G. Balasekaran

Children's OMNI scale of perceived exertion: mixed gender and race validation.

PURPOSE The newly developed Childrens OMNI Scale of Perceived Exertion (category range: 0 to 10) was validated using separate cohorts of female and male, African American and white subjects. Each of the four cohorts contained 20 clinically normal, nonobese children, 8-12 yr of age. METHODS A cross-sectional, perceptual estimation paradigm using a single multi-stage cycle ergometer test protocol was used. Oxygen uptake (VO2; mL x min(-1)), heart rate (HR; beats x min(-1)) and ratings of perceived exertion for the overall body (RPE-Overall), legs (RPE-Legs), and chest (RPE-Chest) were determined at the end of each continuously administered 3-min power output (PO) (i.e., 25, 50, 75, and 100 W) test stage. RESULTS The range of responses over the four POs for all cohorts was VO2: 290.8 to 1204.0 mL x min(-1); HR: 89.2 to 164.4 beats x min(-1); and RPE-Overall, RPE-Legs, and RPE-Chest: 0.85 to 9.1. First-order correlation and linear regression analyses were performed for each cohort separately and the total sample using a repeated measures paradigm over the four POs. For all correlation/regression paradigms RPE-Overall, RPE-Legs, and RPE-Chest distributed as a positive linear function of both VO2 and HR; r = 0.85 to 0.94; P < 0.01. Differences between RPE-Overall, RPE-Legs, and RPE-Chest were examined with ANOVA for the repeated measures paradigm. RPE-Legs was higher (P < 0.01) than RPE-Chest and RPE-Overall at 25, 50, 75, and 100 W. RPE-Chest did not differ from RPE-Overall at 25 and 50 W but was lower (P < 0.01) than RPE-Overall at 75 and 100 W. CONCLUSION The psycho-physiological responses provide validity evidence for use of the Childrens OMNI Scale over a wide range of dynamic exercise intensities.

Prediction of 2000 m indoor rowing performance using a 30 s sprint and maximal oxygen uptake

The aim of this study was to predict indoor rowing performance in 12 competitive female rowers (age 21.3 - 3.6 years, height 1.68 - 0.54 m, body mass 67.1 - 11.7 kg; mean - s ) using a 30 s rowing sprint, maximal oxygen uptake and the blood lactate response to submaximal rowing. Blood lactate and oxygen uptake ( V O 2 ) were measured during a discontinuous graded exercise test on a Concept II rowing ergometer incremented by 25 W for each 2 min stage; the highest V O 2 measured during the test was recorded as V O 2max (mean = 3.18 - 0.35 l· min -1 ). Peak power (380 - 63.2 W) and mean power (368 - 60.0 W) were determined using a modified Wingate test protocol on the Concept II rowing ergometer. Rowing performance was based on the results of the 2000 m indoor rowing championship in 1997 (466.8 - 12.3 s). Laboratory testing was performed within 3 weeks of the rowing championship. Submitting mean power (Power), the highest and lowest five consecutive sprint power outputs (Maximal and Minimal), percent fatigue in the sprint test (Fatigue), V O 2max (l· min -1 ), V O 2max (ml·kg -1 ·min -1 ), V O 2 at the lactate threshold, power at the lactate threshold (W), maximal lactate concentration, lactate threshold (percent V O 2max ) and V E max (l·min -1 ) to a stepwise multiple regression analysis produced the following model to predict 2000 m rowing performance: Time 2000 =- 0.163 (Power)14.213 ·( V O 2max l· min -1 ) + 0.738· (Fatigue) + 567.259 ( R 2 = 0.96, standard error = 2.89). These results indicate that, in the women studied, 75.7% of the variation in 2000 m indoor rowing performance time was predicted by peak power in a rowing Wingate test, while V O 2max and fatigue during the Wingate test explained an additional 12.1% and 8.2% of the variance, respectively.

OMNI scale perceived exertion at ventilatory breakpoint in children: response normalized.

