G-43 Free Communication/Poster - Sport Science: JUNE 4, 2011 7:30 AM - 11:00 AM: ROOM: Hall B
PURPOSE: The purpose of this study is to get an insight into physiological demands of sailing-specific isometric bilateral knee extension exercise (cfr. hiking) and whether specialised sailors respond differently compared to untrained controls.
METHODS: Eleven optimist sailors and 4 matched controls (preliminary data) performed 12 bouts of 90 s bilateral knee extension at 60° knee angle and 30-40 % MVC. The bouts were separated by 6 s of rest (simulation of tacking & gybing). Median Power Frequency (MPF) and deoxygenation (deoxy[Hb+Mb]) from M. Vastus Lateralis were recorded, using sEMG and NIRS. Reoxygenation index (RI) was determined during the 6 s rest by setting out the decrease in deoxy[Hb+Mb] as a function of the amplitude from baseline deoxy[Hb+Mb] (prior to the start of the exercise) to "peak"deoxy[Hb+Mb] (final 30 s of each hiking bout).
RESULTS: Deoxy[Hb+Mb] - as expression of micro vascular O2-extraction - and Tot[Hb+Mb] - as expression of micro vascular blood supply - of sailors and controls showed a sequence of 12 identical cycles. Each one consisted of 3 phases: (1) start contraction (increase in Deoxy[Hb+Mb]), (2) steady state (Deoxy[Hb+Mb] stagnates), (3) relaxation/reoxygenation (Deoxy[Hb+Mb] drops enormously). Additionally, Tot[Hb+Mb] increases slightly during contraction, while it peaks very fast and high during relaxation. Further, during resting periods, sailors displayed significantly higher reoxygenation index (53,44 ± 9,98 %) compared to controls (40,55 ± 6,09 %) (p < 0,05). MPF - as indication of the appearance of muscle fatigue - for sailors did not change throughout the entire protocol (0,21 ± 0,44 %), whereas for controls, MPF decreased slightly (-0,38 ± 0,23 %) (p < 0,05). In addition, lactic acid concentration for sailors and controls were resp. 2,3 ± 0,6 and 1,8 ± 0,2 mmol·l-1.
CONCLUSIONS: The results of the present study show that sailors respond more accurately to the sailing-specific exercise protocol, compared to controls. For sailors, the M. Vastus Lateralis RI is higher, compared to controls. Although it is not possible to draw cause-effect relationship from this study, the results suggest that the slower reoxygenation for controls is related to the decrease in MPF and thus the appearance of muscle fatigue.
Supported by Flemish Government, Ministry of Culture, Youth, Sport & Media.