Interval Training?

[gonnabe2huge]

I've been researching interval training for cardio and most of the routines I've found seem to total under 45 min, is there any specific reason why? Is it for safety or muscle preservation or something? I've always done cardio for long sessions 90 minutes plus, it helps me clear my head and think and I enjoy it. Is a longer interval training routine acceptable or a bad idea?
If it makes any difference I do cardio on the rowing machine.

 

[pullups]

I've been researching interval training for cardio and most of the routines I've found seem to total under 45 min, is there any specific reason why? Is it for safety or muscle preservation or something? I've always done cardio for long sessions 90 minutes plus, it helps me clear my head and think and I enjoy it. Is a longer interval training routine acceptable or a bad idea?
If it makes any difference I do cardio on the rowing machine.

my man if you can do it for 45 mins, then you aint pushing yourself hard enough. Or maybe you are and you just in very good shape. But the reason its so not as long is because it combines anerboic and aerobic forms of conditioning making it optimial for burning FAT. I just dont see it being possible to go 90 minutes of sprint jog sprint jog sprint. As for doing it on a row machine....I think you are cheat yourself I really think the 2 best ways are to do it on a elipticial (no knee impact) or to actually doing by really running. To be honest the only better forms of cardio might be high rep low rest time squats and powercleans....Im sure a shit load of people are gonna disagree but o well.

 

[gonnabe2huge]

my man if you can do it for 45 mins, then you aint pushing yourself hard enough.

Yeah, I could honestly try quite a bit harder but I like the time, I guess a reduction in time would be worth a more exhausted feeling though (I like that feeling), and it would give me a reason to go at it twice a day.