Effects of prior warm-up regime on severe-intensity cycling performance

Burnley, M, Doust, J and Jones, A (2005) Effects of Prior Warm-up Regime on Severe-Intensity Cycling Performance. Medicine and Science in Sports and Exercise, 37 (5). pp. 838-845. ISSN 1530-0315 RAE2008

Development and validation of a sport-specific exercise protocol for elite youth soccer players

Thatcher, Rhys, and Alan Batterham, 'Development and validation of a sport-specific exercise protocol for elite youth soccer players', Journal of Sports Medicine and Physical Fitness, (2004) 44(1) pp.15-22 RAE2008

A modified TRIMP to quantify the in-season training load of team sport players

Thatcher, Rhys, et al., 'A modified TRIMP to quantify the in-season training load of team sport players', Journal of Sport Sciences, (2007) 25(6) pp.629-634 RAE2008

A 3-min all-out test to determine peak oxygen uptake and the maximal steady state

Burnley, M., Doust, J., Vanhatalo, A., A 3-min all-out test to determine peak oxygen uptake and the maximal steady state, Medicine & Science in Sports & Exercise. 38(11):1995-2003, November 2006. RAE2008

Time required for the restoration of normal heavy exercise Vo(2) kinetics following prior heavy exercise

Burnley, M., Doust, J. and Jones, A. (2006). Time required for the restoration of normal heavy exercise Vo(2) kinetics following prior heavy exercise. Journal of Applied Physiology. 101(5), pp.1320-1327 RAE2008

The impact of short duration, high intensity exercise on cardiac troponin release

The aim of this study was to assess the appearance of cardiac troponins (cTnI and/or cTnT) after a short bout (30 s) of ‘all-out’ intense exercise and to determine the stability of any exercise-related cTnI release in response to repeated bouts of high intensity exercise separated by 7 days recovery. Eighteen apparently healthy, physically active, male university students completed two all-out 30 s cycle sprint, separated by 7 days. cTnI, blood lactate and catecholamine concentrations were measured before, immediately after and 24 h after each bout. Cycle performance, heart rate and blood pressure responses to exercise were also recorded. Cycle performance was modestly elevated in the second trial [6·5% increase in peak power output (PPO)]; there was no difference in the cardiovascular, lactate or catecholamine response to the two cycle trials. cTnI was not significantly elevated from baseline through recovery (Trial 1: 0·06 ± 0·04 ng ml−1, 0·05 ± 0·04 ng ml−1, 0·03 ± 0·02 ng ml−1; Trial 2: 0·02 ± 0·04 ng ml−1, 0·04 ± 0·03 ng ml−1, 0·05 ± 0·06 ng ml−1) in either trial. Very small within subject changes were not significantly correlated between the two trials (r = 0·06; P>0·05). Subsequently, short duration, high intensity exercise does not elicit a clinically relevant response in cTnI and any small alterations likely reflect the underlying biological variability of cTnI measurement within the participants.

Aggressiveness as a component of fighting ability in pigs using a game-theoretical framework

Understanding animal contests has benefited greatly from employing the concept of fighting ability, termed resource-holding potential (RHP), with body size/weight typically used as a proxy. However, victory does not always go to the larger/heavier contestant and the existing RHP approach thereby fails to accurately predict contest outcome. Aggressiveness, typically studied as a personality trait, might explain part of this discrepancy. We investigated whether aggressiveness forms a component of RHP, examining effects on contest outcome, duration and phases, plus physiological measures of costs (lactate and glucose). Furthermore, using the correct theoretical framework, we provide the first study to investigate whether individuals gather and use information on aggressiveness as part of an assessment strategy. Pigs, Sus scrofa, were assessed for aggressiveness in resident-intruder tests whereby attack latency reflects aggressiveness. Contests were then staged between size-matched animals diverging in aggressiveness. Individuals with a short attack latency in the resident-intruder test almost always initiated the first bite and fight in the subsequent contest. However, aggressiveness had no direct effect on contest outcome, whereas bite initiation did lead to winning in contests without an escalated fight. This indirect effect suggests that aggressiveness is not a component of RHP, but rather reflects a signal of intent. Winner and loser aggressiveness did not affect contest duration or its separate phases, suggesting aggressiveness is not part of an assessment strategy. A greater asymmetry in aggressiveness prolonged contest duration and the duration of displaying, which is in a direction contrary to assessment models based on morphological traits. Blood lactate and glucose increased with contest duration and peaked during escalated fights, highlighting the utility of physiological measures as proxies for fight cost. Integrating personality traits into the study of contest behaviour, as illustrated here, will enhance our understanding of the subtleties of agonistic interactions.

