Force profile during tethered rowing: Big blades with vs without Randall foils

Cardoso, R1, Rios, M2, Leão, J3, Gomes, B4, Abraldes, JA5, Fernandes, RJ6
1Faculty of Sport, University of Porto, Porto, Portugal.
2Faculty of Sport, University of Porto, Porto, Portugal.
3Faculty of Sport, University of Porto, Porto, Portugal.
4Faculty of Sport Sciences and Physical Education, University of Coimbra, Portugal.
5Facultad de Ciencias del Deporte. Universidad de Murcia.
6Faculty of Sport, University of Porto, Porto, Portugal.

The rowing blade behavior during the propulsive phase of the rowing cycle influences rowers technique and force production, with field observations supporting that the addition of a strip of plastic – the Randall foils – on its top edge improve overall efficiency. Our aim was to characterize the force profile along maximal intensity rowing using Big blades with and without Randall foils. Five experienced female rowers with 22.9 ± 4.5 years of age, 167.5 ± 6.3 cm of height, 63.9 ± 5.8 kg of body mass, 22.6 ± 1.2 kg∙m2 of body mass index and 8 ± 4 years of training competitive experience volunteered to participate. After a typical warm-up, rowers performed two maximum 90 s tethered rowing bouts using Big blades with and without Randall foils. Experiments were conducted in a 25 m indoor swimming pool 24 h apart, with the boat being fixed to a starting block. A load-cell with 4.905 N measurement capacity and 200 Hz recording rate was used to measure force. Five consecutive rowing cycles were analyzed at the start, middle and end of the test using a MATLAB routine (MATLAB R2020a, The MathWorks Inc., Natick, MA, USA). All tests were randomized and the paired samples t-test was used to compare the assessed variables (p < 0.05). The peak and mean force values observed along the test presented a similar profile between Big blades with and without Randall foils (293.9 ± 84.9, 316.2 ± 91.9, 286.8 ± 103.04 vs 289.5 ± 78.7, 290.6 ± 91.8, 264.8 ± 99.7 N and 164.6 ± 43.1, 172.1 ± 41.4, 154.8 ± 36.5 vs 158.4 ± 37.3, 150.1 ± 42.8, 138.7 42.2 N, for the start, middle and end periods). In addition, the impulse presented higher values using the Randall foils (372.3 ± 146.8, 367.9 ± 135.6, 352.1 ± 105.5 vs 267.4, ± 124.6 215.1 ± 131.7, 172.1 ± 137.5 N.s, respectively). Big blades with Randall foils presented higher time to reach peak force (0.4 ± 0.2, 0.4 ± 0.2, 0.3 ± 0.1 vs 0.3 ± 0.1, 0.3 ± 0.0, 0.3 ± 0.0 s, respectively). The values observed suggest that the Randall foil increased the production of force and impulse, which may be attributed to a better stabilization of the blades and boat during the propulsion phase of the rowing cycle. Considering the small differences between racing times, the use of this foil can have a positive impact on competitive performances.

To the Portuguese Foundation for Science and Technology, I.P. (FCT 2021.04976.BD individual grant), to the clubs, coaches and rowers involved and Manoel Rios (FCT 2021.04701.BD)

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