Fiabilidad de los tests de salto vertical en gimnastas prepuberales

Introducción y objetivos: La fiabilidad de los tests de salto vertical es inferior en ni˜nos que en adultos. El objetivo del presente estudio es determinar si ni˜nas prepúberes que practican un entrenamiento específico de gimnasia artística son más fiables en distintas pruebas de salto vertical que un grupo control de ni˜nas de la misma edad. Método: Participaron en el estudio 36 prepúberes (19 gimnastas y 17 control), con edades comprendidas entre 7 y 12 a˜nos. Para estudiar la fiabilidad de la capacidad de salto «entre intentos» y «entre sesiones» se utilizaron las siguientes pruebas de salto: squat jump (SJ), countermovement jump (CMJ), countermovement jump with arm swing (CMJA) y drop jump (DJ). Se administraron las pruebas en dos ocasiones, realizándose tres intentos en cada sesión. Resultados: Se observaron altos coeficientes de correlación intraclase (ICC ≥ 0,75) entre intentos y entre sesiones para todas las pruebas. Se cuestiona la fiabilidad del CMJ en gimnastas al encontrarse diferencias significativas en la comparación entre intentos y entre sesiones (p ≤ 0,05). Conclusiones: Se concluye que desde temprana edad la capacidad de salto es reproducible y fiable, y que la práctica de gimnasia artística, en niveles de iniciación, no mejora la fiabilidad de la mayoría de tests de salto vertical. © 2011 Consell Català de l’Esport. Generalitat de Catalunya. Publicado por Elsevier España, S.L. Todos los derechos reservados

Nutritional behavior of cyclists during a 24-hour team relay race: a field study report

Background Information about behavior of energy intake in ultra-endurance cyclists during a 24-hour team relay race is scarce. The nutritional strategy during such an event is an important factor which athletes should plan carefully before the race. The purpose of this study was to examine and compare the nutritional intake of ultra-endurance cyclists during a 24-hour team relay race with the current nutritional guidelines for endurance events. Additionally, we analyzed the relationship among the nutritional and performance variables. Methods Using a observational design, nutritional intake of eight males (mean ± SD: 36.7 ± 4.7 years; 71.6 ± 4.9 kg; 174.6 ± 7.3 cm; BMI 23.5 ± 0.5 kg/m2) participating in a 24-hour team relay cycling race was assessed. All food and fluid intake by athletes were weighed and recorded. Additionally, distance and speed performed by each rider were also recorded. Furthermore, before to the race, all subjects carried out an incremental exercise test to determine two heart rate-VO2 regression equations which were used to estimate the energy expenditure. Results The mean ingestion of macronutrients during the event was 943 ± 245 g (13.1 ± 4.0 g/kg) of carbohydrates, 174 ± 146 g (2.4 ± 1.9 g/kg) of proteins and 107 ± 56 g (1.5 ± 0.7 g/kg) of lipids, respectively. This amount of nutrients reported an average nutrient intake of 22.8 ± 8.9 MJ which were significantly lower compared with energy expenditure 42.9 ± 6.8 MJ (P = 0.012). Average fluid consumption corresponded to 10497 ± 2654 mL. Mean caffeine ingestion was 142 ± 76 mg. Additionally, there was no relationship between the main nutritional variables (i.e. energy intake, carbohydrates, proteins, fluids and caffeine ingestion) and the main performance variables (i.e. distance and speed). Conclusions A 24-hour hours cycling competition in a team relay format elicited high energy demands which were not compensated by energy intake of the athletes despite that dietary consumption of macronutrients did not differ to the nutritional guidelines for longer events

