A Reappraisal of Ventilatory Thresholds in Wheelchair Athletes With a Spinal Cord Injury: Do They Really Exist?

The ventilatory threshold (VT) separates low- from moderate-intensity exercise, the respiratory compensation point (RCP) moderate- from high-intensity exercise. Both concepts assume breakpoints in respiratory data. However, the objective determination of the VT and RCP using breakpoint models during upper-body modality exercise in wheelchair athletes with spinal cord injury (SCI) has received little attention. Therefore, the aim of this study was to compare the fit of breakpoint models (i.e., two linear regression lines) with continuous no-breakpoint models (i.e., exponential curve/second-order polynomial) to respiratory data obtained during a graded wheelchair exercise test to exhaustion. These fits were compared employing adjusted R2, and blocked bootstrapping was used to derive estimates of a median and 95% confidence intervals (CI). V̇O2-V̇CO2 and V̇E/V̇O2-time data were assessed for the determination of the VT, and V̇CO2-V̇E and V̇E/V̇CO2-time data for the determination of the RCP. Data of 9 wheelchair athletes with tetraplegia and 8 with paraplegia were evaluated. On an overall group-level, there was an overlap in the adjusted R2 median ± 95% CI between the breakpoint and the no-breakpoint models for determining the VT (V̇O2-V̇CO2: 0.991 ± 0.003 vs. 0.990 ± 0.003; V̇E/V̇O2-time: 0.792 ± 0.101 vs. 0.782 ± 0.104, respectively) and RCP (V̇E-V̇CO2: 0.984 ± 0.004 vs. 0.984 ± 0.004; V̇E/V̇CO2-time: 0.729 ± 0.064 vs. 0.691 ± 0.063, respectively), indicating similar model fit. We offer two lines of reasoning: (1) breakpoints in these respiratory data exist but are too subtle to result in a significant difference in adjusted R2 between the investigated breakpoint and no-breakpoint models; (2) breakpoints do not exist, as has been argued previously.

Shoulder Tendon Adaptations Following a Graded Exercise Test to Exhaustion in Highly Trained Wheelchair Rugby Athletes With Different Impairments.

Objective: This study aimed to identify acute changes in biceps and supraspinatus tendon characteristics before and after a graded exercise test to exhaustion (GXT) in highly trained wheelchair rugby (WR) athletes. A secondary aspect was to define chronic tendon adaptations related to the impairment of the athlete and the occupation of the tendon within the subacromial space (occupation ratio). Methods: Twelve WR athletes with different impairments (age = 32 ± 6 years; body mass = 67.2 ± 11.2 kg; 9.0 ± 3.6 years competing) volunteered for this study. Performance Corrected Wheelchair Users Shoulder Pain Index was used to quantify shoulder pain. Quantitative Ultrasound Protocols (QUS) were used to define supraspinatus and biceps tendon thickness, echogenicity, and echogenicity ratio of both dominant and non-dominant shoulder before and after the GXT including 22 ± 3.1 min submaximal propulsion and 10.2 ± 1.7 min maximal propulsion on a treadmill. Furthermore, the acromio-humeral distance (AHD) defined from ultrasound (US) images was used to calculate the occupation ratios. Results: A mixed-effect multilevel analysis that included shoulder as grouping variable, demonstrated a significant reduction in the echogenicity of the biceps following GXT whilst controlling for impairment [spinal cord injury (SCI) and non-SCI] and the occupation ratio (ß = -9.01, SEß = 2.72, p = 0.001, 95% CI = [-14.34; -3.68]). This points toward fluid inflow into the tendon that may be related to overload and acute inflammation. In addition, persons with a SCI (n = 8) had a thicker supraspinatus tendon in comparison to persons with non-SCI (n = 3) which may be related to chronic tendon adaptations (ß = -0.53 mm, SEß = 0.26, p = 0.038, 95% CI = [-1.04; -0.03]). Finally, a greater occupation ratio was associated with signs of tendinopathy (i.e., greater biceps and supraspinatus tendon thickness, and lower supraspinatus echogenicity and echogenicity ratio). Conclusion: Acute biceps tendon adaptations in response to the GXT in highly trained WR athletes were evident with chronic adaptations in the supraspinatus tendon being related to the impairment of the athlete. Ultrasound can be used to monitor tendon adaptations in WR athletes for medical diagnosis to assist the scheduling and type of training.

