Task failure from inspiratory resistive loaded breathing: a role for inspiratory muscle fatigue?

The use of non-invasive resistive breathing to task failure to assess inspiratory muscle performance remains a matter of debate. CO2 retention rather than diaphragmatic fatigue was suggested to limit endurance during inspiratory resistive breathing. Cervical magnetic stimulation (CMS) allows discrimination between diaphragmatic and rib cage muscle fatigue. We tested a new protocol with respect to the extent and the partitioning of inspiratory muscle fatigue at task failure. Nine healthy subjects performed two runs of inspiratory resistive breathing at 67 (12)% of their maximal inspiratory mouth pressure, respiratory rate ( f R), paced at 18min-1, with a 15-min pause between runs. Diaphragm and rib cage muscle contractility were assessed from CMS-induced esophageal (P es,tw), gastric (P ga,tw), and transdiaphragmatic (P di,tw) twitch pressures. Average endurance times of the first and second runs were similar [9.1 (6.7)and 8.4 (3.5)min]. P di,tw significantly decreased from 33.1 to 25.9cmH2O in the first run, partially recovered (27.6cmH2O), and decreased further in the second run (23.4cmH2O). P es,tw also decreased significantly (-5.1 and -2.4cmH2O), while P ga,tw did not change significantly (-2.0 and -1.9cmH2O), indicating more pronounced rib cage rather than diaphragmatic fatigue. End-tidal partial pressure of CO2 (P ETCO2) rose from 37.2 to 44.0 and 45.3mmHg, and arterial oxygen saturation (S aO2) decreased in both runs from 98% to 94%. Thus, task failure in mouth-pressure-targeted, inspiratory resistive breathing is associated with both diaphragmatic and rib cage muscle fatigue. Similar endurance times despite different degrees of muscle fatigue at the start of the runs indicate that other factors, e.g. increases in P ETCO2, and/or decreases in S aO2, probably contributed to task-failur

Improvements in cycling but not handcycling 10 km time trial performance in habitual caffeine users

Caffeine supplementation during whole-/lower-body exercise is well-researched, yet evidence of its effect during upper-body exercise is equivocal. The current study explored the effects of caffeine on cycling/handcycling 10 km time trial (TT) performance in habitual caffeine users. Eleven recreationally trained males (mean (SD) age 24 (4) years, body mass 85.1 (14.6) kg, cycling/handcycling peak oxygen uptake (V peak) 42.9 (7.3)/27.6 (5.1) mL·kg·min−1, 160 (168) mg/day caffeine consumption) completed two maximal incremental tests and two familiarization sessions. During four subsequent visits, participants cycled/handcycled for 30 min at 65% mode-specific V peak (preload) followed by a 10 km TT following the ingestion of 4 mg·kg−1 caffeine (CAF) or placebo (PLA). Caffeine significantly improved cycling (2.0 (2.0)%; 16:35 vs. 16:56 min; p = 0.033) but not handcycling (1.8 (3.0)%; 24:10 vs. 24:36 min; p = 0.153) TT performance compared to PLA. The improvement during cycling can be attributed to the increased power output during the first and last 2 km during CAF. Higher blood lactate concentration (Bla) was reported during CAF compared to PLA (p < 0.007) and was evident 5 min post-TT during cycling (11.2 ± 2.6 and 8.8 ± 3.2 mmol/L; p = 0.001) and handcycling (10.6 ± 2.5 and 9.2 ± 2.9 mmol/L; p = 0.006). Lower overall ratings of perceived exertion (RPE) were seen following CAF during the preload (p < 0.05) but not post-TT. Lower peripheral RPE were reported at 20 min during cycling and at 30 min during handcycling, and lower central RPE was seen at 30 min during cycling (p < 0.05). Caffeine improved cycling but not handcycling TT performance. The lack of improvement during handcycling may be due to the smaller active muscle mass, elevated (Bla) and/or participants’ training status

The risk of malnutrition in patients with spinal cord injury during inpatient rehabilitation–A longitudinal cohort study

