Prone hip extension with lower abdominal hollowing improves the relative timing of gluteus maximus activation in relation to biceps femoris

Abstract

Hamstring injuries are common. The hamstrings and gluteus maximus (GM) work as synergists during hip extension. When contraction of GM is delayed relative to Biceps Femoris (BF) the hamstrings may be predisposed to injury due to increased demand. This study investigated whether specific training affected neuromuscular control of BF and GM during Prone Hip Extension (PHE). Twenty healthy volunteers were randomly allocated to the intervention or the control group. Mean onset times for BF and GM during PHE were recorded via surface electromyography (sEMG). The intervention group performed a 10 min exercise with focus on proximal to distal muscle activation involving abdominal hollowing and active GM contraction prior to PHE. The control group undertook an exercise which included only PHE. Post exercise descriptive analysis indicated that the intervention exercise reduced the delay of GM firing relative to BF, however, when baseline differences between the two groups are taken into account as a covariant, the difference attributable to the intervention is not statistically significant (P = 0.166). The results suggest that a short duration exercise intervention has the potential to alter the timing of activation of GM relative to BF during PHE but this needs validation through future research.

Introduction

The incidence of hamstring injuries within the field of sports medicine is high (Kroll and Raya, 1997, Askling et al., 2000). Bahr and Mæhlum (2004) suggest that hamstring strains are the most common injury among football players and sprinters. Hoskins and Pollard (2005) suggest prevalence rates of 11% in cricket, 11–12% in football and 16% in Australian Rules football. Recurrence rates may be as high as 31% (Petersen and Hölmich, 2005). Hamstring injuries may require a protracted period of recovery and some athletes may encounter difficulty returning to their pre-injury standard of performance (Croisier et al., 2002). The development of strategies to reduce risk factors for hamstring injuries would seem warranted.

It has been suggested that a pattern of dominance of one of the synergists in a force couple, such as the hamstrings and gluteus maximus (GM) in hip extension, and rectus abdominis and hamstrings in posterior pelvic tilt, can lead to an impairment of the dominant muscle (Sahrmann, 2002, Jonkers et al., 2003). The GM is linked anatomically to the lumbar paraspinal muscles via the thoracolumbar fascia which allows load transfer from the lumbopelvic area to the lower extremities (Vleeming et al., 1995). Fatigue of stabilising muscles in the lumbopelvic area can create inefficiencies in the running style, thereby increasing the workload of multiarticular muscles, e.g. the hamstrings. This may predispose to early muscle fatigue and subsequent injury (Devlin, 2000).

By targeting neuromuscular control of hip extensors, this preliminary study aims to investigate the effect of Prone Hip Extension (PHE) exercise with and without lower abdominal hollowing on the relative timing of muscle activation of GM and Biceps Femoris (BF).