Final answer:
The contracted muscle when a cyclist's foot is dorsiflexed and inverted is the tibialis anterior, which is located in the anterior compartment of the leg.
Step-by-step explanation:
If a cyclist's foot is dorsiflexed and inverted, the muscle that is contracted is the tibialis anterior. This muscle is located in the anterior compartment of the leg and is responsible for raising the front of the foot (dorsiflexion) and inverting it.
The tibialis anterior is a long and thick muscle on the lateral surface of the tibia, which, along with the extensor hallucis longus and the extensor digitorum longus, contributes to dorsiflexion. When considering the actions of dorsiflexion and inversion together, the tibialis posterior muscle primarily performs the inversion action but not in a dorsiflexed position. Meanwhile, the fibularis longus (peroneus longus) and the fibularis brevis (peroneus brevis) muscles are involved in evertion and plantar flexion, not inversion and dorsiflexion.