Cameron M. Gee

Peak heart rates and sympathetic function in tetraplegic nonathletes and athletes.

PURPOSE To examine differences in peak heart rate (HR) and measures of sympathetic function between nonathletes and athletes with chronic, motor-complete, cervical spinal cord injury (SCI). METHODS Eight nonathletic men with SCI (C4-C7; age 47 ± 9 yr, with injury duration of 16 ± 9 yr) and 13 athletic men with SCI (C5-C8; age 37 ± 8 yr, with injury duration of 16 ± 6 yr) participated in the study. Measures of sympathetic function included palmar sympathetic skin responses (SSR) to median nerve stimulation, and systolic (SBP) and diastolic (DBP) blood pressure responses to a passive sit-up test. Peak HR responses were assessed during a maximal exercise test. RESULTS Compared to the athletic group, the nonathletic group exhibited lower peak HR (102 ± 34 vs 161 ± 20 bpm, P < 0.001) and average SSR scores (0.13 ± 0.35 vs 2.41 ± 1.97, P = 0.008), along with greater reductions in SBP and DBP in response to passive sit-up (SBP: -22 ± 10 vs -9 ± 12 mm Hg, P = 0.019; DBP: -18 ± 8 mm Hg vs -4 ± 9 mm Hg, P = 0.003). On the basis of the criteria for orthostatic hypotension (OH) (drop in SBP ≥ 20 mm Hg or DBP ≥ 10 mm Hg), 88% and 23% of nonathletes and athletes had OH. CONCLUSIONS Attenuated peak HR in nonathletic individuals with tetraplegia may be secondary to impairments in sympathetic function including absent SSR and OH. Furthermore, the degree of preserved sympathetic function documented in tetraplegic athletes may suggest a predisposition to engage in high-performance sports. Collectively, our findings provide novel insight into the importance of the sympathetic nervous system for exercise performance.

Cardiovascular control, autonomic function, and elite endurance performance in spinal cord injury

We aimed to determine the relationship between level of injury, completeness of injury, resting as well as exercise hemodynamics, and endurance performance in athletes with spinal cord injury (SCI). Twenty‐three elite male paracycling athletes (C3‐T8) were assessed for neurological level/completeness of injury, autonomic completeness of injury, resting cardiovascular function, and time to complete a 17.3‐km World Championship time‐trial test. A subset were also fitted with heart rate (HR) monitors and their cycles were fitted with a global positioning systems device (n = 15). Thoracic SCI exhibited higher seated systolic blood pressure along with superior time‐trial performance compared with cervical SCI (all P < 0.01). When further stratified by autonomic completeness of injury, the four athletes with cervical autonomic incomplete SCI exhibited a faster time‐trial time and a higher average speed compared with cervical autonomic complete SCI (all P < 0.042). Maximum and average HR also tended to be higher in cervical autonomic incomplete vs autonomic complete. There were no differences in time‐trial time, HR, or speed between thoracic autonomic complete vs incomplete SCI. In conclusion, autonomic completeness of injury and the consequent ability of the cardiovascular system to respond to exercise appear to be a critical determinant of endurance performance in elite athletes with cervical SCI.

Physical exercise improves arterial stiffness after spinal cord injury.

Abstract Objective/background Aortic pulse wave velocity (PWV), the gold-standard assessment of central arterial stiffness, has prognostic value for cardiovascular disease risk in able-bodied individuals. The aim of this study was to compare aortic PWV in athletes and non-athletes with spinal cord injury (SCI). Design Cross-sectional comparison. Methods Aortic PWV was assessed in 20 individuals with motor-complete, chronic SCI (C2–T5; 18 ± 8 years post-injury) using applanation tonometry at the carotid and femoral arterial sites. Ten elite hand-cyclists were matched for sex to 10 non-athletes; age and time since injury were comparable between the groups. Heart rate and discrete brachial blood pressure measurements were collected throughout testing. Outcome measures Aortic PWV, blood pressure, heart rate. Results Aortic PWV was significantly lower in athletes vs. non-athletes (6.9 ± 1.0 vs. 8.7 ± 2.5 m/second, P = 0.044). There were no significant between-group differences in resting supine mean arterial blood pressure (91 ± 19 vs. 81 ± 10 mmHg) and heart rate (60 ± 10 vs. 58 ± 6 b.p.m.). Conclusion Athletes with SCI exhibited improved central arterial stiffness compared to non-athletes, which is in agreement with the previous able-bodied literature. This finding implies that chronic exercise training may improve arterial health and potentially lower cardiovascular disease risk in the SCI population.

Active-Arm Passive-Leg Exercise Improves Cardiovascular Function in Spinal Cord Injury.

ABSTRACTIn a 43-yr-old male subject with a chronic T3 AIS A spinal cord injury, the acute cardiorespiratory responses to active upper-extremity exercise alone and combined active-arm passive-leg exercise (AAPLE) were investigated, along with the cardiorespiratory, cardiac, vascular, and body composition responses to a 6-wk AAPLE interval training intervention. AAPLE elicited superior acute maximal cardiorespiratory responses compared with upper-extremity exercise alone. In response to a 6-wk interval training regimen, AAPLE caused a 25% increase in peak oxygen uptake, a 10% increase in resting stroke volume, and a 4-fold increase in brachial artery blood flow. Conversely, there were no changes in femoral arterial function, body composition, or bone mineral density in response to training. As a potential clinical intervention, AAPLE may be advantageous over other forms of currently available exercise, owing to the minimal setup time and cost involved and the nonreliance on specialized equipment that is required for other exercise modalities.

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.

A 20×20 metre repeated sprint field test replicates the demands of wheelchair rugby

OBJECTIVES To assess the physiological responses to, and the agreement between, a 20×20m repeated sprint field test and wheelchair rugby game play, as well as the reliability of the test. DESIGN Cross-sectional and longitudinal. METHODS Heart rate (HR), blood lactate ([La-]B), and ratings of perceived exertion (RPE) were collected in nineteen elite wheelchair rugby athletes before, during, and after a 20×20m repeated sprint field test and game play. Times to complete 5, 10, and 20m during the field test were also collected. RESULTS Peak HR and peak [La-]B were positively correlated during the field test (r=0.470, p=0.043), as were peak HR and peak speed (r=0.493, p=0.031), and peak [La-]B and peak speed (r=0.559, p=0.013). During game play, peak [La-]B was correlated with peak RPE (rho=0.703, p=0.001). Intra-class correlations (ICCs) between the field test and game play were significant for peak HR (ICC=0.922, p<0.001) and peak [La-]B (ICC=0.845, p<0.001). Bland-Altman analysis revealed good agreement between HR and [La-]B obtained during the field test and game play and excellent between-day reliability of the 20×20m sprint test. CONCLUSIONS The physiological demands of a 20×20m repeated sprint field test are similar to those of elite wheelchair rugby game play and the test is highly reliable. This simple to implement field test may be useful as a component of team selection and in assessing the effectiveness of training interventions or monitoring athletes across training phases.