Recent Examples on the WebFindings show the downstroke of both pairs of flippers proved more powerful than the upstroke. Tim Newcomb, Popular Mechanics, 21 June 2022 Krahl credits the evolution of four uniform wing-like flippers for the Plesiosaur’s ability to twist and produce a powerful downstroke to propel itself with force underwater. Tim Newcomb, Popular Mechanics, 21 June 2022 Instead, butterfly wings bend, which researchers suspected might cup air between them to strengthen their downstroke. Rachael Lallensack, Smithsonian Magazine, 29 Dec. 2021 The receiving partner leads on rocking with the upstroke and the penetrating partner leads on the downstroke. Dr. Nan Wise, Glamour, 19 Mar. 2021 In our hippogriff, the muscles of the back drive the upstroke, and the muscles of the chest power the downstroke, just as in living bats and long-extinct pterosaurs. Michael B. Habib, Scientific American, 17 Mar. 2021 The wing segments close during the following downstroke to create a more powerful downstream force; the smaller the bird robot makes itself, by contracting its wings, the less friction. Courtney Linder, Popular Mechanics, 9 July 2020 By observing smoke added to the wind, the researchers noticed the dragonflies twisted their wings on each downstroke.Anchorage Daily News, 20 July 2019 Whereas ordinary birds pull themselves aloft with just the downstroke of their wings, insects and hummers generate lift in both directions. Jonathon Keats, Discover Magazine, 21 June 2019 See More