Injury prevention: why lumbopelvic stability matters

Paul Gamble explains why not all core training exercises are created equal, and why lumbopelvic stability is crucial for injury prevention

The profile of core stability training has risen massively in recent years, with growing use by both athletes and recreational trainers. Core work has become an integral part of athlete’s training with the aim of improving performance, and core exercises are commonly prescribed by physiotherapists for therapeutic training applications. Walk into any gym in the country (once lockdown restrictions are lifted of course!) and chances are you will find Swiss balls and a personal trainer extolling the virtues of core training.

What is ‘core stability?’

Core stability is described in the sports medicine literature as ‘the product of motor control and muscular capacity of the lumbo-pelvic-hip complex’. In reality, the term ‘core training’ has become an all-purpose label for any exercise that addresses some aspect of lumbopelvic stability. A number of different muscles are associated with the lumbar spine, pelvis and hips. In view of this, ‘core training’ could refer to any mode of exercise that addresses any one of the various different systems of muscles involved with providing lumbopelvic stability. Training the ‘core’ is therefore a bit more complex than the term core training implies.

Importance of lumbopelvic stability

Especially when in neutral position, the spine depends heavily upon active stability provided by various muscles. An illustration is that when stripped of muscle and left to rely upon passive (bone and ligament) support, the human spine will collapse under 20lb (»9kg) of load⁽¹⁾. Obviously this doesn’t happen in healthy athletes, and it is the muscular systems that contribute to lumbopelvic stability which take up the slack.

Lumbopelvic stability comprises different functional components: deep muscles that stabilise the lumbar spine; the superficial abdominal musculature; and hip muscles that help support and stabilise the pelvis. In addition, neural coordination and motor control play a key role. There is a need for specific training to address each of these functional areas. Weakness or impairment at any point in this integrated system of support can lead to damage to structural tissues (ligament and joint capsule), causing injury and pain⁽¹⁾. Athletes therefore have a need for both strength and endurance for the muscles that stabilise the spine.

Movements in athletic events and team sports occur in multiple directions. As a result athletes must possess lumbopelvic stability in all three planes of motion⁽²⁾. The combination of muscles that contribute to providing stability varies with the direction of movement and magnitude of loading on the spine. Furthermore, these capabilities are required under both static and dynamic conditions during competition, and so must be developed accordingly⁽²⁾.

Lumbopelvic stability and injury

To date, some studies have generally failed to find improvements in performance measures following ‘core’ training interventions^(3,4). By contrast however, a role for training to develop the various areas contributing to lumbopelvic stability in reducing incidence of injury is supported by the majority of studies^(1,5,6).

After the ankle and knee, the lower back is commonly reported to be the third most common site of injury in sports⁽⁷⁾. This is particularly the case in female athletes – a study of injury incidence in NCAA collegiate athletes for the 1997-1998 season indicated almost twice the number of lower back injuries in females, compared to male athletes⁽⁸⁾.

Lumbopelvic stability issues can affect the function of all lower extremity joints, as part of the lower extremity kinetic chain described by the ‘Link Theory’⁽⁷⁾. Most movements in sports are closed kinetic chain, meaning they are executed with one or both feet planted. The integrated function of the lower extremity kinetic chain means that any disturbance at one joint in the chain may impact upon all joints in the chain between the planted foot and the lumber spine, where forces are transmitted upwards. Consequently lumbopelvic stability has the potential to affect the function and injury risk at all lower extremity joints – in particular knee and ankle⁽²⁾.

Components of lumbopelvic stability

*Deep lumbar spine stabiliser muscles

The deep lumbar spine stabilisers consist of muscles that originate from or insert directly onto the lumbar vertebrae. The muscles help provide rigidity for each individual segment of the lumbar spine. In doing so, these muscles act to maintain the integrity of these structures in opposition to internal forces generated during movement performed with and without external loading. The importance of these muscles can be inferred from the finding that these muscles are atrophied in individuals with chronic lower back pain. These deep muscles also play a key role in kinaesthetic sense and proprioception – the sense of the position and movement occurring at a joint or limb⁽¹⁾. Specific training for these muscles thereby can offer the secondary benefit of improved neuromuscular function and postural control.

*Abdominal muscles

Whereas the deep lumbar spine stabiliser muscles handle internal forces, the large superficial abdominal muscles have a key role in handling external loads. The individual abdominal muscles act in a load and velocity specific manner to assist in stabilising the trunk during rapid actions, such as athletic activities. These muscles thus serve an important function for team sports – allowing players to handle heavy loads in training and competition, in addition to providing stability and mobility to the trunk during sports movements.

In athletes with impaired deep lumbar muscle strength or function, these superficial abdominal muscles may try to compensate. These muscles are not mechanically able to stabilise the lumbar spine as effectively, so attempting to perform this stabilising role actually compromises their effectiveness⁽¹⁾. Co-contraction of the superficial abdominal musculature can interfere with normal movement and restrict breathing. Often the first step with neuromuscular training for athletes with over-active abdominal muscles is training them to selectively isolate and recruit the deep lumbar stabiliser muscles without activating the larger superficial abdominal muscles⁽⁸⁾.