Background and aimPatients with spinal cord injury (SCI) show an increased risk of malnutrition. Studies found that about 50% of patients with a recent SCI are affected by malnutrition when they enter a rehabilitation institution. However, there is a lack of data during the course and at discharge of initial rehabilitation as well as missing knowledge about the factors promoting such a risk. The aim of this study was to assess the risk of malnutrition in individuals with SCI 3 months post injury and at the end of inpatient rehabilitation and to identify factors associated with a high risk of malnutrition.MethodsRetrospective, monocentric, longitudinal cohort study, using the data set of the Swiss Spinal Cord Injury Cohort Study and additional data from the patients’ medical records. Individuals with SCI were assessed for the risk of malnutrition using the Spinal Nutrition Screening Tool 3 months post injury and at discharge from initial inpatient rehabilitation. Odds ratios (OR) for potential risk parameters were calculated.ResultsOf the 252 participants included, 62% were at risk for malnutrition 3 months post injury and 40% at discharge (p = 0.000). Moderate to high risk of malnutrition was found regardless of age and BMI. The highest odds for an increased risk at 3 months post injury was identified in ventilator-dependent persons (OR 10.2). At discharge from inpatient rehabilitation, pressure injury (OR 16.3) was the most prominent risk factor.ConclusionIn the population with SCI the risk of malnutrition is widespread during inpatient rehabilitation, but also at discharge. Ventilated persons and persons with pressure injuries are clear risk groups and need special attention. Based on these findings and the known negative impact of malnutrition on clinical outcomes, the awareness of malnutrition should be increased in the population with SCI. Therefore, a regular and standardized screening of the malnutrition risk is highly recommended

Locomotor-respiratory coupling in wheelchair racing athletes: a pilot study

Purpose: In wheelchair racing, respiratory muscles of the rib cage are concomitantly involved in non-ventilatory functions during wheelchair propulsion. However, the relationship between locomotor-respiratory coupling (LRC: the ratio between push and breathing frequency), respiratory parameters and work efficiency is unknown. Therefore, the aim of the present study was to investigate the LRC in wheelchair racers over different race distances. Methods: Eight trained and experienced wheelchair racers completed three time-trials over the distances of 400m, 800m and 5000m on a training roller in randomized order. During the time trials, ventilatory and gas exchange variables as well as push frequency were continu-ously registered to determine possible LRC strategies. Results: Four different coupling ratios were identified, namely 1:1; 2:1, 3:1 as well as a 1:1/2:1 alternating type, respectively. The 2:1 coupling was the most dominant type. The 1:1/2:1 alternating coupling type was found predominantly during the 400m time-trial. Longer race distances tended to result in an in-creased coupling ratio (e.g., from 1:1 towards 2:1), and an increase in coupling ratio towards a more efficient respiration was found over the 5000m distance. A significant correlation (r=0.80, p<0.05) between respiratory frequency and the respiratory equivalent for oxygen was found for the 400m and the 800m time-trials. Conclusions: These findings suggest that a higher coupling ratio indicates enhanced breathing work efficiency with a concomitant deeper and slower respiration during wheelchair racing. Thus, the selection of an appropriate LRC strategy may help to optimize wheelchair racing performance

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/ non-use; (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 non-elite (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

Spinal cord injury level influences acute plasma caffeine responses

Purpose. 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 (8 able-bodied (AB), 8 PARA and 8 TETRA) consumed 3 mg∙kg-1 caffeine anhydrous (CAF) in a fasted state. Plasma caffeine [CAF], glucose, lactate, free-fatty acid [FFA] and catecholamine concentrations were measured during a 150 min rest period. Results. Peak [CAF] was greater in TETRA (21.5 µM) compared to AB (12.2 µM) and PARA (15.1 µM), and mean peak [CAF] occurred at 70, 80 and 80 min, respectively. Moderate and large ES were revealed for TETRA compared to PARA and AB (-0.55 and -1.14, respectively) for the total area under the [CAF] versus time curve. Large inter-individual responses were apparent in SCI groups. The change in plasma catecholamine concentrations following CAF did not reach significance (p>0.05) however both adrenaline and noradrenaline concentrations were lowest in TETRA. Significant increases in [FFA] were seen over time (p0.05). Conclusion. Level of SCI influenced the caffeine absorption curve and there was large inter-individual 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 prior to exercise performance. The study also supports caffeine’s direct effect on adipose tissue, which is not secondary to catecholamine release

Physical activity and cardiometabolic risk factors in individuals with spinal cord injury: a systematic review and meta-analysis.

