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Neuropathies

Acute nerve injuries can occur during weight training, but most neuropathies associated with the activity develop over weeks to months from repetitive traction or focal compression. The most common neuropathies associated with weight training include thoracic outlet syndrome, suprascapular neuropathy, scapular winging, musculocutaneous neuropathy, and notalgia paresthetica. Other conditions that have been reported in the literature include ulnar neuritis (18) and lateral plantar nerve entrapment (19).

Thoracic outlet syndrome.
There have been no reports of specific sports that cause thoracic outlet syndrome (TOS); however, any upper-limb activity can cause symptoms. Because there is no diagnostic "gold standard," the diagnosis and treatment of TOS are controversial. Some authors claim it is rare and largely overdiagnosed, while others claim it is common and underrecognized (20,21).

The subclavian vessels and the brachial plexus pass through several anatomic spaces at the thoracic outlet. In weight lifters, hypertrophy of the scalene muscles can impinge the subclavian vessels and the brachial plexus in the scalene or costoclavicular triangles. Pectoralis minor hypertrophy may impinge the same nerves and vessels in the pectoralis minor space during hyperabduction and external rotation of the shoulder. TOS can be neurogenic and/or vascular.

TOS should be considered whenever a patient reports vague upper-extremity symptoms. In "classic" neurogenic TOS, patients describe insidious upper-limb pain, ulnar hand paresthesias, and thenar weakness consistent with a lower trunk plexopathy. In the majority of patients who have suspected TOS, the history includes pain, nonspecific numbness in the hands, and subjective weakness. The objective physical examination, electromyography (EMG), and vascular studies are usually normal.

Provocative physical examination tests are used to detect TOS, but their specificity is rather low (22,23). One such test is the Roos hyperabduction/external rotation test, in which the patient opens and closes his or her hands for 1 to 3 minutes with elbows bent and arms abducted to 90° and externally rotated (24). The test is positive if the maneuver reproduces the patient's symptoms. But, again, the specificity of this test is low.

To confirm or rule out arterial compression, the physician should examine the supraclavicular or infraclavicular fossa for a mass or bruit, palpate all distal pulses, and take blood pressure measurements of both arms. Laterally rotating the patient's head and extending it backward may increase the accuracy of tests for arterial compression, as can asking the patient to perform Valsalva's maneuver. EMG can be diagnostic if performed proximal to the areas of compression.

For symptomatic patients who test positive for the provocative maneuvers and for those in whom no definitive abnormality can be identified--and TOS is still suspected--management should focus on muscle strength balance between the anterior and posterior thorax, stretching of the pectoral muscles and the anterior shoulder, and patient education about avoiding provocative positions.

Suprascapular neuropathy.
The suprascapular notch, under the transverse scapular ligament, is the most common site for impingement of the suprascapular nerve (figure 6: not shown). Compression of this nerve affects both the supraspinatus and infraspinatus muscles. At this level, the nerve can be traumatized by repetitive shoulder abduction, as in the military press (25,26).

Patients typically present with gradually increasing pain with or without weakness. The weakness may not be apparent to the patient until late in the course when atrophy is noticeable.

The clinical distinction between atrophy from rotator cuff injury and atrophy from suprascapular neuropathy can be difficult, but examining the muscles involved and assessing the degree of atrophy may help differentiate the conditions. Atrophy involving only the supraspinatus muscle could be seen with a supraspinatus tear, but would be unusual for suprascapular neuropathy, which can lead to atrophy in both the supraspinatus and infraspinatus muscles. Isolated infraspinatus atrophy would be unusual for a rotator cuff injury, but could suggest compression of the infraspinatus branch of the suprascapular nerve at the spinoglenoid notch, perhaps from a ganglion cyst.

Nerve conduction studies of the suprascapular nerve and needle EMG can assist with the diagnosis. Magnetic resonance imaging of the shoulder can confirm the integrity of the rotator cuff tendons and can rule out a neuroma in the suprascapular notch (27).

Treatment involves pain medication, gentle assisted range-of-motion exercises to avoid contracture, and strengthening exercises for surrounding muscles--the rhomboids, latissimus dorsi, trapezius, serratus anterior, and especially the scapular stabilizers. Patients can gradually strengthen the affected muscles when pain is gone and the muscle can be moved against some resistance. An EMG may be helpful to document evidence of reinnervation; if the condition is present, strength training can gradually be initiated in a controlled manner. If nonoperative treatment fails, surgery may be needed.

