Skipping - You just need a skipping rope, that is all.
Skipping is a good form of exercise for the whole body, the hand and leg, and including the core area as well. One will need to balance at all the time. The calve and feet will get stronger over time.
Skipping 20min is equivalent to 1 hour of running, according to experts and researchers, using heart-rate as an indicator. Compared to other exercises, skipping is as good as hill workouts in running. In Loughborough University, in the past, when I was in England as a University cross-country runner, we do circuits that has subtle skipping exercises, but we did this without a skipping rope.
For the duration of exercise and training, it is important to do it with skipping rope, as it will take at least 20min to finish the training. One could do 1 minute skipping and 1 minute of rest and cover the entire 40min like this. A fit person can do a moderate speed during skipping. For 1 minute, one could do moderate intensity and one could rest for a while or slow down the speed for a minute, and then continue the training. It is good to cover 40min of this activity. If one is very fit and he or she could not get an intensity workout done, one could do a hard 1min skipping and 1min of slow skipping or rest 1min in between sets and do the whole 40min of the time. If the rope touches the leg and one's skipping stops, one should just continue the training or keep the flow going. I hope that you enjoy this kind of optimum training. You can choose your training to your fitness.
If one is old, and also for a young man who is not fit enough, it is a good idea to do 1 minute of skipping, taking one's time to rest for a minute and then continue like this for the whole 20 minute of the total time taken.
Take note that skipping increases one's cadence and including stride length as well. If one is supervised and monitored to get the optimum result that is also good. If you can't find someone to help, you could actually do it by yourself.