When I speak about "efficiency", I don't want to use a word having physiological or biomechanical means, but only to say that the situation of the body was completely ok.
When you come from a long injury and from a surgery, and, after several months of "physical" training, using a lot of exercises for rebuilding your balance in the body, your ability in coordination, your strength, your reactivity, we can say that you were able to recover a full "efficiency". A high jumper able to jump 2.30, of course in in full efficiency (biomechanic), but is not trained for running 5000m (bioenergetic). It's true that without "efficiency" you cannot be a good athlete in long distances too, but without training of endurance you cannot use the efficiency of your body in that direction.
Don't forget that an athlete can easy appreciate
"directly" his mechanical situation (efficiency),that is an expression "outside" his body, but is very much more difficult to understand his enzymatic and bioenergetic shape, that is hidden "inside" his body.
Particularly for African runners, the idea of "shape" is connected with the mechanical situation, that I call
"efficiency", not depending on the distance they go to run. So, if a marathon runner is able to run very well 20 x 200m with 200m recovery, he supposes to be in shape.
There is not a "shape", but a "specific shape", and of sure, if you are in shape for your best in 800m, you cannot be in shape for your best in Marathon.
Remember always the most important principle of training : for going in shape, you need NOT to replace some type of training with something else, but to ADD something that before you didn't do, maintaining the level you reached in all the other training. So, if you have the same endurance, but more strength and/or reactivity, you run faster. But, if you have a lot of speed, good strength and reactivity, but your endurance is 50% of your best, forget you can be in shape for middle distances.
An example : before winning WCh 2005, one week after winning Golden Gala in Rome in July in 7'56", Shaheen ran 37 km in Iten in 2 hr 02'. In July 2008, he was not able running 10 km at the same speed. So, the problem was not speed, but endurance.