exercises
Axial Loading Goal: Determine whether vertical spinal compression recreates your client’s pain. Stand behind your client, interlace your fingers, and place your hands on top of her head. From this position, simply press downward using a light pressure (2-5 lb, or 0.9-2.2 kg) to give vertex compression. Normally this could be expected to give pain with cervical pathology but not with lumbar conditions. If the client reacts intensely, “Yes, that’s it—you’ve hit my pain,” this response is likely exaggerated where no cervical pathology coexists with her lumbar pain.
Trunk Rotation Goal: Determine if the appearance of trunk rotation (false trunk rotation) recreates your client’s pain. With this test, you again stand behind your client. Grip her pelvis at the greater trochanters and rotate her whole body to one side and then the other. The rotation movement actually occurs at the feet and hips, but to the client it appears that her spine is rotating as she turns from side to side. Normally, whole-body rotation of this type should not give lumbar pain because the lumbar spine is actually staying still. The presence of an obvious pain response suggests exaggeration.
306
exercises
Straight-Leg Raise Goal: Determine whether the range of motion gained using a standard lying straight-leg raise (SLR) is the same as that performed indirectly when your client is simply in a long (couch) sitting position. The final test uses the straight-leg raise (SLR), which is normally quite familiar to the client because it will have been tested by a number of practitioners. Measure the client’s range of motion in the SLR with the client lying on a couch. Note the range, and then in casual conversation ask the client to sit up. As he sits up, he will actually move into a straight-leg position. If his SLR was limited but he shows no expression of pain or distress to sit with his legs out straight (long sitting), it is likely that his pain response is exaggerated.
307
Chapter 3
Stabilization Mechanisms of the Lumbar Spine Devoid of its musculature, the human spine is inherently unstable. The spine of a fresh cadaver stripped of muscle can sustain a load of only 4 to 5 lb (1.8-2.3 kg) before it buckles into flexion (Panjabi et al. 1989). Moreover, the center of gravity of the upper body (when one is standing upright) lies at sternal level (Norkin and Levangie 1992). This combination of flexibility and weight distribution is approximately comparable to balancing a 75 lb (34 kg) weight at the end of a 14 in. (35.5 cm) flexible rod (Farfan 1988). From a strictly mechanical standpoint, discs don’t contribute as much as one might think to the spine’s strength: Lifting heavy objects imposes on the lower lumbar spine a compressive force that greatly exceeds the failure load of the vertebral discs unless additional support is present (Bartelink 1957; Morris et al. 1961). Moreover, if compressive and shear forces are not attenuated by muscle contraction, they place considerable stress on the facet joints of the lumbar spine, leading to inflammation of joint structures and eventually joint damage through erosion. By reducing these forces acting on the lumbar spine, several mechanisms help stabilize the spine (Norris 1995a). These mechanisms, on which this chapter focuses, include the posterior ligamentous system, several processes involving the thoracolumbar fascia, actions of trunk muscles, and intra-abdominal pressure.
Key point:  The spinal column by
itself is inherently unstable. Without muscle action, severe stress is imposed on the delicate joints and discs. Stability training aims to reduce these forces using muscle action.
Posterior Ligamentous System The interspinous and supraspinous ligaments, facet joint capsules, and thoracolumbar fascia (TLF) together provide passive support for the spine said to be sufficient to balance between 24% and 55% of imposed flexion stress (Adams et al. 1980). However, the cadaveric experiments on which these figures are based have been questioned (discussed later). In the unstretched position, collagen fibers within the anterior and posterior longitudinal ligaments and the ligamentum f lavum (see figure 2.3) are aligned haphazardly. When the ligaments are stretched as the spine flexes or extends, however, the collagen fibers become aligned and the ligament becomes stiffer (Hukins et al. 1990; Kirby et al. 1989). Stressed by 10% to 13% at rest, the ligaments retract when cut (Hukins et al. 1990). The longitudinal ligaments therefore maintain a compressive force along the axis of the spine, causing it to act somewhat like a stressed beam (Aspden 1992). The ligaments are viscoelastic (i.e., they stiffen when loaded rapidly). Rapid loading therefore increases the thrust within the spine and tends to approximate (bring closer together) the vertebrae, enhancing spinal stability. Power created by the hip extensors posteriorly tilts the pelvis and is transmitted through the spine to the thorax and upper limbs via the ligamentous system. Some authors have maintained that for this passive mechanism to work, the spine must remain flexed. They argued that if the spine extends, tightness of the posterior ligaments will decrease and their ability to stabilize the spine will
39
40 Back Stability
be lost (McGill and Norman 1986). More recently, however, it has been shown that the spine need not become kyphotic before it can create tension by stretching the tissues (Gracovetsky et al. 1990). The posterior ligamentous system alone can sustain a maximum torque of only about 50 N·m (Bogduk and Twomey 1991), less than 25% that of the contracting erector spinae. However, two passive systems are at work here (see p. 34). While the posterior ligamentous system is recoiling, the erector spinae are also recoiling. At the point of full flexion, these muscles no longer contract (they are electrically silent), but they do exert a force through recoil much like that of a giant elastic band. The force that the erector spinae create through recoil is about 200 N·m, equal to their potential contractile force. The combined posterior musculoligamentous system therefore provides a substantial stabilizing mechanism in full flexion.
