Are Neuromuscular Disorders That Cause Fatigue a Contraindication to Sports Participation? A Case Report and Narrative Review of the Literature

Abstract

Engaging in sports, particularly at a competitive level, requires sustained muscle contractions before the onset of physical fatigue. Fatigue is highly prevalent in neuromuscular diseases, especially those affecting neuromuscular transmission (e.g., myasthenia gravis) or muscle membrane excitability (e.g., myotonia, certain metabolic myopathies). A decremental response in repetitive nerve stimulation (RNS) represents the neurophysiological analogue of exercise-induced muscle weakness. Patients with such responses exhibit abnormal suppression of muscle activity during repetitive or prolonged effort. Consequently, it is often assumed they should avoid strenuous physical activity. To assess the safety of sports participation in individuals with fatigability-related neuromuscular disorders, we examined the literature and report a new case of a patient with myotonia congenita who engaged in competitive sports without adverse events. The review identified only a few cases involving patients with myasthenia gravis or muscular dystrophies who also participated in competitive sports safely and with favorable outcomes. No adverse events were reported. While these findings suggest that sports participation may be feasible for selected patients, they cannot be generalized. Large-scale studies involving athletes with neuromuscular conditions are needed to evaluate the safety and long-term impact of exercise in these populations.

1. Introduction

Fatigue is a common complaint among both healthy individuals and patients suffering from acute or chronic medical conditions. Muscle fatigue is generally divided into two components: central and peripheral [1]. Central fatigue originates in the central nervous system (CNS) and is believed to impair central neural drive to lower motor neurons, affecting their excitability [2]. Peripheral fatigue can be objectively assessed by measuring force production after stimulation following strenuous exercise. Motor units typically fire at a frequency of 50–60 Hz to maintain force. When motor unit firing declines, maximal force is reduced and fatigue occurs. Firing rate declines either as a result of repetitive activation that exhausts intercellular calcium stocks or due to presynaptic inhibition as a result of decreased muscle spindle firing [1].

Fatigue is highly prevalent across a wide range of neurological and non-neurological disorders [3]. Central fatigue may occur in many neurological disorders that affect the CNS, e.g., multiple sclerosis, neurodegenerative disorders, and cerebrovascular diseases, among others [4]. Peripheral fatigue, on the other hand, is typical in neuromuscular disorders and more prominent in neuromuscular junction (NMJ) disorders and in certain myopathies.

In healthy individuals, low-frequency (3–5 Hz) repetitive nerve stimulation (RNS) applied to a motor nerve depletes presynaptic acetylcholine (Ach) quanta. This depletion reduces the end-plate potential (EPP), which is proportional to the amount of ACh binding to acetylcholine receptors (AChRs), but it remains above the threshold, ensuring the generation of a muscle fiber action potential (MFAP) after each stimulation. The recorded compound muscle action potential (CMAP), representing the summation of MFAPs, remains stable. In patients with NMJ disorders, the safety factor, namely the threshold value needed to generate an MFAP, is reduced. Simple stimulation of a motor nerve produces normal motor responses. But when low frequency RNS is applied, the progressive depletion of ACh quanta leads the EPP below the threshold, resulting in the absence of an MFAP and subsequent progressive decrement of CMAP amplitude. Clinically, these patients do not complain of muscle weakness but of fatigability [5,6].

Although decremental response in RNS is characteristic and pathognomonic to NMJ disorders, it is also observed in certain myopathies, more specifically in myotonias without dystrophic changes such as myotonia congenita and paramyotonia congenita. In these diseases, muscle weakness is not a general feature but occurs periodically when provoked, often by exercise (paramyotonia), while in some cases, muscle weakness is alleviated by exercise (myotonia congenita) [5]. Lastly, RNS may show decremental responses in certain metabolic myopathies like Mc Ardle’s disease, which is dominated by exercise intolerance resulting in prominent fatigue and muscle weakness that is reversible by rest [6].