Complex Interplay Between Determinants of Pacing and Performance During 20 km Cycle Time Trials

Purpose This study examined the determinants of pacing strategy and performance during self paced maximal exercise. Methods Eight well trained cyclists completed two 20 km time trials. Power output, RPE, positive and negative affect, and iEMG activity of the active musculature were recorded every 0.5km, confidence in achieving pre-exercise goals was assessed every 5 km, and blood lactate and pH were measured post-exercise. Differences in all parameters were assessed between fastest (FAST) and slowest (SLOW) trials performed. Results Mean power output was significantly higher during the initial 90% of FAST, but not the final 10%, and blood lactate concentration was significantly higher and pH significantly lower following FAST. Mean iEMG activity was significantly higher throughout SLOW. RPE was similar throughout both trials, but participants had significantly more positive affect and less negative affect throughout FAST. Participants grew less confident in their ability to achieve their goals throughout SLOW. Conclusions The results suggest that affect may be the primary psychological regulator of pacing strategy and that higher levels of positivity and lower levels of negativity may have been associated with a more aggressive strategy during FAST. Although the exact mechanisms through which affect acts to influence performance are unclear, it may determine the degree of physiological disruption that can be tolerated, or be reflective of peripheral physiological status in relation to the still to be completed exercise task.

The effects of altered heat stress on voluntary pacing strategies during prolonged cycling

Central Governor Model (CGM) suggests that perturbations in the rate of heat storage (AS) are centrally integrated to regulate exercise intensity in a feed-forward fashion to prevent excessive thermal strain. We directly tested the CGM by manipulating ambient temperature (Tam) at 20-minute intervals from 20°C to 35°C, and returning to 20°C, while cycling at a set rate of perceived exertion (RPE). The synchronicity of power output (PO) with changes in HS and Tam were quantified using Auto-Regressive Integrated Moving Averages analysis. PO fluctuated irregularly but was not significantly correlated to changes in thermo physiological status. Repeated measures indicated no changes in lactate accumulation. In conclusion, real time dynamic sensation of Tam and integration of HS does not directly influence voluntary pacing strategies during sub-maximal cycling at a constant RPE while non-significant changes in blood lactate suggest an absence of peripheral fatigue.

Chronic versus acute ingestion of sodium citrate: a randomized placebo controlled cross-over trial for swimming 200 metres in well-trained swimmers age 13-17

A double-blinded, placebo controlled, cross-over design was used to investigate sodium citrate dihydrate (Na-CIT) supplementation improve 200m swimming performance. Ten well-trained, male swimmers (14.9 ± 0.4y; 63.5 ± 4kg) performed four 200m time trials: acute (ACU) supplementation (0.5g/kg), acute placebo (PLC-A), chronic (CHR) (0.1g/kg for 3 days and 0.3g/kg on the 4th day pre-trial), and chronic placebo (PLC-C). Na-CIT was administered 120min pre-trial in solution with 500mL of flavored water; placebo was flavored water. Blood lactate, base excess (BE), bicarbonate, pH, and PCO2 were analyzed at basal, 100min post-ingestion, and 3min post-trial via finger prick. Time, lactate, and rate of perceived exertion were not different between trials. BE and bicarbonate were significantly higher for the ACU and CHR trials compared to placebo. “Responders” improved by 1.03% (P=0.043) and attained significantly higher post-trial lactate concentrations in the ACU versus PLC-A trials and compared to non-responders in the ACU and CHR trials.

