Weight training

Training completed by overcoming resistance is called “resistance training.” Weight training is a method of resistance training in which a load (in the form of free weights or a weight stack on a machine) is pushed or pulled as a form of resistance. Weight training can be used as a component of a general fitness program or as part of overall training in order to improve an individual’s capability for sports performance or to satisfy overall fitness goals.

Power lifting is a specific sport in which three lifts are executed: the squat, bench press, and deadlift. Weight lifting (also known as Olympic lifting) is a separate sport in which the lifts performed include the snatch and the clean and jerk. Bodybuilding is a performance competition emphasizing an appearance of extreme muscular hypertrophy achieved by weight training. In the vernacular, “weight lifting” is often used interchangeably with “weight training,” and will be used as such in this article.

Nervous system injury can occur in relation to the process of weight lifting or through drugs such as anabolic steroids or growth hormone used to enhance the effectiveness of training. Nervous system injury can result from the injection, the physiologic effects of the substances used, or the resultant muscular hypertrophy as a contributor to injury. The use of these drugs and other supplements, both legal and illegal, is reported to be common and increasing.

Peripheral nervous system

An excellent, recent review of peripheral nerve injury in weight lifters and bodybuilders incorporating all aspects of diagnosis, pathophysiology and treatment has recently been published.

Peripheral nerve injuries are relatively uncommon in cohort studies that examine types of injury associated with sporting activities, with an estimate that peripheral nerve injuries account for perhaps 0.5% of all injuries associated with athletic endeavors. When specifically related to injuries caused by weight training, the percentages of injuries in studies of 71 power lifters and 354 high-school football players that involved nerve injury were 3.1% and 3.7%, respectively.

Chronic damage to the PNS caused by weight training may occur secondary to prolonged compression or traction of nerves, caused either by the positions and movements required while weight lifting or by the resultant muscular hypertrophy or soft tissue injury. Chronic PNS injury of this type is more common than acute injury, which appears to be rare. Chronic or acute compressive injury often produces a combination of focal segmental demyelination and focal axonal injury.

In two case series examining nerve injury in athletes in a single EMG laboratory, the percentages of confirmed PNS injuries caused by weight lifting were only 16% and 15%, respectively. Several other nerve injuries in athletes from other sports, however, were felt to be related to weight training undertaken for these sports, suggesting that this may be an underestimation.

Distinguishing nerve injuries from more common soft tissue injuries is important in considering the need for investigations, determining prognosis, and assessing the need for aggressive or operative management. Clinical diagnosis can be supplemented by nerve conduction studies and electromyography. In the vast majority of cases cited in the literature, avoidance of the provoking activity (thereby removing the injurious stimulus) and rest usually achieve significant if not complete recovery. This speaks to the nature of the injury, which is usually caused by chronic compression, without nerve laceration or transection.

Peripheral nervous system

An excellent, recent review of peripheral nerve injury in weight lifters and bodybuilders incorporating all aspects of diagnosis, pathophysiology and treatment has recently been published.

Peripheral nerve injuries are relatively uncommon in cohort studies that examine types of injury associated with sporting activities, with an estimate that peripheral nerve injuries account for perhaps 0.5% of all injuries associated with athletic endeavors. When specifically related to injuries caused by weight training, the percentages of injuries in studies of 71 power lifters and 354 high-school football players that involved nerve injury were 3.1% and 3.7%, respectively.

Chronic damage to the PNS caused by weight training may occur secondary to prolonged compression or traction of nerves, caused either by the positions and movements required while weight lifting or by the resultant muscular hypertrophy or soft tissue injury. Chronic PNS injury of this type is more common than acute injury, which appears to be rare. Chronic or acute compressive injury often produces a combination of focal segmental demyelination and focal axonal injury.

In two case series examining nerve injury in athletes in a single EMG laboratory, the percentages of confirmed PNS injuries caused by weight lifting were only 16% and 15%, respectively. Several other nerve injuries in athletes from other sports, however, were felt to be related to weight training undertaken for these sports, suggesting that this may be an underestimation.

