ReviewThe lumbar multifidus: Does the evidence support clinical beliefs?
Introduction
Exercise programmes that aim to improve the “stability” of the lumbar spine are widely utilized in the management of patients with low back pain (LBP) (Grieve, 1982; Saal and Saal, 1989; Porterfield and DeRosa, 1991a, Porterfield and DeRosa, 1991b; Norris, 1995a, Norris, 1995b; Richardson and Jull, 1995, Richardson and Jull, 2000; O’Sullivan et al., 1997; Pool-Goudzwaard et al., 1998; Porterfield and DeRosa, 1998a, Porterfield and DeRosa, 1998b; Richardson et al., 1999a; Taylor and O’Sullivan, 2000; McGill, 2001; Richardson et al., 2004). These programmes target a variety of trunk muscles and aim to optimize the control of segmental motion, spinal stability, spinal stiffness, spinal orientation, or a combination of these characteristics.
Two fundamental principles that underpin these exercise programmes are that trunk muscle activity is necessary to control and stabilize the lumbar spine (Panjabi, 1992a, Panjabi, 1992b) and that this activity must be restored, optimized, or enhanced in LBP (Richardson et al., 1999e; McGill, 2001; Hides, 2004a, Hides, 2004b). In vitro studies have demonstrated that the osseoligamentous lumbar spine is inherently unstable (Lucas and Bresler, 1961; Panjabi, et al., 1989) and is dependent on the integrated function of the active, passive and neural subsystems to control stability and movement (Panjabi, 1992a, Panjabi, 1992b). Therefore, exercise programmes which train trunk muscles to control spinal motion in patients with LBP seem logical (Norris, 1995a, Norris, 1995b; O’Sullivan et al., 1997; Richardson et al., 1999a; Hides et al., 2004), and have been argued to reduce stress on injured osseoligamentous structures, which in turn leads to pain reduction and enhanced function. (Saal and Saal, 1989; Panjabi, 1992a, Panjabi, 1992b; Norris, 1995a, Norris, 1995b; O’Sullivan et al., 1997; Hides et al., 2001).
Although it is agreed that exercise should be part of the management of LBP, there is significant variation in the type of exercise and the proposed mechanisms of effect of each type. Some authors advocate exercises which activate the entire paraspinal muscle group in order to control spinal motion (Grieve, 1982; Porterfield and DeRosa, 1991a, Porterfield and DeRosa, 1991b, Porterfield and DeRosa, 1998a, Porterfield and DeRosa, 1998b; McGill, 2001). These authors propose that the effectiveness of these exercises is due to increased power of the trunk muscles both segmentally and regionally (Grieve, 1982), increased tension in the thoracolumbar fascia through multifidus hypertrophy (Porterfield and DeRosa, 1998a, Porterfield and DeRosa, 1998b), increased segmental compression (Porterfield and DeRosa, 1998a, Porterfield and DeRosa, 1998b), and facilitation of co-contraction of the trunk flexors and extensors to optimize control of buckling (Euler stability) (McGill, 2001).
Other authors suggest that rather than increasing the strength or hypertrophy of the trunk muscles, the aim of therapeutic exercise in LBP should be to enhance the function of trunk muscles which are thought to be preferentially suited to stabilizing the lumbar spine (Richardson and Jull, 1995). In contrast to the general approach, this strategy aims to activate the lumbar multifidus independent of the other paraspinal muscles in the initial stages of rehabilitation, and to then integrate appropriate multifidus activation into functional activities (Richardson and Jull, 1995; O’Sullivan et al., 1997; Richardson et al., 1999a, Richardson et al., 1999c). Specific exercises have been designed to activate the lumbar multifidus in an isometric, low load, tonic manner, while maintaining a neutral lumbar spine, to restore the proposed function of the lumbar multifidus and its contribution to spinal control (Saal and Saal, 1989; Richardson and Jull, 1995; O’Sullivan et al., 1997; Richardson et al., 1999e; Hides, 2004a, Hides, 2004b). Recently, this selective activation of the lumbar multifidus from the other paraspinal muscles has been further refined. The clinical literature has focussed on the deep segmental fibres of the lumbar multifidus (DM) as the target of exercise interventions (Richardson et al., 1999e; Richardson and Jull, 2000; Taylor and O’Sullivan, 2000; Hides, 2004a, Hides, 2004b). This specific type of exercise approach has been demonstrated to reduce recurrence following acute LBP (Hides et al., 2001), and to reduce pain and disability in patients with chronic LBP (O’Sullivan et al., 1997).
