When you do weight training, one of your goals should be to get stronger. To do this, you have to increase, over time, the amount of weight you lift. How quickly you progress depends on genetic factors, where you start (beginners progress faster than experienced trainees), and your training technique and frequency. If you go several weeks without being able to progress, you should change your training routine. Overall, a person who progresses more rapidly will not necessarily do better in the long run than someone who progresses more slowly. Progressing too fast can be counterproductive. Work out consistently and progress when the weight you lift for a given exercise is no longer challenging. Add some variety to your workout and you can continue to progress for months, or even years.
When you finish a weight training workout, try to eat something within half an hour. If you are ready for a meal, go ahead with that. If not, eat a snack of 200-300 calories, including carbohydrate and protein in a ratio of about 3 to 1. For instance, if you eat 240 calories, that would be 180 calories (45 grams) of carbs and 60 calories (15 grams) of protein. Any dietary fat in the snack adds more calories, but is not needed for recovery. The protein gives you the amino acids you need to build or repair your muscles after a hard workout. The carbs release insulin which is necessary for the protein to enter your muscle cells, as well as replenishing the glucose and glycogen you used for energy. Make sure you take into account these calories when you are counting your daily dietary intake. If you are trying to lose or maintain your weight, take this number of calories out of another meal.
The elliptical uses more knee action than some other machines, so your quads are working in ways they are not used to. If your thighs burn when you use it, try 10 or 15 minutes at a time, twice a day, then add a few minutes and eventually go to one long workout. Try adjusting the elevation, if your machine has that function. Warm up by walking around before you work out, and stretch after. You can strengthen your thighs by doing body weight or dumbbell squats or lunges. Your legs should adapt to the elliptical fairly soon. You may still get a little burning at first, but it will subside and you can go on as long as you want.
If you pull a back muscle and it's still not better after several months of stretching exercise, it's time to go back to physical therapy and see if they can offer something else. You might also consider seeing a chiropractor who works with athletes. Acupuncture often relieves the pain, which can help healing. If you smoke, quit, as smoking interferes with circulation. It's may also be helpful to limit saturated fat intake, if you eat a lot of meat.
The best exercises for upper chest are incline bench presses and incline flies. You can also try a cable cross with the handles held rather high. You will probably get better results if you also include some flat presses and military presses to not neglect the surrounding areas.
When you work out at a lower percentage of your maximum heart rate, you burn a higher percentage of calories as fat calories. But when you work out at a higher heart rate, you will burn more calories overall, and a total of more fat calories as well. Don't slow down if you're capable of working out at a faster pace. The harder exercise will burn more fat in the long run.