Neuromuscular Adaptations to Work-matched Maximal Eccentric vs Concentric Training

It is unclear whether the superiority of eccentric over concentric training on neuromuscular improvements is due to higher torque (mechanical loading) achievable during eccentric contractions or due to resulting greater total work. Purpose To examine neuromuscular adaptations following maximal eccentric versus concentric training matched for total work. Methods Twelve males conducted single-joint isokinetic (180°/s) maximal eccentric contractions of the knee extensors in one leg (ECC-leg) and concentric in the other (CON-leg), 6 sets/session (3–5 sets in the initial 1–3 sessions), 2 sessions/week for 10 weeks. The preceding leg performed 10 repetitions/set. The following leg conducted the equivalent volume of work. In addition to peak torque during training, agonist EMG and MRI-based anatomical cross-sectional area (ACSA) and transverse relaxation time (T2) at mid-thigh as reflective of neural drive, hypertrophy, and edema, respectively, were assessed weekly throughout the training period and pre- and post-training. Whole muscle volume was also measured pre- and post-training. Results Torque and EMG (in trained contraction conditions) significantly increased in both legs after week (W)1 and W4, respectively, with a greater degree for ECC-leg (torque +76%, EMG +73%: post-training) than CON-leg (+28%, +20%). ACSA significantly increased after W4 in ECC-leg only (+4%: post-training), without T2 changes throughout. Muscle volume also increased in ECC-leg only (+4%). Multiple regression analysis revealed that changes (%Δ) in EMG solely explained 53–80% and 30–56% of the total variance in %Δtorque through training in ECC-leg and CON-leg, respectively, with small contributions (+13–18%) of %ΔACSA for both legs. Conclusion Eccentric training induces greater neuromuscular changes than concentric training even when matched for total work, while most of the strength gains during 10-week training is attributable to the increased neural drive. Address for Correspondence: Sumiaki Maeo, Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama 359-1192 Japan, E-mail: smaeo1985@gmail.com, Telephone: +81-429-476945, Fax: +81-429-476945 This work was supported by a Grant-in-Aid for Japan Society for the Promotion of Science Research Fellow (15J03228). The authors declare that there is no conflict of interest, that no companies or manufacturers will benefit from the results of the study, and that the results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of the present study do not constitute endorsement by the American College of Sports Medicine. Accepted for Publication: 11 March 2018 © 2018 American College of Sports Medicine

from Sports Medicine via xlomafota13 on Inoreader http://ift.tt/2pE9vYL
via IFTTT