Research on the relationships among sleep, exercise, and cognitive function has constructed a mainstream linear narrative: regular exercise optimizes sleep; exercise enhances cognition through brain-derived neurotrophic factor (BDNF) pathways; digital screen exposure disrupts sleep; and digital cognitive behavioral therapy is generally effective. This narrative has become a core rationale for contemporary workplace health promotion. However, existing studies are characterized by biological reductionism, neglect of individual heterogeneity, methodological flaws, and decontextualization, raising serious questions about the generalizability and ecological validity of their conclusions. Adopting a critical sports medicine and sleep medicine perspective, this article systematically integrates 37 SCI journal articles from the natural sciences, sports medicine, sleep medicine, and public health to conduct a multi-level critical analysis of three core propositions: the dose–response relationship between exercise timing and sleep; the BDNF mechanism of exercise-induced cognitive gains; and the dual effects of digital technology on sleep. The analysis finds that the “4-hour recovery window” before sleep and the claim that “morning exercise is optimal” are highly dependent on individual boundaries, and that the moderating roles of sex, age, exercise habits, and exercise type have long been underestimated. Causal evidence for BDNF as a core mediator of exercise-related cognitive benefits remains insufficient; dimensional bias and publication bias jointly inflate the actual workplace benefits of exercise. The harm of blue light has been exaggerated by commercial discourse; the association between social media and sleep depends more on usage patterns than on use itself; screen-time research generally suffers from inadequate identification of reverse causality; and digital cognitive behavioral therapy for insomnia (dCBT-I) faces high real-world dropout rates and blurred effectiveness boundaries. On this basis, the article critiques the tendency toward individualization of responsibility in workplace health discourse, arguing that reducing sleep and cognitive problems to insufficient personal exercise and digital addiction essentially transfers responsibility away from structural workplace stress and labor regimes. Finally, it proposes a reconstruction from universal prescriptions to individualized precision strategies and from individual behavior change to organizational structural interventions, and outlines future directions for critical, localized workplace sleep health research.