Adult height and glucose tolerance: a re-appraisal of the importance of body mass index.

AIM: To study both the association between adult height and glucose regulation based on findings from a 75-g oral glucose tolerance test, and the combined effect of height and adiposity on glucose values. METHODS: We conducted a population-based, cross-sectional study among apparently healthy people with high cardiovascular risk living in south-western Finland. The study included 2659 participants aged 45-70 years, who had at least one cardiovascular risk factor but no previously diagnosed diabetes or manifested cardiovascular disease. An oral glucose tolerance test was performed in all participants. Height and weight were measured and BMI was calculated. The participants were divided into five height groups based on normal distribution. For further analysis of the association between height and glucose concentrations the participants were divided into four BMI groups (<25.0 kg/m2 ; 25-29.9 kg/m2 ; 30-34.9 kg/m2 ; ≥35 kg/m2 ). Data were analysed using age-adjusted linear regression models. RESULTS: Height was inversely associated with 2-h plasma glucose, but not with fasting plasma glucose concentration. No gender difference was observed. The 2-h plasma glucose values increased with an increase in BMI, so that height was inversely associated with 2-h plasma glucose in the three lowest BMI groups, but not in the highest BMI group (P=0.33). CONCLUSIONS: Taller people had lower 2-h plasma glucose concentrations than shorter people, up to a BMI of 35 kg/m2 . Adjustment for height and BMI is needed for accurate interpretation of oral glucose tolerance tests.

Dietary intake and thiamin, iron, and zinc status in elite Nordic skiers during different training periods.

This study evaluated how different training periods affect dietary intake and biochemical indices of thiamin, iron, and zinc status in elite Nordic skiers. Subjects were 17 skiers and 39 controls, ages 18-38 yrs. Dietary data were collected by 7-day food records at 3-month intervals. Coefficient of variation (CV) was used to indicate magnitude of seasonal changes. Energy intake for the year (28 food record days) was 3,802 kcal/day (CV 19.1%) in male skiers, 2,754 kcal/day (CV 3.7%) in male controls, 2,812 kcal/day (CV 9.1%) in female skiers, and 2,013 kcal/day (CV 5.9%) in female controls. CVs for thiamin, riboflavin, vitamin C, calcium, magnesium, iron, and zinc intake were 14.1-23.9% (male skiers), 2.9-15.0% (male controls), 4.8-24.5% (female skiers), and 4.3-11.5% (female controls). Seasonal changes in energy, carbohydrate, and micronutrient intakes reflected energy expenditure in male endurance athletes particularly. Erythrocyte transketolase activation coefficients and serum ferritin and zinc concentrations did not differ between skiers and controls. Seasonal variations in these biochemical indices of nutritional status were of the same magnitude in skiers and controls, despite large changes in skiers' physical activity.

Fatigue and changes of ATP, creatine phosphate, and lactate during the 400-m sprint.

Fatigue during the 400-m sprint was studied by measuring muscle ATP, creatine phosphate (CP), lactate (M-La), and blood lactate (B-La) in six male runners before and after four experimental sprints (100, 200, 300, and 400 m). During the first 100 m, muscle CP decreased from 15.8 +/- 1.7 to 8.3 +/- 0.3 mmol/kg while M-La increased to 3.6 +/- 0.4 mmol/kg. After 200 m the CP had decreased to 6.5 +/- 0.5 mmol/kg and M-La had increased to 8.3 +/- 1.1 mmol/kg. At the end of the 400 meters, ATP and CP concentrations had decreased by 27% and 89%, respectively, and M-La had increased to 17.3 +/- 0.9 mmol/kg. It was concluded that after 200 m the speed of running decreased, although CP was not depleted and lactate concentration was not at maximum level. Complete fatigue occurred when CP stores were depleted and B-La and M-La attained an individual maximum.

Congenital fiber type disproportion in an adult: a morphometric and microchemical study.

A 20-year-old man with marfanoid habitus had a history of congenital hypotonia and muscle weakness. Muscle biopsy showed extreme fiber type disproportion. There was total absence of Type 2B fibers. The severely hypertrophic Type 2A fibers showed twice the normal concentration of creatine phosphate at rest. These advanced morphometric, histochemical and biochemical changes may be interpreted as compensatory phenomena, which may explain the patient's pronounced functional improvement with advancing age.

