Time is a precious commodity and maximizing your use of it is crucial. I 've been using the workout below to maintain and improve my fitness level. I'll do this for 2 to 4 weeks at a time, and then switch off to another program just to keep things interesting. Give it a shot, especially if you are presed for time and looking to get the most for your time spent. I'll do this routine Monday, Wednesday and Saturday. I get at least 8 hours of sleep at night and eat 4 to 6 , mostly small meals, throughout the day. Here it is:

5 minutes of jumping rope. Vary the speed and intensity. I go at fairly quick pace.

1 minute rest

5 minutes of max effort. You do 10 rounds here. Each round is 20 seconds of max effort followed by 10 seconds of rest. The exercise is up to you. You can do push ups, pull ups, push a very heavy object, clean and press a dumbell or kettlebell etc. You get the idea. I would alternate pushing and pulling motions on different days (i.e. pushing motion on Monday, pulling motion on Wednesday etc.)

1 minute rest

5 minutes Start standing. Squat ,Thrust your legs out behind you, do a pushup, bring your legs back under you, so your feet are flat on the surface, and stand up. That equals one. For added resistance hold a light dumbell in each hand when you do this. I keep a 35lb kettlebell on the surface to the right and left side of my body. After squating and thrusting, when my feet are flat on the mat, I grab the kettlebells, then stand up (something like a Romanian Deadlift motion).

2 minute rest

This is intense. Give a shot. Stay strong.