Distinguishing nerve injuries from more common soft tissue injuries is important in considering the need for investigations, determining prognosis, and assessing the need for aggressive or operative management. Clinical diagnosis can be supplemented by nerve conduction studies and electromyography. In the vast majority of cases cited in the literature, avoidance of the provoking activity (thereby removing the injurious stimulus) and rest usually achieve significant if not complete recovery. This speaks to the nature of the injury, which is usually caused by chronic compression, without nerve laceration or transection.

Median nerve

Median nerve entrapment at the wrist, referred to as carpal tunnel syndrome (CTS), is the most common entrapment neuropathy seen in the general population. Typical symptoms include numbness, tingling, and pain in a median nerve distribution. A nocturnal predominance to episodic symptoms is characteristic. Weakness and wasting in median innervated hand muscles can be seen in more severe cases.

The nerve injury occurs as a consequence of chronic, repeated mechanical compression that results from a combination of positioning with wrist flexion and external factors, including local soft tissue edema and hypertrophy. Repetitive, forceful, muscular activity of the hand and wrist is also seen as a contributing factor to the development of CTS. As such, weight training involving the upper extremities can be considered a risk factor for the development of CTS.

In one study of athletes who had peripheral nerve injuries on EMG, the majority of cases of CTS were seen in weight lifters. In a series of athletes assessed with electrodiagnostic studies, median nerve injuries were seen in 28 of 190 sports-related nerve injuries. Of these, 24 were cases of CTS, 6 symptomatic and 18 asymptomatic. Three of the symptomatic cases occurred in athletes identified as weight lifters; in the others, identified as wrestlers or football players, weight training was included as regular part of their training regimen.

A case series of pediatric patients who had CTS was reported that included 13 male patients who frequently participated in weight training, suggesting that this may have been associated with the development of the condition, because the rate of CTS is generally low in children.

Case reports have described competitive bodybuilders who developed bilateral carpal tunnel syndrome while using recombinant human growth hormone to enhance muscular hypertrophy achieved by weight training, a not uncommon practice among competitive bodybuilders. In one case, the bilateral CTS was accompanied by bilateral ulnar neuropathies. It is thought that this is similar to the pathophysiology seen in acromegalics, with soft tissue hypertrophy secondary to elevated systemic levels of growth hormone.

Acute, self-limiting CTS was also described in a bodybuilder who underwent a “body sculpting” procedure with tumescent liposuction, where fluid is injected into the subcutaneous fat to aid in fat removal. It is felt that fluid redistribution may have occurred, leading to swelling within the carpal tunnel to produce this acute, temporary nerve compression.

Treatment modalities for CTS include splinting, local steroid injections, and carpal tunnel release surgery.

More proximal median neuropathies, pronator syndrome (PS) and anterior interosseous neuropathy (AIN), can be seen in the elbow and forearm region. Although most athletic median nerve injuries are found at the elbow, few are specifically described in association with weight lifting. PS, with proximal median nerve compression at the elbow, generally presents with activity-provoked, deep, proximal, volar, forearm pain. This may be associated with parathesiae in a median nerve distribution. AIN classically presents with proximal, volar forearm pain worsened by exercise involving the affected limb. Weakness of the flexor digitorum profundus and flexor pollicis longus muscles lead to the inability to completely flex the distal phalanges of the index finger and thumb. Both PS and AIN are reported to be associated with weight lifting, in which repetitive forceful gripping and pronation are required. Muscular hypertrophy in the forearm is considered a risk factor for these conditions. There is a single reported case of AIN that initiated during weight training, although no details were provided as to the presence or absence of muscular hypertrophy in this particular patient.

Ulnar nerve

The ulnar nerve is most commonly injured at the cubital tunnel or ulnar groove at the elbow and within Guyon’s canal at the wrist. Both sites of injury are seen in weight lifters and bodybuilders.

