Paddling time parameters and paddling efficiency with the increase in stroke rate in kayaking.

The paddling stroke rate (SR) is one of the key determinants of flat water kayak performance. The aim of this study was to analyse the way in which the kayak paddler changes the duration of the water and aerial phases due to the increase in stroke rate. Ten elite kayak paddlers (five males and five females) were analysed performing 200 m on-water trials in an individual kayak (K1), at four different stroke rates (60, 80, 100 strokes per minute and race pace). The duration of the water and aerial phases, SR and impulse were computed based on the data collected using the FPaddle system. Results corroborate the importance of reaching higher SR to increase kayak velocity (r = 0.904, p < 0.001). Both water and aerial phase durations correlated negatively with SR (r = -0.929, p < 0.001; R = -0.909, p < 0.001, respectively). However, with the first, the correlation was linear (r2 = 0.883), and for the second, the trend of relationship was curvilinear (r2 = 0.893). Due to differences in correlation, the results suggest that at high SR (above 120 strokes per minute) to continue increasing SR it will be more productive to reduce the duration of the water phase.

Effect of wetted surface area on friction, pressure, wave and total drag of a kayak.

Using theoretical principles, the components of drag (friction D F, pressure D PR and wave D W) of a single-seat kayak were analysed. The purpose was to examine the effect of changes in wetted surface area due to changes in kayaker's weight and the relative contribution of D F, D PR and D W to the total passive drag as function of velocity. The total passive drag values were based on experimental data collected in a single-seat kayak. Three different kayaker simulated weights were tested - 65, 75 and 85 kg. D F was the drag component that contributed the greatest percentage (between 60 and 68% at 5.56 m/s the top velocity tested) to the total passive drag for all the velocities tested and simulated weights. D W was the most affected by the increase in kayaker's simulated weight, mainly when comparing 65/75 to 85 kg. Results support the importance of a kayak design selection that minimises the kayak's drag for the individual weight of the kayaker. Also, the results suggest that the path for better hydrodynamic kayak performance should seek changes that can reduce D F, D PR and D W with D F offering the most potential to reduce passive drag.

Paddling Force Profiles at Different Stroke Rates in Elite Sprint Kayaking.

In sprint kayaking the role that paddling technique plays in optimizing paddle forces and resultant kayak kinematics is still unclear. The aim of this study was to analyze the magnitude and shape of the paddle force-time curve at different stroke rates, and their implications for kayak performance. Ten elite kayak paddlers (5 males and 5 females) were analyzed while performing 2000-m on-water trials, at 4 different paces (60, 80, and 100 strokes per minute, and race pace). The paddle and kayak were instrumented with strain gauges and accelerometers, respectively. For both sexes, the force-time curves were characterized at training pace by having a bell shape and at race pace by a first small peak, followed by a small decrease in force and then followed by a main plateau. The force profile, represented by the mean force/peak force ratio, became more rectangular with increasing stroke rate (F[3,40] = 7.87, P < .01). To obtain a rectangular shape to maximize performance, kayak paddlers should seek a stronger water phase with a rapid increase in force immediately after blade entry, and a quick exit before the force dropping far below the maximum force. This pattern should be sought when training at race pace and in competition.