The recent focus on DM in therapeutic exercise, rather than the superficial fibres of the lumbar multifidus (SM) or the erector spinae (ES), appears to be based on five common beliefs: (i) DM stabilizes the lumbar spine whereas SM, like ES, function as extensors/rotators of the lumbar spine (Richardson and Jull, 1995; Richardson et al., 1999f); (ii) DM has a greater percentage of type I (slow twitch) muscle fibres than SM and the ES (Porterfield and DeRosa, 1991a, Porterfield and DeRosa, 1991b; Richardson et al., 1999f); (iii) DM is tonically active during movements of the trunk and gait while SM and the ES are phasically active (O’Sullivan et al., 1997; Richardson et al., 1999f; Taylor and O’Sullivan, 2000; Hides, 2004a, Hides, 2004b); (iv) DM and transversus abdominis (TrA) co-contract during function (Richardson and Jull, 1995; O’Sullivan et al., 1997; Pool-Goudzwaard et al., 1998; Richardson et al., 1999b; Richardson et al., 2000; Taylor and O’Sullivan, 2000; Arokoski et al., 2001; Hides et al., 2004); and (v) changes in the lumbar paraspinal muscles associated with LBP affect DM more than SM or ES (Norris, 1995a, Norris, 1995b; Pool-Goudzwaard et al., 1998; Richardson et al., 1999d; Arokoski et al., 2001; Hides, 2004a, Hides, 2004b).
The purpose of this review is to critically evaluate the literature to determine whether neurophysiological, biomechanical and histological data support these clinical beliefs. A further aim is to consider the implications of this evidence for clinical practice.
Section snippets
Differential contribution of DM, SM and ES to mechanical control of the spine
It has been argued that therapeutic exercise for the paraspinal muscles should focus on DM because these fibres are anatomically and biomechanically suited to the control of segmental motion, whereas SM and ES are not (Richardson and Jull, 1995; Arokoski et al., 2001). Do the anatomical and biomechanical data support this argument?
The lumbar multifidus consists of multiple fascicles that originate from the caudal tip and inferolateral aspect of the spinous process and lamina at one vertebral
Fibre type percentage in DM, SM, and ES
A fundamental belief underpinning the rehabilitation of lumbar multifidus is that DM has a greater percentage of type I muscle fibres than SM or ES (Porterfield and DeRosa, 1991a, Porterfield and DeRosa, 1991b). Type I (slow twitch) muscle fibres, while being fatigue resistant and ideally suited to low load tonic activity, have been argued to be more susceptible to the adverse effects of pain and immobilization than type II (fast twitch) muscle fibres (Appell, 1990). The proposed fibre type
Activation of DM, SM and ES during functional movements
The argument that multifidus has a tonic postural role is based on reports of continuous activity reported during standing, and tonic activation during gait (Richardson et al., 1999f; Hides, 2004a). It has also been argued that absence of electrical silence in multifidus at the end of trunk flexion constitutes evidence that this muscle has a stabilization role (Richardson et al., 1999f; Hides, 2004a). The proposed tonic activation of multifidus and the fibre composition of this muscle, form the
Co-contraction of DM and TrA
It has been proposed that DM and TrA may co-contract during an abdominal hollowing manoeuvre (Richardson et al., 2000). Furthermore, it has been proposed that co-contraction of DM and TrA is required for lumbar stability and must be retrained in patients with LBP (Richardson et al., 1990, Richardson et al., 1992, Richardson et al., 2000; O’Sullivan, 2000; Taylor and O’Sullivan, 2000). Is there evidence to support those proposals?
Several studies have demonstrated activity of the abdominal and
Dysfunction of DM in LBP
Changes in the lumbar paraspinal muscles associated with LBP have been suggested to affect DM more than SM or ES (Norris, 1995a, Norris, 1995b; Pool-Goudzwaard et al., 1998; Richardson et al., 1999d; Arokoski et al., 2001; Hides, 2004b). Changes in activation patterns and cross sectional area (CSA) of the segmental portion of the lumbar multifidus (Hides, 2004b) have been suggested, and therapeutic exercise programmes that target multifidus have been tailored to address these issues.
Several
Summary and clinical implications
The neurophysiological, biomechanical and histological data considered in this review provide a detailed examination of the evidence that underpins the clinical beliefs regarding lumbar multifidus. Although some beliefs are supported by the literature, a range of questions remain unanswered.
Anatomical and biomechanical studies convincingly argue that DM, SM and ES control segmental motion. Although studies refute the clinical belief that SM and ES are solely extensors/rotators of the lumbar
Acknowledgements
Lorimer Moseley and Paul Hodges are supported by the National Health & Medical Research Council of Australia.
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