however, the active systems of the disc stop, and because the disc material naturally absorbs water (it is hydrophilic), the disc actually expands slightly after death. Tissue changes after death are quite common, incidentally; for example, both facial and head hair continue to grow for a short while after death. Because the disc absorbs water in this way (and consequently becomes taller), the ligaments that surround the spinal segment are stretched slightly, making some of the results obtained from cadaveric tests inaccurate (McGill 2002). It has been demonstrated (Sharma et al. 1995) that of the posterior ligaments, the supraspinous ligament, rather than the posterior longitudinal ligament or ligamentum flavum, is the passive structure that most contributes to passive spinal stability.
Key point: The posterior ligaments of
The thoracolumbar fascia performs a number of important functions during back stability, which I briefly review here. Note that the fascia also stabilizes the sacroiliac joints.
the spine can sustain 50 N·m of torque and resist more than 50% of the flexion stress imposed on the spine. The passive tension (elastic recoil) in the stretched erector spinae can create 200 N·m of torque, equal to their maximum contraction.
Structure of the Thoracolumbar Fascia
Many of the original studies on spinal ligaments were conducted on cadavers. When a person dies, Vertebral body
Psoas
Thoracolumbar Fascia
The thoracolumbar (lumbodorsal) fascia (TLF) has three layers that cover the muscles of the back (figure 3.1). The anterior layer derives from fascia
Quadratus lumborum
Internal oblique
Transversus abdominis
1 Anterior
layer
2 Middle layer
External oblique Serratus posterior inferior 3 Posterior
Multifidus
layer
Latissimus dorsi
Erector spinae
Figure 3.1 Cross section of trunk showing thoracolumbar fascia.
E4182/Norris/fig.3.1/298530/alw-pulledr1/jb/R2
86 Back Stability
Table 5.5 Correct Alignment of the Shoulder Girdle From behind
From the side
Medial border of scapula vertical Medial border of scapula no more than three finger breadths from the spinous processes Spine of scapular T3-T4 level, inferior angle at T7 Scapula flat against thoracic wall
Line from ear canal to center of shoulder joint perpendicular to floor No more than one third of head of humerus anterior to acromion Humerus held with elbow crease 45° to sagittal plane
Deviation from the ideal is often described as a round-shouldered posture, a term that covers a number of scenarios. Tightness in the anterior structures pulls the shoulder forward, away from the posture line. The weight of the arm moves farther from the upper body’s center of gravity, dramatically increasing the leverage forces transmitted to the thorax. Eventually, thoracic kyphosis increases. Tightness in the pectoralis minor pulls on the coracoid process, tilting the scapula forward (figure 5.8a). Tightness in the pectoralis major causes both excessive medial rotation at the glenohumeral joint and anterior displacement of the humeral head (figure 5.8b). Lengthening of the lower trapezius and serratus anterior may cause excessive abduction (figure 5.8c) and downward rotation (figure 5.8d) of the scapula. Excessive elevation (figure 5.8e) and upward rotation may result from tightness in the upper fibers of the trapezius. Correction of kyphotic posture depends on flexibility of the thoracic spine. Where the kyphosis appears fixed and thoracic motion is grossly
reduced, thoracic joint mobilization by a PT is required as a first step. Once some mobility has been gained passively by manual therapy, you can use exercise therapy to maintain the newly gained motion. The sternal lift action (p. 103) is the exercise of choice. If the subject is younger and the thoracic spine is mobile, only scapular repositioning is required. Figures 5.9 and 5.10 give examples of suboptimal scapular positions. Figure 5.9a shows the appearance of scapular tipping combined with abduction at rest. At initiation of arm abduction (figure 5.9b), the scapula is not held stable against the rib cage but rotates downward instead. When stress is placed on the arm, scapular instability becomes even more noticeable. Figure 5.10a shows the appearance of scapular instability in four-point kneeling (handsand-knees position). As the arms are bent during the eccentric (lowering) phase of a press-up exercise from this position, the shoulder muscles pull on the scapula, which should remain fixed to the rib cage. As stability fails, the scapulae fall together, showing marked adduction, and actually move farther
b a
c
d
e
Figure 5.8 Postural changes around the shoulder.
