Although how your body becomes more efficient is still somewhat of a mystery, how you can train to make your body adapt is less of a mystery. Numerous studies confirm that interval training, even among well-trained athletes, yields results. High intensity training (HIT) is the latest craze. Everyone knows this, which is why everyone does intervals and tries to maximize time spent > 300w / 90% HR max.
So...hop on the bikes and bring on the pain? Not exactly.
A recent study suggests that by combining intense on-the-bike interval training with intense plyometric training (here, using explosive single-legged jumping), you may see significant improvements--even if you are already a highly trained cyclist. In the study, which was, unfortunately, fairly small, test subjects saw almost 23% improvement in oxygen efficiency in 4-5 weeks compared to baseline and control. That's astonishing improvement, since these were highly trained cyclists.
If you do 5 or more hours a week of training already, you can mimic the test subjects' workouts by adding three 30-minute blocks of plyometric/interval training to your weekly schedule; remove the same amount of time from your schedule.
The workouts are fairly simple:
(1) Warm up
(2) The first set:
a. Jump 20 times on your left and 20 times on your right leg. Climb on your bike.
b. Do a brief interval on your bike (5 x 30 seconds at a cadence of 60-70 rpm with 30-second recoveries between repetitions)
(3) Do three sets.
(4) Cool down.
The study doesn't specify how to do what it terms "explosive single leg jumps." It could mean single leg box jumps:
Or single-legged depth jumps:
Or this dork:
If you're not doing five hours or more of training a week, you probably want to start with at least that much time on the bike before adding plyometrics.