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INTRODUCTION: Endurance capacity of the human skeletal muscle is highly dependent on its mechanistic properties. However, knowledge about the responsiveness of important steps involved in the excitation-contraction (E-C) coupling to acute and chronic endurance exercise in highly-trained endurance athletes remains unclear . The present study investigated acute and chronic effects of endurance training, superimposed with three weekly high-intensity training sessions, on the SR Ca2+ release and uptake in elite endurance athletes. METHODS: 26 elite triathletes and road cyclists completed four weeks of routine endurance training (≈ 20h/week) including three weekly days with a high-intensity cycling session in the morning and a moderate intensity cycling session in the afternoon. In the morning, the athletes performed 8x5min (6x5min @ 85% HRmax and 2x5min as 15s "all-out" - 45s recovery), while the afternoon session consisted of 120 min of moderate intensity cycling at 65% HRmax. Muscle biopsies were obtained from m. vastus lateralis before (Pre) and after (Post) the training period as well as one hour after the 120min moderate intensity bike session on the 7th day with two bike sessions (Acute). The fluorescent dye technique was used to determine Ca2+ uptake and release rates in SR vesicles in homogenate from the biopsies. RESULTS: The maximal SR Ca2+ release rate, measured during resting conditions, increased to 110 ± 4 % of Pre during the 4-week training period (P = 0.01), while the SR Ca2+ uptake rate remained unchanged (99 ± 5 % of Pre, ns). One hour after finishing the 120min session, on the 7th day with two cycling sessions, the SR Ca2+ release rate was reduced to 78 ± 4 % of Pre (P < 0.0001) while the SR Ca2+ uptake rate, measured as the time for free [Ca2+] to decrease by 63%, was increased to 121 ± 10 % of Pre (P = 0.02). CONCLUSION: The present findings demonstrate that the SR Ca2+ handling in the skeletal muscle of highly-trained endurance athletes is plastic and that deteriorations in both SR Ca2+ release and uptake rates may partly explain the development of muscle fatigue during exhaustive exercise. Moreover, improvements in muscle performance after a period of endurance training may be partly explained by chronic adaptations in the SR Ca2+ release rate.
Original languageDanish
Publication date5. Jul 2018
Publication statusPublished - 5. Jul 2018
Event23rd annual congress of the European College of Sport Science, ECSS Dublin - Dublin, Ireland
Duration: 4. Jul 20187. Jul 2018


Conference23rd annual congress of the European College of Sport Science, ECSS Dublin

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