Resting cardiopulmonary function in Paralympic athletes with cervical spinal cord injury

Respiratory Muscle Training in Para-Athletes: A Systematic Review on the Training Protocols and Effects on Reported Outcomes

CONTEXT AND OBJECTIVES

Respiratory muscle training (RMT) is considered an effective tool to improve cardiorespiratory limitations in athletes. The goals of this systematic review were to explore the role of RMT and its implementation within sport rehabilitation programs in para-athletes.

EVIDENCE ACQUISITION

Several databases were searched until January 2024. Eligible studies were independently reviewed by 2 reviewers. Quality assessment was made using the PEDro scale and version 2 of the Cochrane Risk-of-Bias Tool for Randomized Trials. Eight studies (a total of 108 participants) were selected for the analysis.

EVIDENCE SYNTHESIS

Five studies preferred using resistive loading, while 2 studies used normocapnic hyperpnea, and 1 study used threshold inspiratory muscle training. Respiratory functions (respiratory muscle strength and endurance, spirometry measures) and exercise performance were assessed as the main outcomes. Significant increases in respiratory muscle strength were reported in 5 studies. Two studies observed improvement in respiratory muscle endurance and 3 studies reported increased exercise capacity.

CONCLUSIONS

This review suggests that although RMT can enhance respiratory muscle strength and endurance, it should not be considered the primary method for boosting the exercise performance of para-athletes. Additional research is necessary to explore the impact of various RMT techniques on different outcomes from the perspective of sport rehabilitation in para-athletes.

Exercise Training Does Not Attenuate Cardiac Atrophy or Loss of Function in Individuals With Acute Spinal Cord Injury: A Pilot Study

OBJECTIVE

To investigate the effects of 2 modes of exercise training, upper-body alone, and the addition of electrical stimulation of the lower body, to attenuate cardiac atrophy and loss of function in individuals with acute spinal cord injury (SCI).

DESIGN

Randomized controlled trial.

SETTING

Rehabilitation Hospital.

PARTICIPANTS

Volunteers (N=27; 5 women, 22 men) who were <24 months post SCI.

INTERVENTIONS

Volunteers completed either 6 months of no structured exercise (Control), arm rowing (AO), or a combination of arm rowing with electrical stimulation of lower body paralyzed muscle (functional electrical stimulation [FES] rowing).

MAIN OUTCOME MEASURES

Transthoracic echocardiography was performed on each subject prior to and 6 months after the intervention. The relations between time since injury and exercise type to cardiac structure and function were assessed via 2-way repeated-measures analysis of variance and with multilevel linear regression.

RESULTS

Time since injury was significantly associated with a continuous decline in cardiac structure and systolic function, specifically, a reduction in left ventricular mass (0.197 g/month; P=.049), internal diameter during systole (0.255 mm/month; P<.001), and diastole (0.217 mm/month; P=.019), as well as cardiac output (0.048 L/month, P=.019), and left ventricular percent shortening (0.256 %/month; P=.027). These associations were not differentially affected by exercise (Control vs AO vs FES, P>.05).

CONCLUSIONS

These results indicate that within the subacute phase of recovery from SCI there is a linear loss of left ventricular cardiac structure and systolic function that is not attenuated by current rehabilitative aerobic exercise practices. Reductions in cardiac structure and function may increase the risk of cardiovascular disease in individuals with SCI and warrants further interventions to prevent cardiac decline.

Inflammation and Oxidative Stress as Common Mechanisms of Pulmonary, Autonomic and Musculoskeletal Dysfunction after Spinal Cord Injury

Simple Summary

When a spinal cord injury occurs, the neurons that regulate our voluntary movements, those involved in environment and somatic perception and those that regulate vegetative functions are affected. Once neuronal damage is established, the cells of other tissues are also affected in their functions, altering the interaction between organs and altering the proper functioning of the organism. Multiple studies in animal models, as well as in humans, have recognized as factors involved in organ damage the imbalance between the formation of highly reactive molecules called pro-oxidants and defensive mechanisms called antioxidants. Closely associated with this phenomenon, the inflammatory response is also pathologically activated. In this narrative review, we have analyzed the information involving these pathological processes at the level of the lung, the autonomic nervous system and the skeletal musculature after spinal cord injury. Knowing the abnormal functioning mechanisms that occur after a spinal cord injury not only offers a better understanding of the organic events but also offers future possibilities for therapeutic interventions that may benefit the thousands of patients suffering this pathology.

Abstract

One of the etiopathogenic factors frequently associated with generalized organ damage after spinal cord injury corresponds to the imbalance of the redox state and inflammation, particularly of the respiratory, autonomic and musculoskeletal systems. Our goal in this review was to gain a better understanding of this phenomenon by reviewing both animal and human studies. At the respiratory level, the presence of tissue damage is notable in situations that require increased ventilation due to lower thoracic distensibility and alveolar inflammation caused by higher levels of leptin as a result of increased fatty tissue. Increased airway reactivity, due to loss of sympathetic innervation, and levels of nitric oxide in exhaled air that are similar to those seen in asthmatic patients have also been reported. In addition, the loss of autonomic control efficiency leads to an uncontrolled release of catecholamines and glucocorticoids that induce immunosuppression, as well as a predisposition to autoimmune reactions. Simultaneously, blood pressure regulation is altered with vascular damage and atherogenesis associated with oxidative damage. At the muscular level, chronically elevated levels of prooxidants and lipoperoxidation associated with myofibrillar atrophy are described, with no reduction or reversibility of this process through antioxidant supplementation.

