If you are using the Stairclimber, try not to hold on to or put all your weight on the rails. Warm up for 6 mins at around level 4 or 5, then gradually bump up the level 8 or 9 depending on your comfort level. BTW, warning, I am not a doctor or trainer, but have spent many years in the gym. Eventually you do want to increase your HR level to around 160 (HR will fluctuate and that's okay) and maintain that for the duration of your workout. Eventually you want to do cardio for 45 to 60 mins. The Stairclimber is challenging so you may not want to do the whole 45-60 on it. I tend to do 20 mins on Stairclimber, move over to another machine, i.e bicycle, or treadmill for the remaining time. You can walk on treadmill at an incline of 3 or 4. You can start your speed and 3.8 and gradually work up to 4.7. You want to walk at a brisk pace. The above numbers are not set in stone but to be adjusted to your comfort level. Regarding working up to 45 mins, start slow.

I am sure others here have more suggestions. Bottom line, being unable to hold a conversation for 45 mins. You are strengthening the heart by having it endure stress for that period of time. Good luck.

cardio and leg strength. The biggest drawback is that it is boring as heck, but if you don't mind it, then it is a great exercise. I did the stair machine for a year to prepare to hike up Mt Shasta in northern CA a few years ago.

I'm going to hike up Mt St Helens at the end of the month if the weather is OK. For that I've been doing hill sprints, since the gym with the stair machine is no longer conveniently located. There's a long uphill drive out of our apartment complex - I "sprint" up it (I've never been very speedy), then jog slowly down, then repeat until I've done the uphill 10 times. I think that the uphill sprints give me the best bang for the buck - it takes less than half an hour, it alternates high intensity with low intensity, and I don't have to do miles and miles of jogging which would probably hurt my knees (I'm 56).

There's a formula for determining your sweet spot of a cardio workout. Anything more than your target heart rate and you're overdoing it unnecessarily.

so nice to see mature people looking for active lifestyle! Congrats to you! Do you consider enhancing your endurance with the help of supplements or drugs? I suppose you probably know about their action if leading a physically active lifestyle.

I'm pretty much just try eating healthy.
I do take Ubiquinol as a supplement and fish oil.
Part of my lowering cholesterol regime.

you could consider spirulina, that's good in lowering bad cholesterol and also is a good combination with clean eating

I forgot about that stuff.