High cadence pedalling isn’t for everybody

Broadly speaking, higher cadences are fuelled by the aerobic system, where glycogen and fat are oxidised (burned) to power the slow and intermediate fibres of the muscles. As power output increases, the proportion of fats burned decreases in relation to glycogen, although some fat is still used. Glycogen requires more oxygen to burn than the equivalent amount of fats, so as power output increases so does oxygen demand.

High power output using a low cadence recruits a greater percentage of fast-twitch muscle fibres than high power with cadence pedalling. Fast-twitch fibres are fuelled entirely by glycogen, but this metabolic pathway also produces lactic acid as a by-product. High power at low cadences will therefore deplete glycogen quicker, while producing lactic acid, which is partly why low cadence high-power pedalling is so tiring.

But changing to high-cadence pedalling won’t suit everyone. Fast-twitch muscle fibres are bulkier than slow and intermediate ones, which is one reason why sprinters are bigger than climbers – they have a large proportion of fast-twitch fibres. So if a sprinter tries to climb in a low gear with a high cadence they will be pedalling with a lower total number of fibres than a climber, as only their slow-twitch fibres will fire.