Can cycling with single leg improve endurance and increase slow twitch muscles with shorter workouts?
When muscle groups fatigue, they start to recruit larger motor units. That may explain why when you're exhausted, the workouts feel harder, and why polio victims fatigue sooner.
With single leg cycling, one leg VO2 max is close to that of two legs. That means the larger motor units can be targeted sooner given the same oxygen consumption. More of our muscle fibres would be given the signal to increase capillary density, increase mitochondria, increase mitochondrial enzymes, increase antioxidant defenses, and other kinds of adaptations.
Based on my understanding, if we cycle 1 hour with one leg, the exercised leg may think it exercised up to 2 hours in terms of recruitment pattern! Having a meal in between two rides may refuel the smaller motor units, preventing some of the larger motor units from being trained.
If this works, we may be able to break fitness plateaus or maintain endurance with more flexibility in our schedules. According to some commentators, long rides should be done all in one go so biking to work, working 8 hours, and riding home feels different for our bodies than riding twice the distance to work then staying overnight at work.
If you're doing group rides, it can help the slower riders keep up with you while you have a good workout.
It may also decrease blood pressure because a study showed that higher type I fibres reduce blood pressure. https://www.ncbi.nlm.nih.gov/pubmed/15837823
Another benefit is that the exercised leg could push harder than in two-legged workouts at a lower heart rate without causing breathlessness. Those with health problems such as hypertrophic cardiomyopathy or high blood pressure may need to limit their heart rate during exercise to stay safe.
What we may need to do is make sure that we don't pull on the upstroke. We might use the counterweight on the pedal of the unused side or redesign the chainrings to make the upstroke easier. We also need to remember to exercise the other leg on another workout.
Does this actually work in practice?