INTRODUCTION: The importance of managing fatigue has led to an increased interest in finding practicable and objective measures to quantify fatigue 1. A recent study introduced the Myocene device to measure muscle fatigue (MF) based on the force generated by electrical muscle stimulation. Results demonstrated valid measurements of MF after a strenuous series of drop jumps 2. However, there is no data on the effects of a physiological exercise test (PET) or repeated HIIT sessions in form of a shock microcycle (HIIT-SM). HIIT-SM are commonly used in winter sports to efficiently stimulate the aerobic system in short preparation periods and to spend more time on on-snow training 3. The aim of this study was to monitor acute responses of MF induced by a PET and chronic MF changes during a HIIT-SM using the Myocene device. METHODS: Two endurance-trained male participants (age: 33.5 ± 8.5 yr, weight: 70.8 ± 5.2 kg, height: 181.9 ± 7.4 cm, maximal oxygen uptake: 62.1 ± 1.4 ml/min/kg) performed a two-phase PET, consisting of a submaximal incremental test and ramp test until voluntary exhaustion 4. Participant one (P1) was randomly assigned to the running-based HIIT-SM, which consisted of 10 HIIT (5 x 4 min at 90% maximal heart rate followed by 30 min of low-intensity) sessions in 7 days, whereas participant two (P2) continued with his regular running training. Measurements were taken on both legs (quadriceps) before and 10 min after the PET and every morning during the 7-day intervention. In this process, a ratio (%) of low- to high frequency force responses to submaximal electrical stimuli was calculated by the Myocene device. The average score of both legs was calculated and defined as MF. RESULTS: PET resulted in a 14.2% increase (pre 74.7%, post 60.5%) of MF in P1 and a 11.3% increase (pre 79.6%, post 68.3%) of MF in P2. P1 started the HIIT-SM at 68.5% and showed a day-to-day change of +2.2, -4.4, +2.9, +0.5, -0.1, -0.6% during the intervention reaching 69% on the last day. P2 started his regular training week at 78.8% and showed a day-to-day change of +3.2, -5.5, +3.9, -1.8, +4.9, -7.4%, reaching 76.1% on the last day. CONCLUSION: We observed similar acute changes in MF induced by PET in both participants. P1 demonstrated no clear MF changes under the influence of HIIT-SM and also not in comparison to the control condition. The feasibility of chronic MF changes detected by the Myocene remains to be validated. REFERENCES: 1 Thorpe, R.T. et al., 2017. Int J Sports Physiol Perform 2 Ridard, J. et al., 2022. Front Physiol 3 Breil, F.A. et al., 2010. Eur J Appl Physiol 4 Stöggl, T.L. et al., 2022. BMC Sports Sci Med Rehabil
© Copyright 2023 9th International Congress on Science and Skiing, March 18 - 22, 2023, Saalbach-Hinterglemm, Austria. Veröffentlicht von University of Salzburg. Alle Rechte vorbehalten.