You feel it a lot when you first start exercising, but not so much after that. You don't want to over-do it - it seems a lot better to do a little bit of exercise on a regular basis than lots rarely.
There is a substantial difference between resistance and aerobic exercise - I find it's good to have both, and that they both compliment each other. Stronger leg muscles mean higher jumps and a faster stride, and aerobic training means better use of oxygen, so more reps, etc etc etc.
Just push it as hard as you can without risking injury for 20-30m, then quit. Do that with high scheduling variance (one week do it 4 times, the next week 1 time, etc. Variance, not routine, is key). Combine with long walks (to work if you're not too far away), bike riding, anything to reduce your sedentaryness.
This isn't a body-building or triathlete program, it's just a healthy one. Don't think of working out in terms of deterministic, 1:1, input=output. Rather think of it terms of signaling your body in ways that trigger certain gene expression that leads to a healthier metabolism.
Read this book more details:
http://www.amazon.com/The-New-Evolution-Diet-Paleolithic/dp/...
Reviews:
http://www.thedailybeast.com/articles/2011/01/04/new-evoluti...
http://www.marksdailyapple.com/the-new-evolution-diet/#axzz1...
Author's site: http://www.arthurdevany.com/
The degree of soreness you'll feel after your first few workouts is a degree of soreness you'll never feel again (until you stop working out and get out of shape).
A lot of "natural" physical activities (i.e. manual labor) tend to be repetitive in ways that don't exercise your body evenly enough, which can cause greater fatigue.