Cardiorespiratory fitness and health-related quality of life in women at risk for gestational diabetes.

This study examined the associations of cardiorespiratory fitness (CRF) and leisure-time physical activity (LTPA) with health-related quality of life (HRQoL) in women at risk for gestational diabetes mellitus (GDM). The participants were 39 women planning pregnancy with a history of GDM and/or BMI >29 kg/m2 . We assessed CRF by measuring maximal oxygen consumption (VO2max ) during incremental cycle ergometer exercise until voluntary fatigue. LTPA was self-reported, and HRQoL assessed with the SF-36 Health Survey (SF-36). The mean (SD) VO2max was 27 (6) mL·kg-1 ·min-1 , and the mean LTPA was 2.6 (1.7) h/wk. After controlling for BMI, VO2max was positively associated with the SF-36 General Health scale (ß 1.27, 95% CI: 0.09, 2.44, P=.035) and the Physical Component Summary (ß 0.48, 95% CI: 0.14, 0.82, P=.007). The General Health scale (P=.023) and the Physical Component Summary (P=.011) differed even between those with very poor and poor CRF. After controlling for BMI, LTPA was positively associated with the SF-36 Physical Functioning scale (rs =.34, P=.039), the General Health scale (ß 3.74, 95% CI: 0.64, 6.84, P=.020), and the Physical Component Summary (ß 1.13 95% CI: 0.19, 2.06, P=.020). To conclude, CRF and LTPA were positively associated with perceived general health and physical well-being in women planning pregnancy and at risk for GDM. Even a slightly better CRF would be beneficial for well-being among women with low levels of CRF.

Exercise-induced changes in pulmonary function of healthy, elite long-distance runners in cold air and pollen season exercise challenge tests.

Exercise-induced changes in postexercise pulmonary function have not been studied in healthy elite athletes in normal training conditions. Twelve healthy elite runners volunteered. They showed normal resting spirometry and bronchial responsiveness to histamine, and were non-atopic. They performed free running exercise challenge tests (ECT) at subzero temperature and immediately after highest birch pollen season. The mean maximal postexercise changes in FEV(1), PEF, FVC, and FEV(1)/FVC did not differ between the cold air and pollen season ECTs. Compared with pre-exercise values, FEV(1)increased significantly at 10 min (p = 0.028) and 20 min (p = 0.033) postexercise in the cold air ECT, as well as at 10 min (p = 0.024) and 20 min (p = 0.010) postexercise in the pollen season ECT. The mean (SEM) maximal postexercise change in FEV(1) was mostly small + 2.6 (0.6)% in the winter and + 2.7 (0.9)% in the pollen season. In contrast, significant decreases in PEF, compared with baseline, were found at 10 min (p = 0.071) and 20 min (p = 0.0029) postexercise in the cold air ECT, as well as at 10 min (p = 0.060) and 20 min (p = 0.010) postexercise in the pollen season ECT (p = 0.0076). The mean (SEM) maximal postexercise fall in PEF was 5.9 (1.0)% in the winter and 6.0 (1.8)% in the pollen season. Heavy exercise challenge tests in extreme conditions increased FEV(1) post-exercise, while PEF decreased as compared with pre-exercise values. Thus, even small postexercise falls in FEV(1) may be considered as deviate exercise responses in elite athletes.

Oxygen uptake response during maximal cycling in hyperoxia, normoxia and hypoxia.