Use of glycolytic energy sources by human skeletal muscle under anoxic conditions in vitro and during moderate exercise in vivo.

To test a new in vitro model for investigations of muscle metabolism, the most important metabolites of muscle anaerobic metabolism (ATP, creatine phosphate, glucose, glycogen, and lactate) were measured in muscle biopsies from healthy male subjects, endurance-trained cyclists, strength-trained weight lifters, intensively trained long-distance runners, and speed-trained sprinters. The samples were taken at rest and after moderate muscle exercise for 30 s. These samples were analysed as such or after in vitro incubation for 30 s, 60 s, and 5 min under anoxic conditions. Anoxic conditions were created by incubating the muscle specimens in mineral oil through which N2 was bubbled. Under anoxic conditions in vitro, the concentrations of glycogen fell significantly in muscle specimens from sprinters and long-distance runners. The same tendency was observed in all other groups. The concentrations of high-energy phosphates. ATP and creatine phosphate, did not deplete under anoxic conditions. Under anoxic conditions, the rate of energy use, i.e., the metabolic rate calculated from the changes in the energy sources in terms of high-energy phosphate (P) use, was highest during the first 30 s, and declined to zero after 60 s. In the endurance-trained cyclists the metabolic rate was significantly lower than in any other group. In conclusion, muscle tissue behaves in quite a different way under anoxic conditions in vitro as compared with its behavior during exercise in vivo, and so the in vitro model is not suitable to compensate for studies of muscle metabolism in vivo. The in vitro model is of value, however, in, for example, determining the maximal metabolic rate of muscle.

The sauna and sports.

Sauna and sports go well together. Top Finnish athletes have discovered this, taking a sauna almost twice a week. Why do they do this? In the sauna, an athlete cleanses his body, refreshes his mind, recovers more rapidly, and relaxes. Sauna bathing is not a way of adapting before competitions in a hot climate, or of losing weight rapidly, although one might expect the sauna to be ideal for these purposes. An athlete does not look to the sauna to help his performance, the sauna itself is reward enough.

Breakdown of high-energy phosphate compounds and lactate accumulation during short supramaximal exercise.

Muscle ATP, creatine phosphate and lactate, and blood pH and lactate were measured in 7 male sprinters before and after running 40, 60, 80 and 100 m at maximal speed. The sprinters were divided into two groups, group 1 being sprinters who achieved a higher maximal speed (10.07 +/- 0.13 m X s-1) than group 2 (9.75 +/- 0.10 m X s-1), and who also maintained the speed for a longer time. The breakdown of high-energy phosphate stores was significantly greater for group 1 than for group 2 for all distances other than 100 m; the breakdown of creatine phosphate for group 1 was almost the same for 40 m as for 100 m. Muscle and blood lactate began to accumulate during the 40 m exercise. The accumulation of blood lactate was linear (0.55 +/- 0.02 mmol X s-1 X l-1) for all distances, and there were no differences between the groups. With 100 m sprints the end-levels of blood and muscle lactate were not high enough and the change in blood pH was not great enough for one to accept that lactate accumulation is responsible for the decrease in running speed over this distance. We concluded that in short-term maximal exercise, performance depends on the capacity for using high-energy phosphates at the beginning of the exercise, and the decrease in running speed begins when the high-energy phosphate stores are depleted and most of the energy must then be produced by glycolysis.

Muscle metabolism, blood lactate and oxygen uptake in steady state exercise at aerobic and anaerobic thresholds.

Muscle metabolites and blood lactate concentration were studied in five male subjects during five constant-load cycling exercises. The power outputs were below, equal to and above aerobic (AerT) and anaerobic (AnT) threshold as determined during an incremental leg cycling test. At AerT, muscle lactate had increased significantly (p less than 0.05) from the rest value of 2.31 to 5.56 mmol X kg-1 wet wt. This was accompanied by a significant reduction in CP by 28% (p less than 0.05), whereas only a minor change (9%) was observed for ATP. At AnT muscle lactate had further increased and CP decreased although not significantly as compared with values at AerT. At the highest power outputs (greater than AnT) muscle lactate had increased (p less than 0.01) and CP decreased (p less than 0.01) significantly from the values observed at AnT. Furthermore, a significant reduction (p less than 0.05) in ATP over resting values was recorded. Blood lactate decreased significantly (p less than 0.01) during the last half of the lowest 5 min exercise, remained unchanged at AerT and increased significantly (p less than 0.05-0.01) at power outputs greater than or equal to AnT. It is concluded that anaerobic muscle metabolism is increased above resting values at AerT: at low power outputs (less than or equal to AerT) this could be related to the transient oxygen deficit during the onset of exercise or the increase in power output. At high power outputs (greater than AnT) anaerobic energy production is accelerated and it is suggested that AnT represents the upper limit of power output where lactate production and removal may attain equilibrium during constant load exercise.