Experimental high thoracic spinal cord injury impairs the cardiac and cerebrovascular response to orthostatic challenge in rats

Spinal cord injury (SCI) impairs the cardiovascular responses to postural challenge, leading to the development of orthostatic hypotension (OH). Here, we apply lower body negative pressure (LBNP) to rodents with high-level SCI to demonstrate the usefulness of LBNP as a model for experimental OH studies, and to explore the effect of simulated OH on cardiovascular and cerebrovascular function following SCI. Male Wistar rats (n = 34) were subjected to a sham or T3-SCI surgery and survived into the chronic period postinjury (i.e., 8 wk). Cardiac function was tracked via ultrasound pre- to post-SCI to demonstrate the clinical utility of our model. At study termination, we conducted left-ventricular (LV) catheterization and insonated the middle cerebral artery to investigate the hemodynamic, cardiac, and cerebrovascular response to a mild dose of LBNP that is sufficient to mimic clinically defined OH in rats with T3-SCI but not sham animals. In response to mimicked OH, there was a greater decline in stroke volume, cardiac output, maximal LV pressure, and blood pressure in SCI compared with sham (P < 0.034), whereas heart rate was increased in sham but decreased in SCI (P < 0.029). SCI animals also had an exaggerated reduction in peak, minimum and mean middle cerebral artery flow, for a given change in blood pressure, in response to LBNP (P < 0.033), implying impaired dynamic cerebral autoregulation. Using a preclinical SCI model of OH, we demonstrate that complete high thoracic SCI impairs the cardiac response to OH and disrupts dynamic cerebral autoregulation.NEW & NOTEWORTHY This is the first use of LBNP to interrogate the cardiac and cerebrovascular responses to simulated OH in a preclinical study of SCI. Here, we demonstrate the utility of our simulated OH model and use it to demonstrate that SCI impairs the cardiac response to simulated OH and disrupts dynamic cerebrovascular autoregulation.

Reductions in Cardiac Structure and Function 24 Months After Spinal Cord Injury: A Cross-Sectional Study

OBJECTIVE

To determine the alterations in cardiac structure and function that occur in the months after spinal cord injury (SCI).

STUDY DESIGN

Cross-sectional SETTING: Rehabilitation Hospital PARTICIPANTS: Volunteers (N=29; 4 women, 25 men) between 3 and 24 months after SCI.

MAIN OUTCOME MEASURES

Transthoracic echocardiography was performed on each volunteer. The relationships between time since injury and neurologic and sensory levels of injury to cardiac structure and function were assessed via multiple linear regression.

RESULTS

Time since injury was most strongly associated with reductions in left ventricular end diastolic volume (r2=0.156; P=.034), end systolic volume (r2=0.141; P=.045), and mass (r2=0.138; P=.047). These structural changes were paralleled by reduced stroke volume (r2=0.143; P=.043) and cardiac output (r2=0.317; P=<.001). The reductions in left ventricular structure and systolic function were not differentially affected by neurologic or sensory levels of injury (P=.084-.921).

CONCLUSIONS

These results suggest progressive reductions in left ventricular structure and systolic function between 3 and 24 months after SCI that occur independent of neurologic and sensory levels of injury.

How does cervical spinal cord injury impact the cardiopulmonary response to exercise?

We compared cardiopulmonary responses to arm-ergometry in individuals with cervical spinal cord injury (C-SCI) and able-bodied controls. We hypothesized that individuals with C-SCI would have higher respiratory frequency (f_b) but lower tidal volume (VT) at a given work rate and dynamically hyperinflate during exercise, whereas able-bodied individuals would not. Participants completed pulmonary function testing, an arm-ergometry test to exhaustion, and a sub-maximal exercise test consisting of four-minute stages at 20, 40, 60, and 80% peak work rate. Able-bodied individuals completed a further sub-maximal test with absolute work rate matched to C-SCI. During work rate matched sub-maximal exercise, C-SCI had smaller VT (main effect p < 0.001) compensated by an increased f_b (main effect p = 0.009). C-SCI had increased end-expiratory lung volume at 80% peak work rate vs. rest (p < 0.003), whereas able-bodied did not. In conclusion, during arm-ergometry, individuals with C-SCI exhibit altered ventilatory patterns characterized by reduced VT, higher f_b, and dynamic hyperinflation that may contribute to the observed reduced aerobic exercise capacity.

Respiratory muscle training in non-athletes and athletes with spinal cord injury: A systematic review of the effects on pulmonary function, respiratory muscle strength and endurance, and cardiorespiratory fitness based on the FITT principle of exercise prescription

BACKGROUND

Respiratory muscle training (RMT) has been recommended to mitigate impacts of spinal cord injuries (SCI), but the optimal dosage in terms of the frequency, intensity, time, and type (FITT principle) to promote health in SCI individuals remains unclear.

OBJECTIVE

To discuss research related to the effects of RMT on pulmonary function, respiratory muscle strength and cardiorespiratory fitness in athletes and non-athletes with SCI, presenting the FITT principle.

METHODS

We performed a systematic review. PubMed, Lilacs, Scopus, Web of Science, PEDro, SciELO and Cochrane databases were searched between 1989 and August 2018. Participants were athletes and non-athletes with SCI.

RESULTS

4,354 studies were found, of which only 17 met the eligibility criteria. Results indicated that RMT is associated with beneficial changes in pulmonary function and respiratory muscle strength and endurance among athletes and non-athletes, whereas no effect was reported for maximal oxygen uptake. It was not possible to establish an optimal RMT dose from the FITT principle, but combined inspiratory/expiratory muscle training seems to promote greater respiratory changes than isolated IMT or EMT.

