The purpose of the study was to investigate the relationship between muscle fiber composition and the rate of force development (RFD) in well-trained individuals with different training background. Thirty-eight young males with different training background participated: 9 endurance runners, 10 power-trained, 9 strength-trained, and 10 sedentary. They performed maximal isometric leg press for the measurement of RFD. Body composition (dual x-ray absorptiometry) and vastus lateralis fiber type composition was also evaluated. When all participants were examined as a group, moderate correlations were found between the percent of type II muscle fibers and RFD between 100-600ms (r: 0.321 - 0.497, p<0.05). The correlation coefficients were higher for the cross-sectional area (CSA) and the %CSA of type II and IIx muscle fibers (r: 0.599 - 0.847, p<0.001). For the power group, RFD up to 250ms was highly correlated with % type IIx muscle fibers and type IIx fiber CSA (r: 0.670 - 0.826, p<0.05), as well as with %CSA of type IIx fibers (r: 0.714 - 0.975, p<0.05). Significant correlations were found between the relative RFD (·kg-1 lower extremities lean mass) and CSA-%CSA of type II and IIx fibers for the power group (r: 0.676 - 0.903, p<0.05). No significant correlations were found between muscle morphology and RFD for the other groups. In conclusion, the present data suggest that there is a strong link between the type IIx muscle fibers and early RFD and relative RFD in power-trained participants. Type II fibers seem to be moderately linked with RFD in non-power-trained individuals.
1Athletics Laboratory, School of Physical Education & Sports Science, National and Kapodistrian University of Athens, Greece
2A’ Neurology Clinic, Aiginition Hospital, Medical School, National and Kapodistrian University of Athens, Greece
3Department of Nutrition and Dietetics, School of Health Science & Education, Harokopio University of Athens, Greece
Correspondence: Spyridon Methenitis (B) Athletics Laboratory, School of Physical Education & Sport Science, National and Kapodistrian University of Athens, Ethnikis Antistassis 41, 172 37, Daphne, Athens, Greece email: firstname.lastname@example.org Tel.: +30-210-7276194 Fax: +30-210-7276028