Splitting hairs weakens your argument. Why draw the line at indoor riding? --- "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailleur? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

Elevated heart rate, elevated respiration rate, elevated power output. Amateur and pro racers everywhere have relied on indoor trainers for years to meet their workout goals.