BACKGROUND: Oxygen uptake (VO2) on-kinetics is decelerated in acute hypoxia and accelerated in hyperoxia in comparison with normoxia during submaximal exercise. However, the effects of fraction of oxygen in inspired air (FIO2) on VO2 kinetics during maximal exercise are unknown. HYPOTHESIS: The effects of FIO2 on VO2 on-kinetics during maximal exercise are similar to submaximal exercise. METHODS: There were 11 endurance athletes who were studied during maximal 7-min cycle ergometer exercise in hyperoxia (FIO2 0.325), hypoxia (FIO2 0.166) and normoxia (FIO2 0.209). The individual VO2 data were fit to a curve by using a three exponential model. RESULTS: In hypoxia, VO2 on-response amplitude during Phase 2 (approximately 20-100 s from the beginning of exercise) was lower (p < 0.05) when compared with hyperoxia; time constant of VO2 Phase 3 (beyond approximately 100 s after beginning of exercise) was shorter (p < 0.05) when compared with hyperoxia; and mean response time (MRT, O-63%) for VO2peak was shorter (p < 0.05) when compared with normoxia and hyperoxia. VO2peak was higher in hyperoxia (4.80 +/- 0.48 L x min(-1), p < 0.05) and lower in hypoxia (4.03 +/- 0.46 L x min(-1), p < 0.05) than in normoxia (4.36 +/- 0.44 L x min(-1)). CONCLUSIONS: Moderate hypoxia or hyperoxia do not affect VO2 time constants at the onset of maximal exercise. However, MRT for VO2peak is shortened in hypoxia. It is suggested that the differences in VO2peak and power output during the latter half of the test and the point that FIO2 was modified only moderately might explain most of the discrepancy with the previous studies.

Cardiorespiratory responses to exercise in acute hypoxia, hyperoxia and normoxia.

There is a prevailing hypothesis that an acute change in the fraction of oxygen in inspired air (F(I)O2) has no effect on maximal cardiac output (Qcmax), although maximal oxygen uptake (VO2max) and exercise performance do vary along with F(I)O2. We tested this hypothesis in six endurance athletes during progressive cycle ergometer exercise in conditions of hypoxia (FI(O)2 = 0.150), normoxia (F(I)O2 = 0.209) and hyperoxia (F(I)O2=0.320). As expected, VO2max decreased in hypoxia [mean (SD) 3.58 (0.45)l.min(-1), P<0.05] and increased in hyperoxia [5.17 (0.34) l.min(-1), P<0.05] in comparison with normoxia [4.55 (0.32)l.min(-1)]. Similarly, maximal power (Wmax) decreased in hypoxia [334 (41) W, P< 0.05] and tended to increase in hyperoxia [404 (58) W] in comparison with normoxia [383 (46) W]. Contrary to the hypothesis, Qcmax was 25.99 (3.37) l.min(-1) in hypoxia (P<0.05 compared to normoxia and hyperoxia), 28.51 (2.36) l.min(-1) in normoxia and 30.13 (2.06)l.min(-1) in hyperoxia. Our results can be interpreted to indicate that (1) the reduction in VO2max in acute hypoxia is explained both by the narrowing of the arterio-venous oxygen difference and reduced Qcmax, (2) reduced Qcmax in acute hypoxia may be beneficial by preventing a further decrease in pulmonary and peripheral oxygen diffusion, and (3) reduced Qcmax and VO2max in acute hypoxia may be the result rather than the cause of the reduced Wmax and skeletal muscle recruitment, thus supporting the existence of a central governor.

Natural selection to sports, later physical activity habits, and coronary heart disease.

OBJECTIVES: To investigate the associations between natural selection to sports at a young age, continuity of physical activity, and occurrence of coronary heart disease. DESIGN: Prospective cohort study. SETTING: Finland. PARTICIPANTS: Former top level male athletes participating at a young age (1920-1965) in different types of sport (endurance (n = 166), power speed (n = 235), "other" (n = 834)) and controls healthy at the age of 20 years (n = 743). MAIN OUTCOME MEASURES: Data on the occurrence of coronary heart disease were obtained from death certificates, three nationwide registers, and questionnaire studies in 1985 and 1995, and data on later physical activity were obtained from the questionnaires. RESULTS: In 1985 all groups of former athletes were more physically active than controls (p<0.001). Despite similar total volumes of physical activity, compared with power speed athletes, former endurance athletes participated more often in vigorous activity (p = 0.006) and had less coronary heart disease (adjusted odds ratio 0.34, 95% confidence interval 0.17 to 0.73; p = 0.004). In 1985 and 1995, both endurance and other athletes had less coronary heart disease than controls. From 1986 to 1995, the incidence of new coronary heart disease was lower among those who participated in vigorous physical activity in 1985. CONCLUSIONS: Both a previous aptitude for endurance athletic events and continuity of vigorous physical activity seem to be associated with protection against coronary heart disease, but an aptitude for power speed events does not give protection against coronary heart disease.

