A few of these products are also sold in stores. I have included links to reviews here so that you can compare what products work best for you and decide if you want to buy any of them. The best product for anyone who wants to increase their strength is to increase their aerobic fitness. So what type of aerobic fitness does a person need? Aerobic fitness is defined as the capacity to use aerobic energy systems in order to perform physical activity. Aerobic fitness should not be confused with muscular or aerobic capacity. Muscular endurance is a higher capacity of the body to withstand the effort of physical activity. Therefore, if you have very low aerobic fitness, you are not going to be able to train hard to get good results. The most effective way to increase your aerobic fitness is to work out more and stay on the training bike. In general, the greater the training volume, the better your results will be. The more frequent you go, the more frequent you will need to go and the longer you need to train. If you don't regularly do more than 3 workouts per week (or 2 if you have any other activity in your life) then you will not be able to build any better aerobic fitness.