E4182/Norris/fig.5.18a-e/298779-80-81-82-83/alw-pulledr2
Posture 87
b
a
Figure 5.9 (a) Poor scapular alignment at rest. Note the contours of the scapulae. (b) The scapular muscles work hard to fix the scapula to the ribcage. a
b
Figure 5.10 (a) Scapulae move inward when stabilizers do not work. (b) Scapulae fixed to ribcage but alignment is still poor. Note the flaring of medial borders.
away from the rib cage rather than being drawn in toward it (figure 5.10b).
Summary • Posture is the arrangement of body parts in a state of balance that protects the supporting structures of the body against injury or progressive deformity. • Postural sway consists of a small continuous motion in the sagittal plane—an oscillation of the center of gravity that may reduce lower-limb fatigue and aid blood flow.
• You can assess clients’ postures by use of a plumb line or a posture grid. • There are four basic types of abnormal posture:
1. Lordotic posture is characterized by excessive anterior pelvic tilt. 2. Swayback is characterized by anterior displacement of the pelvis. 3. Flat-back posture is characterized by slight posterior pelvic tilting and loss of lumbar lordosis. 4. Kyphosis is characterized by excessive thoracic curve.
exercises
Assessing Muscle Balance in the Iliopsoas Goal: Determine if the iliopsoas muscle is capable of holding the hip at full inner range flexion. While sitting, your client flexes her hip maximally while maintaining 90째 knee flexion so that the foot is lifted clear of the ground. Have her hold this position as long as she can, while you record the time at which phasic movements begin. Note also the position of the pelvis and lumbar spine. Where the iliopsoas is lengthened, one of two things may happen. (1) If lumbar stability is poor, the pelvis will drop back into posterior tilt, flattening or even reversing the lumbar lordosis. (2) If lumbar stability is good, your client will be able to maintain the neutral position of the lumbar spine and pelvis, but the knee will simply drop, indicating that the hip flexor muscles have lengthened (but not necessarily weakened) and are unable to hold the full inner-range position. Hip pain during this action should be assessed by a physical therapist (PT). Pressure on the psoas bursa will be painful if the bursa is inflamed. Also, the joint may glide anteriorly because of imbalance of the hip lateral rotators. Normally, these muscles (especially quadratus femoris) hold the head of the femur back against the anteriorly directed force of the hip flexors. In a swayback posture, the hip lies in extension, and the posterior muscles may be lax or wasted. As flexion progresses, the head of the femur may glide anteriorly, stressing the hip structures and causing pain (Sahrmann 2002).