CONCLUSION

The use of RMT elicits benefits in ventilatory variables of athletes and non-athletes with SCI. However, it remains unclear which RMT type and protocol should be used to maximize benefits.

Sensory-motor and cardiorespiratory sensory rehabilitation associated with transcranial photobiomodulation in patients with central nervous system injury: Trial protocol for a single-center, randomized, double-blind, and controlled clinical trial

BACKGROUND

Central nervous system diseases such as stroke, spinal cord injury, traumatic brain injury, and multiple sclerosis can be fatal or cause sequelae, affecting sensorimotor and cardiorespiratory systems and quality of life. These subjects present a low response to aerobic and resistance exercise, due to decreased recruitment of muscle fibers and reduction of metabolic capacity. Aerobic exercises bring benefits in terms of fatigue retardation, gait improvement, regulation of the autonomic nervous system, neuroprotection of the brain, stimulation of the production of endogenous neutrotransmitters related to general well-being, and a favoring of neuroplasticity. Photobiomodulation (PBM Therapy) (previously known as low-level laser therapy), and especially transcranial PBM Therapy, has shown benefits in animals and humans such as cognitive improvement, memory, and behavioral improvement, including attenuation of depression and anxiety, and increased cortical oxygenation. The aims of this trial will be to evaluate the parameters related to the function of the musculoskeletal and cardiorespiratory system and the impact of PBM therapy on these parameters, as part of a rehabilitation and training program for people with reduced mobility.

METHODS

This is a randomized, double-blind, placebo-controlled trial with 3 groups: Control, only cardiorespiratory rehabilitation (CCR), CCR with PBM Therapy (CR-PBM), CCR and placebo PBM Therapy (CR-PlaceboPBM). n = 90, 30 per group. PBM Therapy parameters: 810 nm laser, 0.028 cm, 100 mW, 3.5 W/cm, 30 seconds per point, 3 J per point, 107.1 J /cm to 3 electroencephalogram points F7 and F8 and AFz. The trial will be conducted at the University Clinics and the sessions will be 1 hour twice a week for 9 weeks. Baseline, intermediate (4th week), final (9th week), and 2-month follow-up will be performed. Muscular activation, heart rate variability, lung volumes and capacities, fatigability, exercise tolerance, cognition, and quality of life at baseline will be evaluated. Subsequent to baseline evaluations, the PBM Therapy groups will be offered laser therapy (active or inactive); all groups will then receive CCR.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov ID - NCT03751306 (approval date: November 22, 2018).

Diaphragm ultrasonography and pulmonary function tests in patients with spinal cord injury

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

To investigate the role of ultrasonographic measurement of the diaphragm thickness on pulmonary function tests in patients with spinal cord injury (SCI).

SETTING

Rehabilitation center in Ankara, Turkey.

METHODS

A total of 42 patients (34 M, 8 F) with SCI and 20 able-bodied volunteers (8 M, 12 F) were enrolled. Patients with SCI were divided into three groups according to their neurological (injury) levels. All participants underwent ultrasonographic measurements for diaphragm thickness on both sides and spirometric tests for pulmonary functions. The thickness ratio of the diaphragm was also calculated.

RESULTS

There were seven patients (5 M, 2 F) in C2-C4 injury group, 14 patients (12 M, 2 F) in C5-T5 group, 21 patients (14 M, 7 F) in T6-L2 group, and 20 able-bodied volunteers (8 M, 12 F). The diaphragms of C2-C4 group were thicker than those of the controls at end-inspirium on the right side (2.7 ± 0.7 mm vs. 2.0 ± 0.5 mm; p = 0.035). The thickness ratios of C2-C4 group were lower than those of controls on the right (0.8 ± 0.4 vs. 1.5 ± 0.5; p = 0.005) and left (0.8 ± 0.5 vs. 1.6 ± 0.7; p = 0.003) sides. For all the pulmonary function tests (except for FEV1/FVC); patients with SCI had worse results than controls; and among the SCI groups, the higher the injury level, the worse the results.

CONCLUSION

Although patients with high-level SCI had worse pulmonary function tests and decreased the contractile capacity of the diaphragm, they had thicker diaphragm muscles than controls. This may have been due to the compensatory effect of the diaphragm (performing its maximum contraction capacity and increasing frequency of inspiration).

Temporal analysis of cardiovascular control and function following incomplete T3 and T10 spinal cord injury in rodents

Spinal cord injury (SCI) is a devastating condition that results in whole‐body dysfunction, notably cardiovascular (CV) disruption and disease. Injury‐induced destruction of autonomic pathways in conjunction with a progressive decline in physical fitness contribute to the poor CV status of SCI individuals. Despite the wide use of exercise training as a therapeutic option to reduce CV dysfunction, little is known about the acute hemodynamic responses to the exercise itself. We investigated CV responses to an exercise challenge (swimming) following both high and low thoracic contusion to determine if the CV system is able to respond appropriately to the challenge of swimming. Blood pressure (BP) telemetry and echocardiography were used to track the progression of dysfunction in rodents with T3 and T10 SCI (n = 8 each) for 10 weeks postcontusion. At 1 week postinjury, all animals displayed a drastic decline in heart rate (HR) during the exercise challenge, likely a consequence of neurogenic shock. Furthermore, over time, all groups developed a progressive inability to maintain BP within a narrow range during the exercise challenge despite displaying normal hemodynamic parameters at rest. Echocardiography of T10 animals revealed no persistent signs of cardiac dysfunction; T3 animals exhibited a transient decline in systolic function that returned to preinjury levels by 10 weeks postinjury. Novel evidence provided here illustrates that incomplete injuries produce hemodynamic instability that only becomes apparent during an exercise challenge. Further, this dysfunction lasts into the chronic phase of disease progression despite significant recovery of hindlimb locomotion and cardiac function.

