Physiological profiles of male and female taekwon-do (ITF) black belts.

Baseline physiological and kinanthropometric data were collected for 11 male and 12 female elite taekwon-do athletes from the Czech national team for evaluation of anthropometry, aerobic and anaerobic capacities, strength, visual reaction time, pulmonary function, flexibility and explosive power of the lower limbs (vertical jump). Both male and female taekwon-do black belts demonstrated low adiposity (8.2 and 15.4% fat, BMI 21.9 and 22.0 kg m(-2), respectively), normal reactivity and pulmonary function, above average muscular strength, PWC-170 (3.4 vs 2.7 W kg(-1)) and aerobic power (54 vs 42 ml min(-1) kg(-1)), and a high flexibility (37 and 38 cm) and anaerobic performance (peak power output from a 30 s Wingate test=14.7 and 10.1 W kg(-1); anaerobic capacity=334 and 242 J kg(-1), in males and females, respectively). In male athletes, competitive performance was significantly related to maximum power output and upper limb reaction time only, whereas in females, performance was related to maximum power output and ventilatory threshold level. These variables accounted for 66 and 67% of the performance rank in males and females, respectively. Time-motion analysis of competition taekwon-do fighting (two times 2 min) revealed 3-5 s bouts of maximum exercise alternating with low-intensity periods. This elicits high heart rates (100% HRmax) and lactate responses (11.4 mmol l(-1) = 81% LAmax), which agrees well with the physiological characteristics of taekwon-do black belts measured in laboratory exercise tests.

Relationship of muscle fibre distribution to body composition in physically trained and normally active human males.

This study was designed primarily to identify relationships among indices of muscle tissue structure (m. vastus lateralis) and of somatic qualities (anthropometric parameters) in 44 untrained men and 105 well-trained athletes. The ratio of glycolytic to oxidative muscle fibres was significantly less (P < 0.05) in endurance athletes as opposed to both the controls and the power athletes. Correlations between anthropometric factors and indices of muscle morphology were stronger in trained men, particularly in power athletes. Relationships between body fat and muscle fibre distribution were low in trained and untrained subjects. Documented muscle plasticity may enhance relationships between somatic and muscle tissue indices. Our results suggest that the response of the three major muscle fibre types to prolonged training may be relatively high. Finally, it was proposed that enhanced oxidative capacity of skeletal muscle might be characteristic of those resistant to heart disease.

Morphologic differences in skeletal muscle with age in normally active human males and their well-trained counterparts.

In this study we elucidate the interaction of physical activity with aging as regards skeletal muscle fiber distribution and size. Thirty-three male athletes and 42 normally active counterparts served as subjects. They were assigned to younger (less than 25.5 years) and older (greater than 25.5 years) subgroups. Serial cross-sections from muscle biopsy samples (musculus vastus lateralis) were stained to distinguish fiber type: fast glycolytic (type IIb), fast oxidative-glycolytic (type IIa), or slow oxidative (type I). We also measured fiber diameters. A greater mean diameter of type I fibers was seen in older as opposed to younger athletes. Older controls had a smaller mean diameter of type IIb fibers than did younger controls. Athletes had a smaller mean percentage of type IIa fibers and a greater mean percentage of type I fibers than did controls. There was a greater mean percentage of type I fibers in older as opposed to younger controls, but this was not the case in athletes. Athletes may have larger fibers and a greater percentage of type I fibers at the expense of type IIa fibers. Atrophy of fibers with aging might be retarded by training, which might also reduce the age-associated rate of type IIb percentage loss and type I percentage gain.

Physiological considerations in training young athletes.

Healthy children evidence smaller values of cardiorespiratory function than adults, but these are in proportion to the smaller body size. At birth, the distribution of muscle fibres and the activity of enzymes in muscle are different from in adults, but these differences disappear at about age 6. On the other hand, muscle fibre thickness increases from birth to about 18 years of age and this is concurrent with increases in muscular strength. The increase in maximal oxygen consumption (VO2max) that accompanies growth and maturation in the human has been attributed in the main to appreciating muscle mass. During exercise, heart rate and cardiac output increase in the child as in the adult, but the heart rate in the child is greater and the stroke volume smaller. Furthermore, the arteriovenous difference in oxygen is greater in the exercising child than in the adult. Children also evidence a diminished blood pressure response to exercise. It seems that control of ventilation at exercise is the same in children as in adults, but exercise ventilation has been reported to be less efficient in the child. The young are less capable of regulating core temperature at exercise than adults and are more readily dehydrated. Very limited data suggest that muscle energy substrate storage and utilisation in children are such that they are less capable of anaerobic metabolism than adults. Generally, children respond to aerobic training as do adults, but such training in the first decade of life has been reported to have negligible effects. Blood lipid levels in children seem to be favourably influenced by persistent endurance activity. Ventilatory efficiency of children at exercise is augmented by aerobic training. Maximal values of ventilation and breathing frequency are increased in children and youth by endurance training. Conflicting data exist regarding the influence of training upon the child's vital capacity. Pulmonary diffusion capacity in well trained children has been seen to be greater than in untrained youngsters and many workers have reported increased VO2max as an outcome of endurance training. Limited data indicate that the nature of training may alter muscle fibre distribution in youthful athletes, and that muscle fibre hypertrophy can be induced in the young by means of strength and power training.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of training at simulated altitude on performance and muscle metabolic capacity in competitive road cyclists.