Fatigue is an inevitable consequence of physical exertion in sporting activities and can potentially impede an athlete’s performance. This raises an important clinical question: can patients with neuromuscular disorders characterized by abnormal RNS responses safely participate in sports activities? The objective of this narrative review was to summarize existing case reports of individuals with these conditions who engage in sports, to evaluate the potential benefits and risks of their participation, and to contribute a novel case to the current literature.

2. Materials and Methods

To perform this narrative review, a literature search was conducted to identify relevant studies published in MEDLINE, Scopus and Web of Science, following the Narrative Review Checklist of the Journal of the Academy of Nutrition and Dietetics (JAND) [7] Supplementary File S1. The combination of search strings applied to query all databases included the following keywords: “myasthenia gravis” OR “myotonic disorders” OR “metabolic myopathies” OR “repetitive nerve stimulation” AND “sports”. The details of the search are given in Supplement File S2. The literature review was performed by two independent researchers (MP, DS). A Prisma Flow Chart shows the steps taken in the review process [8] (Figure 1). The last electronic search was performed in May 2025. Reference lists of identified publications and previous reviews were also searched to identify additional studies. No language or other search restrictions were applied. No time limit was set for the search. Studies were included irrespective of the age of patients.

Inclusion criteria

• Type of study: case reports or case series;
• Diagnosis of a neuromuscular disease that results in muscle fatigue, e.g., myasthenia gravis, myotonia, metabolic myopathies;
• Age of participants: all ages included;
• Sports activity: all types of sports or exercise intervention;
• Positive or negative outcomes after sport activity were recorded.

Exclusion Criteria

• Type of study other than case report or case series, e.g., reviews;
• Diagnosis of another medical condition that might produce fatigue, e.g., multiple sclerosis;
• Physical exercise as part of a rehabilitation program;
• Animal studies.

3. Results

The present narrative review includes ten cases of patients who successfully engaged in sports activity. Despite thorough investigation, no reports of unsuccessful participation or unfortunate events resulting in patient injury or death were identified. The 10 cases reviewed in the study and one new case observed by the research team are summarized in

Table 1. Demographic and clinical characteristics of the reviewed case reports.

Study	Disease	Age/Sex	Muscle Evaluation	Sport	Treatment	Symptoms While Training	Comments
Leddy and Chutkow, 2000 [10]	MG	17/M	decrement in RNS 15% trapezious L	FOOTBALL	PREDNISONE inconsistently	Eyelid ptosis	He participated in football practice, did not return to intercollege competition (physicians’ advise)
Birnbaum et al., 2018 [11]	MG	36/F	decrement in RNS 50% trapezius R 24% anconeus R 15% anconeus L 43% tongue	LONG DISTANCE RUNNING	IVIG pyridostigmine	Slight difficulty	Disease remained stable Quality of life improved
Scheer et al., 2012 [12]	MG	52/M	not reported	LONG DISTANCE RUNNING	Pyridostigmine 10 mg prednisolone	Fatigue, difficulty in speaking, breathing, swallowing	All symptoms subsided with rest and increased pyridostigmine dosing
Hayashi et al., 2013 [13]	MG	22/M	isokinetic strength of muscles in knee flexion and extension	RACE CYCLING	Thymectomy prednisolone	Not reported	Returned to competitive sports after aggressive steroid treatment.
Burnham, 1997 [14]	MC	16/M	myotonic discharges	HOCKEY	Mexiletine	Muscle stiffness, Difficulty initiating skating	Competes at All-Star level
Burnham, 1997 [14]	MF	20/M	minimally prolonged insertional activity	HOCKEY	Mexiletine	Muscle stiffness when exercising strenuously (2nd and 3rd period of hockey game)	Plays professional hockey
Weinberg et al., 1999 [15]	MC	15/M	myotonic discharges 5 min test negative	LACROSSE FOOTBALL BASKETBALL	Carbamazepine Quinine	Stiffness during rest after exercise	Participates in college with no physical limitation “In field” short exercise test provoked symptoms
Chew et al., 2004 [16]	MC	19/M	myotonic discharges	SPORTS	Carbamazepine	Cramps and stiffness when he runs	Responded to treatment and did not have any episodes
Fredericson et al., 2004 [17]	PC	18/M	myotonic discharges	RUNNING	Phenytoin	Cramps and pain after 20 min of exercise	Advised to run less than 50 miles/week “In field” short exercise test provoked symptoms
Perez et at al., 2007 [18]	MAD	38/M	gross muscle efficiency	RUNNING	Dietary modifications	Weakness and exercise intolerance	Improved sense of well-being Continue systematic exercise training.
NEW CASE	MC	19/M	decrement in RNS 41% APB R 37% ADM R myotonic discharges	SOCCER	Phenyntoin	Stiffness occurring at rest after brief periods of exercise	Responded to treatment, continue playing soccer

