"Body Confusion" is the key to an effective workout. Slowing way down and speeding way up again may get you in trouble on the interstate, but when it comes to cardiovascular exercise, it's the key for weight loss. If you vary intensity and variety, your body will burn calories long after you've stopped working out.
BUILD "THE GREAT PYRAMID" WORKOUT! Simply start with short bursts of speed, then peak at the longest surge of energy in the middle of your workout before coming back down in speed (picture a pyramid). Here are some simple at-home ideas for movements to build your pyramid: jumping jacks, jump rope, push ups, punch your arms in the air (at an imaginary punching bag), jog in place, march in place, ski jumps, etc.
Here is an example of how to rotate through a set of movements:
3 minute warm up
1 minute high intensity (action 1 - run in place)
1 minute low intensity (action 1 - walk in place)
1 minute high intensity (action 2 - jumping jacks fast)
1 minute low intensity (action 2 - jumping jacks slow or even side steps)
1 minute high intensity (jog with high knees in place)
1 minute low intensity (march in place)
1 minute high intensity (punch arms quickly)
1 minute low intensity (punch arms slowly)
You get the point.