Mix some cardio into your strength training for a short and intense workout.
Even if you’re a COMPLETE beginner you can introduce yourself to interval training workouts with 3-5 minutes and add 1-2 minutes each week. Here’s my step mill interval training workout on the step mill: 30 minutes of 1 minute intervals. I go HARD (80-90% intensity) for 1 minute and then SLOW (30-40% intensity) for a minute. That means I do 15 HARD intervals in total and this