High-energy phosphate compounds in slow-twitch and fast-twitch muscle fibres. Changes during exercise in some neuromuscular diseases.

Concentrations of the high-energy phosphates, ATP and creatine phosphate, were investigated in slow-twitch (ST) and fast-twitch (FT) muscle fibres of patients with myotonia congenita (n = 6), dystrophia myotonica (n = 5), myopathia ocularis (n = 2) and hyperornithinemia with gyrate atrophy (HOGA) (n = 3) and compared with those of normal subjects (n = 4). At rest, the patients with HOGA had lower values of ATP in ST muscle fibres than the controls (P less than 0.05). They also had lower values of creatine phosphate in these fibres than the patients with dystrophia myotonica (P less than 0.03) and myotonia congenita (P less than 0.05). After 30 s bicycle ergometer exercises there was an increase in ATP in the ST muscle fibres of the patients with myotonia congenita, but in all other patient groups there was a decrease.

High-energy phosphate compounds during exercise in human slow-twitch and fast-twitch muscle fibres.

Concentrations of ATP and creatine phosphate, the high-energy phosphates, were investigated in slow-twitch (ST) and fast-twitch (FT) muscle fibres in sprinters and in long-distance runners at rest, during light sprinting exercise and during an extremely exhaustive running exercise. At rest the long-distance runners had significantly (P less than 0.005) more creatine phosphate in ST than in FT muscle fibres. Both the light and the exhaustive exercise induced breakdown of creatine phosphate to very low levels (10-15 mmol/kg; dry weight) in FT muscle fibres. In response to the exhaustive exercise, creatine phosphate in the ST fibres of the sprinters fell to a significantly (P less than 0.05) lower value than of the long-distance runners in the ST fibres. During the recovery period the synthesis of creatine phosphate seemed to be more rapid in FT than ST muscle fibres in light exercise (P less than 0.02) and in sprinters in exhaustive exercise (P less than 0.05). This study suggests that (1) during short-term exercise FT muscle fibres consume more of their creatine phosphate stores than ST muscle fibres, (2) in vigorous exercise athletes trained for sprinting are able to recruit not only the FT but also the ST muscle fibres, and (3) in such trained sprinters creatine phosphate is possibly resynthesized more rapidly in FT than in ST muscle fibres.

Determination of metabolites and enzymes in muscle.

The advantages of enzymatic fluorometric methods in measuring metabolites and enzymes in tissue samples are described and discussed. A technique is described for separating single muscle fibres for chemical analysis. In this way it is possible to study the metabolism of slow-twitch and fast-twitch muscle fibres in the same muscle and obtain results with accuracy and precision. This will provide better opportunity for understanding the effects of training in athletics and the metabolic changes in muscle diseases.

Cardiovascular function and the renin-angiotensin-aldosterone system in long-distance runners during various training periods.

Blood pressure, heart rate, heart volume, electrocardiogram, plasma renin activity (PRA) and plasma angiotensin II and aldosterone concentrations were followed up in sixteen male long-distance runners during various training periods from January to September. During the most intense training period, the "track-running' period, the athletes had significant increases in all measured parameters of the renin-angiotensin-aldosterone (R-A-A) system when compared to the seven control subjects. In the middle of this period the PRA and angiotensin II concentrations of the athletes had increased 1.9- and 1.5-fold, respectively, from the initial values. The plasma aldosterone concentration increased both in the athletes and in the control group. The systolic blood pressure of the athletes was slightly but significantly increased at the same period as the most marked changes in the R-A-A system were found. In the athletes, positive correlations were found between the relative heart volumes in the roentgenograms and the electrocardiographic signs for both right and left ventricular size. This study demonstrates that during intense training runners may have long-lasting temporary increases in systolic blood pressure level with parallel changes in the components of the R-A-A system. However, the reason for this slight increase in the systolic blood pressure remains unclear.

