Effect of different types of resistance training on muscle strength and hypertrophy

The purpose of this study was to examine the effects of eccentric, concentric, and eccentric-concentric training at different contraction velocities (300s-1, 1800s-1) on muscle strength, hypertrophy and muscle damage. 42 untrained (age 18–24) male subjects volunteered to participate in this study as experimental group (slow concentric group(SC; n=7), slow eccentric group(SE; n=7), fast concentric group(FC; n=7), fast eccentric group (FE; n=7), concentric-eccentric group (CE; n=7), and control group (CN; n=7). Subjects applied leg extensions until they reached the level of exhaustion, one repetition maximum (1RM) values were measured every 3 weeks and the weights used in the trainings were adapted consequently with the increases in strength 3 days/week during 12 weeks of training period. Subjects were measured before and after training for Quadriceps Femoris (QF) muscle volume by a 1.5 Tesla MRI scanner and isokinetic strength (600s-1, 1800s-1 /Cybex). Besides, changes in muscle damage indicators creatine kinase(CK), Aspartat aminotransferaz(AST), Alanin aminotransferaz(ALT), Myoglobin(MYB) activities and some hematological indicators were measured before, immediately after, and 24-48 hours after exercise. As a result of the study, in the values of all strength tests (1RM, 600 sn-1 and 1800 sn-1 isokinetic peak torque) increased significantly in all training groups(p<0,05). 1RM strength values in all training groups increased significantly (SC %25,25 (p<0,01), SE %36,46 (p<0,01), FC %34,31 (p<0,01), FE %28,49 (p<0,05), CE %41,45 (p<0,01)). KO groups 1RM strength decreased %0,59 (p > 0,05). Also, there was a remarkable increase in FC, SE and CE groups after the 6th week of resistance training. Isokinetic strength peak torque values in all training groups increased significantly and the highest increases were observed in CE group(Respectively for 600 sn-1 and 1800 sn-1 peak torque %32,48 (p<0,001), %20,08 (p<0,01)). SE training resulted in greater overall muscle volume change(209 cm3 %10,06; p<0,05)) than FC( %7,99 (p<0,05), CE(153 cm3 % 6,81; p<0,05), SC group (133 cm3 %6,14; p<0,05), FE (94 cm3 % 4,42; p>0,05) and KO(74 cm3 %3,76, p>0,05) groups. In this study, the increases in muscle damage parameters such as CK, AST, ALT and MYB activities were changed significantly for all groups. The increases in muscle damage parameters and hematological values were greater for the slow velocity exercise (SE group) in compared with the other training groups(p<0,05). In conclusion, we found greater strength increases in CE group for all strength tests. The highest increase was observed in the CE group, but there were no differences between groups over the training program for rates of isokinetic peak torque or 1RM development (p >0,05). However, other resistance training methods also increased strength significantly. As a result, dynamic exercise involving both concentric and eccentric contractions (CE group) might be the rapid way to increase the strength values. When eccentric exercise was performed at low velocities compared with other exercises at different velocities muscle volume more increased as a percentage and showed greater muscle damage for slow eccentric exercise. SE group values of AST, CK, ALT and MYB increased significantly immediately after the exercise, 24h or 48h thereafter. According to these results it can be said that also slow eccentric training maybe able to be effective for muscle damage and hypertrophy. Key Words: Strength, Concentric, Eccentric, Velocity, Muscle Damage, Hypertrophy