Purpose This systematic literature review investigates how multimodal instructional design in asynchronous e-learning environments influences motivation, engagement and knowledge retention amongst adult learners. Grounded in cognitive load theory (CLT), the review explores how digital instructional strategies can be optimised for inclusive and cognitively efficient learning in the context of technical and vocational education and training (TVET) and post-compulsory education, within the human-centric framework of Industry 5.0. Design/methodology/approach Fourteen databases were searched for peer-reviewed English-language studies published between 2019 and 2024. Sixty-five studies met the inclusion criteria focusing on adult learners, multimodal strategies and asynchronous digital delivery. Study quality was appraised using the CRAAP framework. The thematic synthesis was situated within an interpretivist paradigm and analytically framed by CLT. Findings Six core themes emerged: inconsistent instructional design; barriers to lifelong learning; motivation and engagement challenges; continued reliance on learning-styles approaches; the cognitive benefits of multimodal strategies and limited attention to workplace learners. Findings reinforce the value of CLT-aligned multimodal design for improving engagement, retention and inclusivity, while highlighting the need for more context-sensitive and practitioner-informed approaches. Originality/value This review addresses the under-representation of adult and TVET learners in asynchronous, multimodal e-learning pedagogy research, offering practical and theory-informed insights for educators, instructional designers and learning-and-development professionals. Although the evidence base is still emerging, particularly regarding longitudinal workplace studies, the review provides new direction for inclusive, cognitively efficient instructional design. No external funding was received, and the review was not pre-registered.
Pimblett et al. (Sat,) studied this question.