Differences between the effects of training at sea level and at simulated altitude on performance and muscle structural and biochemical properties were investigated in 8 competitive cyclists who trained for 3-4 weeks, 4-5 sessions/week, each session consisting of cycling for 60-90 min continuously and 45-60 min intermittently. Four subjects, the altitude group (AG), trained in a hypobaric chamber (574 torr = 2300 m above sea level), and the other four at sea level (SLG). Before and after training work capacity was tested both at simulated altitude (574 torr) and at sea level, by an incremental cycle ergometer test until exhaustion. Work capacity was expressed as total amount of work performed. Venous blood samples were taken during the tests. Leg muscle biopsies were taken at rest before and after the training period. AG exhibited an increase of 33% in both sea level and altitude performance, while SLG increased 22% at sea level and 14% at altitude. Blood lactate concentration at a given submaximal load at altitude was significantly more reduced by training in AG than SLG. Muscle phosphofructokinase (PFK) activity decreased with training in AG but increased in SLG. All AG subjects showed increases in capillary density. In conclusion, work capacity at altitude was increased more by training at altitude than at sea level. Work capacity at sea level was at least as much improved by altitude as by sea level training. The improved work capacity by training at altitude was paralleled by decreased exercise blood lactate concentration, increased capillarization and decreased glycolytic capacity in leg muscle.

Effect of exercise on muscle fibre composition and enzyme activities of skeletal muscles in young rats.

Young Wistar rats underwent dynamic (D) or static (S) exercise from the 5th to 35th day after birth. Histochemical and biochemical analysis were performed in the extensor digitorum longus (EDL) and the soleus muscle (SOL). Lactate dehydrogenase (LDH) (regulating anaerobic metabolism) and citrate synthase (CS) and hydroxyacyl-CoA dehydrogenase (HAD) (both regulating aerobic metabolism) activities were determined spectrophotometrically. An increase of the fast oxidative-glycolytic (FOG) muscle fibres was found in the slow SOL muscle in both trained groups, i.e. by 10% in group D and by 7% in group S in comparison with the C group. The EDL muscle fibre distribution did not differ from those of control animals in respect to the slow oxidative (SO) fibre type. A higher percentage of FOG fibres by 19% was found in group D contrary to a decreased number of the fast glycolytic (FG) muscle fibres in this trained group. The greatest increase of CS (EDL 185%, SOL 176%) and HAD (EDL 83%, SOL 178%) activities were found in group D as compared with control group (C). Only small differences were observed in LDH activity. The values of characteristic enzyme activity ratios show that dynamic training resulted in an elevation of oxidative capacity of skeletal muscle, while the static load led preferentially along the glycolytic pathway. It may be concluded that an adaptive response to the training load during early postnatal development is different due to the type of exercise (dynamic or static) and/or the type of skeletal muscle (fast or slow).

Skeletal muscle characteristics of sprint cyclists and nonathletes.

Muscle fiber distribution and muscle enzyme activity (m. vastus lat.) were investigated in 10 elite sprint cyclists and 12 nonathletes. The ratio of fast to slow muscle fibers was 2:3 in cyclists and 3:2 in nonathletes. The mean diameter of each muscle fiber type was significantly higher in the athletes. The mean enzyme activity values in mu kat X g-1 w.w. for cyclists and nonathletes, respectively, were as follows: triosephosphate dehydrogenase (TPDH), 6.2 and 3.78; lactate dehydrogenase (LDH), 4.4 and 4.59; citrate synthase (CS), 0.154 and 0.13; hydroxyacyl-CoA dehydrogenase (HAD), 0.041 and 0.07. The mean difference between groups in TPDH and in (TPDH + LDH)/(CS + HAD) ratio were statistically significant. Maximum voluntary isometric strength (knee extension) was about 17% greater in cyclists than the mean value for Czechoslovakian men of the same age. A strong positive correlation (r = 0.72) between the percent of fast glycolytic fibers (type II B) and isometric strength was observed in the cyclists. Furthermore, mean weight-compensated maximal oxygen consumption (VO2 max, ml X kg-1 X min-1) for all subjects (n = 22) was significantly related to percent of slow oxidative fibers (type I) (r = 0.75) and to the mean diameter of type II B (r = 0.58), fast oxidative-glycolytic fibers (type II A) (r = 0.68) and type I fibers (r = 0.59).

Effect of hyperthyroidism on fibre-type composition, fibre area, glycogen content and enzyme activity in human skeletal muscle.

