i may have been unclear, but my (very tentative) claim is that, if fixed gear is indeed more efficient than free, then you will use more energy on the free bike per amount of time (or distance, whatever), assuming all other variables to be equal. what is easy and efficient for actual use is not necessarily superior for a workout. hell, you might even want to use the ****tiest bike you can find if you want strength training, etc. again, of course, much of this depends on what you want you want to get out of your "workout."