High Intensity Interval Training
Tabata is a form of HIIT that lasts only four minutes. But it's a tough four minutes! You work hard for 20 seconds, rest for 10 seconds and repeat eight times! Some popular Tabata exercises are pushups, sit ups, mountain climbers or squats.
It works for me. I use a treadmill at the gym three times a week to do 30 second sprint and 30 seconds rest. My favorite trainer Juliette Vagg first introduced me to this routine and I consistently see results when I train like this. I feel leaner and stronger. It's easy for me to stay motivated because I say to myself "It's ONLY a few minutes."
My tip is to start at 5 minutes twice a week on a low setting and work your way up as your fitness improves, adding a minute each week and adjusting the speeds as you get more comfortable. Usually 4-12 minutes is the recommended time for each HIIT session. For me, this is much more effective than spending 20 or 30 minutes on a cross trainer or other cardio machine- Because slogging away on a treadmill can be downright boring, unless you're chatting with a girlfriend, which means you aren't working hard enough anyway!
45 seconds skipping, 45 seconds plank.
45 seconds high knees, 45 seconds slow squats
30 seconds sprint, 30 seconds rest.
Beach sprints- race to the water and walk back several times
Boxing- Continual fast punches while the other holds the pads for you. Switch every minute for 8 minutes.
Skipping/yoga- One partner does 50 skips while the other moves through cat/cow pose. Switch.