PURPOSE The Childrens OMNI Scale of Perceived Exertion was used to identify a response normalized rating of perceived exertion (RPE)-Overall, RPE-Legs, and RPE-Chest that corresponds to the ventilatory breakpoint (Vpt) in 8- to 12-yr-old female and male children. METHODS Subjects were a priori stratified into two fitness groups on the basis of peak oxygen uptake (VO2 peak): average (A) (41.0-49.0 mL x kg(-1) x min(-1); N = 24) and above average (AA) (50.0-58.0 mL x kg(-1) x min(-1); N = 24). Vpt was determined by a progressive cycle ergometer protocol to VO2 peak. RESULTS A gender effect was not observed for any descriptive or dependent variable. Mean VO2peak for the A group was 1.72 L x min(-1) and for the AA group 2.04 L x min(-1). Vpt corresponded to 64.0% VO2 peak for A and 74.0% VO2peak for AA. RPE-Overall (mean A and AA, 6.1), RPE-Legs (mean A and AA, 7.2), and RPE-Chest (mean A and AA, 4.5) did not differ between the fitness groups. CONCLUSION Findings indicated that undifferentiated and differentiated RPE-Vpt were similar between female and male children who varied in VO2peak and Vpt. A comparatively stable RPE-Vpt for 8- to 12-yr-old children that vary in VO2peak and Vpt indicates a group normalized perceptual response.

Receiver-Window Modified Random Early Detection (RED-RWM) Active Queue Management Scheme: Modeling and Analysis

In this paper, we present a mathematical model for a novel TCP congestion control approach called Receiver-Window Modification (RWM). RWM could be used with any of the present Active Queue Management (AQM) schemes, such as Random Early Detection (RED), Adaptive Random Early Detection (ARED), and BLUE queues to reduce congestion at the ingress and gateway routers. We extend the work done on stochastic modeling of RED-ECN gateways to RED-RWM gateways. Using this model, we provide a weak convergence theorem for the number of connections; thus leading the way to more relaxed configuration of RED-RWM gateway parameters. We use a Monte Carlo simulation method to compare outcomes of our mathematical model with those of NS2 simulation experiments.

Analyzing the Receiver Window Modification Scheme of TCP Queues

Explicit congestion notification (ECN) and active queue management (AQM) Schemes such as random early detection (RED), adaptive random early detection (ARED) and BLUE queues have been proposed for TCP/IP networks to compensate network congestion. However, using ECN requires that ECN be supported by both TCP senders and receivers. This paper presents a novel AQM modification called receiver- window modification (RWM). RWM can be used together with RED, ARED and BLUE queues, to provide congestion avoidance in packet switched networks at ingress and gateway routers. RWM does not require modification to all end system TCP/IP stacks but can be solely implemented in routers. Our RWM scheme helps in reducing the average queue sizes of RED, ARED, BLUE and even ARED-ECN, BLUE-ECN and RED- ECN queues. By reducing the average queue sizes, RWM queues reduce the queuing delay resulting in significant improvements in one-way end-to-end packet delays and dropped packets. It is also shown that the performance of RED- ECN, ARED-ECN and BLUE-ECN queues is heavily dependent on the queues of the downstream routers. RWM modified queues in ingress or gateway routers are not influenced by the number and state of the downstream router as they will piggyback congestion information to the source in the next available acknowledgement packet. We carry out extensive ns2 simulations to show our results and to support our claims.

Short-term pharmacologically induced growth study of ontogenetic allometry of oxygen uptake in children.