Cardiac consequences of spinal cord injury: systematic review and meta-analysis

OBJECTIVE

Conduct a meta-analysis to determine the impact of traumatic spinal cord injury (SCI) on echocardiographic measurements of left ventricular (LV) structure and function.

METHODS

MEDLINE and Embase were used for primary searches of studies reporting LV echocardiographic data in individuals with SCI. Of 378 unique citations, 36 relevant full-text articles were retrieved, and data from 27 studies were extracted for meta-analyses. Literature searches, article screening and data extraction were completed by two independent reviewers and compared for agreement. Primary analyses compared echocardiographic indices between individuals with SCI and able-bodied individuals, using a random effects model.

RESULTS

Data are reported as pooled effect estimates (95% CI). Data from 22 articles (474 participants) were included in the primary meta-analysis. Compared with able-bodied individuals, individuals with SCI had reductions to LV stroke volume of 11.8 mL (95% CI -17.8 to -5.9, p<0.001), end-diastolic volume of 19.6 mL (95% CI -27.2 to -11.9, p<0.001) and LV mass_index of -7.7 g/m² (95% CI -11.6 to -3.8, p<0.001), but ejection fraction was not different between the groups (95% CI -2.6% to 0.6%, p=0.236). Individuals with SCI also had altered indices of diastolic function, specifically a lowered ratio of early-to-late filling velocities (p=0.039), and augmented ratio of early diastolic flow-to-tissue velocities (p=0.021).

CONCLUSIONS

Individuals with SCI have smaller LV volumes and mass, and altered systolic and diastolic function. While this meta-analysis demonstrates important alterations to echocardiographic measures of cardiac structure and function at rest, future work should consider the impacts of SCI on the heart's capacity or 'reserve' to respond to physiological challenges.

PROSPERO REGISTRATION NUMBER

CRD42017072333.

Experimental Spinal Cord Injury Causes Left-Ventricular Atrophy and Is Associated with an Upregulation of Proteolytic Pathways

Spinal cord injury (SCI) causes autonomic dysfunction, altered neurohumoral control, profound hemodynamic changes, and an increased risk of heart disease. In this prospective study, we investigated the cardiac consequences of chronic experimental SCI in rats by combining cutting edge in vivo techniques (magnetic resonance imaging [MRI] and left-ventricular [LV] pressure-volume catheterization) with histological and molecular assessments. Twelve weeks post-SCI, MRI-derived structural indices and in vivo LV catheterization-derived functional indices indicated the presence of LV atrophy (LV mass in Control vs. SCI = 525 ± 38.8 vs. 413 ± 28.6 mg, respectively; p = 0.0009), reduced ventricular volumes (left-ventricular end-diastolic volume in Control vs. SCI = 364 ± 44 vs. 221 ± 35 μL, respectively; p = 0.0004), and contractile dysfunction (end-systolic pressure-volume relationship in Control vs. SCI = 1.31 ± 0.31 vs. 0.76 ± 0.11 mm Hg/μL, respectively; p = 0.0045). Cardiac atrophy and contractile dysfunction in SCI were accompanied by significantly lower blood pressure, reduced circulatory norepinephrine, and increased angiotensin II. At the cellular level, we found the presence of reduced cardiomyocyte size and increased expression of angiotensin II type 1 receptors and transforming growth factor-beta receptors (TGF-β receptor 1 and 2) post-SCI. Importantly, we found more than a two-fold increase in muscle ring finger-1 and Beclin-1 protein level following SCI, indicating the upregulation of the ubiquitin-proteasome system and autophagy-lysosomal machinery. Our data provide novel evidence that SCI-induced cardiomyocyte atrophy and systolic cardiac dysfunction are accompanied by an upregulation of proteolytic pathways, the activation of which is likely due to loss of trophic support from the sympathetic nervous system, neuromechanical unloading, and altered neurohumoral pathways.

Augmenting exercise capacity with noninvasive ventilation in high-level spinal cord injury

High-level spinal cord injury (SCI) results in a very limited innervated skeletal muscle mass that strongly reduces exercise capacity. Our recent work showed that when adding functional electrical stimulation (FES) of the paralyzed legs (hybrid FES-exercise) to produce higher exercise capacity, peak ventilation became a limiting factor to training-induced improvement in aerobic capacity. Our assumption was that the systemic adaptations to exercise training are delimited by the maximal ventilation that can be achieved. However, herein, we present a case showing an acute increase in aerobic capacity when using noninvasive ventilatory support (NIV) during FES-rowing test in an individual who had previously experimented a plateau in his aerobic capacity for 18 mo. An 18-yr-old man with C5 SCI trained with arms-only rowing for 6 mo and subsequently trained with hybrid FES-rowing for 18 mo. Peak minute ventilation (V̇e_peak) and peak oxygen consumption (V̇o_2peak) were increased after arms-only training and increased further with 6 mo of hybrid FES-row training. Despite continued intense and frequent, hybrid FES-row training, neither V̇e_peak nor V̇o_2peak increased further over the next year (1.94 and 66.0 l/min). However, when this individual performed a FES-rowing V̇o_2peak test with the addition of NIV, V̇e_peak increased by 5 l/min, resulting in an improved V̇o_2peak (2.23 l/min, +12%). This case demonstrates that noninvasive ventilation can overcome limitations to ventilation in high-level SCI and improve aerobic capacity during hybrid FES-exercise to a level not otherwise achievable. In addition, it broadly illustrates the intimate role of pulmonary function in determining the capacity to perform exercise.