110
Goal: Determine if the gluteus maximus muscle is capable of holding the hip in full inner-range extension. Have your client lie in a prone position with her knee flexed to 90°. Then she should lift her hip to the inner range of extension and hold it steady. Using palpation, note the order of muscle contraction during the hip extension. Normally, the hamstrings should contract first, followed by the gluteus maximus, then the contralateral erector spinae, and finally the ipsilateral erector spinae (Lewit 1991). In many cases of imbalance, the gluteus is poorly recruited or even inhibited (pseudoparesis) by tightness in the opposing hip flexors (Janda 1986). Where this is the case, the order of muscle contraction changes. If the gluteals do not function adequately, the hamstrings dominate the movement—little gluteal activity is apparent, and the muscle mass remains flaccid. Note how long your client can hold the position steady before phasic movement begins. Performing the test with the knee bent reduces the contribution that the hamstrings make to the movement by shortening them. The contribution of the gluteus is therefore more apparent. Your ability to see and feel the subtle changes that indicate the order of muscle contraction, however, takes time to develop. Until you have gained experience in this area of examination, you can use dual-channel electromyography to show the intensity and timing of muscle contraction. Watch carefully to see if your client performs a false hip extension movement; in this action, the pelvis anteriorly tilts because of the powerful action of the erector spinae, and the relationship between the hip and pelvis remains the same. Explain to your client which muscles she should use to perform this activity and in which order. If she tends to make a false hip extension, hold her pelvis down while she raises her leg using only her gluteals, so that she learns what the correct movement feels like. When the gluteus maximus is poorly recruited, hip hyperextension power will be lost. You can see this if you ask your client to walk backward. If the gluteus is poorly recruited, clients will often anteriorly tilt their pelvis and hyperextend their lumbar spine in an attempt to make up for the loss of extension power at the hip.
Key point: Backward walking can make gluteus maximus weakness readily apparent.
111
exercises
Assessing Muscle Balance in the Gluteus Maximus
exercises
Abdominal Hollowing: Standing Goal: Teach a progression from four-point kneeling or provide an initial position for obese individuals or others for whom fourpoint kneeling is uncomfortable. Some subjects find four-point kneeling difficult to control and tend to round their spines as they attempt abdominal hollowing. In this case, wall-supported standing is a more appropriate starting position. Your client should stand with his feet 6 in. (15 cm) from a wall and his back against the wall while maintaining a neutral spinal position (a). An easy way to monitor neutral position is for your client to place one hand behind his back (over the sacrum) and the other in front of the abdomen, enabling him to monitor the position of his pelvis. He can also use his front hand to feel the contraction of the abdominal muscles as he initiates hollowing and draws the abdominal wall away from his hand.
a
Teaching Points In an obese or poorly toned subject, the weight of the digestive organs will pull the abdominal wall out and down (visceral ptosis). If this occurs, position a belt below the client’s navel (b), instructing him to contract the lateral abdominals and to pull the abdominal wall in and up, trying to create a space between the abdomen and the belt. Because motor programming links lateral abdominal action and pelvic floor action as part of the intra-abdominal pressure mechanism, pelvic floor contractions are also useful to aid learning of abdominal hollowing. Instruct a female client to pull in the pelvic floor as though trying to stop herself from urinating. Tell male clients to use the imagery of lifting the penis.
b
154
exercises
Sitting Abdominal Hollowing Goal: Provide further practice for subjects who are already able to maintain the neutral lumbar position and control body sway. Sitting on a stool or office chair is a useful starting position because clients can practice this exercise throughout the day. When your client is sitting on a stool, the upper part of his trunk is unsupported, so he will have to control body sway. Using an office chair supports the thoracic spine, but don’t allow your client to slouch. He must be more active in controlling his upper trunk when it is unsupported, paying attention to the hollowing action as well as to the position of the lumbar spine (maintaining neutral position) and the position of his shoulders (avoiding body sway). Have your client pay close attention to movement of the rib cage, as well as to shoulder position, pelvic tilt, and maintenance of a neutral lordosis. Instruct your client to sit tall to facilitate correct alignment; this concept is also helpful in correcting whole-body posture while standing.
Teaching Points Make sure that your client sits tall and avoids a slouch sitting posture. Closely monitor him to ensure that he controls body sway. To avoid flexion in the lumbar spine, position his knee lower than his hip. This position reduces pull from the hip tissues, which would tend to posteriorly tilt the pelvis and flatten the lumbar lordosis. This client has posteriorly tilted his pelvis. This can encourage contraction of the lower rectus.
155
You’ll find other outstanding rehabilitation resources at
www.HumanKinetics.com In the U.S. call
1-800-747- 4457 Australia.....................................................08 8372 0999 Canada................................................... 1-800-465-7301 Europe........................................... +44 (0) 113 255 5665 New Zealand.........................................0064 9 448 1207 HUMAN KINETICS The Information Leader in Physical Activity
P.O. Box 5076 • Champaign, IL 61825-5076 USA