Effects of 2 weeks of low-intensity cycle training with different pedaling rates on the work rate at lactate threshold.

PURPOSE: This study examined (1) the effects of a single bout of exercise at different pedaling rates on physiological responses, pedal force, and muscle oxygenation, and (2) the effects of 2 weeks of training with different pedaling rates on work rate at lactate threshold (WorkLT). METHODS: Sixteen healthy men participated in the study. An incremental exercise test involving pedaling a cycling ergometer at 50 rpm was conducted to assess maximal oxygen consumption and WorkLT. The participants performed constant workload, submaximal exercise tests at WorkLT intensity with three different pedaling rates (35, 50, and 75 rpm). Oxygen consumption ([Formula: see text]O2), blood pressure, heart rate (HR), blood lactate, and pedal force were measured and oxy-hemoglobin/myoglobin concentration (OxyHb/Mb) at vastus lateralis was monitored by near-infrared spectroscopy during exercise. The participants were then randomly assigned to cycling exercise training at WorkLT in either the low or high frequency pedaling rate (LFTr, 35 rpm or HFTr, 75 rpm) group. Each 60-min training session was performed five times/week. RESULTS: Despite maintaining the same work rate, [Formula: see text]O2 and HR were significantly lower at 35 than 75 rpm. Conversely, integrated pedal force was significantly higher at 35 than 75 rpm. Peripheral OxyHb/Mb was significantly lower at 35 than 75 rpm. After 2 weeks of training, WorkLT normalized to body mass significantly increased in the LFTr, but not the HFTr group. CONCLUSIONS: Pedaling rate and the corresponding pedal force and peripheral oxygenation during cycling exercise influence the effect of training at LT on WorkLT.

Significant effect of a pre-exercise high-fat meal after a 3-day high-carbohydrate diet on endurance performance.

We investigated the effect of macronutrient composition of pre-exercise meals on endurance performance. Subjects consumed a high-carbohydrate diet at each meal for 3 days, followed by a high-fat meal (HFM; 1007 ± 21 kcal, 30% CHO, 55% F and 15% P) or high-carbohydrate meal (HCM; 1007 ± 21 kcal, 71% CHO, 20% F and 9% P) 4 h before exercise. Furthermore, just prior to the test, subjects in the HFM group ingested either maltodextrin jelly (M) or a placebo jelly (P), while subjects in the HCM ingested a placebo jelly. Endurance performance was measured as running time until exhaustion at a speed between lactate threshold and the onset of blood lactate accumulation. All subjects participated in each trial, randomly assigned at weekly intervals. We observed that the time until exhaustion was significantly longer in the HFM + M (p < 0.05) than in HFM + P and HCM + P conditions. Furthermore, the total amount of fat oxidation during exercise was significantly higher in HFM + M and HFM + P than in HCM + P (p < 0.05). These results suggest that ingestion of a HFM prior to exercise is more favorable for endurance performance than HCM. In addition, HFM and maltodextrin ingestion following 3 days of carbohydrate loading enhances endurance running performance.

Long-term effects of home-based bench-stepping exercise training on healthcare expenditure for elderly Japanese.

BACKGROUND: We examined the long-term effects of home-based bench-stepping exercise training on total healthcare expenditure (TOHEX) and number of outpatient visits (NOVIS) in elderly adults. METHODS: A total of 189 elderly Japanese (age 73 ± 4 years) participated in this study. They were randomly assigned to either an exercise or control group. TOHEX, NOVIS, and outpatient expenditure (OPEX) were evaluated every 6 months from 1 year before the start to the end of the intervention period, as well as 1 year after the end of the intervention. The exercise group was encouraged to perform home-based bench-stepping exercise training on most, and preferably all, days of the week for 18 months. RESULTS: The exercise group showed significant increases in lactate threshold as compared with pre-intervention values. There were no significant differences in TOHEX, OPEX, or NOVIS between the exercise and control groups 1 year before the start of the intervention, and the values remained similar during the first 12 months of the intervention period. However, at 18 months, TOHEX, NOVIS, and OPEX were significantly lower in the exercise group than in the control group (TOHEX: 170 007 ± 192 072 vs. 294 705 ± 432 314 yen, P = 0.008; NOVIS: 19.2 ± 26.3 vs. 28.2 ± 32.1 days, P = 0.012; OPEX: 132 973 ± 132 016 vs. 187 799 ± 158 167 yen, P = 0.005). CONCLUSIONS: The data indicate that a long-term home-based bench-stepping exercise program can reduce healthcare expenditure in elderly Japanese.

