I was recently at Planet Fitness for leg day and I'm looking around at all of the different machines and thinking about which are essentially useless. Now this is a personal opinion but there are a lot of machines there that I don't or wouldn't use. Pretty much anything that's designed for the abdomen I avoid. I feel that if you're doing resistance movements correctly, especially squats and rows then you have to tighten the abs. The only ab exercises that I'd advocate are planks and variations of them (knee tucks, pendulums). But I was also considering the 30 minute express zone. This is really a good idea, in fact I tell most people that are just starting to exercise to go there two or three times a week for the first three weeks. If you're not familiar with the 30 minute express, it's an area with 10 aerobic platforms and 10 resistance machines. The concept is to spend 1 minute at each station and 30 seconds moving to the next, alternating cardio and resistance. So one would do aerobics then resistance then aerobics and resistance until all 20 stations are finished. The whole thing takes 30 minutes. I like it for beginners for a couple of reasons. It meets the requirement of exercise being at least 20 consecutive minutes, it works the whole body and gets people familiar with the movements. But that's where I stop, you only do one set for each body part which is not effective in building muscle. The one minute of cardio is good but one minute of resistance is too long. You only want to do 7 to 15 reps, any more than that and the weight is too light and there is the repetitive motion that could cause other problems.
Most people can do 7 to 15 reps in 25 to 40 seconds, the additional time is lost. I also like it for just a few weeks because again for most people just starting out strength gains in the first few weeks aren't muscular so much as they are neurological. It's your brain finding more efficient ways of telling your muscles to work. If you don't regularly train and go to the gym, maybe you can squat 100 pounds for 6 reps, then three weeks later you can squat 170 pounds for 6 reps. Odds are that your muscles could've squatted the 170 back at day 1 but your brain just couldn't get the whole muscle to fire. So this whole thing got me to thinking, how can I use this same idea for a home workout but adjust the times. Here is what I came up with. Nine resistance moves intermixed with high energy cardio at intervals of 10 seconds rest, 45 seconds activity, 10 seconds rest, 25 seconds activity. This yields 13:30, while it doesn't hit the 20:00 definition of exercise, the cardio portion is high energy stuff and if you just don't have time for a 20:00 session this can be a good substitute.
The timer I use is on my Android called 'A HIIT interval timer', it allows me to set multiple actions. In this case 4, rest, cardio, rest, resistance. So here is the "Quickie" workout;
Aerobic step, plank, high knees, triceps press, box hop, biceps curl, jumping jacks or side lunge, shoulder press, burpee, row, aerobic step, pull up, climber, push up, skater, hamstring curls, jump rope, squat or wall sit.
I'll make a video of this as soon as I can and post it. Somebody give it a try and send some feedback.