SportsMed: Minimizing back injury risks in the weight room

Weight training programs should result in reduction of injury-risk, along with gains in muscle strength, power, endurance and improvement in sport performance.

Excessive mechanical stresses imposed on muscles and joints during weight training may directly cause an injury, or they may contribute to an injury that occurs during sport practice or competition. Recovery from these injuries may be prolonged by improper load or progression, or erroneous and ill-timed techniques employed during training or rehabilitation.

Common causes

The most common causes and types of weight training injuries are listed in Figure 1 below. The back, knee and shoulder are the three most commonly injured areas. Many back problems are exacerbated by poor training programs, in which the mechanism of injury is unknowingly incorporated into the lifting technique.

The most frequent contributing factors to back injury in the weight room include extreme flexion (hyperflexion), extreme extension (hyperextension) and rotation (torsion).

Hyperflexion occurs when the low back is allowed to round, and the weight is jerked up (e.g., rows, dead lifts and bent barbell rows). Hyperextension places excessive compression on the posterior aspects of the vertebrae. Thus, exercises such as the bench press, unsupported overhead press, power clean, ballistic back extensions, prone leg curls and squats must be supervised closely. Rotational or twisting-type activities frequently occur in combination with flexion or extension, which places the spine in an extremely vulnerable position.

Remember that the intervertebral disc, or the spine in general, has only a limited number of bends before damage is incurred. These bends need to be saved for competition rather than being used up in training and conditioning programs. This requires creative exercise design to challenge the trunk and core without excessive flexion, extension or rotation.

Unfortunately, there are currently no validated guidelines for lifting volume. We simply do not know how much weight or how many lifts are too many. What is known, however, is that the risk of lifting-related low back injury increases as the demands (load and frequency) of the task increase. Increases in load elevate the spine and disc compression forces. In the occupational setting, load is one of the strongest risk factors for low back injury. This risk increases substantially when movement mechanics are not optimal.

Focus on young athletes

A point about resistance training for young athletes should be addressed. The National Strength and Conditioning Association has recommended adherence to age-specific training guidelines since 1996. A position statement from the National Athletic Trainers’ Association¹ recommends that progression for children should not be increased more than 10 percent in terms of training intensity, load, time or distance. To allow for adequate adaptation and to avoid overload, increase either reps or weight by 10 percent each week, and not both. Vigorous activity should be limited to no more than 16 to 20 hours per week.

Protecting the lumbar spine in the weight room is critically important, particularly if there is a history of back pain. A previous low back injury episode presents a three to six times greater risk for future injury. The presence of pain at the start of a sport season may result in as much as a six-fold increase in injury risk.

This suggests that a motor control impairment may predispose an individual to recurrent injury. This impairment is subtle, but may be a “smoking gun” explanation for the high incidence of recurring back problems. An important concept to embrace is that core muscles function differently than limb muscles, and therefore should be trained differently. The key is to generate power through the hips, which is transmitted through a stiffened core.

This is quite different from challenging the core muscles (e.g., abdominals) through repeated spine flexion or rotation, which is not a good way to train the core. Core muscles function to brace the trunk during motion, acting more as stabilizers than movement generators. Activities that emphasize a push, pull, lift or carry enhance hip power generation through a stiffened core.

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Programs should incorporate exercises that fulfill these tasks, rather than using isolation exercises for the abdominals or back that create “energy leaks” through bending. More motion in the back may increase injury risk. Strength without control increases the risk for injury, as well as lack of endurance to repeatedly execute movements with perfect form.

Although no direct relationship between core training and sport performance has been established, an association between core training and back injury risk reduction is evident. This is a critical component that must be established before a more traditional weight lifting program is initiated.

Preseason and in-season core training should emphasize development of core strength and lower extremity power (Figure 2).

The goal for postseason and offseason core training is to increase core muscle endurance (Figure 3).

The design and progression of a core training program is dependent on the specific demands of the sport or activity, and the performance capabilities/deficiencies of the athlete. The back extensor muscles are frequently undertrained due to the “training what you see syndrome.”

The initial stage of a program should emphasize the posterior muscle group at a ratio of 2-to-1 or 3-to-1 with respect to the front muscle groups. The abdominal muscles make an important contribution to the core stabilization required for heaving lifting. They are essential for counteracting large compressive and twisting loads. Furthermore, muscles imbalances should be addressed.

Tight hip flexors and quadriceps, along with weak hamstrings and gluteal muscles, limit power, range of hip extension and posterior trunk acceleration.

Core exercise stages

Progressive core exercise stages outlined by Dr. Stuart McGill² include:

1. Corrective/therapeutic exercise
2. Groove motor patterns
3. Whole body and joint stability
4. Increase endurance
5. Build strength
6. Develop speed, power and agility

The first two stages are corrective in nature, which should be developed and supervised by an exercise or rehabilitation specialist who has expertise in injury assessment and reconditioning. Stage three would be an appropriate place to start athletes with no prior low back pain/injury history. Once whole body stability and adequate endurance are achieved, the strength stage can begin. Emphasis on the “surrounding the dragon” principle targets joints above and below the core.

Stage five exercises include body weight resistance exercises (e.g., push-ups, pull-ups, etc.) and squats. Both fast and slow sessions can utilize exercises with dumbbells, cables and resistive bands.

Stage six focuses on maintaining a braced core during performance of training motions. Exercises are chosen to accomplish several goals at once (balance, stability, strength, power). This late-stage program focuses less on specific areas of the body and more on asymmetric activities. They include a push (one-arm cable push with stiffened core); carry (one-armed suitcase carry); lift (kettleball swing); or torsional back (rotation challenge with no actual spine twisting).

Functional lift and carry exercises can be extended to many sport levels. By emphasizing three-dimensional joint torques, each joint in the kinetic chain contributes to performance of the task. Asymmetric exercises may assist in training torso bracing and building strength to support the hips, pelvis and spine, all of which are all essential for minimizing back injury risk. Such exercises may also enhance the benefits derived from traditional lifting-based strength programs.

References

¹McCleod T, et al. National Athletic Trainers’ Association Position Statement: Prevention of Pediatric Overuse Injuries. J Athl Train. 2011. 46(2): 206–220.

²McGill S. Core Training: Evidence Translating to Better Performance and Injury Prevention. Strength Cond J. 2010. 32(3): 33-46.

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