 55% range for average folks who don't exercise, and even lower for overweight people.
Above the aerobic threshold, plasma lactate continues to rise as velocity rises. The LT point (which my definition equates to what a runner can do in an all-out 60-70 minute run (in the old days I used 60 minutes because that is what the best researchers said) in which lactate has a steady but not too steep slope. By some protocols and in some runners (particularly with distance runners), the slope halts at the somewhat shallow angle and rise fairly dramatically. This is the visual LT.
In recent times researchers have used 20 minute repeated running tests. Each test had a stable velocity and each subsequent test is run at a faster velocity. Lactate is measured and noted. When lactate reaches a point where it doesn't stablize anymore, it is then determined that the velocity of the previous 20 minute run or an average of the two 20 minute periods is the maximum steady state lactate value and velocity. The researchers call this the MSSL or Max Lass. But, the truth is, the MSSL, Max Lass, LT, AnT, OBLA vare all about the same; so close that it isn't worth arguing about. The actual values (mmols) vary, but the intensity doesn't for trained runners; not much at least.
It appears to be the same for other endurance sports, too. Swimming and cycling, for example, use the same concepts and similar protocols. Miguel Indurain, 5-time Tour de France winner and former 1-hour max distance record holder, had an OBLA (LT) of 88.28% of max aerobic power. This aligns right with what Dr. Jack Daniels said (86-88%). Miguel rode in his 60 minute world record at 89%, by the way).
Max aerobic power or velocity is easily determined by an all-out run that lasts 6-10 minutes (7-8 minutes being the norm). So, when we say that a runner performs at 88% of MAP (maximum aerobic power) or VDOT max (Jack's term and definition of the minimum velocity that elicits VO2 max), it means that if you took the power (wattage or joules) or the velocity (meters per minute or second) or pace (how many minutes per kilometer or mile...something I use for practical purposes with runners), then we intend to communicate that LT or MaxLass or whatever term you want occurs at 88% of that max power, velocity, or pace.
I suggest that it is about 92-93% of 5k pace, too, by the way, or 88-90% of 3k race pace. It just depends upon how fast you run in the 3k and 5k races. Using percentages of your current race pace for 3k to 5k is both practical and effective. Otherwise, you can be effective by simply running at paces that improve what you perceive improve aerobic power to aerobic endurance. For example, I use 3k-5k pace to improve aerobic power. I use 10k to 20k pace if I want to improve the capacity to clear lactate (a stamina element). I will use marathon pace or a little slower to improve endurance of slow twitch fibers exclusively. I will use quite a bit slower than that to improve overall endurance of the cardio-vascular system and enhance beta oxidation (fat metabolism). Tin