european college of sport science

Saturday, June 27th, 2009
10:15 - 11:45
Oral presentations
OP-MB02 Molecular Biology 2
ALTERATION OF MUSCLE FIBRE COMPOSITION IN MALE JUNIOR ELITE ROAD CYCLISTS OVER THE COMPETITION PE-
RIOD
FRESE, S., LOOSER, P., GEHLERT, S., BOELCK, B., BLOCH, W.
GERMAN SPORT UNIVERSITY COLOGNE
The cellular specialization of skeletal muscle fibres enables remodeling of the muscle’s structural makeup according to alterations in
functional demand. The capability to load-dependent muscle fiber type specific adaptations demonstrates the enormous plasticity of
human skeletal muscle and the specificity of the adaptive response.
Close to the annual road cycling exercise planning we focused on the competition period to investigate the chronic skeletal muscle
response to endurance exercise after the repeated impact of stimuli that occurs with competition and training performance.
The aim of this study was to investigate the activity-dependent muscle plasticity allowing for phenotypic stimuli and consequent muscular
modifications.
Ten male elite cyclists (18.1±0.57yr) participated in this study. They had a history of >5yr of race experience and were part of competitive
cycling teams at national level. In february (Pre) before beginning of the competition period and at the end in october (Post) the subject’s
performances have been tested by an incremental cycling step test to exhaustion. There was a spirometry and lactate survey. After the
following two days each with a moderate cycling endurance exercise (~60-65% of subject’s V˙o2peak;~90-120min) standardized
muscle biopsies were taken of vastus lateralis muscle by needle biopsy the third day. The analysis of fibre composition was effected by
histochemical ATPase-staining.
The muscular monitoring over the competition period illustrates no difference in mean value of the absolute ratio of fast twitch
(Pre:36.29±2.56%;Post:41.14±9.99%) and slow twitch fibres (Pre:63.71±2.56%;Post:58.86±9.99%). But remarkable is the individual big
range of relative remodelling of fibre types IIA and IIX within the fast twitch fibre spectrum.
Estimable is the fibre pattern of two subjects with a reduction of fatigue-resistance phenotype decreased by 31% and an accession of
fibre type II increased by 59% compared with Pre (p