Your warm ups should last 3 minutes, your steady pace should last you 22 minutes at about 4.5 and an incline of about 4.5;  your cool down should last 5 minutes. Try that for a week and then every week go up on your incline and speed .

Another workout to try is; Start with a 10 min warm up to interval training and up hill walking/jogging. Do not hold onto the treadmill when you run, your arms will get a better workout than your legs. Then increase the incline to about 3-5 % grade (Uphill).Run hard uphill for 3 minutes then slow the pace for 1 minute 30 seconds (90sec).

Repeat this process for 3-miles the first week, then add 2 more miles for a total of 5-miles. The following week increase the percentage (% )of incline a little more. This will make the run even more challenging for you.

You can also increase the time you run hard (and the recovery as well) by 1-2 minutes. That’s a good workout, but if you’re trying to lose fat with the treadmill,  add an extra 5 or 10 minutes for max results. Maybe 5 minutes of walking, or split it up between a jog and a walk. One thing you might want to try as well, if the run for 3 on 5 kills you, consider adding a minute or two to walk in-between the jog and run. That might help you build up your stamina so you’re not so winded.

Also, if you really want a workout, consider kicking up the incline to 1.0. It doesn’t sound like much, but it makes a big difference. A treadmill is at a natural decline, so putting it at 1 or even .5 will make a difference. If you want to save your knees, you might want to do the bike 2 days a week as well.