Thermoregulatory responses of athletes with a spinal cord injury during rest and exercise

Following on from Rio de Janeiro 2016, the Tokyo 2020 Paralympic Games will present a unique challenge for athletes, needing to prepare and adapt to the potential challenging environmental conditions of 20-27°C and ~73% relative humidity. It is well known that during exercise in hot and/or humid climates, able-bodied athletes experience an increase in thermal strain and a reduction in performance compared to cooler/drier conditions. Yet these conditions prove even more problematic for athletes, who as a consequence of their impairment have a dysfunctional thermoregulatory system, such as athletes with a spinal cord injury (SCI). To date, the thermoregulatory responses of athletes with an SCI have been an under-studied area of research. To gain a greater understanding of how heat balance is altered in individuals with an SCI and the thermoregulatory consequences as a result, studies need to first be conducted at rest, removing the additional metabolic heat production from exercise. Although a large majority of athletes with an SCI compete indoors in wheelchair court sports (e.g. wheelchair basketball and rugby), exercising even in these climate-controlled environments has been shown to place these athletes under considerable thermal strain. In light of this, it is remarkable that existing research on the thermoregulatory responses of athletes with an SCI during exercise is scarce, especially studies encompassing “real-world” sporting environments. Athletes with high level lesions (tetraplegia, TP) are a particularly under-studied population group shown to have a greater thermoregulatory impairment than individuals with low level lesions (paraplegia, PA) during continuous exercise. Thus the aim of this thesis was to investigate the thermoregulatory responses of athletes with an SCI at rest and during “real-world” sporting scenarios, with specific focus on athletes with TP. Study 1 aimed to determine how evaporative heat loss is altered, as a result of an SCI, compared to the able-bodied (AB), and the effect lesion level has on this response. The results provide evidence that in individuals with TP, even at rest, evaporative heat loss is not large enough to balance the heat load, when evaporation is the primary source of heat dissipation. Even though in individuals with PA Tgi increased by a smaller magnitude and they possessed a greater sweating capacity than individuals with TP, at ambient temperatures above Tsk latent heat loss is insufficient to attain heat balance, compared to the AB. To investigate the thermoregulatory responses of athletes with an SCI during “real-world” sporting scenarios Study 2 examined athletes with TP compared to athletes with PA during 60 min of intermittent sprint wheelchair exercise on a wheelchair ergometer. The study was conducted in conditions representative of an indoor playing environment for wheelchair rugby and basketball (~21°C, 40% relative humidity). Results demonstrated that, despite similar external work, athletes with TP were under greater thermal strain than athletes with PA. Study 3’s novel approach investigated both physiological responses and activity profiles of wheelchair rugby players during competitive match play. Despite players with TP covering 17% less distance and pushing on average 10% slower, they were under a greater amount of thermal strain than players with non-spinal related physical impairments (NON-SCI). Furthermore, this study demonstrated that players with TP that had a larger body mass, larger lean mass, covered a greater relative distance and/or were a higher point player had a greater end Tgi. These data provide an insight for coaches and support staff regarding which players may need greater attention in regards to cooling strategies or breaks in play. The effectiveness of cooling practices currently employed by athletes with TP has not been previously investigated. Study 4 determined the effectiveness of pre-cooling, using an ice vest alone and in combination with water sprays between quarters, at attenuating thermal strain in athletes with TP. Using the activity profile data from Study 3, an intermittent sprint protocol, conducted on a wheelchair ergometer, was used to represent a wheelchair rugby match. The combination of cooling methods lowered Tgi and Tsk to a greater extent than pre-cooling only, despite neither cooling condition having a positive or negative effect on performance. Unexpectedly, the pre-cooling only condition lowered Tgi, compared to no cooling, throughout the subsequent exercise protocol, even though the reduction in Tsk was not long lasting. This thesis provides comprehensive evidence that athletes with TP experience heightened thermal strain during both rest and “real-world” sporting scenarios compared to the AB, athletes with PA, and within the sport of wheelchair rugby. Athletes with TP should employ practices, such as appropriate cooling methods or alter playing tactics to reduce thermal strain and the likelihood of attaining a heat related injury