ADM: abductor digiti minimi, APB: abductor policis brevis, F: Female, L: Left, M: Male, MAD: Mc Ardle Disease, MC: Myotonica Congenita, MF: Myotonia fluctuans, MG: Myasthenia Gravis, PC: Paramyotonia congenita, RNS: Repetitive Nerve Stimulation, R: Right.

. Critical appraisal of the selected cross-sectional studies was conducted using a tool for evaluating the methodological quality of case reports and case series proposed by Murad et al. [9]. It consists of eight items that can be categorized into four domains: selection, ascertainment, causality and reporting. The authors of the tool suggest that making an overall judgment about methodological quality based on the questions deemed most critical in a specific clinical scenario then summing the scores of the eight binary responses into an aggregate score. The results are presented in Supplement File S3.

The following sections provide a detailed description of these cases, which have been grouped into clusters of underlying diseases.

3.1. Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune disease in which antibodies bind to ACh receptors in the postsynaptic membrane at the neuromuscular junction [19]. Given its pathophysiological characteristics, MG is characterized exclusively by motor symptoms that tend to be exacerbated by physical exercise. Thus, fatigue appears as a consequence to repetitive muscle contraction. In view of these particular characteristics of the disease, the question of the benefits of engaging in physical exercise has been the subject of considerable controversy. However, reviews of the relevant literature indicate that, as in the case of other neuromuscular disorders, physical exercise can be beneficial, as it improves muscle strength and volume and is also safe [20,21]; however, it has little impact on fatigue. This finding might imply that the fatigue experienced by MG patients is not exclusively due to muscle factors but also encompasses other factors, most likely psychological. In light of the above-mentioned considerations, it is imperative to approach patients with MG with extreme caution regarding their involvement in sports activities.

Only four cases of patients with MG involved in competitive sports activity were identified during the review of the relevant literature. The first one was published in 2000 and reported the case of a 17-year-old college football player [10]. A diagnosis of seronegative generalized mild MG was made, and the patient was started on a course of prednisolone, with satisfactory results, although there was some inconsistency in his compliance with the treatment plan. He continued to engage in training sessions with the team, yet was prevented from participating in competitive matches. He experienced eyelid ptosis after vigorous exercise (weight lifting) that was easily relieved after a few minutes of rest. In his senior year, he participated fully in football practices, but finally decided to quit, due to back pain unrelated to MG. The authors highlighted two points: the lack of guidelines regarding the safety of sport activity in MG and the Walker phenomenon [22], which is the delayed appearance of weakness in a muscle distant from those being exercised (eyelid ptosis after weight lifting). The other two cases describe patients that completed long runs, a marathon and an ultramarathon, even though they were diagnosed with MG and were under treatment. The first case [11] describes a 36-year-old woman who experienced fatigue while running prior to receiving an MG diagnosis. However, despite receiving a confirmed diagnosis, the patient continued to engage in running activities and even improved her personal marathon time, although she experienced slight difficulty at the beginning of a run and towards the end of the pyridostigmine dose. Her disease remained stable through the years under cholinesterase inhibitor treatment, encountering only brief and mild deteriorations. Quality of life was overall improved. The second one [12] reports a case of a 52-year-old man who had also initiated a running routine prior to being diagnosed with MG. Following MG diagnosis, he similarly continued to engage in physical activity. He participated in five ultramarathons. His symptoms were recorded during the fifth one of a 220 km distance. He complained of fatigue after running 30 km during the first stage, facial grimacing and difficulty with speaking at the end (37 km). Other runners observed he had difficulties in breathing and swallowing and he reported generalized muscle weakness on uphill sections. All symptoms subsided easily and quickly with rest and increased pyridostigmine dosing. He successfully completed the race finishing in 35th place among 65 athletes. Finally, a last report [13] described a professional cyclist with generalized myasthenia gravis who successfully returned to competitive cycling after thymectomy and aggressive medical and rehabilitation treatment.

