Let’s see if I can craft a short answer.

1) Physical fitness has three components – flexibility, strength & endurance. All are equally important.

            a) Flexibility benefits from a good instructor but computer based systems are rapidly coming into their own.

            b) The best bang for the buck in strength is a captive weight set and rapid reps at submax weight. But, you can make anything work, even a Bowflex.

            c) For endurance, buy a good heart rate monitor and then learn how to use it. From a technical perspective a swim flume beats all – if you can swim. A rower is next in line because it exercises arms, legs and back. Then comes a x-country ski machine but that is a difficult motion for many. Bikes or ellipticals are preferred if you need to limit impact forces. Treadmills are useful – especially if you have one that is designed for barefoot running. None are worth anything if you don’t use them,

2 Your goal should be to train smart. That is three days of strength and flexibility training and three days of endurance training and one day off per week. One can physically train a world class/age group triathlete on an hour a day. Mental training is another issue entirely. For basic physical fitness, you should be able to change clothes, exerrcise, shower and change back into work clothes in that hour per day.