High-energy phosphate compounds in human slow-twitch and fast-twitch muscle fibres.

A method has been developed for separating slow- and fast-twitch fibres from the same muscle for analysis of high-energy phosphate compounds by an enzymatic fluorometric technique. Since the ATP and creatine phosphate concentrations in single muscle fibres are at pmol levels, enzymatic cycling is necessary to measure the NADPH formed in the reaction. The precision of the method has been found to be 3.3% for ATP and 2.0% for creatine phosphate. Variations in the levels of high-energy phosphate compounds were no greater between fibres of the same type than regionally within a single fibre. When slow- and fast-twitch fibres were compared there were no significant differences in the high-energy phosphate concentrations, except that in women there was significantly more creatine phosphate in slow-twitch than in fast-twitch fibres.

Lipoprotein lipase activity in adipose tissue and skeletal muscle of runners: relation to serum lipoproteins.

Physically well-trained people generally have lower VLDL-triglyceride and higher HDL-cholesterol levels than sedentary subjects. To examine the underlying mechanisms of this lipoprotein pattern, we measured the lipoprotein lipase (LPL) activity in needle biopsy specimens of adipose tissue and skeletal muscle of competitive runners and of body weight-matched, physically less-active controls. The active sportsmen were either sprinters, whose training program consisted mainly of athletics of short duration or long distance runners undergoing a strenuous endurance exercise program. In sprinters (all males) the serum lipid and lipoprotein concentrations did not differ significantly from those of controls and the mean LPL activities in muscle and adipose tissue were also similar in these two groups. The long distance runners (both sexes), on the other hand, had higher means levels of HDL-cholesterol than the respective controls. The LPL-activity of both adipose tissue (p less than 0.05) and skeletal muscle (p less than 0.01) was significantly higher in male long distance runners than in control males. Female runners had higher muscle LPL activity than controls (p less than 0.01) but in adipose tissue the difference in LPL activity was not significant. Rough estimates calculated for LPL activity present in whole body adipose tissue and skeletal muscle indicated that total LPL activity was 2.3 times higher in male long distance runners and 1.5 times higher in female long distance runners than in the respective controls. In combined groups of male runners and controls, there was a highly significant positive correlation between the serum HDL-cholesterol level and the LPL activity of adipose tissue expressed per tissue weight (r = +0.72, p less than 0.001) or per whole body fat (r = +0.62, p less than 0.001). The group means of HDL-cholesterol and adipose tissue LPL activity in the five cohorts studied (male sprinters, distance runners and controls and female distance runners and controls) were also positively correlated (r = +0.94). It is concluded that endurance training is associated with an adaptive increase of LPL activity not only in skeletal muscle but also in adipose tissue. These changes are not observed in sprinters who are trained by exercises of shorter duration. The high HDL-cholesterol levels of physically well-trained people are probably accounted for, at least partly, by the increased LPL activity and the concomitant rapid turnover or triglyceride-rich lipoproteins.

Muscle metabolism during and after strenuous intermittent running.

Muscle and blood metabolites, plasma insulin and cyclic adenosine 3',5'-monophosphate (cAMP) levels were investigated in five male runners before and after strenuous intermittent running exercise of short duration. Immediately after the exercise, the mean muscle creatine phosphate level (CrP) had fallen by 74% (P less than 0.02) and 30 min later the initial level was regained in only one subject. Other immediate results were increases in mean muscle lactate (460%, P less than 0.005), glucose (130%), glucose-6-phosphate (G6P, 320%) and fructose-1,6-diphosphate (FDP, 32%). Muscle ATP and glycogen concentration had decreased by 31 and 23% (P less than 0.05), respectively. However, ATP, glucose, G6P and FDP changes were not significant owing to the great individual variation. This may have been due to the different training programmes of the runners. Immediately after the exercise mean plasma insulin was 210% (P less than 0.01), blood glucose 71% (P less than 0.005) and plasma cAMP concentration 260% (P less than 0.01) higher than the pre-exercise values. After running urinary excretion of cAMP was 29% higher than before the exercise. It is concluded that exhaustive, short-term exercise activates the liver adenylate cyclase system so giving rise to an increased level of blood glucose, which is an important source of energy during this type of exercise.