Force generating protein of cilia required for sperm flagellum motility. Produces force towards the minus ends of microtubules. Dynein has ATPase activity; the force-producing power stroke is thought to occur on release of ADP. Required in spermatozoa for the formation of the inner dynein arms and biogenesis of the axoneme (PubMed:24360805). {ECO:0000250|UniProtKB:Q91XQ0, ECO:0000269|PubMed:24360805}. This is the function of DNAH1 (dynein axonemal heavy chain 1, ENSG00000114841).