I've personally been kicking my own ass with these exercises for a couple weeks now, so I can vouch for their ability to make you work hard. The nice thing is that they're all very scaleable to different levels and don't require any workout gear. There are countless circuits of similar exercises across the internet, but I worked this set up myself over some trial and error to get every major part of the body going in less than half an hour. I'm in reasonably good shape and I have no trouble getting a good sweat going and getting out of breath using this circuit. Like I said, these are all scaleable so you can change the number of reps to what works for you, but I'm listing the numbers I've been working with lately.
Certainly feel free to change up anything and add or subtract exercises if you want to give these a shot. I'd love to hear from you with feedback if you try it and hate it, added something, or anything like that. Some of these may be self-explanatory, but I'll give a rundown on each just to make sure.
1. 25 Pushups
We all know push ups; just keep your back straight and grind them out.
2. 30 Leg Roll Ups
I honestly don't know what these are actually called so I've been calling them everything from leg raises, to extensions, but roll ups sounds about right. You lay on your back - on carpet or something softer than wood or tile is my preference - with your hands at your sides, palms down to brace yourself. Lift your legs off the ground, straight out from your body about 8-12 inches then roll them back towards your chest like you're going into the fetal position, then roll a little onto your back to push your legs straight up above you. I count 1 rep as going from the horizontal position to the raised position.
3. 30 Squats
Feet shoulder width apart,and as far down as you can go. Picking up a weight or moving your hands and arms to different positions can increase your effort as well.
4. 60 Bicycles
Again, not entirely sure this is what they're commonly called, but you lay on your back, hands behind your head, with your legs straight out like a leg lift. Then just alternate bringing one leg back at a time and touching your knee to your elbow, counting 1 each time you make contact.
5. 20 Lunges (on each leg)
Make like you're taking a big step with one leg forward and go down until the knee of your back leg is almost to the ground, then bring your feet back together and repeat for the opposite side.
6. 30 Calf Raises (on each leg)
Put one foot behind the other, kind of rested on the upper ankle and push up on the ball of your foot bringing your ankle up into the air. You may want to stand near something to help you balance.
7. 30 Dips
For this, you can use a chair, the edge of a bathtub, a bench, anything that's the proper height. Put your hands on your object of choice to hold yourself up kind of from behind and set your legs out to where most of your weight is on your arms. Grind them out!
(Optional) 8. As many pull ups as you can do
This one's listen as optional since you do need a pull up bar or something similar, but they're not terribly expensive and pull ups are awesome workouts so I decided to include it here.
My go to has been to do this circuit three times, but you can do them more or less, whatever feels good and is working you hard. Do these quickly with as little time in between reps and sets as you can and you should be able to get a good workout in within a 20 minute time span or so.
I've got another post in my Dumb Health Tips series coming up about dumb diet tips so keep an eye out for that as well!