60-70 rpm is way too low for a trainer, and max resistance is not good. If you want to get in shape, ease up the resistance and go for high rpm, like in the 90's. You'll go longer and benefit you body more.
What I do when I have to use a trainer, thank God I'm in Cali!
10-15 minutes light gear, sight seeing effort(39-17 gear on roadie).
2 intervals at a 60% max dffort....One or two minute intervals to warm up. Esae up and relax for 3 minutes between intervals.
After I'm ready I do one minute intervals at Max effort! (53-13 gear on my roadie). You'll wanna puke, but you got 3 or 4 minutes to recover for the next one. Ease back up to 90 rpm in a comfy gear after you catch your breath during the 4 min recovery.
Repeat the 1 minute max efforts,then 4 minutes ez for as many times as you can repeat. I started with maybe 3 intervals. Last time, I did about 9. You'll get better, stronger and breathing will get so much better. Once ou get out on the road, you'll be cruising at what once used to be your sprint!
After youi complete the interval session, ease up agin to sight seeing pace for about 10 -15 minutes for recovery.
At the start of the recovery session, you'll feel like you can't go anymore. Mid session, you'll feel your legs want to get pick it up again. Amazing what your bod can do!
I don't use a heart rate monitor, just do what my body feels it can do.
Don't be fooled into thinking strong riders always push max resistance gears! It's about fitness too, not raw strength. I used to push big gears trying to hold 20. I learned to spin at high rpm's, now cruise at 22 mph in my small chainring(39-14) for extended periods of time. Done solo centuries in5:45 without ever leaving my small ring. If I had used max resistance, I never would have completed the ride.