Energy balance of locomotion with pedal-driven watercraft

Abstract

In this study, we examined the mechanics and energetics of locomotion with a paddle-wheel boat and a water bike. Power output (Wtot) was measured directly on the water bike by means of an instrumented chain-ring. The simultaneous assessment of oxygen uptake (VO2) allowed the computation of the "overall" efficiency of locomotion (etao = Wtot/VO2). Mean etao was 0.27 (s = 0.02), which was unaffected by the speed, and was assumed to be the same for the two boats as both are semi-recumbent bicycles. For the paddle-wheel boat, Wtot was then obtained from etao and measures of VO2. The power to overcome (passive) drag was calculated as Wd = D x v (where D is the force measured by means of a load cell when towing the boats at given speeds). Propelling efficiency was calculated as etap = Wd/Wtot, which was lower with the paddle-wheel boat (mean 0.35, s = 0.01) than with the water bike (mean 0.57, s = 0.01). The observed differences in etap and Wd explain why at the highest speed tested (approximately 3 m s(-1), the energy required to cover a unit distance with the water bike is similar to that required to move the paddle-wheel boat at 1.3 m s-1).

Human Physiology in an Aquatic Environment

“…In boat locomotion, the values of drag efficiency are higher than reported for swimming: for example, about 0.15 to 0.20 in kayaks and rowing shells (e.g., 307,434). Drag efficiency increases with increasing velocity in both swimming and boat locomotion, as is the case for η O (e.g., 308).…”

Energy cost and efficiency of Venetian rowing on a traditional, flat hull boat (Bissa)

“…The data of C, however, confirm that the ''Bissa'', although now used and built for competitions, is clearly less economical than modern boats with streamlined and curved hulls utilised nowadays for competitions. The C of the ''Bissa'' is also much larger than that of a lightweight carbon-Kevlar, recumbent catamaran driven by pedals connected via a chain unit to a high-efficiency propeller (Zamparo et al 2008). Therefore, the ''Bissa'' would not be the boat of choice for cruising, especially for general people, since it is characterised by a rather large C and it is propelled using a rowing stroke that needs properly trained rowers.…”

“…The data were fitted by a linear function Energy cost In Fig. 3, the energy cost of sculling the ''Bissa'' is plotted as a function of speed, together with data measured in other types of water locomotion, including crawl swimming (Zamparo 2003), rowing a two oars racing shell (di Prampero et al 1971), Olympic kayaking (Zamparo et al 1999), sculling the Venetian gondola (Capelli et al 1990), pedalling on a recumbent paddle-wheel boat and a light, pedal driven streamlined boat with propeller propulsion (Zamparo et al 2008). The C of the ''Bissa'' turned out to be similar to that of the gondola, i.e., of the only one flathull boat considered in the comparison, in the range of speeds from about 2.5-3.8 m s -1 .…”

“…1 being indeed 2, or close to 2, although this is expected in theory. Certainly, the average value of this exponent obtained by several and independent groups of investigators, based on a panoply of different measuring methods on different boats (i.e., gondola, slalom kayak, rowing, paddle-wheel and propeller catamaran), turned out to be 2.00 ± 0.52 (Capelli et al 1990, Celentano et al 1974di Prampero et al 1971;Pendergast et al 1989;Zamparo et al 2008). In conclusion, the choice of assigning the value 2 to the exponent of m appears to be quite reasonable, also considering the high indeterminacy intrinsic in the experimental assessment of D.…”

“…The set of data has been also extended to investigations on different aquatic sports, such as slalom kayak (Pendergast et al 1989), standard K1 Olympic kayak (Tesch et al 1976;Zamparo et al 1999) and rowing racing shells with coxswain (Celentano et al 1974;di Prampero et al 1971;Secher 1993), or to types of aquatic locomotion that have more practical goals or are devoted to leisure time activities. For instance, the energetics of a recumbent, pedal driven watercraft developed for day-touring in protected waters (Zamparo et al 2008) and of the Venetian gondola have been described (Capelli et al 1990). …”