[Evaluation of sub-maximal aerobic capacity level determined by double product break point (DPBP) among Japanese adults].

OBJECTIVES: The purpose of this study was to determine sub-maximal aerobic capacity levels evaluated by metabolic equivalents (unit is METs) at the double product break point (DPBP) and elucidate the safe and effective average exercise intensity among Japanese adults. A total of 438 subjects (123 males and 315 females) who participated in the exercise prescription course with measurement of the DPBP during a continuous incremental exercise test with a bicycle METHODS: ergometer were enrolled in this study. The DP (heart rate-systolic blood pressure product) featured rapid increase with increasing exercise load during the continuous incremental exercise test. RESULTS: The metabolic equivalents at the DPBP level for males and females were 5.3+/-0.9 METs and 4.9+/-0.7 METs, respectively. Interestingly, the metabolic equivalent at the DPBP level in 87.2% of the study subjects was less than 6 METs. CONCLUSIONS: This study indicated that some physical activities above moderate intensity, such as the stair climbing (8 METs), might be inappropriate as health promotion exercises. Thus, the upper limit of exercise intensity for health promotion was 6 METs, especially if the subject was at cardiovascular risk. In addition, it was found necessary to make synthetic judgments in consideration of heart rate and rating of perceived exertion (RPE) during exercise.

Significant lowering of plasma ghrelin but not des-acyl ghrelin in response to acute exercise in men.

Ghrelin, an acylated peptide produced predominantly in the stomach, stimulates feeding and growth hormone (GH) secretion via interaction with the GH secretagogue receptor. Ghrelin molecules are present in two major endogenous forms, an acylated form (ghrelin) and a des-acylated form (des-acyl ghrelin). Recent studies indicated that aerobic exercise did not change plasma total ghrelin levels, however, dynamics of circulating ghrelin and des-acyl ghrelin during aerobic exercise remains unclear. The purpose of this study is to examine the effects of moderate intensity exercise on plasma ghrelin and des-acyl ghrelin concentrations, and to investigate the relationship between ghrelin molecules and other hormonal and metabolic parameters during exercise. Nine healthy males (25.2 ± 0.5 years) exercised for 60 min at 50% of their maximal oxygen consumptions. We measured the plasma concentrations of ghrelin, des-acyl ghrelin, GH, norepinephrine (NE), epinephrine (E), dopamine (DA), insulin, and glucose. Plasma ghrelin level significantly decreased during exercise, whereas plasma des-acyl ghrelin and total ghrelin levels did not change. Plasma NE, E, DA and GH levels were significantly increased during exercise. Plasma insulin level significantly decreased during exercise, and plasma glucose levels remained steady during exercise. NE, E, DA, and GH were correlated negatively with plasma ghrelin levels. These findings suggest that acute moderate exercise may suppress ghrelin release from the stomach, decrease ghrelin O-acyltransferase activity, and/or activate ghrelin utilization in peripheral tissues and that exercise-induced ghrelin suppression may be mediated by activated adrenergic system.

Effect of low-intensity aerobic exercise on insulin-like growth factor-I and insulin-like growth factor-binding proteins in healthy men.