Ulnar neuropathy at the elbow is a common condition in the general population. The injury occurs secondary to a combination of direct compression of the ulnar nerve (caused by resting the elbow on hard surfaces) and tension of the ulnar nerve around the elbow caused by prolonged flexion of the elbow joint. This is also true in athletes. Symptoms of ulnar neuropathy typically include numbness and tingling in the medial aspect of the hand—potentially involving both the volar and dorsal surfaces—as well as in the medial one-and-a-half digits. Symptoms often have a nocturnal predominance. Weakness and wasting of ulnar innervated hand muscles can develop in more severe entrapment of the ulnar nerve.

Weight lifting occasionally be causative for at the elbow, because many exercises completed in the gym may involve resting the elbow on a firm or partially padded surface to minimize use of other muscles, such as when doing bicep exercises. It is also noted that muscular hypertrophy of the medial head of the triceps or the flexor carpi ulnaris can lead to acquired compressive ulnar neuropathy. Such hypertrophy is not uncommon in weight lifters and bodybuilders. A surgically treated case of ulnar neuropathy at the elbow in a competitive weight lifter allowed for direct visualization of compression of the ulnar nerve between the heads of the flexor carpi ulnaris.

Specific case reports or case series of ulnar neuropathy at the elbow directly related to bodybuilding and weight lifting are few in the medical literature, perhaps because this is a common condition in the general population, and although cases may be related to activities of weight training, the underlying problem is one of tension and compression of the ulnar nerve at the elbow, and therefore is considered unremarkable.

Bilateral ulnar neuropathies at the elbows were described as part of a multi-entrapment syndrome in a bodybuilder using growth hormone to supplement his strength training. The pathophysiology was proposed to be increased soft tissue swelling caused by the growth hormone combined with the repetitive activities while lifting weights.

Snapping of the medial head of the triceps over the medial epicondyle at the elbow is not uncommon, and can occur in susceptible individuals with either extension or flexion of the elbow. This is associated with displacement of the ulnar nerve, potentially causing nerve injury. A case series of 17 patients who had recurrent displacement of the medial head of the triceps included a description of 9 patients who had symptoms (one bilateral) attributable to ulnar neuropathy. It was noted by the study authors that weight lifting activities, particularly those with resisted flexion at the elbow past 90° or resisted extension, may produce triceps snapping. It was further noted that several of the symptomatic patients had first noted symptoms only after beginning extensive weight training, suggesting that relative hypertrophy of the triceps may also be a contributor to this condition. A further 2 patients were subsequently described by the same author with a similar presentation after initiating weight lifting.

There is a single case report that described rupture of the tendon of the triceps in a power lifter, with subsequent hematoma formation causing acute compression of the ulnar nerve. Although other cases of triceps tendon rupture have been published, no other reports describe such secondary ulnar nerve injury.

Ulnar nerve injury at the wrist is less common than ulnar neuropathy at the elbow. With a distal ulnar neuropathy, various combinations of injury to the distal motor and sensory branches can occur, depending on the exact site of the nerve injury in Guyon’s canal.

Ulnar neuropathy at the wrist can be provoked by strength training exercises that involve lifting weights with the hands, because direct compression on Guyon’s canal can result. Several patients have been diagnosed with such, thought to be related to gripping barbells in an improper fashion, thereby increasing the pressure applied over Guyon’s canal to produce nerve injury. This is also reported as having been seen in one of 180 nerve injuries demonstrated on EMG in a case series looking at nerve injuries sustained in various athletic endeavors. In a patient who underwent serial electrodiagnostic testing, multiple repetitions of exercises with weights held across the lower to mid palm induced direction compression of Guyon’s canal, leading to conduction block in the ulnar nerve at the wrist that improved with cessation of exercise.

Similar ulnar nerve entrapment has also been described in a patient undertaking a regimen of push-ups on a hard surface; EMG demonstrated isolated injury to the first dorsal interosseous muscle of the affected hand. Symptoms resolved over 3 months with cessation of the excessive push-ups.

Radial nerve

Proximal radial neuropathy can occur because of weight lifting, although actual reports are rare. Patients who have proximal radial nerve injury typically present with weakness of wrist and finger extension and sensory alteration over the lateral dorsal aspect of the hand. Proximal radial neuropathy may also cause weakness in supination and elbow. More proximal injury of the radial nerve may lead to weakness of the triceps and altered sensation of the posterior upper arm.

