Physiological Adaptations Following a Strength Endurance Training Block Performed with Accentuated Eccentric Loading or Traditional Resistance Training

Physiological adaptations were investigated following a strength-endurance (S-E) block prescribed with accentuated eccentric loading (AEL) or traditional resistance training (TRAD). Recreationally trained participants (n = 11 males, 6 females, age = 23.2 ± 4.2 yrs, body mass (BM) = 81.3 ± 22.2 kg, height = 172.1 ± 10 cm) completed a four-week block of concurrent resistance, sprint, and change of direction training. Participants were assigned one of two training conditions, AEL (n = 9) or TRAD (n = 8). Training was identical, except AEL performed 110% eccentric overloading every 1st, 3rd, 5th, 7th, and 9th repetition during back squat (BS) and bench press (BP). Body composition, summated muscle size (ACSAsum) and thickness (MTsum), regional ACSA and MT, and region-specific fascicle angle (FA) and length (FL) were assessed pre- (PRE) and post-training (POST). External work was calculated and exercise displacement was measured to determine the mechanical stimulus provided. Physiological variables were analyzed using multiple mixed analysis of variance (ANOVA). External work and displacement were analyzed with independent Welch’s t-tests. A statistically significant main effect of Time was observed for ACSAsum and ICW (p \u3c 0.05); however, there were no statistically significant Time x Condition interaction effects observed for any dependent variable (p \u3e 0.05). Time x Length interaction effects also failed to reach statistical significance for regional ACSA or regional MT (p \u3e 0.05). Moreover, Time x Position interaction effects were not statistically significant for regional MT (p \u3e 0.05). There were also no statistically significant interaction effects observed for regional FA or FL (p \u3e 0.05). Differences in external work did not reach statistical significance (p \u3e 0.05). A four-week S-E training block, performed with or without AEL, increases muscle size, but results in only minor architectural alterations. Additionally, AEL appears to induce unique region-specific hypertrophy. In contrast, TRAD seems to induce greater increases in ICW, potentially indicating greater sarcoplasmic hypertrophy. Interestingly, 110% eccentric overloading did not lead to statistically greater work performed, although differences may be practically significant when allometrically scaled. Researchers and practitioners should examine region-specific musculoskeletal adaptations, when possible, to more accurately assess training effects