Cooling athletes with a spinal cord injury

Cooling strategies that help prevent a reduction in exercise capacity whilst exercising in the heat have received considerable research interest over the past three decades, especially in the lead up to a relatively hot Olympic and Paralympic Games. Progressing into the next Olympic/Paralympic cycle the host, Rio de Janeiro, could again present an environmental challenge for those athletes competing. Despite the interest and vast array of research into cooling strategies for the able-bodied athlete, less is known regarding the application of these cooling strategies in the thermoregulatory impaired spinal cord injured (SCI) athletic population. Individuals with a spinal cord injury (SCI) have a reduced afferent input to the thermoregulatory centre and a loss of both sweating capacity and vasomotor control below the level of the spinal cord lesion. The magnitude of this thermoregulatory impairment is proportional to the level of the lesion. For instance, individuals with high level lesions (tetraplegia) are at a greater risk of heat illness than individuals with lower level lesions (paraplegia) at a given exercise intensity. Therefore, cooling strategies may be highly beneficial in this population group, even in moderate ambient conditions (~21°C). This review was undertaken to examine the scientific literature that addresses the application of cooling strategies in individuals with a SCI. Each method is discussed in regards to the practical issues associated with the method and the potential underlying mechanism. For instance, site specific cooling would be more suitable for an athlete with a SCI than whole body water immersion, due to the practical difficulties of administering this method in this population group. From the studies reviewed, wearing an ice vest during intermittent sprint exercise has been shown to decrease thermal strain and improve performance. These garments have also been shown to be effective during exercise in the able-bodied. Drawing on additional findings from the able-bodied literature the combination of methods used prior to and during exercise and/or during rest periods/half-time may increase the effectiveness of a strategy. However, due to the paucity of research involving athletes with a SCI, it is difficult to establish an optimal cooling strategy. Future studies are needed to ensure that research outcomes can be translated into meaningful performance enhancements by investigating cooling strategies under the constraints of actual competition. Cooling strategies which meet the demands of intermittent wheelchair sports need to be identified, with particular attention to the logistics of the sport

Sex differences in thermal strain induced by a typical hiking scenario in a cool environment

Most research investigating hill walking has focused on the mechanisms of accidental hypothermia with protocols involving males exposed to prolonged wet and windy environments [1]. No attention has been paid to discomfort associated with the different phases of recreational hiking in non-adverse conditions. The present study was designed to evaluate overall and local thermal strain during a typical hiking scenario and to highlight potential differences between males and females. This knowledge can be of practical importance for improved clothing requirement

Different physiological responses but similar thermal perceptions for males with various body fatness during cold air exposure

There is no consensus regarding the potential effect of body fatness on subjective responses to cold at rest [1,2]. Most studies have examined overall sensation and comfort with no attention to regional values or the influence of exercise on thermal perception. The present study aimed at exploring overall and regional perceptual responses of males, varying in body fat content (¿) in association with their physiological responses, specifically regional skin temperatures (Tsk)

Salivary immunoglobulin A and upper respiratory symptoms during 5 months of training in elite tetraplegic athletes

Purpose: Altered autonomic innervation in tetraplegic individuals has been shown to depress certain immune parameters at rest and alter exercise-related salivary immunoglobulin A (sIgA) responses. The purpose of this study was to examine resting sIgA responses as a function of training load and episodes of upper respiratory symptoms (URS) in elite tetraplegic athletes. Methods: Resting saliva samples were obtained from 14 tetraplegic athletes at 12 predefined time points over 5 months and analyzed for sIgA. Occurrence of self-reported URS and training load was recorded throughout the study’s duration. Regression analyses were performed to investigate the relationship between sIgA responses and training load. Furthermore, the relationships between sIgA responses and URS occurrence were examined. Results: sIgA secretion rate was negatively correlated with training load (P = .04), which only accounted for 8% of the variance. No significant relationships were found between sIgA responses and subsequent URS occurrence. Finally, sIgA responses did not differ between athletes with and without recorded URS during the study period. Conclusions: In line with findings in ablebodied athletes, negative relationships between sIgA secretion rate and training load were found in tetraplegic athletes. This may explain some of the higher infection risk in wheelchair athletes with a high training load, which has been previously observed in paraplegic athletes. However, the nonsignificant relationship between sIgA responses and URS occurrence brings into question the use of sIgA as a prognostic tool for the early detection of URS episodes in the studied population