These four cases, although limited in number, are indicative of the peculiarities of engaging in competitive sports activities while suffering from MG. The rarity of reports may be related to a fear of encouraging patients to participate in sports activities. Cash et al. [23] in their review propose some activity recommendations, that are mostly derived from how the ultramarathon was experienced in the previously described case report [12]. Therefore, these recommendations cannot be generalized and applied to all patients and, as the authors comment in their work, each patient should be assessed individually, depending on the severity of their disease and the activity-specific requirements.

In accordance with the preceding remark, the patients themselves were eager to persist with their exercise routines despite being strongly advised otherwise. They modified training routines, avoiding heat and introducing long rest periods between exercises, and also modified the dosage of drugs. As a result, for the patients (athletes), quality of life improved over time.

Similarly to participation in sports, physical activity in rehabilitation programs has been questioned in terms of its safety and potential benefits. Most studies investigating the effect of physical rehabilitation in MG have a relatively small sample size and many drop-outs. Moreover, interventions varied through studies in terms of type, intensity and duration, as did the outcome measures. However, the main conclusion of these studies was that exercise improved quality of life and increased muscle strength and volume, and that breathing patterns improved as a result of increased respiratory muscle strength. In addition, physical exercise was shown to be safe, with no exacerbations of disease associated with the intervention and no significant adverse events [21,24,25].

It is important to note that not all exercises are appropriate for all patients with MG. Prior to initiating any exercise regimen, it is essential to ensure that the disease is in a stable state. Furthermore, not all muscle groups are equally affected in MG. It is safer for those with an ophthalmic form of MG to engage in sports than for those with generalized disease. But even in those restricted clinical forms, the Walker phenomenon [22] can affect muscles in areas distant from those being exercised.

Another area of concern is the medication that the patient is currently taking. Pyridostigmine, while enticing for running patients as it reduces weakness, can cause bradycardia that limits exercise tolerance or even become life-threatening. Corticosteroids have been associated with the development of myopathy, characterized by reduced muscle strength and further limitation of exercise performance, as well as an increased risk of osteoporosis, which in turn may result in an increased susceptibility to fractures. Although no recommendations are available, studies have shown that resistance training may have a positive effect in preventing or reversing muscle weakness caused by steroids [26].

In conclusion, the rarity of cases of MG athletes may reflect the rarity of the disease itself. On the other hand it is indicative of the concerns and reservations of treating physicians towards the possibility of patients’ participation in sports. It appears that neither physical exercise as a part of a rehabilitation program nor sports participation led to exhaustion.

