Influence of Hip-Flexion Angle on Hamstrings Isokinetic Activity in Sprinters

Abstract

Hip-flexion angle influenced hamstrings peak torque in all muscular contraction types; as hip flexion increased, hamstrings peak torque increased. Researchers should investigate further whether an eccentric resistance training program at sprint-specific hip-flexion angles (70° to 80°) could help prevent hamstrings injuries in sprinters. Moreover, hamstrings-to-quadriceps ratio assessment should be standardized at 80° of hip flexion.

Effects of hip flexion angle on surface electromyographic activity of the biceps femoris and semitendinosus during isokinetic knee flexion

“…II). This is in agreement with some studies 7,8,11 but in contrast to others 6,9 . Comparisons of our data with those reported by previous studies should take into consideration some methodological differences between studies.…”

“…Comparisons of our data with those reported by previous studies should take into consideration some methodological differences between studies. For example, in this present study as well as other studies 7,11 we measured the maximum EMG amplitude during knee flexion during tests performed from different hip joint positions. This differs significantly to other designs which examined the changes in EMG throughout knee joint range of motion (irrespective of hip flexion angle) 6,9 , those who examined the EMG during hip joint motion (with a fixed knee joint angle) 10,12,13 and those who assessed the overall EMG during a combined hip and knee joint exercise 14 .…”

“…Second, different studies used a different method to normalize the EMG. Particularly, the EMG signal was not normalized 11 , it was normalized as a percentage of the EMG recorded during a particular range of the motion (75-90° of knee flexion) 6 or a series of dynamic isokinetic tests 8 , a MVC (present study and 9 ) or during a manual knee flexion test 7 . Further, the present as well as other studies assessed the EMG using a 90° range of motion 7 while others used a higher range of motion 6,8,10 .…”

“…Worrell et al 13 found that the EMG amplitude of the hamstring muscle during isometric hip extension activity was constant at all hip angles. Similarly, two more recent studies have found inconsistent differences in EMG activation either between different hip angles or between individual hamstring muscles 7,11 . In a more recent study, however, rapid knee flexion efforts against a fitball from a prone position have been reported to selectively recruit the BFlh whilst exercises involving combinations of hip and knee motion (such as lunges and single leg Roman dead-lifts) have been reported to recruit the ST 14 .…”

“…However based on other results, exercise near full knee extension may actually decrease BFlh activation 8 or has no particular benefit 7 . The effects of hip flexion angle on muscle activation patterns of the hamstrings have received less attention 7,[10][11][12] . Particularly, it has been shown that increasing hip flexion angle is associated with a higher peak knee flexion torque 7, 10, 11 .…”