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back injury prevention exercises, nordic hamstrings

Back injury prevention exercises - Powerful movement and solid stability both require strength through the posterior chain

The posterior chain (PC) is a group of muscles comprised primarily of the back extensors and hip extensors. More specifically, it includes the force-producing muscles of the lumbar and thoraco-lumbar erector spinae, quadratus lumborum and superficial multifidus. The deep multifidus are considered stabilising muscles and their close proximity to the vertebral axis for lumbar extension make them ineffective as torque producers. However, they are critical in providing segmental vertebral stability of the lumbar spine to prevent shear forces acting across the disc and vertebral segment. The hip muscles involved in the PC include the gluteus maximus, adductor magnus and hamstring muscle group. These are the major torque producers of the hip.

The latissimus dorsi is also involved via its attachment to the thoraco-lumbar fascia and its corresponding attachment to the contra-lateral gluteus maximus. This ‘posterior oblique myo-fascial sling’ has been described by Andre Vleeming and Chris Snijders in their work on sacroiliac joint stability (this concept will be expanded in a future issue of SIB). The erector spinae also works through a ‘posterior longitudinal sling’ consisting of erectors, thoraco-lumbar fascia, attachments on to the long dorsal sacroiliac joint ligament, on to the sacrotuberous ligament and then on to the long head of biceps femoris. Again, this anatomical description has been illustrated by Vleeming and Snijders and the reader is referred to this for a more detailed description1.

Why the posterior chain matters

The PC muscles provide the major torque-producing capacity of the body during locomotion. From hip extension in walking, to powerful hip extension in sprinting and back extension in sprint starts, the PC are the dominant muscles in use. A strong PC will assist an athlete with the explosive requirements of locomotion. Evidence of this can be witnessed in the lower back, gluteal and hamstring musculature of elite level sprinters.

The PC, along with the abdominals, also provides gross global stability for the lumbo-sacral spine. While the small multifidus muscles, the transversus abdominis and the internal oblique provide intrinsic stability from segment to segment, strength and conditioning coaches will agree that power-based athletes need much more than an effectively functioning inner unit of stability muscles. The bulkier PC muscles give additional stability in the lumbo-sacral spine to counteract the large forces acting across this area in power-based sports.

Role in injury prevention

In fast ballistic movements, large forces act across the lumbar spine. Without muscular protection, the joints in the lumbar spine would be subject to an excessive amount of shear force, leading to breakdown and injury, such as disc prolapse/degeneration, facet joint sprain and nerve damage. But the smaller transversus abdominis and multifidus alone will not have sufficient strength to counteract the shear forces produced by explosive movements. A well-developed PC system allows the athlete to secure global stability on a base of efficient local stability.

An emphasis on PC exercises in strength programmes will help to address some of the typical muscle imbalances encountered in athletes. Most strength-trained athletes, for instance, have an observable and functional quadriceps dominance because of their excessive reliance on squat-type movements. Squat-type movements will develop the PC muscles to an extent, but the force transfer of this movement tends to shift load on to the knee and quadriceps instead of the hip and PC muscles. The same thing happens with leg press movements. As a consequence, the athlete becomes quadriceps dominant over hamstrings, and thereby more at risk of knee and hamstring injuries.

Exercises

1. Romanian (stiff-legged) deadlifts

This is performed with barbell in hand, greater than hip width apart. The first movement is initiation of anterior pelvic tilt. This is performed by thinking about ‘sticking the bum out’ and then sitting back. Keeping a straight back and the knees flexed to 10-30 degrees, the weight is lowered to knee level. The lifter will feel a sensation of the hamstrings stretching. The position is held and then the body position is returned to the start.

2. Single-leg Romanian deadlifts

single-leg Romanian deadlifts

Similar to the Romanian deadlift above, but weight is taken on only one leg. The benefit is that the adductors and abductors are then required to stabilise the pelvis and stance leg whilst performing the movement. If done one-handed, say, on the right leg, holding the weight in the right hand will focus on more adductor recruitment, and if held in the left hand it will focus on more abductor recruitment.

3. Powerlifting deadlifts

This is the traditional power-lifter’s deadlift, lifting a barbell from the floor to the hips. Note, however, that the lifter must concentrate on keeping their chest high and shoulder blades together during the lift. This will ensure that the lumbar spine remains in neutral-to-slight-extension, and the force is generated by the hip extensors.