Seven hyperthyroid patients were studied by repeated muscle biopsies (vastus lateralis) before and after a period of medical treatment which averaged 10 months. The biopsies were analysed with regard to fibre-type composition, fibre area, capillary density, glycogen content and enzyme activities representing the glycolytic capacity (hexokinase, 6-phosphofructokinase), oxidative capacity (oxoglutarate dehydrogenase, citrate synthase) and Ca2+- and Mg2+-stimulated ATPase in muscle. In the pretreatment biopsy (hyperthyroid state), there was a significantly lower proportion of type I fibres (30% vs. 41%), a higher capillary density (23%), lower glycogen content (33%), and higher hexokinase activity (32%) compared with the post-treatment biopsy. No significant changes in the activity of the remaining enzymes were observed. The present study indicates that hyperthyroidism induces a transformation from type I to type II fibres in human skeletal muscle. The increase in hexokinase activity probably reflects a higher glucose utilization by skeletal muscle in order to compensate partially for the reduced glycogen content.

The relationship between anaerobic performance and muscle metabolic capacity and fibre distribution.

Relationships between functional anaerobic indicators and the character of cellular muscle energy metabolism were studied. Twelve untrained male students were tested by a specific anaerobic test on the treadmill. The mean values of the anaerobic test were as follows: blood lactate 10.69 mmol . 1(-1), running speed 16.08 km . h-1 and duration 92.67 s. The average distribution of muscle fibres (m. vastus lateralis) was: type I 52.2%, type II A 29.0% and type II B 18.8%. The mean enzyme activity values were: triosephosphate dehydrogenase (TPDH) 4.67 mu kat . g-1 w.w., lactate dehydrogenase (LDH) 5.76 mu kat . g-1 w.w, citrate synthase (CS) 0.21 mu kat . g-1 w.w. and hydroxyacyl-CoA dehydrogenase (HAD) 0.12 mu kat . g-1 w.w. Significant negative correlations were found between delta LA and CS (r = 0.64) and % of fibre type II B and CS (r = 0.78) and positive correlations between % of fibre type I and CS and/or HAD (r = 0.60 and r = 0.62, respectively).

Muscle enzyme activities and fibre composition (m. vastus lateralis) and efficiency of the cardiorespiratory system in cross-country skiers.

Fourteen male cross-country skiers (class I and II, average age 20.5 years) were examined by biochemical and histochemical methods. The activity of selected enzymes of energy metabolism and the percentage ratio of different types of muscle fibres (m. vastus lateralis) were assessed. Furthermore, the maximum values of the cardiorespiratory system and post-loading pH and blood lactate were determined after performance on a treadmill. The mitochondrial enzyme activities were relatively high with a considerable scatter in the values of HOADH activity. The glycolytic enzyme activities were on the same level as in subjects not engaged in sports. The percentage composition of muscle fibres was as follows: FG - 7.56 %, FOG - 30.65 % and SO - 61.79 %. Oxygen consumption VO2 max.kg-1 was 67.44 ml.min-1, pulse oxygen 24.76 ml, post-load pH 7.24 and blood lactate concentration 6.98 mmol.l-1. There was positive correlation between CS enzyme activity and oxygen uptake (VO2 max), pulse oxygen and percentage of SO muscle fibres. The mean values found in the athletes examined in the present study corresponded to values of middle distance runners.

Different changes in contractile and histochemical properties of reinnervated and regenerated slow soleus muslces of the guinea-pig.

The changes in contraction time (CT) and histochemical muscle fibre pattern are compared with respect to ATPase activity of the slow soleus muscle of the guniea-pig during regeneration in free grafts and reinnervation after nerve interruption. Interruption of the nerve by crushing at birth results first in prolongation of CT which later returns to normal (control) values. A homogeneous fibre pattern is established related to the homogeneity of the motor units constituting the muscle. In the regenerating muscle CT and muscle fibre pattern of the graft repeat the changes during postnatal development, i.e. CT shows progressive prolongation accompanied by transformation of a heterogeneous (fibres of high and low ATPase activity) to a homogeneous (fibres of low activity only) fibre pattern. However, the regenerating muscle also shows an initial phase with slow CT. Thus the changes in reinnervation and regeneration of the muscle after birth differ, the reinnervated muscle revealing only prolongation, the regenerated muscle a temporary shortening followed by prolongation, i.e. a biphasic development of CT.

Independence of changes in contraction properties and myofibrillar ATPase activity of denervated mammalian muscle on length of nerve stump.

1. Contractile properties of the fast extensor digitorum longus of one-month-old rats and of the fast peroneus longus muscles of adult rabbits were studied in vitro at 36 degrees C after nerve section close to the muscle. Changes in contraction properties (prolongation) are not observed until 48 hours after denervation in the rat and 14-30 days in the rabbit. 2. At no period after denervation are differences in twitch isometric contraction properties dependent on the length of the sectioned nerve stump. This lack of dependence of contractile behavior after denervation is in contrast to many metabolic changes which show a clear dependence on the length of the nerve stump. 3. It is concluded that the onset of denervation changes in contractile behavior are related to the loss of nerve-impulse activity, while the transient early metabolic changes are related to changes of fast axoplasmic flow, initiated after nerve section and therefore dependent on length of sectioned nerve stump.