No bicycle transmission should ever be shifted under load. I suspect this is why chain breakage has become rampant; a new generation of riders, raised on indexed systems and mountain bikes, is power-shifting its transmissions to death.
The best way to shift any epicyclic in-the-hub transmission is to make sure the cog is turning anticlockwise with respect to the hub shell. One can easily achieve this either by backpedaling while stationary or by coasting while moving.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069