Chronic, complete cervical6-7 cord transection: distinct autonomic and cardiac deficits

Spinal cord injury (SCI) resulting in tetraplegia is a devastating, life-changing insult causing paralysis and sensory impairment as well as distinct autonomic dysfunction that triggers compromised cardiovascular, bowel, bladder, and sexual activity. Life becomes a battle for independence as even routine bodily functions and the smallest activity of daily living become major challenges. Accordingly, there is a critical need for a chronic preclinical model of tetraplegia. This report addresses this critical need by comparing, for the first time, resting-, reflex-, and stress-induced cardiovascular, autonomic, and hormonal responses each week for 4 wk in 12 sham-operated intact rats and 12 rats with chronic, complete C_6-7 spinal cord transection. Loss of supraspinal control to all sympathetic preganglionic neurons projecting to the heart and vasculature resulted in a profound bradycardia and hypotension, reduced cardiac sympathetic and parasympathetic tonus, reduced reflex- and stress-induced sympathetic responses, and reduced sympathetic support of blood pressure as well as enhanced reliance on angiotensin to maintain arterial blood pressure. Histological examination of the nucleus ambiguus and stellate ganglia supports the profound and distinct autonomic and cardiac deficits and reliance on angiotensin to maintain cardiovascular stability following chronic, complete cervical_6-7 cord transection. NEW & NOTEWORTHY For the first time, resting-, reflex-, and stress-induced cardiovascular, autonomic, and hormonal responses were studied in rats with chronic, complete C_6-7 cord transection. Loss of supraspinal control of all sympathetic preganglionic neurons reduced cardiac sympathetic and parasympathetic tonus, reflex and stress-induced sympathetic responses, and sympathetic support of blood pressure as well as enhanced reliance on angiotensin to maintain arterial blood pressure. Histological examination supports the distinct deficits associated with cervical cord injury.

Spinal Cord Injury Causes Systolic Dysfunction and Cardiomyocyte Atrophy

Individuals with spinal cord injury (SCI) have been shown to exhibit systolic, and to a lesser extent, diastolic cardiac dysfunction. However, previous reports of cardiac dysfunction in this population are confounded by the changing loading conditions after SCI and as such, whether cardiac dysfunction per se is present is still unknown. Therefore, our aim was to establish if load-independent cardiac dysfunction is present after SCI, to understand the functional cardiac response to SCI, and to explore the changes within the cellular milieu of the myocardium. Here, we applied in vivo echocardiography and left-ventricular (LV) pressure-volume catheterization with dobutamine infusions to our Wistar rodent model of cardiac dysfunction 5 weeks following high (T2) thoracic contusion SCI, while also examining the morphological and transcriptional alterations of cardiomyocytes. We found that SCI significantly impairs systolic function independent of loading conditions (end-systolic elastance in control: 1.35 ± 0.15; SCI: 0.65 ± 0.19 mm Hg/μL). The reduction in contractile indices is accompanied by a reduction in width and length of cardiomyocytes as well as alterations in the LV extracellular matrix. Importantly, we demonstrate that the reduction in the rate (dP/dtmax) of LV pressure rise can be offset with beta-adrenergic stimulation, thereby experimentally implicating the loss of descending sympatho-excitatory control of the heart as a principle cause of LV dysfunction in SCI. Our data provide evidence that SCI induces systolic cardiac dysfunction independent of loading conditions and concomitant cardiomyocyte atrophy that may be underpinned by changes in the genes regulating the cardiac extracellular matrix.

A comparison of passive hindlimb cycling and active upper-limb exercise provides new insights into systolic dysfunction after spinal cord injury

Active upper-limb and passive lower-limb exercise are two interventions used in the spinal cord injury (SCI) population. Although the global cardiac responses have been previously studied, it is unclear how either exercise influences contractile cardiac function. Here, the cardiac contractile and volumetric responses to upper-limb (swim) and passive lower-limb exercise were investigated in rodents with a severe high-thoracic SCI. Animals were divided into control (CON), SCI no exercise (NO-EX), SCI passive hindlimb cycling (PHLC), or SCI swim (SWIM) groups. Severe contusion SCI was administered at the T2 level. PHLC and SWIM interventions began on day 8 postinjury and lasted 25 days. Echocardiography and dobutamine stress echocardiography were performed before and after injury. Cardiac contractile indexes were assessed in vivo at study termination via a left ventricular pressure-volume conductance catheter. Stroke volume was reduced after SCI (91 µl in the NO-EX group vs. 188 µl in the CON group, P < 0.05) and was reversed at study termination in the PHLC (167 µl) but not SWIM (90 µl) group. Rates of contraction were reduced in NO-EX versus CON groups (6,079 vs. 9,225 mmHg, respectively, P < 0.05) and were unchanged by PHLC and SWIM training. Similarly, end-systolic elastance was reduced in the NO-EX versus CON groups (0.67 vs. 1.37 mmHg/µl, respectively, P < 0.05) and was unchanged by PHLC or SWIM training. Dobutamine infusion normalized all pressure indexes in each SCI group (all P < 0.05). In conclusion, PHLC improves flow-derived cardiac indexes, whereas SWIM training displayed no cardiobeneficial effect. Pressure-derived deficits were corrected only with dobutamine, suggesting that reduced β-adrenergic stimulation is principally responsible for the impaired cardiac contractile function after SCI.NEW & NOTEWORTHY This is the first direct comparison between the cardiac changes elicited by active upper-limb or passive lower-limb exercise after spinal cord injury. Here, we demonstrate that lower-limb exercise positively influences flow-derived cardiac indexes, whereas upper-limb exercise does not. Furthermore, neither intervention corrects the cardiac contractile dysfunction associated with spinal cord injury.