Increased concentrations of circulating insulin-like growth factor-I (IGF-I) or IGF-I relative to IGF-binding proteins (IGFBPs) are associated with increased risk of developing several forms of cancer. Conversely, exercise is linked with reduced risk. This study aims to investigate the effect of a low-intensity exercise program on circulating levels of IGF-I, IGFBP-1, and IGFBP-3, in previously sedentary males. Fourteen healthy men participated in cycle ergometer training at lactate threshold intensity for 60 min/day, 5 days/week for 6 weeks. After aerobic training, insulin sensitivity improved by 20%, while fasting insulin levels decreased by 13%. Simultaneously, low-intensity aerobic training decreased the circulating levels of IGF-I by 9%, while IGFBP-1 levels increased by 16%. An interesting finding was that higher pretraining level of IGF-I was associated with greater decline in IGF-I with training. Insulin-sensitizing low-intensity aerobic exercise is thus considered to be an effective method for downregulating IGF-I and upregulating IGFBP-1 levels.

Hepatic insulin sensitivity assessed by integrated model of hepatic and peripheral glucose regulation.

BACKGROUND: The integrated model of hepatic and peripheral glucose metabolism incorporates a model for liver glucose metabolism into the two-compartment minimal model framework to describe endogenous glucose kinetics during a labeled intravenous glucose tolerance test (IVGTT). This model also provides a parametric description of endogenous glucose production (EGP). The present study extended the theoretical potential of the model by defining hepatic glucose effectiveness (hS(G)(2)) as the ability of glucose per se to inhibit EGP and hepatic insulin sensitivity (hS(1)(2)) as the ability of insulin to enhance glucose suppression of EGP. METHODS: As a retrospective data base review of our previous study, we re-analyzed time courses of exogenous and endogenous glucose concentration during [6,6-(2)H(2)]glucose-labeled IVGTT (0.3 g/kg glucose), performed in 11 exercise-trained and 12 age-matched sedentary subjects. Model parameters of the two-compartment minimal model and of liver glucose metabolism were simultaneously identified to assess insulin sensitivity specific to stimulate glucose uptake (S(1)(2*)) and that specific to inhibit EGP (hS(1)(2)). The abilities of glucose per se to stimulate its own uptake (S(G)(2*)) and to inhibit EGP (hS(G)(2)) were also estimated. RESULTS: Parameters of the integrated model were identified in all the subjects. Hepatic insulin sensitivity consisted of about one-third of total insulin sensitivity (S(1)(2*) + hS(1)(2)). Compared with the sedentary subjects, S(1)(2*), hS(1)(2), hS(G)(2) of the trained subjects were greater. CONCLUSIONS: Because insulin resistance in liver and peripheral tissue may play a differential role in the pathogenesis of diabetes, this analysis can serve as a simple one-step approach to obtain metabolic indexes specific to EGP suppression and stimulating glucose uptake.

Target step count for the secondary prevention of cardiovascular disease.

BACKGROUND: Obtaining an accurate measure of physical activity energy expenditure (PAEE) can be difficult, so the simple measurement of steps per day has become widely promoted and accepted in the general population. However, the relationship between PAEE and steps per day has not been evaluated in patients with cardiovascular disease. METHODS AND RESULTS: A total of 77 (53 men, 24 women) cardiac rehabilitation program participants aged between 46 and 88 years were enrolled. By means of an accelerometer the step count per day, amount of PAEE, as well as time per day spent in physical activity at light (<3 metabolic equivalents (METs)), moderate (3-6 METs) and vigorous (>6 METs) intensity were evaluated for each subject. The number of daily step counts strongly correlated with total PAEE (r=0.92, p<0.001) and time spent in moderate to vigorous intensity physical activity (r=0.85, p<0.001). The mean (95% confidence intervals) step counts associated with 214 and 314 kcal/day (ie, 1,500 and 2,200 kcal/week) were 6,470 and 8,496 steps/day, respectively. CONCLUSION: To achieve the total amount of PAEE generally recommended for the secondary prevention of cardiovascular disease, patients should be encouraged to accumulate 6,500-8,500 steps/day.

Association between silent ST segment depression in exercise electrocardiography and insulin resistance in obese subjects.

