Effect of three different muscle action training protocols on knee strength ratios and performance
Hamstring to quadriceps (H:Q) ratios are often used to assess strength imbalances. The aims of this study were to compare three different muscle action training protocols on H:Q strength balance and functional performance. Forty untrained males (age: 22.87 ± 2.28 y, mass: 70.66 ± 11.049 kg, ht: 174.29 ± 6.90 cm) performed 6 weeks of training on an isokinetic dynamometer. They were randomly assigned to one of 4 groups; concentric quadriceps and concentric hamstring (CON/CON), eccentric quadriceps and eccentric hamstring (ECC/ECC), concentric quadriceps and eccentric hamstring (CON/ECC), or no training (CNTRL). Mixed Factor ANOVAs were used to compare interactions for variables pre- and post-tests between groups (p<0.05). The ECC/ECC group showed significant increases in H:Q functional ratio (pre = 0.73 ± 0.092, post = 0.87 ± 0.098), ECC peak torque (PT) (pre = 226.44 ± 67.80 N.m, post = 331.74 ± 54.44 N.m), isometric PT (IPT) (pre = 173.69 ± 41.41 N.m, post = 203.091 ± 30.82 N.m), counter movement jump (CMJ) (pre = 52.73 ± 6.95 cm, post = 58.16 ± 6.10 cm) and drop jump (DJ) (pre = 52.91 ± 6.080 cm, post = 58.20 ± 7.72 cm), while the CON/CON group increased rate of torque development (RTD) (pre = 152.19 ± 65.0074 Nm.s-1, post = 225.26 ± 88.80 Nm.s-1). There were no differences between groups for CON PT, squat jump (SJ), conventional ratio or 40m sprint. Our findings suggest that ECC/ECC training may be the most effective at increasing functional H:Q strength ratios, as well as ECC PT, IPT, CMJ and DJ performance. ECC training increases ECC PT, thereby increasing the functional H:Q ratio. ECC training also improves vertical jumping involving ECC actions. CON/CON training may be more effective at increasing explosive muscle strength.