Mondays are my LT days, and today I moved it up one notch (8.4 mph to 8.5 mph).
After a 1 mile warm up, I did 6 miles at 8.5 (7:03 pace) at 2% incline. Heart Rate stayed under LT (about 167) until about 4.5 miles into that pace. The rest gradually increased to 174.
No soreness or exhaustion. In fact, it was not hard to complete the workout. I think this is how LT's are supposed to work.
I plan to do the same exact workout next Monday and compare my HR data.
Time and patience will get that pace well under 7.