SEMS-journal
SEMS Educational review
published online on 22.10.2024https://doi.org/10.34045/SEMS/2024/47
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Physiological consequences and challenges related to exercise performance in wheelchair sports

exercise is medicine

Perret Claudio1,2
1 Swiss Paraplegic Research, Nottwil, Switzerland
2 Faculty of Health Sciences and Medicine, University of Lucerne, Lucerne, Switzerland

Abstract

The interest and competitiveness in Paralympic sports continuously increased over the past years. Typical medical impairment types competing at Paralympic games are amputations/limb deficiencies, cerebral palsy, spinal cord related disabilities, visual impairments, les autres (e.g., dwarfism) and intellectual impairments. Among Para-athletes, especially wheelchair athletes with a spinal cord injury (SCI) are faced with drastic physiological consequences and challenges related to exercise performance. These physiological adaptations are a direct or indirect consequence of the partial or total loss of motor, sensory and vegetative functions below the lesion and include musculoskeletal adaptations, pressure sores, shoulder pain, cardiovascular adaptations, thermoregulatory dysfunction, respiratory, urological and gastrointestinal complications. All these topics could negatively impact exercise performance of wheelchair athletes, which will be addressed in more detail in the present article. Further, practical considerations and recommendations for daily sports medical practice will be presented in order to optimize exercise performance in wheelchair athletes.

Zusammenfassung

In den letzten Jahren hat die Leistungsdichte sowie das Interesse am Paralympischen Sport massiv zugekommen. An Paralympischen Spielen nehmen typischerweise Athleten und Athletinnen mit Amputationen, Cerebralparese, Rückenmarksverletzungen, visueller Beeinträchtigung, Kleinwuchs oder mit intellektueller Beeinträchtigung teil. Dabei sind insbesondere Rollstuhlathleten und -athletinnen mit einer Querschnittlähmung von physiologischen Veränderungen und Herausforderungen bezogen auf die sportliche Leistungsfähigkeit betroffen. Die physiologischen Anpassungen sind eine direkte oder indirekte Konsequenz des partiellen oder totalen Verlusts motorischer, sensorischer und vegetativer Funktionen unterhalb der Lähmungshöhe aufgrund der er­littenen Rückenmarksverletzung. Sie umfassen muskuloskelettale Anpassungen, Dekubitalulcera, Schulterschmerzen, kardiovaskuläre Adaptationen, Probleme bezüglich Thermoregulation und Atmungsfunktion sowie urologische und gastrointestinale Komplikationen. All diese Bereiche können die Leistungsfähigkeit von Rollstuhlsportlern und -sportlerinnen negativ beeinflussen und werden im vorliegenden Artikel ausführlich dargelegt. Zudem werden im Sinne der Leistungsoptimierung im Rollstuhlsport praktische Aspekte und Empfehlungen für die tägliche sportmedizinische Praxis diskutiert.

Schlüsselwörter: Rückenmarksverletzung, Paralympische Spiele, Querschnittslähmung, Bewegungsphysiologie, ­Para-Sport

Introduction

The interest and competitiveness of Para-sports continuously increased over the past decades [1]. Paralympic summer games are among the biggest sport events worldwide. At the Paralympic Games in Paris 2024, around 4400 Para-athletes from about 180 countries will compete in 549 medal events. A prerequisite to compete in Para-sports is that athletes meet the minimal impairment criteria to be eligible for a certain sport. Based on the degree of activity limitation resulting from the impairment, Para-athletes are grouped. This process is called classification and aims to minimize the influence of the impairment on the performance of the athletes (for more details on classification please refer to the homepage of the International Paralympic Committee (IPC) under http://www.paralympic.org). Typical medical impairment types competing at Paralympic games are amputations/limb deficiencies, cerebral palsy, spinal cord related disabilities, visual impairments, les autres (e.g., dwarfism) and intellectual impairments [2]. Among Para-athletes, especially wheelchair athletes with a spinal cord injury (SCI) are faced with drastic physiological consequences and challenges related to exercise performance. These physiological adaptations and the typical consequences for exercise performance after SCI are due to the sublesional, total or partial loss of motor, sensory and vegetative function [3] and will be addressed and discussed in more detail below.

Physiological changes after SCI and implications for exercise performance

Musculoskeletal adaptations

A SCI leads to severe muscle atrophy in the paralysed limbs and a concomitant reduction in artery diameter [4]. The consequence of this adaptation is a diminished blood flow and a limited blood redistribution compared to able-bodied individuals [5]. Additionally, a shift towards type-II muscle fibres in the legs is observed in individuals with chronic paraplegia [6]. With the sublesional muscle loss and the lacking motor function of these muscles mechanical loading on paralysed limbs is reduced [7] leading to a so called «immobilization osteoporosis» with sublesional trabecular bone mineral density losses of up to 90 % within the first few years after SCI [8]. The consequence is a highly increased fracture risk also for athletes with SCI, which can cause secondary complications including pressure sores and infections [9,10]. It is self-explanatory that such complications are undesirable because athletes are prevented from keeping a regular training schedule under such circumstances. Additionally, the above described sublesional muscle atrophy implies also a change in body composition and thus resting energy expenditure [11]. In other words, nutritional aspects such as caloric needs and intake [12,13], body composition [14] as well as energy availabilty [15] have to be addressed in wheelchair athletes to keep them healthy and warrant the best performance level possible.

