This paper introduces YA-MAC, an agile Medium Access Control (MAC) protocol to provide high throughput for both unicast and broadcast traffic in Duty-Cycled Multi-hop Wireless Sensor Networks (DCM-WSN). YA-MAC is implemented under the UPMA framework in TinyOS and is evaluated on TelosB and MicaZ testbeds. We observe that YA-MAC significantly outperforms the state-of-the-art SCP-MAC protocol in terms of throughput by 60%, while tolerating a more dynamic network, at a small cost to duty-cycle performance. Further, we show that YA-MAC's idle listening radio power consumption is 35% less than RI-MAC's, while achieving similar throughput and latency.