Valoración de la fatiga neuromuscular en el antebrazo del motorista de velocidad

[spa] Actualmente, es frecuente ver cómo muchas escuderías tienen sus motos paradas en boxes por patologías neuromusculares de sus pilotos oficiales, debiendo recurrir a pilotos substitutos. Durante una carrera de motos la fatiga es alta porque los pilotos tienen que soportar niveles de tensión muscular elevados, particularmente en los brazos y antebrazos y además mantenidos durante un largo periodo de tiempo. Un estudio previo realizado durante una carrera de resistencia de 24 h (Marina, Porta, Vallejo, & Angulo, 2011) sugirió que el sistema central no era el motivo principal que explicaba la disminución en la contracción máxima voluntaria (CMV), sino factores periféricos. De ese estudio surgió la necesidad de simular la posición del piloto durante la frenada, así como proponer un protocolo estandarizado en un entorno controlado, dando lugar a la presente tesis. En el primer estudio comparamos dos protocolos, uno continua y otro intermitente (PIF) modificado a partir del estudio surgido de las 24 h. El incremento de la amplitud electromiográfica (EMG) y el decremento de la frecuencia EMG confirmaron mediante el protocolo continua los resultados obtenidos por autores anteriores, pero no con el PIF. Nuestro PIF se mostr6 mas discriminativo entre pilotos expertos y grupo control, alcanzando los primeros una duración mayor y verificándose una mayor correlación con las molestias en el antebrazo. El segundo estudio examin6 el comportamiento de la serial EMG combinando diferentes intensidades y tiempos de descanso, con el sujeto en posición de pilotaje accionando la maneta de freno con la mano derecha. El objetivo de este estudio era verificar si la disparidad de los resultados EMG en PIFs publicados en la literatura, puede deberse a diferentes duraciones en los periodos de contracción-relajación, así como a las intensidades de contracción (% CMV). Los resultados sugirieron que utilizar intensidades bajas (-30 % CMV) y tiempos de recuperación cortos de no más de 10 segundos es la mejor estrategia para inducir fatiga neuromuscular. El tercer estudio nació de la idea que posiblemente no todo el mundo tiene el mismo patrón de disminución de la CMV a lo largo del tiempo. Desarrollamos un modelo matemático no lineal que permitiese verificar dicha hipótesis. Después de aplicar dicho modelo confirmamos que efectivamente, podríamos distinguir tres perfiles básicos de fatiga funcional (lineal, exponencial y tres fases), valorada a lo largo de un PIF a través de la medición repetitiva de la CMV. Sabiendo que las mejores pilotos presentaban un patrón lineal, este segundo estudio supone un primer paso para estudiar si una determinada preparación física podría cambiar y/u optimizar un patrón inicial hacia uno lineal. De la sucesión de estudios descritos anteriormente, vimos que para progresar en esta línea de investigación teníamos que combinar las contracciones voluntarias y la serial EMG con la valoración de otros marcadores neurofisiológicos de fatiga central y periférica. Por eso en el cuarto estudio aplicamos potenciales evocados mediante estimulación eléctrica periférica y estimulación magnética transcraneal, en el segmento fatigado (derecho) y no fatigado (izquierdo), para estudiar posibles efectos contralaterales de la fatiga durante la recuperación del PIF. En esta nueva versión de protocolo modificamos los tiempos de descanso y añadimos el gesto de girar el puño del gas, para acercarnos más a la situación real de pilotaje. Los resultados obtenidos en este último estudio y en el conjunto de la tesis sugieren que la fatiga experimentada par las motoristas se debe principalmente a factores periféricos. Sin embargo no podemos descartar factores centrales.[eng] During a motorcycle race fatigue levels are high as riders are required to endure high levels of muscle tension for long periods of time, especially in their arms and forearms. For this reason the present thesis focuses on fatigue in the right forearm muscles. In the first study we compared an intermittent fatigue protocol (IFP) especially designed for motorcycle riders with a continuous protocol. The IFP was not only able to discriminate between the riders and the control group, but also proved to have a strong relationship with the level of motorcyclist forearm discomfort. Despite the results obtained with continuous protocol were similar to those reported in the literature, our IFP confirmed the discrepancies between studies suggesting that the combination of different, contraction-relaxation periods, submaximal contraction intensities (% maximal voluntary contraction, MVC), muscle groups and other non-controlled or non-reported factors, are critical to understand muscle fatigue in IFPs. The above mentioned results invited us to investigate the effects of two different recovery periods and two intensities on the EMG signal in the study II, using a unique IFP. The results suggested that using short recovery periods and low intensities is the best approach to evoke fatigue. In study Ill, time course parameters of contraction and relaxation were examined to better characterize the reduction in the maximal force generating capacity of a muscle (MVC) during an IFP specifically designed for road racing motorcycle riders. Also, a mathematical nonlinear force fatigue model was proposed and confirmed a satisfactory adjustment to all participants. The same mathematical expression derived three patterns of force fatigue : three-phase , exponential and linear. Finally, in the fourth study which purpose was to investigate the contribution of central and peripheral mechanisms of fatigue on the exerted and contralateral extensor digitorum communis following an IFP, we examined the time-course of recovery of maximal voluntary contraction (MVC), compound muscle action potential (CMAP), motor evoked potential (MEP) to transcranial magnetic stimuli and the cortical silent period (CSP) throughout 20 min of recovery. The results suggested that local factors were those mainly responsible for the incomplete MVC recovery after the IFP

