Here is an early season (fall) week of an Olympic Finalist who has run sub 44.50. He did this week when he was 24 years old.
M - 3 sets of (500m - rest 1' -500m)
T - weight training
W - 300m - 600m - 900m - 90m - 600m - 300m
Th - weight training
F - 6 x 60m w/ 2' rest + 2 sets of (300m, 250m, 200m with 3 min rest) 5 minutes between sets
S - weight training or off
S - off