*Hip muscles

The hip musculature, including the hip extensor, abductor and rotator muscles groups, has a major role in all dynamic activities performed in an upright stance. These muscles are implicated in various phases of the gait cycle, for example helping to stabilise the pelvis and provide assistance to the supporting leg during the swing phase⁽⁷⁾. In fact in all dynamic movements the hip muscles play a part in assisting transfer of forces from the ground upwards.

The importance of the hip muscles’ role in stabilising the lower limb joints during dynamic movements is seen in the way these muscles impact upon lower limb injury incidence, particularly in female athletes. Inadequate hip muscle function combined with anatomical differences can predispose female players to excessive motion in the lower limb joints, placing these joints in positions where they are at risk of non-contact injury⁽²⁾. Moreover, tests scores for isometric hip abduction and external rotation strength are found to be significant predictors of subsequent lower limb injury during the competitive season in collegiate athletes.

Side-to-side imbalances in hip muscle strength are commonly observed in athletes. Right-handed athletes typically exhibit greater strength in their opposite (left) hip extensors⁽⁷⁾. This may well be due to the use of the left leg as the supporting leg during right-leg dominant sports activities, such as kicking. Likewise, right-hand dominant athletes will tend to take-off from their left leg when jumping. Both these instances place greater demands upon the leg hip extensor muscles. Conversely, right hip abductor strength is generally greater in right-handed athletes. This can be explained by phenomena such as the dominant right hip abductor involvement fine motor skills, for example the kicking action.

Impaired function of the hip extensors and hip abductors are frequently observed with athletes suffering lower back pain⁽⁹⁾. Muscle strength imbalances in these muscles are also implicated in lower back injury, particularly in female athletes. Correcting hip abductor strength imbalances by a core-strengthening program shows the potential to reduce subsequent lower back pain incidence, particularly in female athletes⁽⁹⁾. Specific training to address these factors therefore can help to guard against incidence of injury and lower back pain.

The hip rotators are often overlooked in physical preparation. This is despite the observation that isometric hip external rotation strength is the single best predictor of lower back and lower extremity injury incidence in collegiate athletes⁽²⁾. Inflexible or weak hip rotators can predispose the athlete to poor pelvic alignment. Excessive lumbar spine motion can also occur in an attempt to compensate for impaired hip rotator function. Both of these factors can lead to pain and incidence of lumbar spine injury⁽¹⁰⁾. It follows that these muscles must also be specifically addressed in training.

Neuromuscular control and coordination

Muscle strength on its own is not enough for lumbopelvic stability. Neural control is also critical in the activation and coordination of each of the supporting muscles described above. Lumbopelvic stability in gross movements is underpinned by the firing of various core muscles in preparation for movement. This occurs before the activation of limb muscles involved in the activity, and serves to prevent unwanted trunk motion and provide a stable base for movement. The neuromuscular system must therefore govern function of stabilising muscles - not only in anticipation of expected direction and magnitude of forces, but also in reaction to sudden movement or loading. In this way, postural control, balance and proprioception are also heavily involved in providing lumbopelvic stability.

A reflection of the importance of neuromuscular control is that individuals with chronic lower back pain exhibit impaired neuromuscular feedback and delayed muscle reaction, which is accompanied by reduced capacity to sense the orientation of their spine and pelvis⁽¹⁾. These factors are responsible for the poor performance of these individuals in balance and movement response tasks. However, these deficits in neuromuscular control can be reversed by appropriate training interventions.

Exercises to address each aspect of lumbopelvic stability

Hopefully, you can begin to understand that while generalised core training can form a useful addition to an athlete’s training programme, if injury prevention is the main goal, the focus should be on exercises that improve lumbopelvic stability. There are a number of examples of such exercises; here below are a few examples, together with links to online videos, where you can see the exercise performed.

• #Deep Lumbar Stabiliser Muscle Training
  
  • Single-leg Raise and Reach - www.youtube.com/watch?v=C0X36CJ04X0
  • Modified Superman - www.youtube.com/watch?v=8AjsnwJZhlY

• #Abdominal Muscle Training
  
  • Swiss Ball Obliques - www.youtube.com/watch?v=B4n5akTDPL4
  • Swiss Ball Single-leg Jack-knife - www.youtube.com/watch?v=7PZH5Nv8h4k

• #Hip/Pelvic Muscle Training
  
  • Side-lying Hip Raise and Hold - www.youtube.com/watch?v=hnUfucnLtto
  • Standing Hip Internal Rotation with Theraband - www.youtube.com/watch?v=Wxbr3Ip8nM8

• #Proprioception/Neuromuscular Training
  
  • Overhead Squat with Dumbbell - www.youtube.com/watch?v=azumEfnk-GI

References

1. American Journal of Physical Medicine and Rehabilitation. 84: 473-480. 2005
2. Medicine & Science in Sports & Exercise. 36(6): 926-934. 2004
3. Journal of Strength & Conditioning Research. 18(3): 522-528. 2004
4. Journal of Strength & Conditioning Research. 19(3): 547-552. 2005
5. New Zealand Journal of Sports Medicine. 29(1): 14-18. 2001
6. Spine. 26: E243-248. 2001
7. Clinical Journal of Sports Medicine. 10: 89-97. 2000
8. Manual Therapy. 3(1): 12-20. 1998
9. Medicine & Science in Sports & Exercise. 34(1): 9-16. 2002
10. Strength & Conditioning Journal. 22(6): 7-13. 2000