H.I.T. frequency
 

Hi.
Just checking that I have it right,following Mac master university guidelines, 30 sec bursts followed by 3 mins recovery x 7 reps at the moment as the winter progresses I will add a few more reps. Is there any advantage in training two days together ? I ask because I can't always manage every other day so wondered about squeezing in two days back to back ,or would that be counter productive for a 61 year old ?
I guess I have the intensity of training session right because for an hour after I'm wrecked,shaky legs in the shower .

The length of an interval can vary widely, from 15 seconds to a few minutes. Every "coach" has a different opinion.
I'm a 65 year old, and I don't do intervals on two consecutive days. Intervals put a lot of stress on the muscles, and I need time for recovery. I find that if I do it on consecutive days, I just get weaker, not stronger.

Sounds like you're talking about H.I.I.T., not H.I.T. -- they're very different things. ;)