This work builds on MuChMAC, a dynamic multi-channel MAC solution for low-power wireless sensor networks. We present a distributed algorithm to scale MuChMAC's duty cycle based on the amount of traffic passing through a node. We have implemented this algorithm in Contiki and we have evaluated its performance on a real testbed of Sentilla JCreate wireless nodes. We demonstrate that it significantly improves packet delivery performance MuChMAC under high traffic loads, while preserving its low overhead under low traffic loads.