Muscle fatigue when riding a motorcycle: A case study

This case study was conducted to assess muscle pattern, as measured by surface elec-tromyography (sEMG), and its changes during a controlled superbike closed-road track training session. The sEMG signals were recorded unilaterally from biceps brachii (BB), triceps brachii (TB), anterior and posterior part of the deltoid (DA and DP respectively), flexor digitorum superficialis (FS), extensor carpi radialis (CR), extensor digitorum communis (ED) and pectoralis major (PM) during three rounds of 30 min. sEMG signals selected for analysis came from the beginning of the braking action to the way-out of the curves of interest. Considering the laps and rounds as a whole and focusing on the forearm muscles, ED was more systematically (84%) assigned to a state of fatigue than FS (44%) and CR (39%). On the opposite, the TB and DP muscles showed a predominant state of force increase (72%). Whereas the BB showed alternatively a state of fatigue or force increase depending on the side of the curve, when taking into account only the sharpest curves, it showed a predominant state of force increase. In conclusion, the fact that forearm muscles must endure a long-lasting maintenance of considerable activity levels explains why they easily got into a state of fatigue. Moreover, TB and DA are particularly relevant when cornering.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Forearm muscles fatigue induced by repetitive braking on a motorcycle is best discriminated by specific kinetic parameters.

Maneuvering a motorcycle in racing conditions or for prolonged time is sufficiently demanding that on many occasions forearm muscles reach a state of functional failure when riders cannot properly brake or operate the throttle. This study intends to discriminate which ones of the several dynamometric parameters used in the literature to characterize the Force-time (F-t) curve during voluntary contractions are more sensitive to neuromuscular fatigue in simulated motorcycle-riding conditions. Thirty-three adults performed an intermittent fatiguing protocol (IFP) that simulated the brake-pulling and throttle-twisting actions, by using a hydraulic system equipped with a pressure sensor. Sixty pressure-time (P-t) curve parameters, including the rate of pressure development (RPD) and area under the curve were measured to characterize the time course of the braking maximal voluntary contraction (MVC). Two types of variables were used to analyze the P-t curve: 1) Times interval (from 0 to 30-50-100-500-1000 and 2000 ms); 2) Percentages of MVC (10-30-60-90%MVC). Overall significant (p ≤ 0.05) fatigue-related declines were observed only at time intervals longer than 100 ms and contraction intensities higher than 30%MVC. Strong and significant linear declines (p < 0.001) were observed at 500 ms and 1 s for normalized pressures, as well as for the ratio RPD60%MVC/MVC (p < 0.003) throughout the IFP. Our results suggest considering RPD at time windows of 0-500 ms and 0-1 s, and contraction intensities comprised between 30% and 60% of MVC, as more suitable criteria to study fatigue-related decrements in performance rather than the classical MVC force

Exploring forearm muscle coordination and training applications of various grip positions during maximal isometric finger dead-hangs in rock climbers