Supporting Paralympic wheelchair sport performance through technological, physiological and environmental considerations

Supporting Paralympic wheelchair sport performance through technological, physiological and environmental consideration

The physiological strain index does not reliably identify individuals at risk of reaching a thermal tolerance limit

Purpose The physiological strain index (PSI) was developed to assess individuals’ heat strain, yet evidence supporting its use to identify individuals at potential risk of reaching a thermal tolerance limit (TTL) is limited. The aim of this study was to assess whether PSI can identify individuals at risk of reaching a TTL. Methods Fifteen females and 21 males undertook a total of 136 trials, each consisting of two 40–60 minute periods of treadmill walking separated by ~ 15 minutes rest, wearing permeable or impermeable clothing, in a range of climatic conditions. Heart rate (HR), skin temperature (Tsk), rectal temperature (Tre), temperature sensation (TS) and thermal comfort (TC) were measured throughout. Various forms of the PSI-index were assessed including the original PSI, PSIfixed, adaptive-PSI (aPSI) and a version comprised of a measure of heat storage (PSIHS). Final physiological and PSI values and their rate of change (ROC) over a trial and in the last 10 minutes of a trial were compared between trials completed (C, 101 trials) and those terminated prematurely (TTL, 35 trials). Results Final PSIoriginal, PSIfixed, aPSI, PSIHS did not differ between TTL and C (p > 0.05). However, differences between TTL and C occurred in final Tsk, Tre–Tsk, TS, TC and ROC in PSIfixed, Tre, Tsk and HR (p < 0.05). Conclusion These results suggest the PSI, in the various forms, does not reliably identify individuals at imminent risk of reaching their TTL and its validity as a physiological safety index is therefore questionable. However, a physiological-perceptual strain index may provide a more valid measure

<b>Dataset for 'Prediction of Core Body Temperature from Multiple Variables'</b> and '<b>The physiological strain index does not reliably identify individuals at risk of reaching a thermal tolerance limit</b><b>' PROSPIE project</b>