3.2. Myotonic Disorders

Myotonic Disorders (MD) belong to muscle membrane excitability diseases. Patients report muscle stiffness, pain and muscle weakness, which may be permanent, as in those with dystrophic muscle biopsy changes, or intermittent, as in those without. Muscle membrane excitability is regulated by ion conductance during resting and action potential. Alteration in sodium, chloride and potassium net flow will result in a muscle membrane hyperexcitable state resulting in delayed muscle relaxation after contraction or percussion [6]. In dystrophic MD, type 1 and 2, muscle weakness is constant and progressive. In non-dystrophic MD, weakness is periodic, precipitated by cold, fasting, and exercise or rest after exercise. Decremental responses in low frequency RNS are encountered in congenital non-dystrophic MDs (i.e., Thomsen and Becker myotonia congenita, a chloride channelopathy, caused by mutations in the CLCN1 gene on chromosome 7q), reflecting fatigue occurring after exercise. Short and long exercise tests also result in decline in CMAP amplitude [27]. Sodium channelopathies, like paramyotonia congenita and hyperkalemic periodic paralysis (SCN4A gene defect on chromosome 17q), also show decrement in CMAP amplitude after long exercise tests [5] and after 5 Hz repetitive stimulation [28]. In these cases, muscle weakness may not be evident until a provocative factor occurs, and exercise in one of them. In contrast to patients with dystrophic muscular dystrophies, where persistent muscle weakness precludes participation in competitive sports, in cases where paralysis is periodic, participation in sports may reveal an underlying muscle disease that was not clinically apparent until then.

We have identified four publications reporting on five patients, and we have also assessed an additional one. All patients were referred for muscle stiffness and/or periodic weakness occurring during sports activity. The first study [14] reports two cases of competitive hockey players, 16 and 20 years old, who complained of muscle stiffness but not of muscle weakness. The first patient showed abundant myotonic discharges in Electromyography (EMG), while the other did not. Neither RNS nor the exercise test was described. Consultation from a muscle specialist was sought. The 16-year-old was diagnosed with myotonia congenita (Thomsen) and the 20-year-old with Myotonia fluctuans. They both received Mexiletine and were able to continue hockey at a high competence level. The second case [15] describes a 15-year-old athlete who played lacrosse, football, and basketball and who complained of stiffness in the neck and upper extremities. Symptoms developed insidiously during brief periods of rest after 10 to 20 min of activity. EMG revealed myotonic discharges in all limbs. The five-minute exercise test was normal. Clinical diagnosis was compatible with myotonia congenita, that was later confirmed by DNA testing. The patient was treated with carbamazepine and quinine that alleviated his symptoms and he was encouraged to continue with his sports activity, which he did, without any limitations. The fourth patient was a 19-year-old who described painful cramps and stiffness when he ran or participated in sports [16]. Symptoms were triggered after bursts of movements and lessened as activity continued. EMG revealed myotonic discharges. RNS or exercise test results were not described. The patient denied genetic testing. A diagnosis of myotonia congenita was established based on clinical and neurophysiological characteristics. He received carbamazepine and his symptoms resolved. The last published case [17] was about a 18-year-old runner, who insidiously developed painful cramps and muscle tightness that developed after strenuous exercise (over 20 min), aggravated when he continued the activity and resolved with rest. Symptoms were also provoked by cold. Myotonic discharges were evident in all limbs. RNS or exercise test results were not mentioned. He was treated with phenytoin and advised not to run over 50 miles per week. He eventually gave up competitive running due to the limitations in training duration.

Lastly, we present a case of 19-year-old football player, who was referred to our department due to muscle stiffness occurring at rest after brief periods of exercise. Upon continuation of the exercise, stiffness was resolved. Symptoms were not elicited by cold nor by fasting or carbohydrate loading. His past medical history was normal, and his family history was unremarkable. He had no sensory symptoms, pain, weakness or cramps. Physical examination was normal with no percussion myotonia, no muscle atrophy or hypertrophy. Blood studies, including cell count, electrolytes, chemistry panel including creatine kinase (CK) levels and thyroid testing, were all normal. On electrophysiological testing, routine nerve conduction studies were within normal limits. On needle EMG, abundant myotonic discharges were recorded from every muscle tested (Abductor Pollicis Brevis, Biceps Brachii, Tibialis Anterior) (Figure 2) and motor unit action potentials (MUAPs) were normal, with normal recruitment, with no sign of myopathic pathology. RNS at 3 Hz revealed significant amplitude decrement of CMAP in abductor policis brevis (APB) and abductor digiti minimi (ADM) (Figure 3). Based on the clinical and neurophysiological characteristics, a diagnosis of myotonia congenita was made. DNA testing is pending since the patient initially denied to do it, afraid of being banned from his football team in case of a positive result. He was treated with low doses of phenytoin and responded well.

