>>1213264if you use the middle of your foot or have the seat too low your exercise is more like climbing stairs
working mostly the top of the thigh near the knee (vastus medialis and rectus femoris)
most here will promote using the ball of the foot on the pedals
as this will work the calf muscle more (gastrocnemius)
and having the seat much higher than the handle bars
both for aerodynamic reasons and that it makes more use of the gluteus maximus
>>1213278also this
alternating between the use of different muscle groups can help on long rides
along this line there was the idea of pedalling in reverse while hill climbing to give ones legs a rest