Physical inactivity in individuals with spinal cord injury (SCI) has been suggested to be an important determinant of increased cardiometabolic disease (CMD) risk. However, it remains unclear whether physically active SCI individuals as compared to inactive or less active individuals have truly better cardiometabolic risk profile. We aimed to systematically review and quantify the association between engagement in regular physical activity and/or exercise interventions and CMD risk factors in individuals with SCI. Four medical databases were searched and studies were included if they were clinical trials or observational studies conducted in adult individuals with SCI and provided information of interest. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was applied to rate the certainty of evidence. Of 5816 unique citations, 11 randomized clinical trials, 3 non-randomized trial and 32 cross-sectional studies comprising more than 5500 SCI individuals were included in the systematic review. In meta-analysis of RCTs and based on evidence of moderate certainty, physical activity in comparison to control intervention was associated with: (i) better glucose homeostasis profile [WMD of glucose, insulin and Assessment of Insulin Resistance (HOMA-IR) were - 3.26 mg/dl (95% CI - 5.12 to - 1.39), - 3.19 μU/ml (95% CI - 3.96 to - 2.43)] and - 0.47 (95% CI - 0.60 to - 0.35), respectively], and (ii) improved cardiorespiratory fitness [WMD of relative and absolute oxygen uptake relative (VO2) were 4.53 ml/kg/min (95% CI 3.11, 5.96) and 0.26 L/min (95% CI 0.21, 0.32) respectively]. No differences were observed in blood pressure, heart rate and lipids (based on evidence of low/moderate certainty). In meta-analysis of cross-sectional studies and based on the evidence of very low to low certainty, glucose [WMD - 3.25 mg/dl (95% CI - 5.36, - 1.14)], insulin [- 2.12 μU/ml (95% CI - 4.21 to - 0.03)] and total cholesterol [WMD - 6.72 mg/dl (95% CI - 13.09, - 0.34)] were lower and HDL [WMD 3.86 mg/dl (95% CI 0.66, 7.05)] and catalase [0.07 UgHb-1 (95% CI 0.03, 0.11)] were higher in physically active SCI individuals in comparison to reference groups. Based on limited number of cross-sectional studies, better parameters of systolic and diastolic cardiac function and lower carotid intima media thickness were found in physically active groups. Methodologically sound clinical trials and prospective observational studies are required to further elaborate the impact of different physical activity prescriptions alone or in combination with other life-style interventions on CMD risk factors in SCI individuals

nIFTy galaxy cluster simulations - IV. Quantifying the influence of baryons on halo properties

Building on the initial results of the nIFTy simulated galaxy cluster comparison, we compare and contrast the impact of baryonic physics with a single massive galaxy cluster, run with 11 state-of-the-art codes, spanning adaptive mesh, moving mesh, classic and modern smoothed particle hydrodynamics (SPH) approaches. For each code represented we have a dark-matteronly (DM) and non-radiative (NR) version of the cluster, as well as a full physics (FP) version for a subset of the codes. We compare both radial mass and kinematic profiles, as well as global measures of the cluster (e.g. concentration, spin, shape), in the NR and FP runs with that in the DM runs. Our analysis reveals good consistency (<≈ 20 per cent) between global properties of the cluster predicted by different codes when integrated quantities are measured within the virial radius R200. However, we see larger differences for quantities within R2500, especially in the FP runs. The radial profiles reveal a diversity, especially in the cluster centre, between the NR runs, which can be understood straightforwardly from the division of codes into classic SPH and non-classic SPH (including the modern SPH, adaptive and moving mesh codes); and between the FP runs, which can also be understood broadly from the division of codes into those that include active galactic nucleus feedback and those that do not. The variation with respect to the median is much larger in the FP runs with different baryonic physics prescriptions than in the NR runs with different hydrodynamics solvers

nIFTy galaxy cluster simulations – I. Dark matter and non-radiative models

We have simulated the formation of a galaxy cluster in a Ʌ cold dark matter universe using 13 different codes modelling only gravity and non-radiative hydrodynamics (RAMSES, ART, AREPO, HYDRA and nine incarnations of GADGET). This range of codes includes particle-based, moving and fixed mesh codes as well as both Eulerian and Lagrangian fluid schemes. The various GADGET implementations span classic and modern smoothed particle hydrodynamics (SPH) schemes. The goal of this comparison is to assess the reliability of cosmological hydrodynamical simulations of clusters in the simplest astrophysically relevant case, that in which the gas is assumed to be non-radiative. We compare images of the cluster at z = 0, global properties such as mass and radial profiles of various dynamical and thermodynamical quantities. The underlying gravitational framework can be aligned very accurately for all the codes allowing a detailed investigation of the differences that develop due to the various gas physics implementations employed. As expected, the mesh-based codes RAMSES, ART and AREPO form extended entropy cores in the gas with rising central gas temperatures. Those codes employing classic SPH schemes show falling entropy profiles all the way into the very centre with correspondingly rising density profiles and central temperature inversions. We show that methods with modern SPH schemes that allow entropy mixing span the range between these two extremes and the latest SPH variants produce gas entropy profiles that are essentially indistinguishable from those obtained with grid-based methods