Non-dystrophic MDs are very rare disorders, but surprisingly, more cases involving athletes are described in the medical literature than in MG. In both disorders, weakness is not constant but occurs after exercise or, in the case of myotonia congenita, after rest following exercise. Besides myotonic discharges, decremental response of CMAP, either after repetitive stimulation or after short/long exercise, is described. Unfortunately, among the previously described cases, only one reports results from a 5 min exercise test, which was negative. Metaphorically, a short exercise test was conducted in the field, when patients were asked to run for 20 min [17] or play basketball for 20 min [15] to reproduce clinical symptoms.

It is noteworthy that patients did not encounter any difficulties in everyday life. Probably, if they had not trained intensely due to their participation in competitions, the disease might not have been revealed. Supporting this is the fact that, after evaluating other family members who did not participate in sports activities, a myotonic phenotype was identified in four out of six cases. In all cases, medical treatment substantially alleviated symptoms and all six could continue with their athletic performance. Only the runner gave up competing because of training restrictions.

Based on the description of these case reports, one can conclude that athletic activity, even at a competitive level, is not contraindicated in cases of MDs. Medications relieve symptoms of muscle stiffness. Furthermore, these disorders are not progressive and do not affect other organs, as is the case with dystrophic myotonias, which are associated with cardiac arrhythmias and endocrine dysregulation.

3.3. Metabolic Mypathies

McArdle’s disease (MAD) is a metabolic disorder caused by inherited deficiency of myophosphorylase, the enzyme that initiates glycogen breakdown in skeletal muscles. MAD is characterized by marked exercise intolerance, clinically expressed as myalgia, premature fatigue, and stiffness or weakness of exercising muscles, which is relieved by rest [29]. Traditionally, these patients are advised to adopt a sedentary lifestyle to prevent episodes of rhabdomyolysis, which could be life threatening [30]. However, refraining from physical activity may worsen exercise intolerance by further reducing the limited oxidative capacity caused by blocked glycogenolysis [31]. It is suggested that regular moderate aerobic training (resulting in a heart rate of no more than 60–70% of maximum) is an effective means of improving exercise capacity [31].

We were not able to identify any case report of an athlete suffering from MAD. The only case of sports activity, and not just supervised physical exercise, was the case reported by Perez et al. [18] with the semantic title “Can patients with McArdle’s disease run?”. In their work, they evaluated an MAD patient, not an athlete, that was advised to adopt a sedentary lifestyle to prevent episodes of severe and potentially life-threatening rhabdomyolysis. The patient underwent 3–4 supervised training sessions (running) per week of gradually increased duration, at an intensity of 80–85% maximum heart rate. At the end, he was able to complete 60 min of continuous running (approximately 10 km) after 4 months of training. Creatine kinase levels never exceeded the usual limits for this patient.

RNS may also be abnormal in McArdle’s disease [32]. This is explained by the fact that exercise intolerance is not only due to the inability to generate enough ATP (adenosine triphosphate) but also to reduced concentrations of the sodium–potassium ATPase pump. Decreased sodium–potassium ATPase may lead to an exercise-induced increase in extracellular potassium that partially depolarizes the muscle membrane, inactivating sodium channels and reducing membrane excitability [33]. It is not well understood why sodium–potassium ATPase pumps are reduced in McArdle’s disease, but it seems that reduced physical activity may further downregulate their number. On those grounds, advising against physical exercise in MAD patients may harm rather than protect.