Significance of skeletal muscle properties on fitness, long-term physical training and serum lipids.

The percentage of slow-twitch (ST) fibers in a person's skeletal muscle, e.g. muscle fiber composition (ST-%), may have a significant impact on physical activity, fitness level, serum high density lipoprotein cholesterol (HDL-C) concentration, and ultimately, on the risk of coronary heart disease (CHD). We studied the effect of a 12 month home-based exercise training program on skeletal muscle metabolic activity, serum lipids, and hormones in 12 healthy middle-aged men (sedentary men) with a low level of fitness and leisure-time physical activity (LTPA). Their parameters and changes in them were compared with 12 men of the same age with defined CHD and with two groups (15 each) of physically active men, who had either a high ST-% (high-ST-men) or a low ST-% (low-ST-men). In the sedentary men, CHD-patients and low-ST-men, the mean ST-% (42, 44, and 49%, respectively) was similar but was significantly higher in the high-ST-men (73%). The sedentary men whose LTPA mean was 34 and 19% of the mean of low-ST-men (mean of 2137 kcal/week) and high-ST-men (mean of 3845 kcal/week), respectively, increased their LTPA from a mean of 728-1526 kcal/week (P < 0.01). After training, we found an increase in serum HDL-C by 21%, (P < 0.01) and apo A-I by 36% (P < 0.01), and a decrease in serum LDL-C by 8%. The cholesterol/HDL-C ratio decreased by 17(% (P < 0.01) and the LDL-C/HDL-C ratio decreased by 22% (P < 0.01). Skeletal muscle lipoprotein lipase (LPL) activity increased by 65% (P < 0.001). Moreover, the increase in LPL as well as in HDL-C concentration tended to be more pronounced the higher the level was before training. The oxidative enzyme activity of alpha-ketoglutarate dehydrogenase (KGDH) in skeletal muscle and the activity of carnitine palmitoyltransferase (CPT) in lipid metabolism increased, whereas glycolytic phosphofructokinase (PFK) did not change but the PFK to CPT ratio decreased, which was reflected as a decrease of lactate accumulation during exercise. Increase in CPT activity correlated significantly (r(s) = 0.81, P < 0.01) with the increase in HDL-C concentration. In all men (n = 54), the CPT activity correlated negatively with serum triglyceride concentration (r(s) = -0.34, P < 0.05) but positively with serum HDL-C concentration and ST-% (r(s) = 0.34, P < 0.05 and r(s) = 0.47, P < 0.01, respectively). In all healthy men, (n = 42) LTPA correlated with both Vo2max, and ST-% (r(s) = 0.76, P < 0.001 and r(s) = 0.54, P < 0.001, respectively) and with serum HDL-C and apo A-I concentrations (r(s) = 0.35, P < 0.05 and r(s) = 0.54, P < 0.001, respectively). Serum sex hormones did not show significant associations with serum lipids, but in sedentary men, serum total and free testosterone as well as the ratio of free testosterone to free estradiol decreased significantly after training. These findings confirm the pronounced effects of a home-based exercise training program on CHD risk factors and they underline the importance of considering skeletal muscle properties when studying serum lipids and lipoproteins and their modifications in the field of health-related fitness and physical activity.

Occurrence of exercise induced bronchospasm in elite runners: dependence on atopy and exposure to cold air and pollen.

