Abstract
Resistance training is often recommended for combined increases in traditional and alternative hamstrings-to-quadriceps (H:Q) ratios in order to reduce knee strength imbalance and associated hamstrings and knee ligament injury risk. The aim of this study was to investigate the effect of different concentric and eccentric resistance training programs on traditional and alternative H:Q ratios. Forty male volunteers were assigned to one of 4 groups: concentric quadriceps and concentric hamstrings (CON/CON, n = 10), eccentric quadriceps and eccentric hamstrings (ECC/ECC, n = 10), concentric quadriceps and eccentric hamstrings (CON/ECC, n = 10), or no training (control (CNTRL), n = 10). Traditional conventional (CR) and functional (FR), alternative rate of torque development (RTD), muscle size (MS), and muscle activation (MA) H:Q ratios were measured before and after six weeks of unilateral nondominant knee extension–flexion resistance training performed on an isokinetic dynamometer. The ECC/ECC training significantly increased FR (pre = 0.75 ± 0.11; post = 0.85 ± 0.15), whereas the lack of training (CNTRL) decreased the RTD H:Q ratio (pre = 1.10 ± 0.67; post = 0.73 ± 0.33). There were no differences between groups for the other traditional and alternative ratios following resistance training protocols. These findings suggest eccentric exercise for quadriceps and hamstrings as the most beneficial training program for inducing increases in the traditional FR. However, different resistance training strategies may be needed to also elicit increases in the alternative RTD, MS, and MA H:Q ratios for fully restoring muscle balance and reducing potential hamstrings and knee ligament injury risk.
Highlights
Anterior cruciate ligament (ACL) and hamstring strain injuries are common lower extremity noncontact injuries in sports
CON/CON and CNTRL, hamstrings peak torque (PT) increased from pre- to post-testing (p < 0.05), but quadriceps PT
CON and protocols involving muscle actions on other traditional and training alternative muscle actions were effective at increasing traditional or alternative. These findings revealed that ECC quadriceps and ECC hamstring (ECC/ECC) training led to increases in FR, but no other resistance training protocols suggest may be the most intervention impacting the quadriceps involving
Summary
Anterior cruciate ligament (ACL) and hamstring strain injuries are common lower extremity noncontact injuries in sports. These may occur when the hamstrings fail to produce enough strength to decelerate high anterior tibial shear and rotation movements induced by maximal quadriceps strength actions [1,2,3,4]. The assessment of the hamstrings-to-quadriceps (H:Q) muscle strength ratio calculated by peak torque (PT) is often used to screen imbalances between these muscle groups, which could be associated with injury risk [2,3,5]. Sports 2019, 7, 221 strength ratios are more likely to sustain hamstring injuries during competition [5,6]. Since noncontact injuries are multifactorial, recent research has questioned if the H:Q ratio calculated by PT should be used as a single measurement of injury risk [8,9]
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