Control of the lateral abdominal muscles during walking
Highlights
► During gait, the lateral abdominal muscles are engaged in multiple tasks. ► These tasks include respiration, trunk motion, and stability. ► No single muscle is specifically assigned a particular task. ► Conflicting constraints are coordinated by co-contraction. ► This co-contraction produces desired effects, and offsets unwanted effects.
Introduction
The human body has three lateral abdominal muscles: transversus abdominis (TA), obliquus internus (OI), and obliquus externus (OE). Their anatomy suggests a range of functions. In the frontal plane, unilateral OI and OE activity may be involved in ipsilateral bending of the trunk (Standring, 2008). In the transverse plane, OE contributes to contralateral rotation, whereas OI and TA contribute to ipsilateral rotation (Benninghoff and Goerttler, 1964, Hodges, 2008, Urquhart and Hodges, 2005). In the sagittal plane, bilateral activity of the lateral abdominal muscles can contribute substantially to trunk flexion (McGill, 1996).
Bilateral activity of the lateral abdominal muscles may also be involved in stability. Bilateral TA activity was suggested to stabilize the lumbar spine (Hodges, 1999, Hodges and Richardson, 1997a), and concerted action of the lateral abdominal muscles can press the iliac bones against the sacrum, thus providing pelvic stability (“force closure”, cf. Hu et al., 2010, Snijders et al., 1993, Vleeming et al., 1990).
Together with the rectus abdominis, the lateral abdominal muscles form the abdominal wall. Continuous activity of the abdominal wall can be seen as holding the viscera; it regulates intra-abdominal pressure, which implies a role in breathing (Standring, 2008). Finally, activity of the abdominal wall plus the diaphragm and the pelvic floor, contributes to spinal stability (Cholewicki et al., 1999, Hodges et al., 1997, Hodges et al., 2005, Pel et al., 2008).
Several studies have attempted to verify the roles of the lateral abdominal muscles through electromyographic recordings during the performance of specific tasks. In subjects holding loads, OE was involved in lateral bending (Seroussi & Pope, 1987). OI and OE played a role in trunk rotation during twisting efforts against resistance (McGill, 1991), and TA was active during ipsilateral rotation (Urquhart & Hodges, 2005). Considerable activity of all three muscles was reported in flexion exercises (Juker, McGill, Kropf, & Steffen, 1998). OE was involved in expiration (Campbell, 1952), and the activity of all three muscles was modulated at the frequency of breathing (Saunders, Schache, Rath, & Hodges, 2004). Bilateral TA activity preceded rapid movements of upper and lower extremities, which supports the idea that TA stabilizes the spine (Hodges and Richardson, 1996, Hodges and Richardson, 1997a, Hodges and Richardson, 1997b). Furthermore, the use of a pelvic belt led to decreased EMG amplitudes of these muscles during the Active Straight Leg Raise, in accordance with their assumed function in sacroiliac stabilization (Hu et al., 2010).
As a rule, the mechanical effects of any single muscle will not coincide with the exact 3-dimensional demands of a task, and when constraints are conflicting, there will be no perfect solution. More important, the lateral abdominal muscles may subserve multiple functions simultaneously (Benninghoff and Goerttler, 1964, Hodges, 2008). Some evidence for such multitasking has been provided for trunk postural control plus breathing (Hodges et al., 2002, Saunders et al., 2004). Still, how multiple functions are coordinated has received limited attention only. In multitasking, or dealing with conflicting constraints, the control system may prioritize one function and ignore the other (cf. Hodges, Heijnen, & Gandevia, 2001). Also, the control system may exploit muscle redundancy by assigning specific functions to specific muscles or parts thereof (Puckree, Cerny, & Bishop, 1998). Finally, problems of multitasking may be alleviated when the system can deal with different task demands consecutively (task switching) rather than simultaneously (multitasking).
The present study focused on control of the lateral abdominal muscles during gait, which is an activity that involves all functions mentioned above (cf., e.g., Callaghan et al., 1999, Saunders et al., 1953, Saunders et al., 2004). We used electromyography (EMG), calculated trunk moments using a dynamic 3-dimensional linked segment model, and cross-correlated EMG linear envelopes with moment data. The stride cycle was split into different phases (cf. Ivanenko et al., 2004, Perry, 1992), with peak detection in the time series of moments and of EMG. Fourier analysis of the EMG linear envelopes was performed to determine absolute and relative power at the main frequencies (Saunders et al., 2004). Since the relative importance of different functions changes with speed (Anders et al., 2007, Saunders et al., 2004), walking speed was manipulated.
