There are many approaches to strength exercises, and not all of them come from the same philosophy. People used to think about the strength exercise in a pretty limited way. Back in the day, strength training exercise programs consisted of lifting heavy weights. Basically, it was thought that the more weight that you could lift, the stronger you were. The number of repetitions that you could make was secondary. It was all about the dead lift.
Nowadays, however, strength training exercises are broader and more diverse. Not everyone has the same opinions about strength. For many people, the key to strength training exercise is a core workout routine. Basically, instead of strengthening your arms and legs, you are supposed to put most of the emphasis on your chest, back, and stomach muscles. These will make you stronger, healthier, and more fit. They will help you to keep your belly thin, and to avoid back problems in the future.
Nonetheless, the old philosophy of strength training exercises still has a lot of pull in some circles. Products like the Bowflex, Free weights, and resistance training are all very popular courses of exercise. In my mind, it does not make sense to choose one over the other. A strength training exercise routine should contain elements of all of the different approaches. You can use yoga or Pilates to help train your core muscles, do sit-ups and push-ups to further refine them, and do weight lifting on exercise gym equipment to give yourself strong arms and legs. Basically, every strength training exercise will make you stronger, so why just use one set?
Of course, when you are doing weight lifting exercise you have to be extremely careful. If you are just working at your core muscles with sit-ups, push-ups, or other calisthenics, it is hard to injure yourself. With weight lifting, however, it is much easier to have an inadvertent injury. You see, this kind of strength training exercise can put your body under such a tremendous amount of strain that things can break. You can tear muscles, you can suffer temporary fatigue and drop the weights, and you can even break bones if you are unlucky.
This is why I put more emphasis on the core strength part of my strength training exercise routine. I would rather have trim, healthy muscles than the bulky ones that you get through weight training exercises anyway. Just because you are strong, it does not mean that you have to be oversized.