A 45-year-old elite bodybuilder presented with a gradual-onset wrist drop over 2 weeks, without provoking trauma. Clinical and electrophysiologic evaluation showed a severe, axonal radial nerve lesion at the level of the spiral groove, and surgical exploration revealed compression by a markedly hypertrophied teres major. It was felt that the nerve injury was as a direct result of the patient’s bodybuilding and subsequent muscular hypertrophy.

More distal involvement of the radial nerve, posterior interosseous nerve (PIN), may also be associated with weight training. Radial tunnel syndrome (RTS) has occurred in a power lifter who used anabolic steroids to boost performance. Pain developed in the region of the right brachioradialis during specific exercises, and this pain could be reproduced with deep palpation over the same location. There were no motor or sensory deficits on history or examination; electrophysiologic studies were not completed. Transient relief occurred with injection, and the symptoms subsequently resolved with cessation of the excessive weight lifting. It was hypothesized that the extreme muscular hypertrophy of the supinator muscle predisposed the patient to PIN entrapment.

Radial nerve injury has also been reported as a complication of steroid injection. A recreational bodybuilder presented with sensory alteration in the territory of the left distal radial nerve and mild wrist extensor weakness following the self-injection of steroids into the left triceps, producing trauma to the radial nerve.

Musculocutaneous nerve

The musculotaneous nerve (MCN), an uncommon site of injury in the general population, can be injured in weight lifters. MCN injury presents as painless weakness of elbow flexion, which can be accompanied by sensory alteration in the territory of the lateral antebrachial cutaneous nerve. In two male weight lifters using anabolic steroids presenting with weakness and atrophy of the biceps, electromyograph (EMG) identified denervation in the biceps muscle. This nerve injury may have resulted from either direct compression of a terminal motor branch of the MCN (related to muscular hypertrophy) or from stretching of the MCN nerve during weight training. In another small case series, two of three patients reported to have MCN injuries with EMG confirmation had a history of habitual weight lifting.

Injury to the MCN has been reported in a patient who did excessive, frequent push-ups, leading to onset of progressive atrophy of the left upper arm and decrease in elbow flexion strength, with electrophysiologic studies demonstrating neurogenic changes within the biceps and brachialis consistent with injury to the MCN.

Suprascapular nerve

The suprascapular nerve (SSN) is typically injured in volleyball players and baseball pitchers, in whom repetitive overhead motions occur, but SSN injury is also reported as a consequence of weight training. The nerve can be injured at the suprascapular notch (thus affecting both the supra- and infraspinatus muscles) or at the spinoglenoid notch (affecting the infraspinatus in isolation). The latter of the two sites is more commonly seen in injury caused by weight lifting or bodybuilding. In some cases, anatomic abnormalities such as ganglia are present at the suprascapular or spinoglenoid notch, and the neuropathy may be related more to this than the muscular hypertrophy common to other weight lifting and bodybuilding entrapment neuropathies.

In a series of 28 patients who had EMG-documented SSN injury, 16 had symptoms related to athletic activities. Of these, one was identified as a bodybuilder and another as a weight lifter. Two separate case series of peripheral nerve injuries in weight lifters each include a case of SSN. One case occurred in a female bodybuilder who was using anabolic steroids, whereas the other was in a recreational weight lifter not taking steroids. Both presented with mild pain with SSN injury present at the level of the spinoglenoid notch, with isolated denervation in the infraspinatus muscle found during EMG.

Other weight lifting-induced injuries at the level of the suprascapular notch have also occurred soon after an aggressive weight training program was initiated. In both cases, a suprascapular localization for SSN injury was documented by both EMG and MRI, and in one patient, surgical release of the nerve at the suprascapular notch led to a full recovery.

Long thoracic nerve

Long thoracic nerve (LTN) injury leads to isolated weakness of the serratus anterior muscle and to scapular winging. This has been reported in association with weight training activities in a very small number of cases. Bilateral LTN palsies have been described in a single patient undertaking a weight training program without other obvious contributing causes.