Author(s): OSTRE, B., ALGOURDIN, P., CHARLES, P.E., JOLIFF, Y., NUNEZ, M., RANGHEARD, L., SERRALHEIRO, A. , Institution: LABORATOIRE MAPIEM, Country: FRANCE, Abstract-ID: 856

INTRODUCTION:
DownWind (DW) Stand-Up Paddle (SUP) Foil is a brain new watersport activity. It consists to fly above the surface of the sea in the same direction as the wind thanks to the propulsion of the waves created at the surface of the water. The rider has meanly 3 gears to achieve his goal: a paddle in the hands giving propulsion for take-off, a board flying in the air under his feet and an hydrofoil under water keeping the board over the surface. Due to early birth of this sport, many brands offer a huge amount of new gear every week. Currently, the foil/board/paddle association is not based on any scientific fact demonstrating suitability for the practitioner. The aim of this work is to optimise this association from muscular energy measurements.
METHODS:
This project is design to set a multi factorial experiment. A first demonstrator was design to set the process on land. A specific board has been modified (embedded strain gauges) in order to measure the force applied by the rider and his center of gravity (CG) position during the ride. Datas are collected through ARDUINO board and it gives a structural analysis of how exactly the rider act on the board. In addition the rider’s body has been monitored thank’s to wireless Emgs (Cometa MiniWave Infinity) at a sample rate of 2000Hz. Electrodes were placed according to SENIAM recommendations after skin preparation. The leg muscles activity (Tibialis Anterior, Gastrocnemius Medialis) were recorded because these muscle are known to be the most expensive during riding sport [5]. Finally the full body position was analyzed with inertial measurement units (IMU) (Cometa WaveTrack) [1]. IMUs were calibrated using standing T-pose acquisition. Heart Rate (HR) was also recorded throughout the trials. Datas collected by EMGs were then filtered using a 4th order Butterworth filter with a cut-off frequency between 20 and 400Hz, rectified with low pass frequency of 15Hz and then normalized using Matlab [3]. IMUs’ signals were filtered using a Kalman filter until the Euler angles were obtained [4]. A professional rider performed the same 2km path through 40 knots wind ride the same day in ecological conditions. The trace was tracked by Garmin GPS. After 10 min warm-up, 8 trials were performed following the order of an experimental design with adjustable factors of the hydrofoil: Mast longer, fuselage length, hydrofoil Rake and Wing-set. Each test was repeated 3 times and a separated by a 10 min break to avoid fatigue [2].
RESULTS:
The study proved that gear parameters affect energy consumption and body position for riding sport. Indeed it has been showed that a 15% HR and a 10% reduction in Gastrocnemius Medialis activation of the back leg could be achieve by setting the gear properly. In addition, body position is modified.
CONCLUSION:
The power of gear fitting method has been confirmed by reducing energy consumption by at least a 10 % in muscles activity and 12 Bpm HR for the right gear setting.[1]Cordillet [2]Jobson [3]Munera Ramirez [4]Nez [5]Ruess