Karla,
You're not being an alarmist...you're being investigative. Good for you.
If I were you in this position, I'd do away with giving him heart rates numbers as a guage. I stopped using heart rate as an indicator a long time ago. Instead of giving him the ever popular "HIIT" that we like to use sooooo loosely, I suggest just give him very lite interval training. And instead of heart rate, use RPE's. Better scale... and in my opinion, gives you more feedback than HR.
Feedback from the client...which is more important to me than a digital number on a wristwatch or machine.
Sounds crazy right? I mean, how the hell did Polar become this millionaire company making these chest straps?
For your first session with your obese client, pick his speeds on the treadmill (or wherever you have him) and use a RPE scale to fixate his intervals. For instance:
2 minutes at an RPE of 5
1 minutes at an RPE of 8
and so on...
Teach him what signs to look for at a RPE higher than 8, and this way, you can both be aware of the feedback from the activity.
Sorry, I don't have any links to share...just that damn experience again
.