These are datafiles for two papers. The first tried to develop prediction equations for body core temperature based on non-invasive measurement. The second analyses the PSI, the Physiological Strain Index, and evaluates whether this has predictive power for people dropping out from work in the heat.Below the abstracts of the two papers:Prediction of Core Body Temperature from Multiple VariablesThis paper aims to improve the prediction of rectal temperature (Tre) from insulated skin temperature (Tis) and micro-climate temperature (Tmc) previously reported (Richmond et al., Insulated skin temperature as a measure of core body temperature for individuals wearing CBRN protective clothing. Physiol Meas 2013; 34:1531–43.) using additional physiological and/or environmental variables, under several clothing and climatic conditions. Twelve male (25.8±5.1 years; 73.6±11.5kg; 178±6cm) and nine female (24.2±5.1 years; 62.4±11.5kg; 169±3cm) volunteers completed six trials, each consisting of two 40-min periods of treadmill walking separated by a 20-min rest, wearing permeable or impermeable clothing, under neutral (25°C, 50%), moderate (35°C, 35%), and hot (40°C, 25%) conditions, with and without solar radiation (600W m−2). Participants were measured for heart rate (HR) (Polar, Finland), skin temperature (Ts) at 11 sites, Tis (Grant, Cambridge, UK), and breathing rate (f) (Hidalgo, Cambridge, UK). Tmc and relative humidity were measured within the clothing. Tre was monitored as the ‘gold standard’ measure of Tc for industrial or military applications using a 10cm flexible probe (Grant, Cambridge, UK). A stepwise multiple regression analysis was run to determine which of 30 variables (Tis, Ts at 11 sites, HR, f, Tmc, temperature, and humidity inside the clothing front and back, body mass, age, body fat, sex, clothing, Thermal comfort, sensation and perception, and sweat rate) were the strongest on which to base the model. Using a bootstrap methodology to develop the equation, the best model in terms of practicality and validity included Tis, Tmc, HR, and ‘work’ (0 = rest; 1 = exercise), predicting Tre with a standard error of the estimate of 0.27°C and adjusted r2 of 0.86. The sensitivity and specificity for predicting individuals who reached 39°C was 97 and 85%, respectively. Insulated skin temperature was the most important individual parameter for the prediction of Tre. This paper provides novel information about the viability of predicting Tc under a wide range of conditions, using predictors which can practically be measured in a field environment.The physiological strain index does not reliably identify individuals at risk of reaching a thermal tolerance limitPurposeThe physiological strain index (PSI) was developed to assess individuals’ heat strain, yet evidence supporting its use to identify individuals at potential risk of reaching a thermal tolerance limit (TTL) is limited. The aim of this study was to assess whether PSI can identify individuals at risk of reaching a TTL.MethodsFifteen females and 21 males undertook a total of 136 trials, each consisting of two 40–60 minute periods of treadmill walking separated by ~ 15 minutes rest, wearing permeable or impermeable clothing, in a range of climatic conditions. Heart rate (HR), skin temperature (Tsk), rectal temperature (Tre), temperature sensation (TS) and thermal comfort (TC) were measured throughout. Various forms of the PSI-index were assessed including the original PSI, PSIfixed, adaptive-PSI (aPSI) and a version comprised of a measure of heat storage (PSIHS). Final physiological and PSI values and their rate of change (ROC) over a trial and in the last 10 minutes of a trial were compared between trials completed (C, 101 trials) and those terminated prematurely (TTL, 35 trials).ResultsFinal PSIoriginal, PSIfixed, aPSI, PSIHS did not differ between TTL and C (p > 0.05). However, differences between TTL and C occurred in final Tsk, Tre–Tsk, TS, TC and ROC in PSIfixed, Tre, Tsk and HR (p < 0.05).ConclusionThese results suggest the PSI, in the various forms, does not reliably identify individuals at imminent risk of reaching their TTL and its validity as a physiological safety index is therefore questionable. However, a physiological-perceptual strain index may provide a more valid measure.</p

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

Blood lactate and ventilatory thresholds in wheelchair athletes with tetraplegia and paraplegia

Purpose: The purpose of this study was to analyse the influence of spinal cord injury level on blood lactate (BLa) and ventilatory thresholds. Methods: Ten athletes with tetraplegia (TETRA) and nine athletes with paraplegia (PARA) performed a graded wheelchair propulsion treadmill exercise step test to exhaustion. The aerobic and anaerobic BLa thresholds, the ventilatory threshold and the respiratory compensation point (RCP) were determined. Results: The BLa thresholds were determined in 34 of 38 cases, ventilatory thresholds and RCPs in 31 of 38 cases. The anaerobic BLa threshold (76 ± 7 % V ̇ O 2 peak) and the RCP (77 ± 8 % V ̇ O 2 peak) did not differ significantly from each other (P = 0.92), with a coefficient of variation of 4.8 ± 3.4 % between thresholds. All other thresholds differed significantly from each other (P 0.05) despite altered breathing in TETRA, which included a higher ventilatory equivalent for oxygen and a lower tidal volume. Conclusion: Measuring BLa leads to a higher threshold determination rate compared with ventilatory data and the anaerobic BLa threshold can be used to predict the RCP. The altered breathing in TETRA does not seem to have a pronounced effect on the ventilatory threshold or the RCP. © 2014 Springer-Verlag Berlin Heidelberg