My first question is why are you wedded to long duration cardio? Contrary to current myth it is not critical for fat loss, the critical component is nutrition(diet). With strength training second in importance that places cardio in third place. Longer duration cardio can cass stress with produces cortisol which is a fat retaining hormone.
The key is to exchange intensity for duration to produces the same results in a shorter time. Skipping rope done properly is low impact, you only need to get your feet up enough to clear the rope passing under. If you can march in place without the neighbors coming after you at 6AM with torches and pitchforks you can skip rope at the same time of day. Not being snooty but I bet you can not skip rope for an uninterrupted 10 minutes today. Try it, you will find the intensity will replace the duration and produce results.
Edited by: SERGEANTMAJOR at: 2/18/2013 (23:10)