common sense really.
what separates an elite endurance athlete from a lower grade counterpart is not usually fitness, but power and speed output. both levels of athlete are extremely fit.
I once divided a B grade athlete's best 400m into his 5000m time; his ratio was similar to the world record holder.
what separated the two athletes was speed, and that is best trained by power training. that is why elite endurance trainers do some sort of strength work, although it may not necessarily be in the gym. it ma be short fast sprints, bounding or weights.
the power an endurance cyclist like wiggins would generate would be staggering. he s also a world champion of 4000m individual pursuit.