Recent research in Energy-efficient MAC protocols for Wireless Sensor Networks (WSNs) emphasizes optimizing communication schedules and reducing energy wastage caused by idle listening, collisions, and control overhead. Novel MAC designs integrate adaptive duty cycling, wake-up radio mechanisms, and cross-layer coordination to dynamically adjust transmission timing based on traffic load and residual energy levels. Studies also explore hybrid contention and TDMA-based approaches to balance latency and throughput while extending network lifetime. By combining energy-aware slot allocation, low-power listening, and event-driven communication models, these protocols achieve significant improvements in energy conservation, responsiveness, and scalability, making them crucial for sustainable WSN deployments in real-time sensing applications.