Background: A range of allometric coefficients have been proposed in describing the maximal oxygen uptake (VO2max): body mass relation in children using weight-bearing ergometry. However, a wide deviation in the allometric coefficients for VO2max may be apparent when selected pediatric cohorts are studied in conjunction with clinical intervention for growth abnormalities. Aim: The purpose of this study was to determine the allometric coefficients for VO2max after short-term pharmacologically induced growth in pre- and early pubescent children. Subjects and methods: The treatment group consisted of nine subjects with non-growth hormone (GH)-deficient short stature and one with GH-deficient short stature (mean age: 13.7 ± 1.7 years). Ten pre- and early pubescent children matched for age, height, weight, VO2max and body mass index (BMI) were controls. The treatment group were evaluated before (Pre-GH) and after (Post-GH) 4 months of subcutaneous GH therapy (0.05 mg kg−1day−1 × 6 days week−1). Results: The mean ontogenetic coefficient for the treatment group was 1.50 ± 0.20 and for the control group was 0.77 ± 0.34. The mean allometric coefficient for body mass relative to VO2max was significantly higher in the treatment group compared with the control group (p<0.05). Height, weight, fat free mass (FFM), VO2max indexed to body mass (mL kg−1 min−1) and FFM (mL kgFFM−1 min−1) increased (p<0.05) with GH therapy. GH therapy also increased insulin-like growth factor-I (IGF-I) and served as a biochemical marker of GH therapy (p<0.05). The control group had no significant differences in all the variables tested (p<0.05). Conclusion: The scaling for oxygen uptake (VO2) for body mass varies with GH treatment and the increase in VO2max that commonly occurs in conjunction with physical growth in the pre-and early pubescent individual may be linked to an increase in FFM and linear size. Résumé. Arrière plan: Une gamme de coefficients d’allométrie a été proposée pour décrire la relation entre consommation d’énergie maximum (VO2max) et masse corporelle, chez des enfants examinés par ergométrie avec charge pondérale. On observe cependant qu’une large déviation des coefficients d’allométrie pour le VO2max peut apparaître lorsque des cohortes pédiatriques sont étudiées pour les anomalies de la croissance, en conjonction avec une intervention clinique. But: Le but de cette étude est de déterminer les coefficients d’allométrie pour le VO2max à la suite d’une courte poussée de croissance induite par pharmacologie chez des enfants prépubères ou de puberté récente. Sujets et méthodes: Le groupe sous traitement consiste en neuf sujets de stature courte sans déficience d’hormone de croissance (HC) et d’un sujet de stature courte suite suite à une déficience de l’hormone de croissance (âge moyen : 13,7 ± 1,7 ans). On a pris comme contrôles, dix enfants prépubères et de puberté récente appariés pour l’âge, la stature, le poids, le VO2max et l’IMC. Le groupe en traitement a été évalué avant (Pré-HC) et après (post-HC) quatre mois d’injections d’HC sous cutanée (0,05 mg kg−1 jour−1 × 6 jours semaine−1). Résultats: Le coefficient ontogénique moyen pour le groupe sous traitement est de 1,50 ± 0,20 et pour le groupe de contrôle 0,77 ± 0,34. Le coefficient allométrique moyen pour la masse corporelle en rapport avec VO2max est significativement plus élevé dans le groupe traité que dans le groupe contrôle (p<0,05). La stature, le poids, la masse maigre, le VO2max rapporté à la masse corporelle (mL kg−1 min−1) et à la masse maigre (mL kg−1 min−1) s’accroissent avec la thérapie par HC (p < 0,05). La thérapie HC accroît également le facteur I de croissance insulino mimétique, lequel sert de marqueur biochimique de la thérapie HC (p < 0,05). Le groupe de contrôle ne présente pas de différence significative pour toutes les variables examinées (p < 0,05). Conclusion: L’échelle de VO2 en fonction de la masse corporelle, varie avec les traitement par HC et l’augmentation en VO2max qui se produit en général en conjonction avec la croissance physique chez l’individu prépubère ou pubère récent, peut être liée à l’accroissement de la masse maigre et de la taille linéaire. Zusammenfassung. Hintergrund: Eine Vielzahl allometrischer Koeffizienten ist vorgeschlagen worden, um die Relation von maximaler Sauerstoffaufnahme (VO2max) zu Körpermasse im Kindesalter unter Verwendung von gewichtsbezogener Ergometrie zu beschreiben. Allerdings wird eine weite Abweichung allometrischer Koeffizienten für VO2max offensichtlich, wenn ausgewählte pädiatrische Stichproben in Verbindung mit klinischen Interventionen bei Wachstumsstörungen untersucht werden. Ziel: Sinn dieser Studie war die Bestimmung von allometrischen Koeffizienten für VO2max nach kurzzeitigem medikamenteninduzierten Wachstum bei präpubertären Kindern und Kindern in der frühen Pubertät. Probanden und Methoden: Die Behandlungsgruppe bestand aus neun Probanden mit nicht-wachstumshormonbedingtem Kleinwuchs und einem Patienten mit Kleinwuchs aufgrund eines Wachstumshormonmangels (mittleres Alter: 13,7 ± 1,7 Jahre). Die Kontrollgruppe bestand aus zehn gleichaltrigen präpubertären Kindern und Kindern in der frühen Pubertät von vergleichbarer Körperhöhe und vergleichbarem Gewicht, VO2max und BMI. Die Behandlungsgruppe wurde vor (prä-GH) und nach (post-GH) 4-monatiger subkutaner Wachstumshormontherapie (0,05 mg kg−1 Tage–1 × 6 Tage Woche−1) untersucht. Ergebnisse: Der mittlere ontogenetische Koeffizient für die Behandlungsgruppe war 1,50 ± 0,20 und für die Kontrollgrupp.,77 ± 0,34. Der mittlere allometrische Koeffizient für Körpermasse relativ zu VO2max war in der Behandlungsgruppe signifikant höher als in der Kontrollgruppe (p < 0,05). Körperhöhe, Gewicht, fettfreie Masse (FFM), VO2max in Bezug zu Körpermasse (mL kg−1 min−1) und FFM (mL kg FFM−1 min−1) stiegen mit Wachstumshormontherapie (p < 0,05). Die Wachstumshormontherapie führte auch zu einem Anstieg des Insulin-like Growth Factor-I (IGF-I) und diente als biochemischer Marker der Wachstumshormontherapie (p < 0,05). Die Kontrollgruppe zeigte keine signifikanten Unterschiede bei den getesteten Variablen (p < 0,05). Zusammenfassung: Die Anpassung von VO2 an Körpermasse variiert mit der Wachstumshormontherapie, und der Anstieg von VO2max, der üblicherweise in Verbindung mit körperlichem Wachstum vor und zu Beginn der Pubertät auftritt, könnte mit einer Vermehrung von FFM und Körperlänge verknüpft sein. Resumen. Antecedentes: Se ha propuesto un rango de coeficientes alométricos para describir la relación entre el consumo máximo de oxígeno (VO2max) y la masa corporal en niños, utilizando la prueba de esfuerzo (ergometría “weight-bearing”). Sin embargo, puede ponerse de manifiesto una amplia desviación de los coeficientes alométricos para el VO2max cuando se estudian las cohortes pediátricas seleccionadas junto con la intervención clínica para las anomalías del crecimiento. Objetivo: El objetivo de este estudio fue determinar los coeficientes alométricos para el VO2max tras un crecimiento a corto plazo inducido farmacológicamente en niños pre-puberales y con pubertad temprana. Sujetos y métodos: El grupo de tratamiento consistió en nueve individuos con baja estatura no deficientes de hormona de crecimiento (GH) y uno con baja estatura y deficiente para la GH (edad media: 13,7 ± 1,7 años). Diez niños pre-puberales y con pubertad temprana de la misma edad, estatura, peso, VO2max e IMC fueron los controles. El grupo de tratamiento fue evaluado antes (Pre-GH) y después (Post-GH) de 4 meses de terapia subcutánea con GH (0,05 mg kg−1 día–1 × 6 días por semana−1). Resultados: El coeficientes ontogénico medio para el grupo de tratamiento fue de 1,50 ± 0,20 y para el grupo de control de 0,77 ± 0,34. El coeficiente alométrico medio para la masa corporal respecto al VO2max fue significativamente mayor en el grupo que recibía tratamiento que en el grupo control (p < 0,05). La estatura, el peso, la masa libre de grasa (FFM), el VO2max indexado para la masa corporal (mL kg−1 min−1) y la FFM (mL kg FFM−1 min−1) aumentaban (p < 0,05) con la terapia con GH. Esta terapia también incrementaba el factor de crecimiento semejante a la insulina tipo I (IGF-I) y sirvió como un marcador bioquímico de la terapia con GH (p < 0,05). El grupo de control no mostró diferencias significativas en ninguna de las variables testadas (p < 0,05). Conclusión: la escala del VO2max para la masa corporal varía con el tratamiento con GH; el incremento en el VO2max que ocurre habitualmente junto con el crecimiento físico en los individuos pre-puberales y de pubertad temprana puede estar asociado con un incremento de la FFM y del tamaño lineal.