Pressure sores

There is a high incidence of pressure sores after SCI worldwide (for review see [16]) mainly due to immobilization and loss of sensitivity in the paralyzed limbs. The most common areas where pressure sores arise are points where skin and bones are closely aligned such as e.g., elbows, heels, sit bones, hips, shoulder, etc. Thus, sensitization of athletes and preventive interventions (e.g., frequent repositioning/weight-relief lifts, daily skin inspection, skin care, cushioning, nutritional interventions) are highly recommended. Further, athletes have to be aware that – especially during long-haul flights – they are at an increased risk for pressure sores. Moreover, sport equipment should be adapted to the needs of the athletes keeping the problems of pressure sores in mind. The consequences of pressure sores for athletes are reduced or missed training sessions leading to a decrease in performance or missed competitions. In general, pressure sores lead to long hospitalization and rehabilitation times and generate massive health care costs.

Shoulder pain

Manual wheelchair users in Switzerland show a high prevalence of 39 % for shoulder pain [17] which is thought to be the consequence of upper-extremity overuse presumably related to wheelchair propulsion, weight-relief lifts and transfers. However, severe shoulder pain not only prevents athletes from keeping their regular training activities and schedules but also limits activities of daily life (ADL) such as transfers. Thus, shoulder health is of utmost interest not only to athletes but for all wheelchair users in order to prevent from shoulder pain by avoiding shoulder muscle imbalance [18]. To reach this goal, a well-directed preventive strength training program including shoulder stability exercises (Figure 1) and a proper development of shoulder strength in athletes over time seems mandatory to reach an adequate shoulder capacity to sustain the requirements of the sports discipline as well as to avoid muscle imbalance.

Figure 1: Athlete during her regular preventive shoulder stability exercise program using a rubber band

Cardiovascular adaptations and peak oxygen uptake

A complete lesion of the spinal cord above a lesion level of Th6 leads to limited or absent sympathetic nerve innervation of the heart. Additionally, venous return after SCI is reduced and the available active muscle mass small, which leads to inadequate heart rate and blood pressure adaptations during physical activity and exercise. The consequences are reductions in cardiac output and peak oxygen uptake and thus a highly limited exercise performance. In case of a complete tetraplegia peak heart rate is mostly limited to 120 bpm or less, which impedes the possibility of a heart rate-based training guidance. However, heart rate and blood pressure adaptions in athletes with a low paraplegia are comparable with able-bodied counterparts and world-class athletes with these lesion levels are able to reach values for peak oxygen uptake of over 50 ml/min/kg [19].

Autonomic dysreflexia and boosting

The acute syndrome of excessive, uncontrolled sympathetic output caused by spinal reflex mechanisms is termed autonomic dysreflexia. Typically, individuals with SCI above the sixth thoracic neurological level and especially persons with a cervical lesion suffer from autonomic dysreflexia [20]. This reaction is caused by a noxious stimulus such as e.g., a full bladder below the lesion and leads to typical symptoms including high blood pressure (up to 300 mmHg for systolic and 220 mmHg for diastolic pressure [21]), headache, flushing, mydriasis, sweating in the head and neck region as well as nasal congestion. The appearance of autonomic dysreflexia in persons with SCI is a severe complication and can lead to life-threatening situations. However, the intentional induction of autonomic dysreflexia (e.g., by filling the bladder) by athletes with SCI in order to enhance sports performance is called «boosting» and showed improvements in race times of up to 9.7% [22]. As competing in a hazardous state of dysreflexia would lead to an extreme health risk for athletes, boosting is rigorously banned by the IPC. The IPC Handbook states that the symptom is present when the systolic blood pressure reaches values of 160 mmHg or higher. Thus, if an athlete with a high thoracic or cervical lesion exhibits a systolic blood pressure of 160 mmHg or more before a competition, he/she will be re-examined 10 min later and – in case the blood pressure remains unchanged – excluded from the competition.

Thermoregulatory dysfunction

The thermoregulatory capacity in individuals with SCI is impaired, due to the impairment of the autonomic and somatic nervous system (for review refer to [23]) leading to a disturbed skin blood flow and the absence of a sweating response below the lesion (Figure 2). This problem is more pronounced the higher the level and the completeness of the lesion is, which puts athletes with tetraplegia at the highest risk for heat illness, especially in hot environments. Thus, cooling interventions such as the use of cooling vests or ice slurries before and during competitions are recommended but should be individually tested in advance [23]. Although promising, the application of heat acclimatization protocols in athletes with SCI have to be elaborated in more detail in the future [24]. Finally, it is often neglected that the impaired thermoregulation combined with the absent sublesional sensory function can also have some negative consequences for athletes with SCI in a cold environment [19].