Background Maximal isometric finger dead-hangs are used in rock climbing to strengthen finger flexors. Although various grip positions are often used when performing finger dead-hangs, little is known regarding how these grip positions can affect forearm muscle activity. Understanding how forearm muscles are recruited during dead-hangs could help foreseeing the potential for training of different grip positions. The aim of the present study was to explore the training applications of the various grip positions by comparing the activity of forearm muscles during maximal dead-hangs in rock climbers. Materials & Methods Twenty-five climbers performed maximal dead-hangs in three climbing-specific grip positions: CRIMP, SLOPE, and SLOPER. We recorded the maximal loads used and the sEMG of the flexor digitorum profundus (FDP), the flexor digitorum superficialis (FDS), the flexor carpi radialis (FCR), and the extensor digitorum communis (EDC). Individual and global (sum of all muscles) root mean square (RMS) and neuromuscular efficiency (NME) values were computed. Repeated measures analysis were performed to assess grip differences (p < 0.05). Results SLOPER showed the largest maximal load values among the three grip positions (p < 0.001, d ≥ 2.772). Greater global (p ≤ 0.044, d ≥ 0.268), FDS (p ≤ 0.005, d ≥ 0.277), and FCR (p < 0.001, d ≥ 1.049) activity was observed for the SLOPER compared to CRIMP and SLOPE, while EDC (p ≤ 0.005, d ≥ 0.505) showed lower activity in the SLOPER compared to the other two grip positions. SLOPER presented the highest global (p < 0.001, d ≥ 0.629), FDP (p < 0.001, d ≥ 0.777), FDS (only CRIMP vs SLOPER: p < 0.001, d = 0.140), and EDC NME (p < 0.001, d ≥ 1.194). The CRIMP showed greater FDS activity (p = 0.001, d = 0.386) and lower NME (p = 0.003, d = 0.125) compared to SLOPE. Conclusions These results revealed that, under maximum intensity conditions, SLOPER could stimulate the FDS and FCR better than the other grip positions at the expense of using greater loads. Similarly, maximum CRIMP dead-hang could better stimulate the FDS than the SLOPE, even when using similar loads

High energy deficit in an ultraendurance athlete in a 24-hour ultracycling race

This case study examined the nutritional behavior and energy balance in an official finisher of a 24-hour ultracycling race. The food and beverages consumed by the cyclist were continuously weighed and recorded to estimate intake of energy, macronutrients, sodium, and caffeine. In addition, during the race, heart rate was continuously monitored. Energy expenditure was assessed using a heart rate–oxygen uptake regression equation obtained previously from a laboratory test. The athlete (39 years, 175.6 cm, 84.2 kg, maximum oxygen uptake, 64 mL/kg/min) cycled during 22 h 22 min, in which he completed 557.3 km with 8760 m of altitude at an average speed of 25.1 km/h. The average heart rate was 131 beats/min. Carbohydrates were the main macronutrient intake (1102 g, 13.1 g/kg); however, intake was below current recommendations. The consumption of protein and fat was 86 g and 91 g, respectively. He ingested 20.7 L (862 mL/h) of fluids, with sport drinks the main fluid used for hydration. Sodium concentration in relation to total fluid intake was 34.0 mmol/L. Caffeine consumption over the race was 231 mg (2.7 mg/kg). During the race, he expended 15,533 kcal. Total energy intake was 5571 kcal, with 4058 (73%) and 1513 (27%) kcal derived from solids and fluids, respectively. The energy balance resulted in an energy deficit of 9915 kcal

Profiling with near-infrared spectroscopy of the forearm’s extensor digitorum during intermittent muscle fatigue protocol with motorcycle riders and control group

<p>An intermittent protocol of cyclic breaking bouts at distinct submaximal intensity of the maximal voluntary contraction does not reflect any significant changes in order to differentiate between the control group and the group of the professional motorcyclist, in terms of the TSI% value, or the other traces, separately. We feel that several trial and error measurements for developmental purposes, will eventually give us a good map for oxygenation profiling as it is not yet explored to its potential advantages.</p