Cardiac Structure and Function in Elite Para-cyclists with Spinal Cord Injury

PURPOSE

We sought to explore the association between the spinal cord injury (SCI) level on the cardiac structure and the function observed in elite para-cyclists.

METHODS

Cross-sectional echocardiographic data from 44 elite SCI hand cyclists (39.8 ± 9 yr, 68% male/32% female) stratified by the level of SCI (cervical, N = 9; T1-T5, N = 10; below T5, N = 25) and 19 non-SCI blind/visually impaired (BVI) tandem cyclists (32.4 ± 7 yr, 58% male/42% female) were analyzed before the initiation of international competition.

RESULTS

Compared with non-SCI BVI cyclists, cervical SCI para-cyclists were observed with lower indexed left ventricular (LV) mass (99.6 ± 12 vs 125 ± 20 g·m, P = 0.01), posterior wall thickness (4.5 ± 0.3 vs 5.8 ± 0.7 mm·m, P < 0.001), interventricular septal wall thickness (4.8 ± 0.5 vs 5.7 ± 0.7 mm·m; P = 0.03), and left atrial volume (21 ± 3.5 vs 28 ± 7 mL·m; P = 0.02). In multivariable analyses, cervical SCI was independently associated with decreased LV wall thickness [interventricular septum (β = -0.67, P = 0.01), posterior wall (β = -0.98, P = 0.001)], decreased LV mass (β = -21, P < 0.001), and decreased left atrial volume index (β = -6.9, P = 0.001) compared with other levels of SCI and non-SCI BVI cyclists. There were no differences in ventricular function among any of the athlete groups.

CONCLUSION

Compared with para-cyclists with lower levels of SCI, the athletes with cervical SCI demonstrate attenuated cardiac size and concentric LV hypertrophy.

Paralympic Medicine: The Road to Rio

Over the past 10 years, our team has attended numerous Paralympic games and International Paralympic Committee (IPC)-sanctioned events where we have accumulated the largest data set to date from elite athletes with spinal cord injury (SCI). This empirical evidence has allowed us to address critical questions related to health and athletic performance in these incredibly medically complex individuals. Namely, does autonomic function influence performance? Can we account for this with the present sport classification? How can we prevent the doping practice of self-inducing life-threatening episodes of hypertension to improve performance (termed "boosting")? How does extremely high participation in routine upper-body wheelchair exercise impact cardiovascular and cerebrovascular disease risk? Is it possible to improve the sport classification to level the playing field between athletes with and without autonomic dysfunction? Herein, we will narratively address these questions, and provide our perspective on future directions and recommendations moving forward. Our extensive clinical experience and comprehensive dataset suggest preserved autonomic function is critical for elite performance. We will explore how an easy-to-execute test may be able to predict which individuals are most likely to develop autonomic dysfunctions that may negatively affect their health and performance. We also will evaluate the possibility that a level playing field may be even more difficult to establish than once thought, considering the importance of not only voluntary movement to performance, but also autonomic function. Finally, we also will discuss new changes in screening guidelines at Rio to assess the occurrence of boosting, which is a banned practice by the IPC.

Abdominal Binding Improves Neuromuscular Efficiency of the Human Diaphragm during Exercise

We tested the hypothesis that elastic binding of the abdomen (AB) would enhance neuromuscular efficiency of the human diaphragm during exercise. Twelve healthy non-obese men aged 24.8 ± 1.7 years (mean ± SE) completed a symptom-limited constant-load cycle endurance exercise test at 85% of their peak incremental power output with diaphragmatic electromyography (EMGdi) and respiratory pressure measurements under two randomly assigned conditions: unbound control (CTRL) and AB sufficient to increase end-expiratory gastric pressure (Pga,ee) by 5-8 cmH₂O at rest. By design, AB increased Pga,ee by 6.6 ± 0.6 cmH₂O at rest. Compared to CTRL, AB significantly increased the transdiaphragmatic pressure swing-to-EMGdi ratio by 85-95% during exercise, reflecting enhanced neuromuscular efficiency of the diaphragm. By contrast, AB had no effect on spirometric parameters at rest, exercise endurance time or an effect on cardiac, metabolic, ventilatory, breathing pattern, dynamic operating lung volume, and perceptual responses during exercise. In conclusion, AB was associated with isolated and acute improvements in neuromuscular efficiency of the diaphragm during exercise in healthy men. The implications of our results are that AB may be an effective means of enhancing neuromuscular efficiency of the diaphragm in clinical populations with diaphragmatic weakness/dysfunction.

Autonomic testing for prediction of competition performance in Paralympic athletes

While we now appreciate that autonomic dysfunction can impact wheelchair rugby performance, this is currently not being assessed during classification, largely due to lack of a standardized and evidence-based strategy to assess autonomic function. Our aim, therefore, was to establish the optimal autonomic testing protocol that best predicts cardiovascular capacity during competition by comprehensively examining autonomic function in elite wheelchair rugby athletes with cervical SCI and thereby enhance the standardized classification. Twenty-six individuals with cervical SCI (C4-C8; AIS A, B, C) participated in this study during the 2015 Parapan American Games in Toronto, Canada. Clinic autonomic testing included: sympathetic skin responses, baseline hemodynamics, orthostatic challenge test, and cold-pressor tests. Further, we completed standard motor/sensory assessments and obtained each participants' International Wheelchair Rugby Federation classification. These clinic metrics were correlated to in-competition heart rate monitoring obtained during competition. The current study provides novel evidence that the change in systolic blood pressure during an orthostatic challenge test predicts approximately 50% of the in-competition peak heart rate (P<.001). Conversely, International Wheelchair Rugby Federation classification was poorly associated with in-competition peak heart rate (R² =.204; P<.05). Autonomic testing provides deep insight regarding preserved autonomic control after SCI that is associated with performance in elite wheelchair rugby athletes. As such, incorporating assessments of cardiovascular capacity in classification will help to ensure a level playing field and may obviate the need for practices such as boosting to gain an advantage due to poor cardiovascular control.

