Increased fascicle length but not patellar tendon stiffness after accentuated eccentric-load strength training in alread

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ORIGINAL ARTICLE

Increased fascicle length but not patellar tendon stiffness after accentuated eccentric‑load strength training in already‑trained men Simon Walker1   · Joanne Trezise2,3 · Guy Gregory Haff2,4,5   · Robert U. Newton2,4   · Keijo Häkkinen1 · Anthony J. Blazevich2  Received: 20 May 2020 / Accepted: 4 August 2020 © The Author(s) 2020

Abstract Purpose  This study examined whether additional external load during the eccentric phase of lower limb strength training exercises led to greater adaptations in knee extensor strength, muscle architecture, and patellar tendon properties than traditional concentric–eccentric training in already-trained men. Methods  Twenty-eight men accustomed to strength training were randomized to undertake 10 weeks of supervised traditional (TRAD) or accentuated eccentric loading (AEL) or continue their habitual unsupervised (CON) strength training. TRAD and AEL trained 2∙week−1 with a six-repetition maximum (RM) session and a ten-RM session. TRAD used the same external load in both concentric and eccentric phases, while AEL used 40% greater load during the eccentric than concentric phase. Tests were performed at pre- and post-training, including: maximum unilateral isokinetic (30°·s−1) concentric, eccentric and isometric torques by isokinetic dynamometry, unilateral isometric ramp contractions with muscle–tendon ultrasound imaging to measure tendon stiffness and hysteresis, and resting vastus lateralis and medialis fascicle angle and length measured by extended-field-of-view ultrasound. Results  After training, both TRAD and AEL significantly increased maximum concentric and isometric torque (p