Abstract
PurposeThis 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.MethodsTwenty-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.ResultsAfter training, both TRAD and AEL significantly increased maximum concentric and isometric torque (p < 0.05), but only AEL increased eccentric torque (AEL: + 10 ± 9%, TRAD: + 4 ± 9%) and vastus lateralis (AEL: + 14 ± 14%, TRAD: + 1 ± 10%) and medialis (AEL: + 19 ± 8%, TRAD: + 5 ± 11%) fascicle length.ConclusionBoth TRAD and AEL increased maximum knee extensor strength but only AEL increased VL and VM fascicle length. Neither training program promoted changes in fascicle angle or changes in patellar tendon properties in our already-trained men.
Highlights
Short-term strength training interventions provoke robust increases in muscle mass and size (Häkkinen et al 1985; Narici et al 1989) as well as the ability to recruit the available muscle mass (Häkkinen and Komi 1983; Knight and Kamen 2001) in previously untrained individuals
Some researchers consider the eccentric contraction mode itself to be the predominant stimulus in these cases (Franchi et al 2017; Timmins et al 2016), leading to the conclusion that eccentric contractions embedded within strength training programs are an important factor leading to fascicle lengthening
Post hoc analyses revealed that significant training-induced increases occurred in maximum unilateral concentric, eccentric and isometric torques in accentuated eccentric loading (AEL) (Table 1, Fig. 2)
Summary
Short-term strength training interventions provoke robust increases in muscle mass and size (Häkkinen et al 1985; Narici et al 1989) as well as the ability to recruit the available muscle mass (Häkkinen and Komi 1983; Knight and Kamen 2001) in previously untrained individuals. Changes in both muscle structure, i.e. architecture Some researchers consider the eccentric contraction mode itself to be the predominant stimulus in these cases (Franchi et al 2017; Timmins et al 2016), leading to the conclusion that eccentric contractions embedded within strength training programs are an important factor leading to fascicle lengthening
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