Differences in Left Ventricular Global Function and Mechanics in Paralympic Athletes with Cervical and Thoracic Spinal Cord Injuries

Following a spinal cord injury, there are changes in resting stroke volume (SV) and its response to exercise. The purpose of the following study was to characterize resting left ventricular structure, function, and mechanics in Paralympic athletes with tetraplegia (TETRA) and paraplegia (PARA) in an attempt to understand whether the alterations in SV are attributable to inherent dysfunction in the left ventricle. This retrospective study compared Paralympic athletes with a traumatic, chronic (>1 year post-injury), motor-complete spinal cord injury (American Spinal Injury Association Impairment Scale A-B). Eight male TETRA wheelchair rugby players (34 ± 5 years, C5-C7) and eight male PARA alpine skiers (35 ± 5 years, T4-L3) were included in the study. Echocardiography was performed in the left lateral decubitus position and indices of left ventricular structure, global diastolic and systolic function, and mechanics were derived from the average across three cardiac cycles. Blood pressure was measured in the supine and seated positions. All results are presented as TETRA vs. PARA. There was no difference in left ventricular dimensions between TETRA and PARA. Additionally, indices of global diastolic function were similar between groups including isovolumetric relaxation time, early (E) and late (A) transmitral filling velocities and their ratio (E/A). While ejection fraction was similar between TETRA and PARA (59 ± 4 % vs. 61 ± 7 %, p = 0.394), there was evidence of reduced global systolic function in TETRA including lower SV (62 ± 9 ml vs. 71 ± 6 ml, p = 0.016) and cardiac output (3.5 ± 0.6 L/min vs. 5.0 ± 0.9 L/min, p = 0.002). Despite this observation, several indices of systolic and diastolic mechanics were maintained in TETRA but attenuted in PARA including circumferential strain at the level of the papillary muscle (−23 ± 4% vs. −15 ± 6%, p = 0.010) and apex (−36 ± 10% vs. −23 ± 5%, p = 0.010) and their corresponding diastolic strain rates (papillary: 1.90 ± 0.63 s⁻¹ vs. 1.20 ± 0.51 s⁻¹, p = 0.028; apex: 3.03 ± 0.71 s⁻¹ vs. 1.99 ± 0.69 s⁻¹, p = 0.009). All blood pressures were lower in TETRA. The absence of an association between reduced global systolic function and mechanical dysfunction in either TETRA or PARA suggests any reductions in SV are likely attributed to impaired loading rather than inherent left ventricular dysfunction.

Effect of abdominal binding on respiratory mechanics during exercise in athletes with cervical spinal cord injury

We asked whether elastic binding of the abdomen influences respiratory mechanics during wheelchair propulsion in athletes with cervical spinal cord injury (SCI). Eight Paralympic wheelchair rugby players with motor-complete SCI (C5-C7) performed submaximal and maximal incremental exercise tests on a treadmill, both with and without abdominal binding. Measurements included pulmonary function, pressure-derived indices of respiratory mechanics, operating lung volumes, tidal flow-volume data, gas exchange, blood lactate, and symptoms. Residual volume and functional residual capacity were reduced with binding (77 ± 18 and 81 ± 11% of unbound, P < 0.05), vital capacity was increased (114 ± 9%, P < 0.05), whereas total lung capacity was relatively well preserved (99 ± 5%). During exercise, binding introduced a passive increase in transdiaphragmatic pressure, due primarily to an increase in gastric pressure. Active pressures during inspiration were similar across conditions. A sudden, sustained rise in operating lung volumes was evident in the unbound condition, and these volumes were shifted downward with binding. Expiratory flow limitation did not occur in any subject and there was substantial reserve to increase flow and volume in both conditions. V̇o2 was elevated with binding during the final stages of exercise (8-12%, P < 0.05), whereas blood lactate concentration was reduced (16-19%, P < 0.05). V̇o2/heart rate slopes were less steep with binding (62 ± 35 vs. 47 ± 24 ml/beat, P < 0.05). Ventilation, symptoms, and work rates were similar across conditions. The results suggest that abdominal binding shifts tidal breathing to lower lung volumes without influencing flow limitation, symptoms, or exercise tolerance. Changes in respiratory mechanics with binding may benefit O2 transport capacity by an improvement in central circulatory function.