OBJECTIVES: To study factors affecting the occurrence of exercise induced bronchospasm (EIB) in elite runners. METHODS: Fifty eight elite runners, 79% of them belonging to Finnish national teams, volunteered. The athletes answered a questionnaire on respiratory symptoms. Skin prick tests were used to investigate atopy, and spirometry to examine lung function at rest and after an exercise challenge test (ECT) at subzero temperature in the winter and after a similar ECT in the summer at the end of the birch pollen season. RESULTS: Definitive EIB (a post-exercise reduction of 10% or more in forced expiratory volume in one second (FEV1) was observed in five (9%) of the 58 runners. A subgroup consisting of 19 non-atopic symptom-free runners with no family history of asthma was used to establish a normal range for post-exercise reduction in FEV1. When this group's mean exercise induced change in FEV1 minus 2 SDs (a reduction of 6.5% or more in FEV1) was taken as the lower limit of the reference range, 15 (26%) of the runners had probable EIB in either the winter or the pollen season. The occurrence of probable EIB depended on atopy (odds ratio increased with number of positive skin prick test reactions, p < 0.05). Nine (22%) of the 41 runners, challenged in both the winter and the pollen season, had probable EIB only in the winter, and three (7%) had it only in the pollen season. Only one runner (2%) had EIB in both tests. CONCLUSIONS: Mild EIB is common in Finnish elite runners and is strongly associated with atopy. Seasonal variability affects the occurrence of EIB, and thus exercise testing should be performed in both cold winter air and the pollen season to detect EIB in elite runners.

Associations between skeletal muscle properties, physical fitness, physical activity and coronary heart disease risk factors in men.

High physical fitness and physical activity are associated with favourable lipid levels, especially a high level of high density lipoprotein cholesterol (HDL-C). A person's skeletal muscle properties, metabolism and percentage of different muscle fibres (ST-%), which may modify coronary heart disease (CHD) risk factors, such as serum insulin, obesity and serum sex hormones may also influence his fitness level and leisure-time physical activity. We studied the associations of physical fitness, physical activity and ST-% with serum lipids and lipoproteins in 72 healthy men. Their parameters were compared with those of 20 men with defined CHD. Significant interrelationships between ST-%, fitness and leisure-time physical activity index (LTPAI) were observed. Multiple regression analysis showed that ST-%, fitness and leisure-time physical activity explained about 32% of the variation in HDL-C in the healthy men. In healthy men ST-% correlated positively with fitness (r(s) = 0.62, P < 0.001) and with LTPAI (r(s) = 0.62, P < 0.001). Fitness level also correlated significantly with LTPAI (r(s) = 0.81, P < 0.001). Serum insulin showed negative associations with ST-% (r(s) = -0.63, P < 0.001) and fitness (r(s) = -0.54, P < 0.001) and LTPAI (r(s) = -0.62, P < 0.001). Free fraction of testosterone correlated negatively with serum HDL-C level (r(s) = -0.34, P < 0.01), with fitness (r(s) = -0.41, P < 0.001) and with LTPAI (r(s) = -0.54, P < 0.001). In sedentary men with the lowest fitness and physical activity the mean of ST-% (45%) was similar to that in CHD patients (44%). However, ST-% in men in the highest tertile of physical activity and fitness (68%) was significantly higher than in CHD patients and in men in the lowest tertile of physical activity and fitness. Skeletal muscle enzyme activity in lipid metabolism was significantly lower in both CHD patients and in sedentary and low-fit men than that in fitter and physically active men. The present data imply that skeletal muscle properties are important determinants of risk profiles, such as physical activity, fitness and serum lipid and lipoprotein patterns. Although fitness is a graded, independent predictor of mortality from CHD, a relatively high fitness level is not enough. This was clearly observed in the clustering analysis, in which the healthy men, according to their ST-%, fitness, leisure-time physical activity and serum sex hormone binding globulin (SHBG), fell into three natural groups: (i) Inactive men with lowest ST-% (mean 42%), lowest fitness (10.7 METs) and lowest HDL-C (1.36 mm/l); (ii) Fit men with high ST-% (66%), high fitness (14.5 METs) and moderately high HDL-C (1.54 mol/l); (iii) Active men with high ST-% (66%), highest fitness (14.9 METs) and highest serum HDL (1.83 mmol/l). The results support the idea that both fitness and physical activity give further protection against CHD by modifying risk factors. Our findings also suggest that skeletal muscle properties should be considered in the studies which assess CHD risk factors and their modifications especially in the field of health-related fitness.

