You increase the setting to make it a little more difficult but you don't increase the time until you are quite comfortable at the higher resistance. I don't use a rower but I use a resistance bike at PT where they slowly build you from beginner with no resistance to 'better' with resistance. Most important is to not overdo it so that's why you don't increase the amount of minutes when you're just starting to strengthen. Always stop before you feel it's a drain because you will get turned off from it--go at your pace and move to higher levels whe you think you can handle it. Also, go back to lower levels when you need to. Some days it's better to set it to three instead of six, we all have extra-low energy days--it doesn't make sense to do a lot when you can really do just a little. Listen to your body and keep at it! I truly believe that exercise, in any form, is going to increase your stamina and strength. You look better for it, too.