The correct answer is option 1: Calcium. Calcium is a mineral element that is essential for muscle contraction.

Muscle contraction is a complex process that requires the interaction of various molecules and minerals. Calcium plays a crucial role in this process by binding to a protein called Troponin, which is present in muscle cells. When calcium binds to Troponin, it triggers a series of events that lead to muscle contraction.

Option 2: Iron is not directly involved in muscle contraction. Iron is primarily required for the production of hemoglobin, which is responsible for carrying oxygen in the blood.

Option 3: Sodium is important for various physiological functions, including nerve impulse transmission and maintaining the balance of fluids in the body. However, it is not directly involved in muscle contraction.

Option 4: Zinc is an essential mineral that plays a role in many enzymatic reactions and supports immune function. While zinc is important for overall health, it is not directly involved in muscle contraction.

Therefore, the correct answer is option 1: Calcium.