Scapular winging.
Scapular winging is caused by weakness of the serratus anterior muscle from a long thoracic nerve injury, or by weakness of the trapezius muscle from an accessory nerve injury (cranial nerve XI). The injury mechanism is not clear; in many cases, these injuries are idiopathic. No specific exercise has been found to predispose patients to scapular winging, but perhaps the pads on some machines that rest on the shoulders (ie, calf raises, leg presses) could contribute to injury.

Scapular winging from long thoracic nerve palsy is typically more prominent at the inferior medial border of the scapula with shoulder flexion, whereas accessory nerve palsies cause superior medial scapular winging (28).

The diagnosis should include laboratory tests to screen for infectious and inflammatory causes, as well as EMG and nerve conduction studies to establish the level of injury. Treatment consists of relative rest and close follow-up--scapular winging often resolves spontaneously within 3 to 24 months.

Musculocutaneous neuropathies.
In a report (29) of three patients who had musculocutaneous neuropathies, all occurred in the patients' dominant arm and spared the coracobrachialis muscle. The patients' symptoms were precipitated by repetitive biceps curls. Symptoms included biceps muscle pain and weakness. Theoretically, symptoms are caused by impingement of the musculocutaneous nerve from coracobrachialis muscle hypertrophy. Because the symptoms of C-5 or C-6 cervical radiculopathy, brachial plexopathy, and biceps muscle rupture are similar, EMG may be required to establish the diagnosis.

Management is nonoperative, consisting of activity restriction. The three patients described above regained biceps and brachialis muscle function within 3 months (29).

Notalgia paresthetica.
Notalgia paresthetica is thought to be caused by a lesion of a thoracic dorsal primary ramus. It's not known if this condition is seen in weight trainers; the injury mechanism is essentially unknown. Patients typically report chronic pain and sensory symptoms that are frequently described as intense itching in an area 4 to 10 cm in diameter over the thoracic paraspinal muscles at the inferomedial scapula.

Capsaicin can help alleviate symptoms (30). It acts by depleting the local C fiber store of neuropeptides, which are the principal substance responsible for transmitting pain and itching.


Chronic Medical Conditions

Vascular stenosis.
Though uncommon, vascular stenoses may result from repetitive trauma to a blood vessel. Several cases of external iliac artery stenosis in the region of the inguinal ligament have been reported in bicyclists (31). Khaira et al (32) reported on a young bodybuilder who had a similar injury. They hypothesized that the injury resulted from repetitive hip flexion during leg press and squat exercises. Symptoms may include anterior thigh pain. The diagnosis may require vascular studies; treatment in bicyclists has involved vessel grafting.

Weight lifter's cephalgia.
Weight lifters headache is generally sudden in onset and occurs during active lifting (33-35). In many cases, the weight training exercise being performed at the time of headache onset was the bench press. The pain is described as burning or boring in quality and localized to the posterior head and neck. Though onset is abrupt, the headache may persist for several days to weeks, gradually resolving. No clear cause has been identified; the presumed mechanism is ligament or soft-tissue injury.

Initial management consists of avoidance of weight training, cervical range-of-motion exercises and stretches, and pain medication. After a patient's pain resolves, training technique should be reviewed to eliminate incorrect technique.

Weight lifter's heart.
Physiologic stress on the cardiovascular system during weight training changes the myocardial architecture in "weight lifter's heart (36)." The intraventricular septum thickens relative to the ventricular free wall (37). The condition may be inaccurately diagnosed as hypertrophic obstructive cardiomyopathy (HOCM); however, the ratios of intraventicular septum thickness to body surface area and of ventricular free wall thickness to body surface area are the same in weight trainers and controls (37). In patients who have HOCM, these ratios are significantly greater than in controls.

Hernias.
Though hernias are commonly mentioned in association with weight training, and popular weight lifting magazines have many advertisements for hernia repairs, no incidence or prevalence studies have been completed.


Know What to Expect

Becoming aware of the host of chronic conditions that can arise during weight training will help physicians make more efficient use of the time they spend with the next weight trainer who walks through the door with, for example, vague upper-extremity symptoms or a sore shoulder. Questioning patients about their weight lifting practices and making them aware of incorrect technique can help them get back to their fitness routines faster and enable them to work out pain free.

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Dr Reeves is chief resident, Dr Laskowski is a consultant, and Dr Smith is a senior associate consultant in the department of physical medicine and rehabilitation at the Mayo Clinic in Rochester, Minnesota. Dr Laskowski is codirector and Dr Smith is a staff physician at the Mayo Sports Medicine Center, and Dr Laskowski is an associate professor and Dr Smith is an assistant professor at Mayo Medical School in Rochester. Address correspondence to Edward R. Laskowski, MD, Mayo Sports Medicine Center, 200 First St SW, Rochester, MN 55905; e-mail to laskowski.edward@mayo.edu.