Passive hind-limb cycling improves cardiac function and reduces cardiovascular disease risk in experimental spinal cord injury

Spinal cord injury (SCI) causes altered autonomic control and severe physical deconditioning that converge to drive maladaptive cardiac remodelling. We used a clinically relevant experimental model to investigate the cardio-metabolic responses to SCI and to establish whether passive hind-limb cycling elicits a cardio-protective effect. Initially, 21 male Wistar rats were evenly assigned to three groups: uninjured control (CON), T3 complete SCI (SCI) or T3 complete SCI plus passive hind-limb cycling (SCI-EX; 2 × 30 min day(-1), 5 days week(-1) for 4 weeks beginning 6 days post-SCI). On day 32, cardio-metabolic function was assessed using in vivo echocardiography, ex vivo working heart assessments, cardiac histology/molecular biology and blood lipid profiles. Twelve additional rats (n = 6 SCI and n = 6 SCI-EX) underwent in vivo echocardiography and basal haemodynamic assessments pre-SCI and at days 7, 14 and 32 post-SCI to track temporal cardiovascular changes. Compared with CON, SCI exhibited a rapid and sustained reduction in left ventricular dimensions and function that ultimately manifested as reduced contractility, increased myocardial collagen deposition and an up-regulation of transforming growth factor beta-1 (TGFβ1) and mothers against decapentaplegic homolog 3 (Smad3) mRNA. For SCI-EX, the initial reduction in left ventricular dimensions and function at day 7 post-SCI was completely reversed by day 32 post-SCI, and there were no differences in myocardial contractility between SCI-EX and CON. Collagen deposition was similar between SCI-EX and CON. TGFβ1 and Smad3 were down-regulated in SCI-EX. Blood lipid profiles were improved in SCI-EX versus SCI. We provide compelling novel evidence that passive hind-limb cycling prevents cardiac dysfunction and reduces cardiovascular disease risk in experimental SCI.

Bronchial hyperresponsiveness testing in athletes of the Swiss Paralympic team

BACKGROUND

The aim of this study was to assess airway hyperresponsiveness to eucapnic voluntary hyperventilation and dry powder mannitol challenge in athletes aiming to participate at the Paralympic Games 2008 in Beijing, especially in athletes with spinal cord injury.

METHODS

Forty-four athletes with a disability (27 with paraplegia (group 1), 3 with tetraplegia (group 2) and 14 with other disabilities such as blindness or single limb amputations (group 3) performed spirometry, skin prick testing, measurement of exhaled nitric oxide, eucapnic voluntary hyperventilation challenge test (EVH) and mannitol challenge test (MCT). A fall in FEV1 of ≥10% in either challenge test was deemed positive for exercise-induced bronchoconstriction.

RESULTS

Fourteen (32%) athletes were atopic and 7 (16%) had a history of physician-diagnosed asthma. Absolute lung function values were significantly lower in patients of group 1 and 2 compared to group 3. Nine (20%) athletes were positive to EVH (8 paraplegics, 1 tetraplegic), and 8 (18%) athletes were positive to MCT (7 paraplegics, 1 tetraplegic). Fourteen (22.7%) subjects were positive to at least one challenge; only three athletes were positive to both tests. None of the athletes in group 3 had a positive test. Both challenge tests showed a significant association with physician-diagnosed asthma status (p = 0.0001). The positive and negative predictive value to diagnose physician-diagnosed asthma was 89% and 91% for EHV, and 75% and 86% for MCT, respectively.

CONCLUSION

EVH and MCT can be used to identify, but especially exclude asthma in Paralympic athletes.

Assessment of pulmonary restriction in cervical spinal cord injury: a preliminary report

OBJECTIVE

To compare the prevalence of pulmonary restriction on the basis of a vital capacity (VC) below the lower limit of normal (LLN) and a normal or high forced expiratory volume in 1 second (FEV(1))/VC ratio with the criterion standard of total lung capacity (TLC) less than LLN in individuals with spinal cord injury (SCI) and able-bodied (AB) controls.

DESIGN

Method comparison with criterion standard.

SETTING

University research center.

PARTICIPANTS

Individuals with cervical SCI (n=12; injury level, C5-7) and AB controls (n=12) matched for age, stature, and body mass.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

TLC via plethysmography; FEV(1) and VC via spirometry; and maximum inspiratory and expiratory pressures (P(Imax) and P(Emax)).

RESULTS

All participants with SCI exhibited a VC less than LLN and a normal-to-high FEV(1)/VC ratio, whereas significantly fewer (8 of 12) participants with SCI exhibited a TLC less than LLN (P=.046). For the AB group, no participant exhibited a VC or TLC less than LLN. Percent-predicted VC was lower than the percent-predicted TLC in SCI (P=.013), whereas percent-predicted VC was higher than percent-predicted TLC in AB controls (P=.001). Percent-predicted P(Imax) was higher than P(Emax) in SCI (P=.001) but not AB controls (P=.146).

CONCLUSIONS

A VC less than LLN with a normal-to-high FEV(1)/VC ratio does not accurately predict pulmonary restriction in cervical SCI. When using spirometry to infer pulmonary restriction in cervical SCI, we recommend using a VC below 60% of the AB predicted value.

Effects of abdominal binding on cardiorespiratory function in cervical spinal cord injury

We asked whether abdominal binding improves cardiorespiratory function in individuals with cervical spinal cord injury (SCI). 13 participants with chronic SCI (C(5)-C(7)) and 8 able-bodied controls were exposed to varying degrees of elastic abdominal compression (unbound [UB], loose-bound [LB], and tight-bound [TB]) while seated. In SCI, TB increased vital capacity (14%), expiratory flow throughout vital capacity (15%), inspiratory capacity (21%), and maximal expiratory mouth pressure (25%). In contrast, TB reduced residual volume (-34%) and functional residual capacity (-23%). TB increased tidal and twitch transdiaphragmatic pressures (∼45%), primarily by increasing the gastric pressure contributions. TB increased cardiac output (28%), systolic mitral annular velocity (22%), and late-diastolic mitral annular velocity (50%). Selected measures of cardiorespiratory function improved with LB, but the changes were less compared to TB. In able-bodied, changes were inconsistent and always less than in SCI. In conclusion, abdominal-binding improved cardiorespiratory function in low-cervical SCI by optimising operating lung volumes, increasing expiratory flow, enhancing diaphragmatic pressure production, and improving left-ventricular function.