
Thanks for your replies.
Dan, he said that it would be good to prevent injuries. He sometimes trained with Mbulaeni Mulaudzi but I am not sure what was his approach. We lost contact when the forum where we met suddenly stopped working.
If anyone wants to check his progress, I remember his first name was Francois (it's ok to tell it here as he never hid his identity on the forum - nickname there was "legolas").
Francois also never gave it all when doing reps. He said that if you could do, say, 10x400m for 70'', you should be doing them for 72'' finishing with one or two at 71'', 70'' (I have no idea what sort of times he did but probably closer to 1 minute)

This way you wouldn't be dead the next day and you could be fully recovered for the next track/hill session.
steepler, I don't do much water jump practice because I train on an old track and can't get water in it and when I tried to do it without the water I found I was very scared before jumping, the technique went and I landed badly. But definitely, not something to do without spikes
When I started training, 11 years ago, I saw all the guys doing reps with spikes (apart from the longer distances - > 1500m).
Personally I find that they help my form when training, especially on the 200s and 300s.