Perceptually regulated training does not influence the differentiated RPE response following 16-weeks of aerobic exercise in adults with spinal cord injury.

This study investigated the effect of prolonged familiarisation with ratings of perceived exertion (RPE) on the peripheral (RPEP) and central (RPEC) RPE responses to moderate-vigorous exercise in adults with spinal cord injury (SCI). RPEP and RPEC characterise the exertion of the working musculature and cardiorespiratory systems, respectively. Nineteen participants (age, 41.4 ± 11.4 years; peak oxygen uptake, 19.2 ± 7.2 mL·kg-1·min-1) with chronic SCI were randomly assigned to RPE-guided (n = 11; EXP) or active control (n = 8; CON) groups. EXP performed 16-weeks of RPE-guided, supervised aerobic training for 20 min, twice weekly, at RPE 3-6 (Category-Ratio 10 scale). CON had access to the same exercise equipment but received no specific advice on their exercise-training regime. Participants completed a graded exercise test, using an arm crank ergometer at pre- and post-training to determine peak oxygen uptake, with RPEP and RPEC recorded every minute throughout tests. Sixteen weeks training did not improve peak oxygen uptake. RPE decreased post-training at 50% (p = 0.02) and 70% peak oxygen uptake (p = 0.03), though there was no effect of group at either intensity (p = 0.54, 0.42, respectively). At 70% peak oxygen uptake, RPEP was greater than RPEC (4.2 ± 1.7 vs 3.4 ± 1.8, p < 0.005). Training with RPE-guidance for 16 weeks had no additional effect on the differentiated RPE responses to moderate-vigorous exercise in adults with SCI. Novelty In adults with SCI, differentiated RPE responses were not different between those who did, and did not, perform 16 weeks of RPE-guided training. This challenges whether familiarisation with RPE is necessary to be an effective regulator of exercise intensity in this population.

Peak oxygen uptake measured during a perceptually-regulated exercise test is reliable in community-based manual wheelchair users.

This study compares test-retest reliability and peak exercise responses from ramp-incremented (RAMP) and maximal perceptually-regulated (PRETmax) exercise tests during arm crank exercise in individuals reliant on manual wheelchair propulsion (MWP). Ten untrained participants completed four trials over 2-weeks (two RAMP (0-40 W + 5-10 W · min-1) trials and two PRETmax. PRETmax consisted of five, 2-min stages performed at Ratings of Perceived Exertion (RPE) 11, 13, 15, 17 and 20). Participants freely changed the power output to match the required RPE. Gas exchange variables, heart rate, power output, RPE and affect were determined throughout trials. The V̇O2peak from RAMP (14.8 ± 5.5 ml · kg-1 · min-1) and PRETmax (13.9 ± 5.2 ml · kg-1 · min-1) trials were not different (P = 0.08). Measurement error was 1.7 and 2.2 ml · kg-1 · min-1 and coefficient of variation 5.9% and 8.1% for measuring V̇O2peak from RAMP and PRETmax, respectively. Affect was more positive at RPE 13 (P = 0.02), 15 (P = 0.01) and 17 (P = 0.01) during PRETmax. Findings suggest that PRETmax can be used to measure V̇O2peak in participants reliant on MWP and leads to a more positive affective response compared to RAMP.

Spinal Cord Injury Level Influences Acute Plasma Caffeine Responses.

