What is crucial for effective chest compressions during CPR?

The emphasis on pushing hard and fast during chest compressions is crucial because this technique is designed to create adequate blood flow to the brain and vital organs during cardiac arrest. Compressions should be delivered at a rate of 100 to 120 compressions per minute, providing enough force to circulate blood effectively.

Leaning on the chest between compressions, as suggested in other options, can prevent the heart from fully refilling with blood, which reduces the effectiveness of each subsequent compression. Maintaining a consistent rhythm without leaning allows for continuous blood flow, maximizing the chances of survival until emergency medical help arrives.

Overall, adhering to the recommended depth and rate for chest compressions is vital for sustaining life in a critical situation.