Asthma and increased bronchial responsiveness in elite athletes: atopy and sport event as risk factors.

BACKGROUND: High prevalence of bronchial hyperresponsiveness and asthma has been found in cross-country skiers. There is limited evidence that asthma and bronchial responsiveness would be common also in athletes with summer events. OBJECTIVES: The objective of this study was to investigate occurrence of and risk factors for increased bronchial responsiveness and asthma in elite athletes with summer events and to compare their results with those of control subjects. METHODS: Forty-nine speed and power athletes (mean age 21.1 years, range 16 to 31), 71 long-distance runners (mean age 26.6 years, range 16 to 39), 42 swimmers (mean age 18.6 years, range 14 to 25), and 45 control subjects (mean age 26.7 years, range 21 to 37) were studied. The subjects answered questionnaires and were given a resting spirometric examination, a skin prick test, and a histamine challenge test. RESULTS: Current asthma (current asthmatic symptoms and increased bronchial responsiveness) was observed in 14% (22 of 162) of the athletes and in 2% (1 of 45) of the control subjects (p = 0.041). Total asthma (current asthmatic symptoms and increased bronchial responsiveness or physician-diagnosed asthma) occurred in 23% (37 of 162) of the athletes and in 4% (2 of 45) of the control subjects (p = 0.0048). Atopy according to skin prick test results was found in 48% (77 of 162) of the athletes and in 36% (16 of 45) of the control subjects (not significant). Clinical pollen allergy (positive skin test reaction to pollen and symptoms of rhinoconjunctivitis) was significantly (p = 0.037) more common in athletes than in control subjects. Atopic athletes showed significantly more often increased bronchial responsiveness, current asthma, and total asthma than nonatopic athletes (p = 0.011, p = 0.0049, and p < 0.0001, respectively), and the odds ratios of increased bronchial responsiveness and asthma increased with the number of positive skin test reactions. After adjustment for confounding factors, the odds ratio for the occurrence of current asthma was 5.49 (95% confidence interval 0.56 to 53.7) in speed and power athletes, 2.88 (0.30 to 27.7) in long-distance runners, and 10.8 (1.10 to 106.0) in swimmers compared with control subjects. The adjusted odds ratios for the occurrence of total asthma were 3.56 (0.62 to 20.5) in speed and power athletes, 6.01 (1.19 to 30.2) in long-distance runners, and 5.89 (1.00 to 34.5) in swimmers. CONCLUSIONS: Asthma is more common in highly trained athletes than in control subjects. Asthma is especially common in elite swimmers, but the risk of asthma is increased also in long-distance runners. Increased bronchial responsiveness and asthma are strongly associated with atopic disposition and its severity in elite athletes.

Respiratory symptoms, bronchial responsiveness, and cellular characteristics of induced sputum in elite swimmers.

To investigate respiratory symptoms, increased bronchial responsiveness, and signs of airway inflammation in elite swimmers, we examined 29 swimmers from the Finnish national team and 19 healthy control subjects (nonasthmatic, symptom-free). They answered a questionnaire and were interviewed for respiratory symptoms. Lung volumes were measured and bronchial responsiveness assessed by a histamine challenge test. Induced sputum samples were also collected. Fourteen (48%) of the swimmers and three (16%) of the control subjects showed increased bronchial responsiveness (P<0.05). The sputum cell differential counts of eosinophils (mean 2.7% vs 0.2%) and neutrophils (54.7% vs 29.9%) from swimmers were significantly higher than those from controls (P<0.01). Eosinophilia (sputum differential eosinophil count of >4%) was observed in six (21%) of the swimmers and in none of the controls (P<0.05). Symptomatic swimmers had significantly more sputum eosinophils than did the symptom-free. The concentrations of sputum eosinophil peroxidase (EPO) and human neutrophil lipocalin (HNL) were significantly higher in swimmers than control subjects (P<0.001 and P=0.05). We conclude that elite swimmers had significantly more often increased bronchial responsiveness than control subjects. Sputum from swimmers contained a higher percentage of eosinophils and neutrophils, and higher concentrations of EPO and HNL than sputum from controls. Long-term and repeated exposure to chlorine compounds in swimming pools during training and competition may contribute to the increased occurrence of bronchial hyperresponsiveness and airway inflammation in swimmers.

