Joan Parra

A SHORT TRAINING PROGRAMME FOR THE RAPID IMPROVEMENT OF BOTH AEROBIC AND ANAEROBIC METABOLISM

Abstract The aim of this study was to evaluate the changes in aerobic and anaerobic metabolism produced by a newly devised short training programme. Five young male volunteers trained daily for 2 weeks on a cycle ergometer. Sessions consisted of 15-s all-out repetitions with 45-s rest periods, plus 30-s all-out repetitions with 12-min rest periods. The number of repetitions was gradually increased up to a maximum of seven. Biopsy samples of the vastus lateralis muscle were taken before and after training. Performance changes were evaluated by two tests, a 30-s all-out test and a maximal progressive test. Significant increases in phosphocreatine (31%) and glycogen (32%) were found at the end of training. In addition, a significant increase was observed in the muscle activity of creatine kinase (44%), phosphofructokinase (106%), lactate dehydrogenase (45%), 3-hydroxy-acyl-CoA dehydrogenase (60%) and citrate synthase (38%). After training, performance of the 30-s all-out test did not increase significantly, while in the maximal progressive test, the maximum oxygen consumption increased from mean (SD) 57.3 (2.6) ml · min−1 · kg−1 to 63.8 (3.0) ml · min−1 · kg−1, and the maximum load from 300 (11) W to 330 (21) W; all changes were significant. In conclusion, this new protocol, which utilises short durations, high loads and long recovery periods, seems to be an effective programme for improving the enzymatic activities of the energetic pathways in a short period of time.

Effects of low-frequency stimulation on soluble and structure-bound activities of hexokinase and phosphofructokinase in rat fast-twitch muscle.

Several glycolytic enzymes exist in muscle as free and structure-bound forms. A fraction of hexokinase (HK) is associated with the outer mitochondrial membrane. Phosphofructokinase (PFK) and aldolase (ALD) bind to F-actin, and AMP deaminase (AMPase) interacts with myosin. Using low-frequency stimulation (10 Hz, 24 h/d), we studied in rat fast-twitch muscle effects of contractile activity on soluble and structure-bound forms of these enzymes. Phosphoglucose isomerase (PGI), a soluble enzyme, was also examined. Fractional extraction was applied to study the intracellular distribution of soluble and bound enzyme activities 5 min, 1 h, 3 h, 1 d, and 7 d after the onset of stimulation. Confirming previous findings, total HK activity increased 7-fold in 7-d-stimulated muscles, whereas PFK, ALD, and PGI were reduced, ranging between 55% and 80% of their normal activities. AMPase activity was unaltered. At the time points studied, no changes were found in the extraction behavior of PGI and AMPase. The fraction of bound ALD increased slightly (12%). However, the distribution of HK and PFK was markedly altered. Bound PFK increased from 50% in the control to 85% in 7-d-stimulated muscles. Bound HK rose from 52% to 83% during the same time period. The increase in PFK binding was steep and occurred mainly within the first minutes and hours. The increase in HK binding occurred with some delay, but was significant in muscles stimulated for more than 1 h. In view of the altered kinetic properties of F-actin-bound PFK (alleviated allosteric inhibition by ATP) and bound HK (elevated catalytic activity), these changes are interpreted as early responses to match the metabolic demands during maximal contractile activity imposed on a muscle not programmed for sustained activity: Enhanced binding of PFK serves to accelerate glycolytic flux immediately after the onset of stimulation, whereas mitochondrial binding of HK facilitates the phosphorylation of exogenous glucose when glycogen stores have been depleted.

Responses of fatigable and fatigue-resistant fibres of rabbit muscle to low-frequency stimulation.

This study investigates early adaptive responses of fast-twitch muscle to increased contractile activity by low-frequency stimulation. Changes in metabolite levels and activities of regulatory enzymes of carbohydrate metabolism were investigated in rabbit tibialis anterior muscle after 24 h of stimulation. In addition, changes elicited during a 5-min lasting acute stimulation experiment were compared between 24-hprestimulated and contralateral control muscles. Stimulation for 5 min reduced energy-rich phosphates and glycogen, and increased lactate in the control muscle. A transient elevation of fructose 2,6-bisphosphate demonstrated that activation of phosphofructokinase 2 was an immediate response to contractile activity. Prestimulated muscles displayed nearly normal values for ATP, phosphocreatine and glycogen, and did not augment lactate. Increased activities of hexokinase and phosphofructokinase 2 and permanently elevated levels of fructose 2,6-bisphosphate pointed to enhanced glycolysis with glucose as the main fuel in the prestimulated muscle. Isometric tension of the control muscle decreased rapidly a few minutes after the onset of stimulation. In the prestimulated muscles, tension was almost stable, but amounted to only 30%–40% of the initial tension of the control muscle. In view of the fibre type distribution of rabbit tibialis anterior, these findings suggested that a large fibre fraction of the prestimulated muscle, possibly the glycolytic type IID fibres, did not contract. Therefore, the possibility must be considered that the metabolite pattern of the 24-h-stimulated muscle primarily reflected metabolic activities of the contracting, less fatigable fibres, most likely type IIA and type I fibres. The suggestion that a large fibre fraction did not produce force, in spite of metabolic recovery, points to factors responsible of their refractoriness to low-frequency stimulation other than metabolic exhaustion.

