Improving performance requires a multidisciplinary approach. Hence there are a number of factors which can result in either a positive manner (improving performance) or in a negative manner (attenuating performance).
The gears dramatically illustrate the connectivity between these factors as they revolve around, turn and effect performance. The movement of one gear dictates the movement of the other gears. Ideally all should be moving in concert and all should be turning in a favorable manner. Essentially if all gears are efficiently working for the good of the athlete, then performance will be maximized, but even if most are supporting the work load, and one is not, then the gears are unable to move and achieving maximum performance will be impeded.