INTRODUCTION: Cross-country skiers are allowed to freely and dynamically choose the technique according to track slope and ambient condition. The recording of the technique adopted by the athlete on field is usually performed by filming the subject. This method provides a lot of Information but requires that the athlete is always in the field of view of the camera (Andersson E., 2010). The aim of the study was to describe the technique distribution automatically identified using a new methodology based on the pole force acquisition System. METHOD: The system is based on a microcontroller that acquires pole force Signals (Bortolan L., 2009) and transmits via Bluetooth to an UMPC that acquires simultaneously the GPS strings. The system was tested in a classic race simulation on a path of 1.6 km repeated 8 times. Blood lactate concentration was measured at each lap to evaluate the intensity level. A custom written Matlab routine was built to discriminate which technique (DS: diagonal stride, DP: double poling; DH: downhill technique; no double poling and kicking were performed) were adopted by the skier during the performance (figure 1). RESULTS: The lap duration increased linearly (p<0.01; R=0.984) from 254 s. (1st lap) to 272 s. (8th lap). The mean lactate concentration was 7.5 mmol/l with no values being below 6 mmol/l. About 28% of the lap length were performed using DS technique with a mean velocity of 4.02±0.14 m/s. DP technique were adopted to cover about 32% of the lap length with a mean velocity of 6.24±0.19 m/s. No significant variations were found for these two parameters between the laps. DH mean velocity increased from 4.82 m/s in the first lap up to 6.90 m/s in the 6th lap and the athlete covered about 40% of the track length with this technique. DISCUSSION: The increase in lap time may indicate the occurrence of fatigue and the high lactate concentration confirms that the exercise was performed at high intensity. No significant variation of technique distribution has been found. We speculate that the increase of DH velocity until 6th lap might be due to the increasing temperature; the test was in fact performed in a sunny morning (10.00 AM). CONCLUSION: The possibility offered by this methodology in discriminating the technical distribution along with the GPS data can optimizes the analysis of pole forces on the field test simplifying the acquisition setup and data processing.
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