The goal of this study was to understand the coordination of the lateral abdominal muscles during gait. We expected that these muscles would be engaged in multitasking most of the time. Because normal walking is relatively undemanding, we expected that no function would be ignored, and, given the literature (Hodges, 2008), that no (part of a) specific muscle would be specifically dedicated to a single task. On the contrary, we hypothesized that the control system co-activates muscles to produce the desired effect, dealing with conflicting constraints by co-contraction to offset unwanted mechanical side-effects of any individual muscle.
Section snippets
Subjects
Sixteen healthy, nulliparous females were enrolled (mean ± SD age 27.5 ± 2.7 years, weight 61.2 ± 9.8 kg, height 167.9 ± 7.6 cm, BMI 21.6 ± 2.4 kg/m2). Exclusion criteria were: previous orthopaedic surgery, walking-related disorders, or a history of low blood pressure. Participants gave written informed consent. The protocol was approved by the local Medical Ethical Committee.
Data collection
Kinematic and electromyographic data were collected during treadmill walking at six different speeds (1.4–5.4 km/h, with increments of
Stride frequency and step length
All subjects walked at all speeds. Stride frequency increased with speed from 0.52 Hz to 0.99 Hz, and step length from 0.38 m to 0.76 m (Table 1). Step length was largely symmetric, with an average difference between right and left of 0.005 ± 0.03 m.
Moments
To assess the consistency of trunk moment data, PCA was used over all subjects and all speeds. The first principal component contained 80.4% (lateral bending), 56.2% (flexion/extension), or 90.1% (rotation) of the variance. These numbers are rather high,
The effects of speed
We expected that the same functions would be performed by the lateral abdominal muscles at all speeds, and that no function would be ignored at the higher speeds. The necessity to control trunk motion in three planes defines mechanical constraints for the control of the lateral abdominal muscles. In the frontal plane, trunk muscles need to maintain equilibrium against the moment caused by gravity during single stance. These lateral bending moments thus varied with stride frequency, and were
Limitations
It can be argued that speed was experimentally manipulated in the present study. Nevertheless, the study was largely descriptive, using biomechanics to understand muscle coordination in multitasking. Each specific explanation still awaits experimental tests. The study was limited to young healthy women, whereas gender (Anders, Wagner, Puta, Grassme, & Scholle, 2009) as well as pathology (e.g., Huang et al., 2011) are known to affect gait.
Conclusion
During gait, all three lateral abdominal muscles are involved in simultaneous task execution (multitasking) as well as consecutive task execution (task switching). Activity of the lateral abdominal muscles contributes to breathing, trunk motion in three dimensions, and lumbar spine as well as pelvic stability. Task execution is distributed over all three muscles, and no muscle is exclusively assigned a particular task. The effects of speed are gradual, without sudden transitions, and no
Grants
Financial support was obtained from Stryker Howmedica Nederland, Biomet Nederland, and the Dutch Society of Exercise Therapists Cesar and Mensendieck (VvOCM). PH is supported by a Research Fellowship from the National Health and Medical Research Council (NHMRC) of Australia.
Acknowledgements
The authors gratefully acknowledge Erwin van Wegen, Mark Scheper, Ilse van Dorst, Kitty Bos, Annemarie ten Cate, Margot Prins, and Hans van den Berg (Biomet Nederland) for their help and suggestions. This project could not have been performed without the stimulating initiative of the late Paul I.J.M. Wuisman, Professor of Orthopaedic Surgery at the VU University Medical Centre.
References (52)
- et al.
Trunk muscle activation patterns during walking at different speeds
Journal of Electromyography and Kinesiology
(2007) - et al.
Coordination of leg swing, thorax rotations, and pelvis rotations during gait: The organisation of total body angular momentum
Gait & Posture
(2008) - et al.
Low back three-dimensional joint forces, kinematics, and kinetics during walk
Clinical Biomechanics
(1999) - et al.
Position and orientation in space of bones during movement: Anatomical frame definition and determination
Clinical Biomechanics
(1995) - et al.
PCA in studying coordination and variability: A tutorial
Clinical Biomechanics
(2004) Is there a role for transversus abdominis in lumbo-pelvic stability?
Manual Therapy
(1999)An explicit expression for the moment in multibody systems
Journal of Biomechanics
(1992)- et al.
