There are several factors that can contribute to getting injured in sports. Most commonly discussed are overtraining, undertraining or improper kind of training along side poor technique. As an example, in triathlon 80-85% of injuries are due to functional overuse1. The underlying culprit to all those factors in many instances is, however, muscle imbalance.

Muscle imbalance is by definition an alteration of muscle length surrounding a joint. Certain muscles become shortened and overactive while the opposing muscles become lengthened and weaker due the phenomenon knows as reciprocal inhibition. Put in simple words, the body is designed so that when a prime mover, such as biceps brachii, for example, fires, the opposing muscle, in this case triceps brachii, needs to relax for the movement to happen. The brain cannot distinguish when the prime mover is acutely engaged or when it is chronically shortened and overactive, therefore it will shut off the opposing muscle in either instance. A good example would be an overactive illiopsoas causing a weakened gluteus maximus.
In the early 1970s Janda described three basic postural distortion syndromes that translate into movement impairments2.
Lower Crossed Syndrome
Lower crossed syndrome is characterized by increased arching of the back also know as increased lumbar lordosis and anteriror pelvic tilt. The overactive muscles in this case are hip flexor complex as well as latissimus dorsi and erector spinae, while gluteus maximus and medius, internal oblique and transevrse abdominis are commonly weak and lengthened.
A common injury related to the lower crossed syndrome is a hamstring complex strain. Biomechanical analysis shows that hamstrings are active for the entire gait cycle with the peak during the terminal swing and early stance phases3. Of the two phases the terminal swing phase is considered to be more hazardous because muscle-tendon units are at their maximum length or the gait cycle and must heavily activated. One of the major risk factors for developing a hamstring strain is indeed strength imbalance. The low ratio of knee flexor to knee extensor strength (also known as hamstring (H) to quadriceps (Q) ratio) is the most significant. Athletes (in this study football players were assessed)3 with a ratio H:Q less than 0.5 are believed to be at an elevated risk of hamstring strain injury. The best course of treatment is correction of the imbalance: releasing the quadriceps (using foam roller for 30 sec on each sensitive spot on the quadriceps followed by static stretching) and strengthening the hamstrings.
Upper Crossed syndrome
The upper crossed syndrome is characterized by rounded shoulders and forward head posture. Overactive and shortened muscles in this case are pectoralis major and minor, subscapularis, latissimus dorsi, levator scapulae, upper trapezius and sternocleidomastoid to name the major ones. The lengthened and weak muscles include (but are not limited to) rhomboids, lower trapezius, serratus anteriror and deep cervical flexors.
A common injury related to the upper crossed syndrome is functional shoulder impingement. Shoulder impingement accounts for 44-65% of shoulder injuries4. There are two kinds of shoulder impingement: structural and functional. Due to the nature of this article the focus will be placed on the later. Functional impingement occurs due to glenohumeral instability and is most common in overhead athletes over the age of 354. The main contributor to stability in the shoulder is the muscular system hence any imbalance between agonistic and antagonistic muscles in terms of strength and flexibility will likely result in dysfunction and consequent injury. A tight pectoral (major) musculature will create an anterior pull on the glenohumeral joint leading to instability. A tight pectoralis minor, on the other hand, will alter proper scapular motion (when the arm is moved to the side greater than 30 degrees, the shoulder blade must upwardly rotate, tilt and externally rotate to allow for the arm to move properly). Releasing the pectoral girdle using the foam roller (see appendix) together with strengthening the middle and lower trapezius would be a good start. Further, overly active deltoid, can generate excessive force and “jam” the humerus in the socket of the shoulder causing pain when moving the arm when swimming for example. The over active deltoid musculature needs to balanced by the rotator cuff. The best exercises to strengthen the middle/lower trapezius and the rotator cuff were presented in the article “Coaching Tips to Gain Swimming Speed” written by this author and published in the March Newsletter.
Pronation distortion syndrome
Pronation distortion syndrome is characterized by excessive foot pronation. The overactive and short muscles in this case are peroneal muscles, gastrocnemius, soleus, iliotibial band, hamstring and adductor complex as well as iliopsoas. Weak and lengthened muscles are porterior and anterior tibialis, vastus medialis, gluteus medius, maximus and external hip rotators.
A common injury related to the pronation distortion syndrome is patella-femoral pain syndrome (PFPS) also known as runners knee. Research shows that one of the most common factors contributing to PFPS is muscle imbalance between the medial and lateral quadriceps muscles5. Vastus medialis obliquus (VMO) is a medial stabilizer of the patella and is often overpowered by the vastus lateralis. Further, tightness in the iliotibial band can alter the patellar excursion and cause lateral patellar tilt as well as lateral tracking. A good strategy to correct the imbalance is myofascial release of the TFL and quadriceps on the foam roller, followed by static stretching of both muscles. Despite common practice research has not confirmed the effectiveness of exercises aiming to isolate VMO, therefore the agreement to rehabilitate PFPS seems to be inclusion of dynamic strengthening such as step down with controlled eccentric motion, which also engages the core and the hip musculature.
There is a quick and reliable test to gain a general insight in muscle imbalance and it is called an Overhead Squat.
Overhead Squat
The overhead squat is executed with bare feet on firm ground. The subject lifts the arms over the head and squats down as close to parallel to the ground as he or she can without lifting the heels. The observation is done form the front (anterior) side (lateral) and the back (posterior). In each instance the subjects squats five times. From the front the observer looks at the knee (are they travelling inward or outward) and ankles (are the toes moving outward). From the side the observer checks for the excessive forward lean, arms falling forward and arching or rounding of the lower back. The rear view checks for the collapse of the arches (excessive pronation).
Each movement alteration indicate over and under-activity of a respective muscle and calls for an intervention that includes releasing and lengthening overactive and short muscles while re-engaging the inhibited muscles.
A typical scenario would include overactive gastrocnemius and weak anterior and posterior tibialis. The best way to treat gastrocnemius is perform a self myofascial release on the foam roller by holding on the tender area for at least 30 seconds followed by a static stretch. To engage the anterior and posterior tibialis towel scrunches 10-15 reps with 2-second hold plus, 10-15 repetitions of weighted cable pulls with the foot (dorsiflexion) also with a 2-second hold and 4-second eccentric release. The dynamic strengthening would include a single balance reach forward, back and to the side (touching cones with the foot).
Balance in anything with do in life is the best recipe for success and muscle balance is no exception. For initial evaluation and consultation I can be reached through D3 Multisport.
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REFERENCES:
1). Migliorini, Sergio. “Risk Factors and injury mechanism in Triathlon.” Journal of Human Sport & Science 6 (2011): 309-314.
2) Clark, Michael, Lucett Scott. NASM Essentials of Corrective Exercise Training. Baltimore: Lippincott Williams & Wilkins, 2011
3) Opar, David A et all. “Hamtring Strain Injuries.” Sport Med 42 (2012):209-226
4) Page, Phil.”Shoulder Muscle Imbalance and Subacromial Impingement Syndrome in Overhead Athletes.” IJSPT 6 (2011): 51-58
5) Collado, Herve, Frederickson, Michael. “Patellofemoral Pain Syndrome”. Clin Sport Med 29 (2011): 379-398
6) Hirth, Christopher. “Clinical Movement Analysis to Identify Muscle Imbalances and Guide Exercise. Athletic Physical Therapy Today 12 (2007):10-14

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