Association between type of training and risk of asthma in elite athletes.

BACKGROUND: Intensive endurance training has been associated with a high prevalence of symptoms compatible with asthma in elite athletes. It is not known, however, whether there is an association between the type of training for competitive events and the risk of asthma in highly trained athletes. METHODS: Two hundred and thirteen track and field athletes, mostly from Finnish national teams, and 124 controls of the same age completed a respiratory symptom questionnaire. Positive answers to physician diagnosed asthma were confirmed by personal interviews. The athletes were divided into two groups depending on whether they were speed and power athletes (n = 106) or long distance runners (n = 107). RESULTS: According to a logistic regression model the prevalence of physician diagnosed asthma was not associated with age, sex, or a family history of asthma. Long distance runners (OR 6.7; 95% CI 2.1 to 22.1) and speed and power athletes (OR 3.2; 95% CI 0.90 to 11.4) had a higher prevalence of physician diagnosed asthma than control subjects. Physician diagnosed asthma was found in 18 of 107 long distance runners (17%), in nine of 106 speed and power athletes (8%; p = 0.07 (chi 2 test)), and in four of 124 controls (3%; p < 0.0004 (chi 2 test for trend)). CONCLUSIONS: The prevalence of physician diagnosed asthma is high in elite athletes and an association with the competitive event is suggested with long distance runners having a greater risk of developing asthma than speed and power athletes. This may be due to prolonged hyperventilation and increased exposure to inhalant allergens and irritants during endurance training and competition.

Exercise-induced bronchospasm at low temperature in elite runners.

BACKGROUND: Healthy elite runners often report bronchial symptoms when training in subzero temperatures. The occurrence and causes of exercise-induced bronchospasm after heavy exercise in cold air were investigated in elite runners. METHODS: Thirty two non-asthmatic runners, mostly from Finnish national teams, volunteered to take part in the study. They answered a questionnaire and were subjected at subzero temperature to a heavy exercise challenge test combined with lung function testing. RESULTS: Sixteen of the runners were atopic on skin prick tests. The mean (SD) maximal change in forced expiratory volume in one second (FEV1) after the exercise challenge was -4.8 (7.1)% in the atopic runners, and +2.1 (3.4)% in the non-atopic runners. When the mean maximal change in FEV1 minus 2SD (-4.7%) of the exercise response of the non-atopic runners was taken as the lower limit of a "normal" result, eight of the atopic runners responded abnormally. CONCLUSIONS: Heavy exercise at temperatures below zero causes bronchospasm in a high proportion of elite runners with atopy. Although the changes in lung function are mostly small, they may affect the maximal performance of atopic runners. Non-atopic runners are not affected.

Skeletal muscle fiber distribution influences serum high-density lipoprotein cholesterol level.

Earlier we have shown a significant positive association between muscle fiber distribution, i.e. percentage of slow-twitch (ST) fibers in the vastus lateralis muscle, and serum high-density lipoprotein cholesterol (HDL-C) level. This association may be due to the fact that ST fibers have a high capacity for oxidative energy metabolism and a high number of surrounding capillaries. These fibers have a high capacity to metabolize fatty acids liberated by lipoprotein lipase (LPL) from triglyceride-rich lipoproteins. This in turn elevates serum HDL-C levels. Thus, a high percentage of ST fibers (ST-%) may be one factor having a beneficial effect on serum HDL-C concentration. A high ST-% may also increase the likelihood that a person will become involved in an endurance type of physical activity, which further increases serum HDL-C concentration by increasing further LPL activity in the capillary bed of skeletal muscle. In this paper we present a hypothetical background of the role that ST fibers may have on serum lipid and lipoprotein profile.