Coût bioenergetique des modes de déplacements irréguliers en sport

The objective of this thesis was to quantify the physiological responses such as O2 uptake (VO2), heart rate (HR) and blood lactate ([LA]) to some types of activities associated with intermittent sports in athletes. Our hypothesis is that the introduction of accelerations and decelerations with or without directional changes results in a significative increase of the oxygen consumption, heart rate and blood lactate. The purpose of the first study was to measure and compare the VO2 and the HR of 6 on-court tennis drills at both high and low displacement speeds. These drills were done with and without striking the ball, over full and half-width court, in attack or in defense mode, using backhand or forehand strokes. Results show that playing an attacking style requires 6.5% more energy than playing a defensive style (p < 0.01) and the backhand stroke required 7% more VO2 at low speed than forehand stroke (p < 0.05) while the additional cost of striking the ball lies between 3.5 and 3.0 mL kg-1 min-1. Finally, while striking the ball, the energy expanded during a shuttle displacement on half-width court is 14% higher than running on full-width court. Studies #2 and #3 focused on different modes of displacement observed in irregular sports. The objective of the second study was to measure and compare VO2, HR and [LA] responses to randomly performed multiple fractioned runs with directional changes (SR) and without directional changes (FR) to those of in-line running (IR) at speeds corresponding to 60, 70 and 80% of the subject’s maximal aerobic speed (MAS). All results show that IR’s VO2 was significantly lower than SR’s and FR’s (p<0.05). SR’s VO2 was greater than FR’s only at speeds corresponding to 80%MAS. On the other hand, HR was similar in SR and FR but significantly higher than IR’s (p<0.05). [LA] varied between 4.2 ± 0.8 and 6.6 ± 0.9 mmol L-1 without significant differences between the 3 displacement modes. Finally, the third study’s objective was to measure and compare VO2 , HR and [LA] responses during directional changes at different angles and at different submaximal running speeds corresponding to 60, 70 and 80% MAS. Subjects randomly performed 4 running protocols 1) a 20-m shuttle running course (180°) (SR), 2) an 8-shaped running course with 90-degree turns every 20 m (90R), 3) a Zigzag running course (ZZR) with multiple close directional changes (~ 5 m) at different angle values of 91.8°, 90° and 38.6°, 4) an In-line run (IR) for comparison purposes. Results show that IR’s was lower (p<0.001) than for 90R’s, SR’s and ZZR’s at all intensities. VO2 obtained at 60 and 70%MAS was 48.7 and 38.1% higher during ZZR when compared to IR while and depending on the intensity, during 90R and SR was between 15.5 and 19.6% higher than during IR. Also, ZZR’s VO2 was 26.1 and 19.5% higher than 90R’s, 26.1 and 15.5% higher than SR’s at 60 and 70%MAS. SR’s and 90R’s VO2 were similar. Changing direction at a 90° angle and at 180° angle seem similar when compared to continuous in-line running. [LA] levels were similar in all modalities. Overall, the studies presented in this thesis allow the quantification of the specific energetic demands of certain types of displacement modes in comparison with conventional forward running. Also, our results confirm that the energy cost varies and increase with the introduction of accelerations and decelerations with and without directional changes.

Correlacion entre lactato arterial y venoso central en niños con sepsis en estado critico

Este estudio fue conducido para evaluar la correlación entre lactato arterial y venoso central en niños con sepsis y choque séptico de una unidad de cuidado intensivo pediátrico. Se incluyeron 42 pacientes con edades comprendidas entre 1 mes y 17 años 364 días con diagnóstico de sepsis y choque séptico que ingresaron a la Unidad de Cuidado Intensivo en un hospital universitario de referencia. Se registró el valor del lactato obtenido de una muestra de sangre arterial y de sangre venosa central tomadas simultáneamente y dentro de las primeras 24 horas del ingreso a la unidad. Por medio de la prueba de Rho de Spearman se encontró una correlación de 0,872 (p<0,001) y se ajustó al uso de medicamentos, vasoactivos, edad y peso (modelo de regresión no paramétrico quantílico), manteniéndose una correlación fuerte y significativa.

El uso de sangre fresca total en cardiopatías congénitas complejas

Objetivos: Describir si el uso de sangre fresca total (SFT) intraoperatoria en pacientes llevados a procedimientos RACHS 3 y 4 en la Fundación Cardioinfantil, disminuye el sangrado postoperatorio y el volumen de transfusión de elementos sanguíneos, en comparación a aquellos en quienes no se usa SFT. Materiales y métodos: Se realizó un estudio de cohorte histórica, tomando una población menor de 1 año expuesta a la sangre fresca total y comparándola con una población de similares características, llevadas a procedimientos de riesgo similar no expuesta. Los análisis se realizaron mediante pruebas estándar para variables continuas y discretas. Un valor de p menor a 0.05 fue aceptado como signficativo. Resultados: 46 pacientes expuestos a SFT y se compararon con 50 pacientes no expuestos. La principal diferencia entre los grupos fue la edad, siendo mayor en el grupo de no expuestos (3.8 años vs 0.9; p<0.001). El volumen de sangrado postoperatorio fue similar, sin embargo los pacientes expuestos a SFT recibieron mayor volumen de transfusiones, sin ser una diferencia estadísticamente significativa (155cc vs 203cc, P=0.9). No hubo diferencia significativa en complicaciones o mortalidad. Conclusiones: En nuestro estudio no se encontró una disminución en el volumen de sangrado postoperatorio en los pacientes menores de 1 año, sometidos a cirugías catalogadas como RACHS 3 y 4, expuestos a SFT, sin embargo se necesitan estudios clínicos controlados que respondan definitivamente a la pregunta.

