There are only two events, for which some deacceleration is required and one should embrace deacceleration, 100m & 200m. For 400m/400mH/800m, athletes and coaches have assumed deacceleration is necessary in order to achieve optimum results. Not true. We have seen 800m athletes D.N.F. 800m races due to going out 2 1/2 to 3 1/2 seconds over 400m personal best. Johnny Gray, a man who was willing to split first 400m in 48.xx, 49.xx and 50.xx, set his 800m personal best in a negative split race, 51.xx first 400m. Female world record, 800m is negative split I believe. Doesn't Athing Mu race close to even splits? James Robinson, USA raced 800m close to even splits or slightly negative splits. The last time I recall Sebastian Coe racing sub-50 first 400m in an important 800m race was 1978 European Championships. Cannot tell me it is efficient for many elite 400m athletes to finish last 100m, slower than 11.5. As with longer races, ideal splits for 600m are even splits but most do not have a feel for the event.