PURPOSE: This study aimed to investigate the absorption curve and acute effects of caffeine at rest in individuals with no spinal cord injury (SCI), paraplegia (PARA), and tetraplegia (TETRA). METHODS: Twenty-four healthy males (eight able-bodied [AB], eight PARA, and eight TETRA) consumed 3 mg·kg caffeine anhydrous (CAF) in a fasted state. Plasma caffeine [CAF], glucose, lactate, free fatty acid, and catecholamine concentrations were measured during a 150-min rest period. RESULTS: Peak [CAF] was greater in TETRA (21.5 µM) compared with AB (12.2 µM) and PARA (15.1 µM), and mean peak [CAF] occurred at 70, 80, and 80 min, respectively. Moderate and large effect sizes were revealed for TETRA compared with PARA and AB (-0.55 and -1.14, respectively) for the total area under the [CAF] versus time curve. Large interindividual responses were apparent in SCI groups. The change in plasma catecholamine concentrations after CAF did not reach significance (P > 0.05); however, both adrenaline and noradrenaline concentrations were lowest in TETRA. Significant increases in free fatty acid were seen over time (P < 0.0005), but there was no significant influence of SCI level. Blood lactate concentration reduced over time (P = 0.022), whereas blood glucose concentration decreased modestly (P = 0.695), and no difference between groups was seen (P > 0.05). CONCLUSION: The level of SCI influenced the caffeine absorption curve, and there was large interindividual variation within and between groups. Individual curves should be considered when using caffeine as an ergogenic aid in athletes with an SCI. The results indicate TETRA should trial low doses in training and PARA may consider consuming caffeine greater than 60 min before exercise performance. The study also supports caffeine's direct effect on adipose tissue, which is not secondary to catecholamine release.

Nutritional Supplement Habits of Athletes With an Impairment and Their Sources of Information.

The consumption of nutritional supplements (NS) is common among able-bodied (AB) athletes yet little is known about NS use by athletes with an impairment. This study examined the: (i) prevalence of NS use by athletes with an impairment; (ii) reasons for use/ nonuse; (iii) sources of information regarding NS; and (iv) whether age, gender, impairment, performance level and sport category influence NS use. The questionnaire was completed by 399 elite (n = 255) and nonelite (n = 144) athletes (296 M, 103 F) online or at a sporting event/training camp. Data were evaluated using chi-square analyses. Fifty-eight percent (n = 232) of athletes used NS in the previous 6-month period and 41% (n = 102) of these followed the instructions on the label to determine dose. Adherence to these AB recommendations may partly explain why 9% (n = 37) experienced negative effects from NS use. As expected, the most popular NS were: protein, sports drinks, multivitamins and carbohydrate supplements, which were obtained from health food/sport shops, internet and supermarkets (top 3) where evidence-based, impairment-specific advice is limited. The nutritionist/dietitian was the most used and trusted source of information, which is a promising finding. The most prevalent reasons for use were to support exercise recovery, support the immune system and provide energy. Elite athletes were more likely to use NS, which may reflect greater training hours and/or access to nutritionists. Fifty-two percent of athletes (n = 209) requested more information/ education regarding NS. NS use is prevalent in this population. Education on dosage and appropriate sources of information is required.

Mucosal immune responses to treadmill exercise in elite wheelchair athletes.

PURPOSE: The study's purpose was to examine salivary secretory immunoglobulin A (sIgA) responses and α-amylase activity after constant load and intermittent exercise in elite wheelchair athletes. METHODS: Twenty-three wheelchair athletes divided into three groups (eight tetraplegic (TETRA), seven paraplegic, and eight non-spinal cord-injured) performed two randomized and counterbalanced 60-min sessions on a treadmill. These consisted of constant load (60% peak oxygen uptake) and intermittent (80% and 40% peak oxygen uptake) exercise blocks. Timed unstimulated saliva samples were obtained before, mid, after, and 30 min after exercise and analyzed for sIgA and α-amylase. Furthermore, oxygen uptake, blood lactate concentration, and RPE were measured during both sessions. RESULTS: SIgA secretion rate and α-amylase activity were increased during exercise in all groups (P < 0.05). However, the increase of sIgA secretion rate during exercise was greater in TETRA individuals (postexercise average data for both trials in comparison with preexercise data: TETRA = +60% ± 31%, paraplegic = +30% ± 35%, non-spinal cord-injured = +11% ± 25%; P < 0.05). Yet, groups were comparable with respect to blood lactate concentration and RPE for both exercise sessions. CONCLUSIONS: Despite the disruption of autonomic salivary gland innervation in TETRA athletes, their ability to increase sIgA secretion rate seems comparable to wheelchair athletes with intact autonomic salivary gland innervation. The similar responses between groups may stem from sympathetic reflex activity during exercise or a predominant contribution of parasympathetic activity, which are still intact systems in the TETRA population. The results of this study support the positive role of acute exercise on oral immune function in wheelchair athletes independent of disability type.