DESCRIPCIÓN DEL ESTADO ÁCIDO BASE POR MODELO DE STEWART EN PACIENTES POSTOPERATORIO DE TRASPLANTE HEPÁTICO

Introducción: Los pacientes en postoperatorio de trasplante hepático presentan múltiples cambios hemodinámicos y alteraciones hidroelectrolíticas que generan cambios en el estado ácido base. El presente trabajo, busca describir el comportamiento ácido base en pacientes pos trasplante hepático, a través del análisis del modelo de Stewart, enfocado en la búsqueda etiológica de cada trastorno y planteando posibles formas de optimizar el manejo en Cuidado Intensivo (CI). Metodología: Estudio observacional, descriptivo histórico de los gases arteriales de los pacientes en post operatorio de trasplante hepático por cualquier causa, interpretados por método de Stewart. Se realizó con el universo de pacientes ingresados en el año 2014 en la Fundación Santa Fe de Bogotá. Resultados: Ingresaron en total 24 pacientes al estudio, entre el 1 de enero al 31 de septiembre de 2014. La mediana de pH fue de 7.36 con un valor mínimo de 7.05 y el máximo de 7.49. El 41% de los pacientes al ingreso a cuidado intensivo tenían lactato normal (menor a 2), y el 88% tenían niveles de albumina bajos. El trastorno electrolítico más común fue hipercloremia (58%), seguido de hipomagnesemia (25%). Conclusiones. El análisis de gases arteriales por el modelo de Stewart permite realizar un diagnóstico de un trastorno específico y adicionalmente, permite buscar la etiología del trastorno. Esta serie de casos mostró que el 95% de los pacientes tenían algún trastorno metabólico al ingreso, siendo el más frecuente la acidosis metabólica (66%).

Test performance indicators from a single soccer specific fitness test differentiate between highly trained and recreationally active soccer players

Aim. The aim of this study was to investigate whether a single soccer specific fitness test (SSFT) could differentiate between highly trained and recreationally active soccer players in selected test performance indicators. Methods. Subjects: 13 Academy Scholars (AS) from a professional soccer club and 10 Recreational Players (RP) agreed to participate in this study. Test 1-(V)over dotO(2) max was estimated from a progressive shuttle run test to exhaustion. Test 2-The SSFT was controlled by an automated procedure and alternated between walking, sprinting, jogging and cruise running speeds. Three activity blocks (1A, 2A and 3A) were separated by 3 min rest periods in which blood lactate samples were drawn. The 3 blocks of activity (Part A) were followed by 10 min of exercise at speeds alternating between jogging and cruise running (Part B). Results. Estimated (V)over dotO(2) max did not significantly differ between groups, although a trend for a higher aerobic capacity was evident in AS (p<0.09). Exercising heart rates did not differ between AS and RP, however, recovery heart rates taken from the 3 min rest periods were significantly lower in AS compared with RP following blocks 1A (124.65 b(.)min(-1) +/-7.73 and 133.98 b(.)min(-1) +/-6.63), (p<0.05) and 3A (129.91 b.min(-1) +/-10.21 and 138.85 b.min(-1) +/-8.70), (p<0.01). Blood lactate concentrations were significantly elevated in AS in comparison to RP following blocks 2A (6.91 mmol(.)l(-1) +/-2.67 and 4.74 mmol(.)l(-1) +/-1.28) and 3A (7.18 mmol(.)l(-1) +/-2.97 and 4.88 mmol(.)l(-1) +/-1.50), (p<0.05). AS sustained significantly faster average sprint times in block 3A compared with RP (3.18 sec +/-0.12 and 3.31 sec +/-0.12), (p<0.05). Conclusion. The results of this study show that highly trained soccer players are able to sustain, and more quickly recover from, high intensity intermittent exercise.