Muscle activity during the active straight leg raise (ASLR), and the effects of a pelvic belt on the ASLR and on treadmill walking
Journal of Biomechanics
(2010) - et al.
Segment inertial parameter evaluation in two anthropometric models by application of a dynamic linked segment model
Journal of Biomechanics
(1996) - et al.
An electromyographic study of isokinetic axial rotation in young adults
The Spine Journal
(2003)
Effect of experimentally induced pain and fear of pain on trunk coordination and back muscle activity during walking
Clinical Biomechanics
Activity of deep abdominal muscles increases during submaximal flexion and extension efforts but antagonist co-contraction remains unchanged
Journal of Electromyography and Kinesiology
A revised anatomical model of the abdominal musculature for torso flexion efforts
Journal of Biomechanics
Less is more: High pass filtering, to remove up to 99% of the surface EMG signal power, improves EMG-based biceps brachii muscle force estimates
Journal of Electromyography and Kinesiology
Postural and respiratory activation of the trunk muscles changes with mode and speed of locomotion
Gait & Posture
The relationship between trunk muscle electromyography and lifting moments in the sagittal and frontal planes
Journal of Biomechanics
Transfer of lumbosacral load to iliac bones and legs. Part 1: Biomechanics of self-bracing of the sacroiliac joints and its significance for treatment and exercise
Clinical Biomechanics
Effects of EMG processing on biomechanical models of muscle joint systems: Sensitivity of trunk muscle moments, spinal forces, and stability
Journal of Biomechanics
Methodological aspects of SEMG recordings for force estimation. A tutorial and review
Journal of Electromyography and Kinesiology
Abdominal and erector spinae muscle activity during gait: The use of cluster analysis to identify patterns of activity
Clinical Biomechanics
Healthy humans use sex-specific co-ordination patterns of trunk muscles during gait
European Journal of Applied Physiology
Motor control patterns during an active straight leg raise in pain-free subjects
Spine
Lehrbuch der Anatomie des Menschen, Erster Band [Textbook of human anatomy, Volume One]
An electromyographic study of the role of the abdominal muscles in breathing
Journal of Physiology
Comparison of trunk activity during gait initiation and walking in humans
PLoS One
Stabilizing function of trunk flexor–extensor muscles around a neutral spine posture
Spine
Cited by (24)
Expiratory abdominal muscle nerve is active at flexor phase, while inspiratory phrenic nerve is not active during locomotion evoked by 5-HT and NMDA in the neonatal rat
2022, Neuroscience ResearchCitation Excerpt :The abdominal muscles also have roles in various functions such as locomotion and postural control (Iscoe, 1998). In humans and horses, the abdominal muscles are tonically active with phasic modulation during locomotion (Hu et al., 2012; Zsoldos et al., 2010). However, since these observations were obtained under the condition of awake and intact sensory feedback, they could not reveal the existence and extent of direct synaptic inputs from the central pattern generator (CPG) for locomotion to motoneurons of the abdominal muscles.
Low back pain in the overhead athletes: Evaluation and treatment based on movement system
2017, Polish Annals of MedicineCitation Excerpt :Such findings were observed in the patient’s examination. Abdominal oblique muscles participate in trunk rotation control.31,32 Generally, it is known that abdominal muscles provide stability of the lumbo-pelvic complex; especially the role of transversus abdominis (TrA) is underlined.33
Effect of gait retraining for reducing ambulatory knee load on trunk biomechanics and trunk muscle activity
2016, Gait and PostureCitation Excerpt :A similar pattern has been observed for persons with lower extremity amputations where transtibial and transfemoral amputees had higher lateral bending moments than healthy controls directly related to increased lateral trunk sway to stabilize the body [27]. Muscle activation patterns of all trunk muscles were comparable to those previously reported [19,20,28]. As for normal walking, external oblique muscle is more active on the contralateral than the ipsilateral side during the first half of the stance phase [20].
Dynamic balance assessment during gait in spinal pathologies - A literature review
2015, Orthopaedics and Traumatology: Surgery and ResearchCitation Excerpt :Given to phasic activity between abdominal muscles and ES, results are controversial. Only one study used fine-wires and emphasizes a near constant activity of lateral abdominal muscles during gait [31]. Thirteen studies reported gait anomalies related to scoliosis and are presented in Table 2 [10–22,34].
Dynamic balance assessment during gait in spinal pathologies: A literature review
2015, Revue de Chirurgie Orthopedique et Traumatologique