Given we all have limited training time, finding ways to get greater performance in shorter workouts is always an attention grabber. While intensity is always the major factor in terms of adaptation, as has been demonstrated time and again, time on task is a major component in elite fitness. If elite levels are not what you are after however, you have other options.
Interval running (as discussed many times previously on this blog) is a way to generate physiological adaptations in short workouts. Gunnarsson and Bangsbo 2012 used the 10-20-30 running program on 18 moderately trained runners. The metrics were total time to complete a 1500m run, a 5000m run and VO2max.
The training program was set up that the runners completed a 1km warm up jog. They would then train at 10 seconds at 90% of their max, 20 secs at 60% of their max and finally 30 seconds at 30% of their max. This is repeated 5 times followed by a 2 min rest. This entire 10-20-30 block series would be repeated 3-5 times during a training session.
In 7 weeks, 1500m run time improved by 23secs and 5km time by 1 min. VO2max improved by 4% in a mere 7 weeks.
The authors noted that there were changes in resting blood pressure, resting heart rate and blood cholesterol which were unexpected given that most of the runners already had healthy profiles. So when you are way too busy to go for a 1 hour run, throw out a few blocks of 10-20-30 and see what happens.