Figure 2: Thermoregulatory response of a wheelchair athlete with a complete lesion level at the thoracic level Th5/6 during strenuous handcycling exercise. Note that sweating is completely absent below the lesion.

Respiratory complications

A lesion-dependent loss of respiratory muscle innervation reduces lung function and thus respiratory capacity of athletes with SCI. Especially in individuals with tetraplegia coughing is a problem and impedes secretion clearance of the airways. As a consequence, these persons are prone to respiratory complications such as dysspnoea or pneumonia [25], which is still one of the leading causes of death after SCI [26]. Even if there would occur no severe life-threatening events in the Para-athletic population, respiratory capacity and thus e.g., peak oxygen uptake is limited compared to able-bodied counterparts. Further, one has to keep in mind that during wheelchair propulsion respiratory muscles are used not only for breathing but are also involved in wheelchair propulsion. Thus, the application of an appropriate respiratory-locomotory coupling strategy seems important to optimize wheelchair exercise performance [27]. Although study results on respiratory muscle training in wheelchair athletes are scarce, it seems to be an interesting approach to keep in mind [28,29] when it comes to performance optimization in wheelchair sports.

Urological complications

Genitourinary illness including urinary tract infections (UTIs) were among the most reported illness during Paralympic summer [30] and winter games [31]. Especially in individuals with SCI an increased risk for the development of UTIs was reported [32]. The increased risk is based on the impaired bladder function (neurogenic bladder), which means reduced bladder storage and voiding function [32] often leading to the application of intermittent catheterization [33]. Dehydration (e.g., during long-haul flights or in a hot environment) seems also to be an important factor in Para-athletes in the context of UTIs [34]. Antibiotics or supplements such as cranberry juice are widely used to prevent from UTIs, although there is no clear evidence for the effectiveness of such interventions [32]. However, it is a fact that UTIs are responsible for many lost training and competition days in Para-athletes and future studies are urgently necessary to address this topic.

Gastrointestinal problems

The so-called neurogenic bowel is a consequence of a SCI and leads to several physiological adaptations. These include impaired gastric emptying and gastrointestinal (GI) transit times, constipation and other GI symptoms [35]. Thus, it is not surprising that gastrointestinal problems are common in Para-athletes and belong to the top three reasons for illness during Paralympic games since years [30,31,34,36]. In combination with a reduced resting and exercising energy expenditure and the above-mentioned changes in body composition, fluid, micro- and macronutrient needs have to be taken into account to support a proper bowel management and enable athletes to perform at their best level possible.
In conjunction with the afore mentioned GI problems in Para-athletes, the following aspects should be considered as well. The regular intake of medications to manage secondary conditions (e.g., spasticity, pain) is common after SCI. However, athletes have to be sentisized that they have to respect and adhere to the antidoping rules published by the world anti-doping agency. Further, it is not warranted that substances were absorbed and metabolized to the same amount or within the same time frame as known from the able-bodied population. This statement is also valid for the use of nutritional supplements as there seems to be a lack of information related to specific risks and benefits in Para-athletes [37] although supplement use is highly prevalent in international and Swiss Paralympic athletes [38,39].

Practical considerations and recommendations

Knowledge of the above-mentioned physiological adaptations after SCI and its consequences have some practical implications for the daily work with athletes in the field and may essentially contribute to maintain health and warrant optimal exercise performance. The most important problems are summarized in Table 1 and the given practical recommendations should serve as a guide for physicians, physiotherapists and coaches working with athletes suffering from a SCI.

Table 1: Practical considerations and recommendations for physicians, physiotherapists and coaches working with wheelchair athletes taking into account physiological challenges and changes after spinal cord injury

Take home message, conclusions and practical implications

Para-athletes, especially wheelchair athletes with SCI experience fundamental physiological consequences and challenges related to exercise performance. These physiological adaptations include shoulder pain, pressure injuries, musculoskeletal, respiratory, cardiovascular, thermoregulatory, gastrointestinal and urologcial complications, which can impair exercise performance. Physicians, physiotherapists and coaches working in Para-sports should be aware of the potential consequences and risks in order to handle and adequately address the challenges wheelchair athletes are faced with.

Acknowledgments, conflict of interest and ­funding

The author has to declare no conflict of interest related to this article.

Corresponding author

Prof. Dr. sc. nat. Claudio Perret
Swiss Paraplegic Research
Guido A.-Zächstrasse 4, CH-6207 Nottwil
Tel: +41 41 939 66 50
Email: claudio.perret@paraplegie.ch

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