4. Back extension exercises

Back extension

This can be done on traditional roman chair benches, on the floor (with partner sitting on legs) or on a weights bench. It can be performed as a repetitive movement or as a sustained hold in extension. A good yardstick for the strength athlete is to be able to hold the body horizontal for three sets of 45 seconds before noticeable fatigue.

5. Reverse hyper-extensions

This is done lying prone on a bench with the hips at the end of the bench and the legs hanging over. Support is generated either by a partner applying weight to the upper body or the lifter holding on tightly to the bench. With the knees held in extension, and the feet and knees together, the gluteals are contracted and the legs are lifted to horizontal. This can be done as a slow movement, a holding movement or ballistically.

6. Nordic hamstrings

Nordic hamstrings

The origin of this one has been lost to this author, but it is a fantastic exercise to develop eccentric loading in the hamstrings. It is performed with the athlete kneeling on the floor or a bench with a partner firmly holding on to the ankles. The athlete keeps their arms folded across their body, their gluteals contracted firmly and the spine kept in neutral-to-slight-lumbar-extension.

The athlete then lowers the body forward with all the movement coming from the knee. Viewed from side-on, the thigh, hip, back, shoulders and head should all remain aligned. The athlete goes to the point where they feel they can no longer hold it, or their hips need to bend to maintain that position. They then return to the starting position. Top-heavy athletes (eg rugby players) will not drop as far as bottom-heavy athletes (eg sprinters) because of their centre of mass being higher. A caution to the uninitiated: this exercise will cause hamstring cramps and spasms the first time you do it!

A variation on this exercise is to lower to the point where the athlete feels they can no longer hold the position; then, maintaining body alignment, the athlete falls to the floor, using their hands to break the fall. This adds in a component of rapid eccentric contraction.

7. Single-leg bridging

This is done with the athlete lying on their back, and the foot up on a chair or Swiss ball (for those wanting a challenge). The body is raised off the floor so that weight is taken only on the heel of the foot and on the shoulders. The athlete attempts to align the heel, knee, hip, trunk and shoulders. Athletes should be able to do this comfortably with one leg.

A variation is to start with the knee flexed to 45 degrees, and then flexed to 90 degrees. Each position will load the PC in slightly different ways.

Programme structure

The above exercises can form the focus of an entire lower-body weight-training session. A good starting point is to work on 11 work-sets in total for the programme, periodised to fit in with other aspects of strength and conditioning. This can be varied from one work-set of 11 different exercises, through to one exercise of 11 sets. Repetitions and tempo can be varied to suit the athlete’s particular stage of training.

Example: Beginners
1. Single-leg Romanians 1 x 10 (3 sec lower; 3 sec hold; 3 sec return)
2. Romanian deadlifts 1 x 10 (3; 2; 3)
3. Back extension holds 2 x 30 seconds
4. Reverse hyper-extensions 1 x 10 (slow speed eg; 3; 3; 3)
5. Reverse hyper-extensions 1 x 10 (moderate speed 1; 2; 1)
6. Nordic hamstrings 2 x 6 (2; 2; 2)
7. Single-leg bridge (0 degrees) 1 x 10 (2; 2; 2)
8. Single-leg bridge (45 degrees) 1 x 10 (2; 2; 2)
9. Single-leg bridge (90 degrees) 1 x 10 (2; 2; 2)

Example: Intermediate
1. Romanian deadlifts 3 x 6 (2; 1; 2)
2. Deadlifts 3 x 6
3. Back extension holds 3 x 45 seconds
4. Nordic hamstring 3 x 6 (weight)

Do not be afraid of imposing heavy resistance sets in any of these exercises where you judge the athlete capable of doing them. Even Nordic hamstrings and bridging can have weight added to ensure the athlete works to failure on sets of four reps.

Chris Mallac

Illustrations by Viv Mullett

Reference:

  1. See, for example, Pool-Goudzwaard AL, Vleeming A, Stoeckart R, Snijders CJ and Mens JMA (1998) ‘Insufficient lumbopelvic stability: a clinical, anatomical and biomechanical approach to ‘a-specific’ low back pain’ Manual Therapy 3(1), pp 12-20.

back injury prevention exercises, nordic hamstrings