Resistance training increases in vivo quadriceps femoris muscle specific tension in young men

摘要

Aim: The present study investigated whether in vivo human quadriceps femoris (QF) muscle specific tension changed following strength training by systematically determining QF maximal force and physiological cross-sectional area (PCSA).Methods: Seventeen untrained men (20 ± 2 years) performed high-intensity leg-extension training three times a week for 9 weeks. Maximum tendon force (F_t) was calculated from maximum voluntary contraction (MVC) torque, corrected for agonist and antagonist muscle activation, and moment arm length (d_PT) before and after training. QF PCSA was calculated as the sum of the four component muscle volumes, each divided by its fascicle length. Dividing F_t by the sum of the component muscle PCSAs, each multiplied by the cosine of the respective fascicle pennation angle, provided QF specific tension.Results: MVC torque and QF activation increased by 31% (P  0.01) and 3% (P  0.05), respectively, but there was no change in antagonist co-activation or d_PT. Subsequently, F_t increased by 27% (P  0.01). QF volume increased by 6% but fascicle length did not change in any of the component muscles, leading to a 6% increase in QF PCSA (P  0.05). Fascicle pennation angle increased by 5% (P  0.01) but only in the vastus lateralis muscle. Consequently, QF specific tension increased by 20% (P  0.01).Conclusion: An increase in human muscle specific tension appears to be a real consequence of resistance training rather than being an artefact of measuring errors but the underlying cause of this phenomenon remains to be determined.