Fast and slow myosins as markers of muscle injury

Objective: The diagnosis of muscular lesions suffered by athletes is usually made by clinical criteria combined with imaging of the lesion (ultrasonography and/or magnetic resonance) and blood tests to detect the presence of non-specific muscle markers. This study was undertaken to evaluate injury to fast and slow-twitch fibres using specific muscle markers for these fibres. Methods: Blood samples were obtained from 51 non-sports people and 38 sportsmen with skeletal muscle injury. Western blood analysis was performed to determine fast and slow myosin and creatine kinase (CK) levels. Skeletal muscle damage was diagnosed by physical examination, ultrasonography and magnetic resonance and biochemical markers. Results: The imaging tests were found to be excellent for detecting and confirming grade II and III lesions. However, grade I lesions were often unconfirmed by these techniques. Grade I lesions have higher levels of fast myosin than slow myosin with a very small increase in CK levels. Grade II and III lesions have high values of both fast and slow myosin. Conclusions: The evaluation of fast and slow myosin in the blood 48 h after the lesion occurs is a useful aid for the detection of type I lesions in particular, since fast myosin is an exclusive skeletal muscle marker. The correct diagnosis of grade I lesions can prevent progression of the injury in athletes undergoing continual training sessions and competitions, thus aiding sports physicians in their decision making.

Effect of chronic electrostimulation of rabbit skeletal muscle on calmodulin level and protein kinase activity.

(a) Chronic electrostimulation of fast-twitch skeletal muscles makes them resemble slow-twitch muscles. The involvement of second-messenger cascades in this muscle reprogramming is not well understood. The goal of this study was to examine protein kinase activities and calmodulin levels as a function of the duration of electrostimulation. (b) Fast-twitch rabbit muscle was subjected to continuous low-frequency electrostimulation for 2 weeks. The extensor digitorum longus was taken and examined for calmodulin concentration and cAMP-dependent (PKA). Ca(2+)-phospholipid-dependent (PKC) and Ca(2+)-calmodulin-dependent (CaM kinase or PKB) protein kinase activities. (c) Electrostimulation for 14 days led to a significant increase in total calmodulin level and PKB activity, both rising in the cytosolic fraction. Protein kinase C translocated to the membrane fraction, although total activity did not change. (d) These changes could be related with electrostimulation-induced changes in excitation-contraction coupling.

CONTRACTILE ACTIVITY MODIFIES FRU-2,6-P2 METABOLISM IN RABBIT FAST TWITCH SKELETAL MUSCLE

Modification of muscular contractile patterns by denervation and chronic low frequency stimulation induces structural, physiological, and biochemical alterations in fast twitch skeletal muscles. Fructose 2,6-bisphosphate is a potent activator of 6-phosphofructo-1-kinase, a key regulatory enzyme of glycolysis in animal tissues. The concentration of Fru-2,6-P2 depends on the activity of the bifunctional enzyme, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2), which catalyzes the synthesis and degradation of this metabolite. This enzyme has several isoforms, the relative abundance of which depends on the tissue metabolic properties. Skeletal muscle expresses two of these isoforms; it mainly contains the muscle isozyme (M-type) and a small amount of the liver isozyme (L-type), whose expression is under hormonal control. Moreover, contractile activity regulates expression of muscular proteins related with glucose metabolism. Fast twitch rabbit skeletal muscle denervation or chronic low frequency stimulation can provide information about the regulation of this enzyme. Our results show an increase in Fru-2,6-P2 concentration after 2 days of denervation or stimulation. In denervated muscle, this increase is mediated by a rise in liver PFK-2/FBPase-2 isozyme, while in stimulated muscle it is mediated by a rise in muscle PFK-2/FBPase-2 isozyme. In conclusion, our results show that contractile activity could alter the expression of PFK-2/FBPase-2.

Valor diagnóstico de las miosinas séricas en las lesiones musculares

Resumen El diagnostico de las lesiones musculares que sufren los deportistas se realiza mediante un diagnostico clinico acompanado de pruebas de confirmacion por tecnicas de imagen de la lesion (ecografia y/o resonancia magnetica nuclear) y tecnicas de laboratorio por analisis de sangre que detectan la presencia de marcadores sericos inespecificos de lesiones musculares. Las pruebas por imagen han demostrado ser excelentes para la deteccion y confirmacion de las lesiones de Grado II y III. Sin embargo las lesiones de Grado I quedan en muchas ocasiones sin confirmacion por estas tecnicas. Los marcadores sericos tradicionales se comportan de forma parecida, siendo todos ellos no especificos del musculo esqueletico. La valoracion de las miosinas rapida y lenta en sangre despues de 48 horas de producirse la lesion ha demostrado ser un buen parametro para la deteccion de las lesiones tipo I especialmente, basandose en ei hecho de que la miosina rapida es un marcador exclusivo del musculo esqueletico. El diagnostico correcto de las lesiones Grado I puede facilitar la prevencion de la progresion de la lesion en deportista sometidos a entrenamientos y competiciones continuadas, pudiendo ayudar al medico deportivo en sus decisiones.

