INTRODUCTION: Ski-mountaineering is one of the most demanding endurance sports. Researchers have extensively proven the relevance of VO2max, VO2@VT2, and GE on race performance. Different laboratory tests have been developed to measure the above-mentioned parameters on ski mountaineering athletes, while adequate methods for field evaluation are still lacking. Here, we tested the feasibility of performing an incremental test by using a GNSS-RTK to provide feedback to the athletes related to their punctual vertical speed. METHODS: The system consisted of a GNSS-RTK device corrected via NTRIP protocol to get the skiers' vertical speed and in a custom build app to provide the information to the skiers once a second. The acquisition system was validated by recording the altitude data in an undulating movement with an amplitude of 6 cm and a frequency of approximately 0.6 Hz to simulate the oscillation when walking. To test the protocol, an expert skier performed two incremental tests to exhaustion with 1 minute long stages: a laboratory test with skis on a treadmill (LIT) and a second one on an alpine skiing slope (SIT) using the feedback system to induce the skiers to maintain the vertical speed prescribed by the protocol. The field protocol started with 600 m h -1 of vertical speed and increased by 130 m h -1 every minute, adapting the speed required in function of the slope recorded. Metabolic data were collected by a K5 portable device. RESULTS: During the validation test, the vertical swing amplitude was always within acceptable ranges (mean amplitude: 6.1 ± 0.9 cm; error around zero: -0.3 cm). Although the slope of the climb was not constant (mean 23.6 ± 6.4%; [12.1-36.0%]), the speed feedback system allowed the skier to keep the vertical speed reasonably close and stable with respect to that set during each stage (CV max : 4.68%). Metabolic parameters show differences between the two incremental tests (VO2max: 62.9 Vs 58.8 ml·kg -1·min -1 ; HRmax: 185 Vs 173 bpm; VE: 149 Vs 157 l·min -1; VO2@VT2: 3.8 Vs 3.7 l·min -1; HR@VT2: 169 Vs 158 bpm; for LIT and SIT respectively). DISCUSSION/CONCLUSION: The validation of the system has given good results keeping the measurement correct without drifts. This allows us to modulate the speed according to the hill to keep the required mechanical. The differences found in the metabolic values between the two tests could be, almost partially, compatible with the different altitudes of execution. Although further tests will have to be carried out on several athletes to validate the protocol, the possibility of using GNSS data to correct the speed as a slope function seems to guarantee good workload feedback. REFERENCES: Duc, S. et al., 2011. IJSM; Doucende, G. et al., 2022. Sports
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