(WSNs) is increasingly growing as they allow a large number of applications. In a large-scale sensor network, data transmission among sensors is achieved by using a multihop communication model. However, since its resources limit the sensor, sensors' Operating Systems (OSs) are developed in order to optimize the management of these means, especially the power consumption. Therefore, the hybrid operating system Contiki uses a low consumption layer called Rime, which allows sensors to perform multihop sending with a low energy cost. This is favored by the implementation of lightweight processes called protothreads. These processes have a good efficiency/consumption ratio for monolithic tasks, but the management of several tasks remains a problem. In order to enable multitasking, Contiki provides to users a preemptive multithreading module that allows the management of multiple threads. However, it usually causes greater energy wastage. To improve multithreading in sensor networks, a Multithreading Model for an Efficient Data Delivery (MMEDD) using protothreads is proposed in this paper. Intensive experiments have been conducted on COOJA simulator that is integrated in Contiki. The results show that MMEDD provides better ratio message reception rate/energy consumption than other architectures.