Consider this as it is how a great genius trained…

E = The number of days you have cycled (or other) more than E number of miles (or other)

Now the great genius was Eddington & his cycling E = 87

But you could do this with Kettlebell swings, snatches, hindu squats, any number of things. You could substitute weight vest hiking for cycling for example.

So E is your Endurance personal best.

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