400m or 1/4 mile walking lunges
Go to a track or measure a distance with you phone. The goal is to lunge walk for 400m without stopping. Put one front in foot of the other until you reach the goal. Do not rest for more than 2 seconds between lunges. This will blow up your legs (in a positive way; ladies do not be shy it will not cause you get big). Lunge walking is like low impact cardio. I sweat more and am more exhausted after 400m of lunges vs jogging a mile.
Give it a try this week. You may have to build up to 400m over a few days. If that is the case try lunging for 5 minutes at least twice before going for 400m. You might be sore if you do so, but trust me once you get going on lunging the pump will nullify the soreness.
I do this for cardio more often than running. Less impact on the joints. Shores up the hips, knees and ankles. Great muscle builder.