4. Discussion

The objective of this narrative review was to present the published cases of patients suffering from neuromuscular diseases characterized by physical fatigue and to evaluate the effect, positive or negative, of sporting activity on their medical condition. Decremental response in RNS, a neurophysiological analogue of muscle fatigue, was the most frequently reported measure in the reviewed cases. This review elucidates two primary findings. Firstly, the total number of reported cases was very limited. Secondly, all documented cases reported successful participation in sports, with no adverse events described. To our knowledge, no other similar review has ever been published.

Despite the limited medical literature on the subject of sports participation in cases where muscle fatigue was the main clinical symptom, some general inferences can be drawn. In MG, physical exercise appears to be safe, when appropriate precautions are followed. In myotonia, physical exercise appeared to be safe, and in most cases, it was the key to diagnosis. On the other hand, in MAD, exercise increases the risk of rhabdomyolysis, and thus most patients are advised against it.

The absence of any reported adverse events from sports participation in neuromuscular patients is a matter of debate. It could be argued that only positive outcomes (“success stories”) find their way into publication. Furthermore, patients afflicted with more severe forms of the disease are unable to engage in sporting activities, let alone competitive ones.

Decremental RNS is the neurophysiological analogue of transitory weakness occurring after exercise. However, the extent of the reduction does not necessarily correlate with the degree of fatigue. Decremental RNS is the hallmark of MG and other neuromuscular junction disorders, such as Lambert–Eaton myasthenic syndrome and Botulism [32]. In such instances, synaptic transmission is disrupted, occurring either at the pre- or post-synaptic level. Therefore, following repeated stimulation or prolonged exercise, fatigue ensues, thereby impeding patients’ ability to sustain their activities.

RNS is also often described abnormal in the rare cases of altered muscle membrane excitability. In cases on myotonia congenita, mild weakness appears transiently during rest after exercise, while these patients also show a decremental response in RNS. In myotonia, the decrementing response is not due to impaired neuromuscular transmission but due to prolonged after-depolarization attributed to potassium accumulation [34]. The same applies in cases of McArdle Disease, where potassium accumulates due to low concentrations of sodium–potassium ATPase pumps and subsequent depolarization of muscle membrane [35].

Limitations

The main limitation of this review is its nature, i.e., its narrative form. It consists mainly of case reports and case series subject to a high degree of bias. In addition, the patient data are not comparable, as patients belong to different age groups, mainly being younger, suffer from different neuromuscular diseases and participate in different types of sports. Thus, the points derived from this review may not be applicable to older patients or to other types of sports activities.

The absence of negative references further underlines this weakness. In some cases, the diagnosis was not confirmed genetically, either because a genetic test was not yet available at the time of publication or because patients refused it for personal reasons. Neurophysiological data were also rare, either because tests were not performed or were not reported. Furthermore, all of the data were obtained from separate case reports that did not include subsequent follow-ups with patients. Many years of observation of these patients are required in order to draw conclusions.

5. Conclusions

The ability to maintain adequate muscle activity over an extended period is a prerequisite for participation in sports. This necessitates the capacity to manage fatigue effectively. RNS may be the most appropriate tool for detecting fatigue, but it is important to note that it does not allow for correlations with the severity of the condition.

Participation in sports, at a competitive level, for patients with neuromuscular diseases raises several concerns. The patients’ desires and hesitations on the one hand and the physicians’ scientific knowledge on the other hand counterbalance each other to reach a weighted decision.

The present review, due to the limitations mentioned above, particularly with regard to the nature of the data presented, cannot provide definitive answers regarding the safety and the effectiveness of sporting activity in such patients, nor can it be considered as providing definitive guidelines. What emerges from the present review is the need for a prospective study involving a large cohort of athlete patients who wish to continue participating in sporting activities under strict medical supervision, with simultaneous measurement of specific parameters, such as decremental responses in RNS, that would enable the quantification of fatigue and the assessment of the effects of strenuous exercise.