Mode-specific effects of concentric and eccentric isokinetic training of the hamstring muscle at slow angular velocity on the functional hamstrings-to-quadriceps ratio-a randomized trial

BACKGROUND: Previous studies have examined the mode specificity of eccentric and concentric isokinetic training, but have reported conflicting results. Few studies have reported that eccentric and concentric isokinetic training are mode-specific, i.e., they will increase only the eccentric or concentric strength, respectively. Other studies have reported that mode specificity does not exist. Therefore, this study aimed to assess the mode-specific effects of eccentric and concentric isokinetic training of the hamstring muscle at slow angular velocity on eccentric peak torque of the hamstring (PT(ecc)), concentric peak torque of the quadriceps (PT(con)), acceleration time of the hamstring (AT(hams)) and quadriceps (AT(quad)), deceleration time of the hamstring (DT(hams)) and quadriceps (DT(quad)), time to peak torque of the hamstring (TPT(hams)) and quadriceps (TPT(quad)), and functional Hamstring-to-Quadriceps ratio (PT(ecc)/PT(con)). SUBJECTS: A total of 30 participants were randomly divided into eccentric and concentric groups. METHODS: Two groups pre-test-post-test experimental design was used. In the eccentric and concentric groups, eccentric and concentric isokinetic training of hamstring muscle was performed respectively, at an angular velocity of 60°/s for 6 weeks duration. PT(ecc), PT(con), AT(hams), AT(quad), DT(hams), DT(quad), TPT(hams), TPT(quad,) and PT(ecc)/PT(con) were measured before and after the completion of training. RESULTS: In the eccentric group, a significant difference (p < 0.05) was observed in PT(ecc) (increased by 21.55%), AT(hams) (decreased by 42.33%), AT(quad) (decreased by 28.74%), and PT(ecc)/PT(con) (increased by 17.59%). No significant difference (p > 0.05) was observed in PT(con), TPT(hams), TPT(quad), DThams, and DT(quad). In the concentric group, a significant difference (p < 0.05) was observed in PT(ecc) (increased by 12.95%), AT(hams) (decreased by 27.38%) AT(quad) (decreased by 22.08%), DT(quad) (decreased by 26.86%), and PT(ecc)/PT(con) (increased by 8.35%). No significant difference (p > 0.05) was observed in PT(quad), TPT(hams), TPTquad, and DT(hams). Between-group analysis revealed a significant difference (p < 0.05) only in TPT(quad); otherwise, in the rest of the parameters, no significant difference (p > 0.05) was observed. CONCLUSIONS: Both eccentric and concentric isokinetic training of the hamstring for 6 weeks increased PT(ecc), PT(ecc)/PT(con), and decreased AT(hams) and AT(quad). The effects of eccentric and concentric isokinetic training of the hamstring on PT(ecc), PT(ecc)/PT(con), AT(hams,) and AT(quad) were not mode specific.