Elliptical machines are designed to limit the impact on the body so you can get a workout without having to stress your joints and muscles, but what they really do is something more. They cause certain mechanic inhibitors to occur that you probably will not notice right away; however over time this will cause some knee, hip, and low back issues.
In reality I'm sure that sounds like an oxymoron on how to achieve great physical conditioning because these machines are peppered along the cardio floor of your local big box gym.
Elliptical machines force you to run in sometimes an unorthodox way because the machine is typically measured for individuals of a certain height, stride length, etc. While performing the elliptical trainer your feet are essentially locked in place while the rest of the body is simulating a running pattern which in turn can strain the joints at certain points throughout the abnormal range of motion. The hip flexor/rotator is connected to your hamstrings which also pulls on the knees and right down to your achillies tendon. That being said, if you hip is out of wack- or it soon will be by continued elliptical use- it could be causing real problems for all the muscles in the legs as well as the knees and low back.
1. Cardio machines with swinging handles offer very little to no benefit than if you swung your hands naturally at your sides. You'll get a better workout by working your stabilizing core muscles.
2. Keep in mind the elliptical will make you better at 'elliptical' and burn some calories, improve general cardio- which is way better than being sedentary- BUT will most likely not translate to anything else that you do. ie. walking, running, stair climbing etc. It is very common that people can do an hour on elliptical, but have trouble running for 20 minutes.
In summation the elliptical trainer will help with burning some needed calories, but doesn't make you better at anything except itself. Personally I believe it is harder to get a good workout on the elliptical machine. It takes a lot more concentration to work hard enough to work up a sweat and it's very easy to make the elliptical an easy workout. It typically takes 3 times as long to burn the amount of calories you do with other exercise and cardio types.
It is interesting to note, an observation I have made at the gym over the years is that when you look at the people who regularly use elliptical machines compared to those on treadmills, stairs, or who interval train with weight resistance, is the people using the ellipticals are on average at least 20lbs. heavier and don't look nearly as fit. Food for thought...