The oxygen uptake-heart rate relationship in trained female wheelchair athletes.

We examined the relationship between the percentage of peak heart rate (HR) and the percentage of peak oxygen uptake VO2 during steady-rate incremental wheelchair propulsion in 10 trained female wheelchair athletes (WAs) to determine the appropriateness of using American College of Sports Medicine (ACSM) target HRs for training prescription. Oxygen uptake was calculated during each submaximal exercise stage, and HR was monitored continuously. Peak VO2 was determined with the use of a separate protocol. Linear regression equations of percentage of peak HR versus percentage of peak VO2 were measured for each participant. Subsequently, we calculated the percentage of peak HR values corresponding with 40%, 60%, 80%, and 85% peak VO2. The linear regression formula (derived as the group mean of the slope and intercept terms determined from each individual participant) was % peak HR = 0.652 x % peak VO2 + 35.2 (standard error of the estimate [SEE] 3.41). The group mean of the individual correlation coefficients for the VO2-HR relationship was r = 0.973. The percentage peaks of HRs for the WAs were slightly, though not significantly, greater than those suggested by the ACSM across the exercise intensity continuum. These findings suggest that training programs prescribed on the basis of ACSM target HR guidelines need not be altered for trained female WAs with lesions of T6 and below. Notably, the discrepancy between the WA values and the population norm (ACSM) decreased from 6% at 40% peak VO2 (i.e., 61% vs. 55%) to <1% at 85% peak VO2 (i.e., 90.6% vs. 90.0%). This discrepancy indicates a tendency for the use of percentage of HR peak at the lower exercise intensities to slightly underestimate the relative exercise intensity (i.e., percentage of peak VO2) in the WA population.

Effect of push frequency and strategy variations on economy and perceived exertion during wheelchair propulsion.

Wheelchair locomotion is a cyclical activity and participants are free to select any push frequency-propulsion strategy combination that suits their needs at a given power output. The aim of the study was to examine the physiological effects of varying push frequency and strategy on pushing economy. Twelve male, able-bodied participants completed four, randomly assigned, 5-min bouts of submaximal exercise at 32 W on a wheelchair ergometer. Each bout of exercise combined two different push frequencies (40 and 70 push min(-1)), with one of two different push strategies [synchronous (SYN): both arms pushing together, and asynchronous: one arm applying force to the wheel at a time). Physiological measures included oxygen uptake ( VO(2)), heart rate (HR) and blood lactate [La](b )concentration. Differentiated ratings of perceived exertion (RPE) were also recorded (overall, local and central). Separate ANOVA were used for VO(2), HR, [La](b) and RPE as the dependent variables. Where significant differences were identified, a Bonferroni post hoc test was used. The main effect for push frequency by strategy was significant for VO(2) ( P<0.01). Scrutiny of the HR values showed that the SYN 40 condition was significantly less stressful than all other frequency-strategy combinations ( P<0.01). RPE data supported these findings although they were found to be non-significant. When looking at [La](b,) both of the main effects were also significant showing the concentration was lower on average when the push rate was 40 as opposed to 70 (1.65 vs 2.14 mmol l(-1); P<0.01). This study provides further evidence that a low push frequency provides the most economical form of wheelchair propulsion especially when combined with a SYN strategy.