The typical introductory physics lecture requires students to consolidate and assimilate a large quantity of complex information that is often novel to them. This can leave students overwhelmed, slow the pace of their learning, and lower their motivation. We find that carefully designed multimedia summaries in the form of one-minute videos and short text summaries can significantly increase students' understanding of the material as well as their ability to organize information into a useful mental framework, as measured by their performances on a concept mapping exercise and a conceptual test of learning. Notably, we show that these improvements can be achieved with negligible increase in overall time students spend on the course material each week. We discuss reasons why these short postlecture summaries helped students learn more, namely, that (i) they likely increased students' ability to chunk and organize information while minimizing the extraneous cognitive load imposed by the materials, and (ii) they likely improved students' ability to consolidate and transfer knowledge through the use of contrasting cases. We provide a set of detailed recommendations that instructors can use to develop effective postlecture multimedia summaries. We suggest that one of the most important and impactful recommendations is incorporating student thinking in the design of these types of summaries informed by the input of qualified former students or teaching assistants with significant experience interacting with students in the course.