Alteration of regulatory enzyme activities in fast-twitch and slow-twitch muscles and muscle fibres in low-intensity endurance-trained rats.

The effect of progressive, low-intensity endurance training on regulatory enzyme activities in slow-twitch (ST) and fast-twitch (FT) muscle fibres was studied in 32 rats. Of those rats 16 were trained on a treadmill at a running speed of 10 m.min-1 5 days a week over an 8-week period. Running time was progressively increased from 15 min to 2 h.day-1. Of the rats 4 trained and 4 sedentary rats were also subjected to acute exhausting exercise. Enzyme activities of phosphofructokinase 1 (PFK1) from glycolysis, alpha-ketoglutarate dehydrogenase (alpha-KGDH) from the Krebs cycle and carnitine palmitoyltransferase (CPT I and II) from fatty acid metabolism in soleus, tibialis anterior and gastrocnemius muscles were measured in trained and sedentary rats. Enzyme activities of individual ST and FT fibres were measured from the freeze-dried gastrocnemius muscle of 8 trained and 8 sedentary rats. In the sedentary rats the activity of PFK1 in tibialis anterior and soleus muscles was 141% and 41% of the activity in gastrocnemius muscle, respectively. The activity of alpha-KGDH in tibialis anterior and soleus muscles was 164% and 278% of the activity in gastrocnemius muscle, respectively. The activity of CPT I in tibialis anterior and gastrocnemius muscles were at the same level, but in soleus muscle the activity was 127% of that in mixed muscle. Endurance training increased enzyme activities of alpha-KGDH and CPT I significantly (P < 0.05) in gastrocnemius muscle but not in soleus or tibialis anterior muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of skeletal muscle fiber type to serum high density lipoprotein cholesterol and apolipoprotein A-I levels.

We measured the percentage of slow-twitch (ST) muscle fibers in the lateral portion of the quadriceps femoris muscle in 41 healthy sedentary male controls, 35 active male joggers, and 26 male coronary heart disease (CHD) patients. We then compared these percentages with serum levels of total cholesterol (TC), triglycerides (TG), high density lipoprotein cholesterol (HDL-C) and apolipoprotein A-I (apo A-I) found in these 102 middle-aged men. The percentage of ST muscle fibers in all men correlated positively with serum HDL-C (r = 0.57, P less than 0.001) and with apo A-I (r = 0.60, P less than 0.001) and negatively with triglycerides (r = -0.43, P less than 0.001). The proportion of ST fibers in joggers (65%; 61-69%, 95% confidence interval) was higher (P less than 0.001) than in sedentary controls (48%; 44-52%) or in CHD patients (44%; 39-49%). Moreover, 89% of the joggers had a proportion of ST fibers higher than 50%, whilst in sedentary controls and in CHD patients these values were 46% and 38%, respectively. Positive correlations were found between the percentage of ST fibers and both HDL-C and apo A-I in controls (r = 0.33, P less than 0.05 and r = 0.34, P less than 0.05) and in joggers (r = 0.46, P less than 0.01, and r = 0.40, P less than 0.05), respectively. Negative correlations in controls (r = -0.34, P less than 0.05) and in CHD patients (r = -0.43, P less than 0.05) were also found between the percentage of ST fibers and serum TG.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate loading in practice: high muscle glycogen concentration is not certain.

It is believed that muscle glycogen resynthesis can be stimulated by depleting the glycogen stores by heavy physical exercise and then eating a diet rich in carbohydrates. In this study, we compared muscle glycogen concentrations after two different depletion and loading procedures in six male runners. The depletion runs for the procedures were a half-marathon race and an easier fartlek. The mean muscle glycogen concentrations (+/- s.e.m.), analysed after the procedures, did not differ significantly between the race and the fartlek being 285 (+/- 25) mmol/kg d.w. (dry weight) versus 315 (+/- 32) mmol/kg d.w. (P greater than 0.05). Moreover, the subjects' glycogen concentrations were not clearly increased above the predepletion values following either procedure. The results show that higher glycogen levels do not necessarily occur after classical carbohydrate-loading procedures.