La distribució de periodes de descans durant l'entrenament afecta el rendiment i l'adaptació del metabolisme energètic del múscul.

Resumen Se estudio el efecto de la distribucion de los periodos de descanso sobre la eficacia de un entrenamiento anaerobico. Un grupo de diez voluntarios, divididos en dos grupos, realizo dos entrenamientos de 14 sesiones, con periodos de descanso diferentes. El grupo “programa de corta duracion” (PCD) entreno todos los dias durante 2 semanas; el grupo “programa de larga duracion” (PLD) entreno durante 6 semanas con un periodo de descanso de dos dias entre cada sesion. Los voluntarios realizaron un test de esfuerzo maximo de 30 segundos en un cidoergome-tro antes y despues del entrenamiento. Biopsias musculares del vastus lateralis se obtuvieron antes y despues de cada test. Los dos programas provocaron un aumento en la actividad de enzimas glucoliticos (fosfofructoquinasa 107%, PCD -68% y aldolasa -PCD 46%, PLD -28%) y del metabolismo aerobico (citrato sintetasa -PCD 38%, PLD -28,4% y 3-hidroxiacil-CoA deshidrogenasa -PCD 60%, PLD 38,7%). La actividad creatin-quinasa (44%), piruvato quinasa (35%) y lactato deshidrogenasa (45%) aumentaron significativamente solo en el PCD.Al final del entrenamiento, los voluntarios del PCD mostraban una reduccion significativa en el consumo de ATP (P

Un programa de entrenamiento intenso para un rápido mejoramiento tanto del metabolismo aeróbico como del anaeróbico

Resumen El objetivo de este estudio fue valorar los cambios en el metabolismo aerobico y anaerobico producidos por un nuevo programa de entrenamiento de corta duracion. Cinco voluntarios (hombres) entrenaron diariamente durante 2 semanas en un cicloergometro. Las sesiones consistieron en series de 15-s de esfuerzo maximo en cicloergometro con 45-s de descanso, seguidas por series de 30-s de esfuerzo maximo con 12-min de descanso. El numero de series fue gradualmente aumentado hasta un maximo de siete. Fueron efectuadas biopsias musculares en el vastus lateralis antes y despues del entrenamiento. Las variaciones de rendimiento se evaluaron mediante dos tests, uno de esfuerzo maximo de 30-s y un test de esfuerzo maximo progresivo. Como respuesta al entrenamiento, se encontraron aumentos significativos en la concentracion de fosfocreatina (31%) y glucogeno (32%).Ademas,se observo un aumento significativo en la actividad muscular de los enzimas: creatin-quinasa (44%),fosfofructoquinasa (I06%),lactato desi-drogenasa (45%), 3-hidroxi-acil-CoA desidrogenasa (60%) y citrato sintetasa (38%). Despues del entrenamiento, el rendimiento en el test de esfuerzo maximo de 30-s no mostro mejora significativa, mientras que en el test de esfuerzo progresivo, el consumo maximo de oxigeno aumento de 57,3 (±2,6) ml.min-1.kg-1. a 68,3 (±3,9) ml.min-1.kg-1,y la carga muscular maxima paso de 300 (±11) Wa 330 (±21) W;siendo todas las variaciones significativas. En conclusion, este nuevo protocolo en el que se utilizan periodos de entrenamiento de corta duracion, altas cargas y largos periodos de recuperacion, parece ser un programa efectivo para el mejoramiento del rendimiento y de las vias energeticas en un corto periodo de tiempo.

Consecuencias del descanso estival sobre el endimiento de jóvenes deportistas

Summary Basis In all sporting schedules, and particularly in the case of young people, the summer rest period between seasons eluded trainers’ control. The aim of this work was to study the effect of some weeks of rest on three groups of young footballers who had trained for one season (I I months). Method Based on muscular blopsies conducted before and after the summer break, biochemlcal and histological parameters could be measured, which were correlated with the evolution of sporting performance. Results We observed an area loss in the type I and type II fibres and a decrease in the activity of creatine kinase, citrate synthase, phosphofructokinase, lactate dehydrogenase and aspartate aminotransferase. Sporting performance was also evaluated using a 35-metre running test and a Navette race. ConclusiOns The summer break aitered the season muscular pattern to conditions that made it possible to maintain anaerobic capacity, demonstrated by consistent results in the 35-metre run, but with a deterioration in aerobic capacity because all the groups deteriorated significantiy as can be sean i n the results of the Navette race.