OBJECTIVES: This study was designed to clarify the association between ST segment depression in exercise electrocardiography (ECG) and insulin resistance in obese subjects. METHODS: A multistage graded submaximal exercise stress test on the bicycle ergometer was performed under CM5-lead ECG monitoring in 114 obese subjects (39 men and 75 women, mean age 50.9 +/- 12.2 years, mean body mass index 28.6 +/- 3.1 kg/m(2)). RESULTS: In 27 patients showing ST segment depression at the final exercise intensities (abnormal ST), insulin resistance index by homeostasis model assessment (HOMA-IR) was higher and insulin sensitivity index was lower than in the remaining 87 patients with normal ST segment level (normal ST). The abnormal ST group showed significantly higher plasma glucose and serum insulin levels during the oral glucose tolerance test (OGTT) than the normal ST group. The abnormal ST group showed a significantly higher prevalence of hypertension, impaired glucose tolerance and metabolic syndrome than the normal ST group. Multiple logistic regression analysis showed that insulin resistance as evaluated by fasting insulin, sigma insulin during OGTT, HOMA-IR, insulin sensitivity index, the levels of uric acid, fasting glucose, systolic blood pressure and maximal oxygen uptake were independently associated with ST segment depression. CONCLUSIONS: These results suggest that insulin resistance may involve pathological ST depression during exercise, as well as previously reported factors such as hyperglycemia, hyperuricemia, hypertension and lower aerobic capacity.

Angiotensin I converting enzyme gene polymorphism and exercise trainability in elderly women: an electrocardiological approach.

Angiotensin I converting enzyme (ACE) gene Insertion / Deletion (I/D) polymorphism is associated with exercise trainability and exercise induced left ventricular hypertrophy. However, it is unclear whether this polymorphism influences exercise trainability in the elderly, and the electrocardiological alterations by exercise training is unknown among the genotypes. We herein investigated the association between ACE gene insertion/deletion (I/D) polymorphism, exercise trainability and the electrocardiological alternations by exercise in elderly women. Eighty four elderly women participated in this study. In all subjects the leg extension power (LEP) and lactate threshold (LT) were determined in order to evaluate the muscle strength, aerobic capacity and to also select the appropriate training intensity for each individual. They performed bench step exercise training for 12 weeks. A resting electrocardiogram was recorded for the obtained QTc interval in before and after the program. The baseline of aerobic capacity was higher in I/I than that in I/D, and the QTc interval was shorter in I/I than that in I/D. All other characteristics were similar among the genotypes. The QTc interval tended to be shorten only in the D/D. Furthermore, the value of the QTc interval change showed a significant difference between the I/I and D/D genotype after the program. The LT and LEP demonstrated a similar response among the genotypes. The D allele of ACE gene I/D polymorphism may therefore play a role in the electrocardiological aspect during exercise training, however, it was not found to influence the aerobic capacity. Key pointsThe D allele of ACE gene I/D polymorphism may play a role in the electrocardiological aspects during exercise trainingACE gene I/D polymorphism was not determined the aerobic capacity and leg strength in elderly people.The ACE gene I/D polymorphism did not influence aerobic and strength trainability in elderly people.

The physical activity patterns of cardiac rehabilitation program participants.

PURPOSE: This investigation aimed to examine the physical activity patterns of cardiac rehabilitation program (CRP) participants. METHODS: The investigation enrolled 53 male and 24 female CRP participants between 46 and 88 years of age. By means of a uniaxial accelerometer (Life-Corder), the amount of physical activity (in kilocalories) and the time spent in physical activity at light (<3 metabolic equivalents [METs]), moderate (3 to 6 METs), and vigorous (>6 METs) intensity were evaluated. In addition to these variables, the MET levels for the CRP and non-CRP periods were calculated. RESULTS: The weekly amount of physical activity energy expenditure averaged 1597 +/- 846 kcal/week, and the time spent in light, moderate, and vigorous physical activity averaged, respectively, 375.5 +/- 124.5 minutes, 125.2 +/- 109.4 minutes, and 5.7 +/- 12.8 minutes per week. These levels were significantly lower on non-CRP days than on CRP days: 177 +/- 113 versus 299 +/- 161 kcal/day and, respectively, 49.3 +/- 19.3 versus 59.7 +/- 19.8 minutes, 10.5 +/- 14.6 versus 26.4 +/- 20.4 minutes, and 0.4 +/- 1.7 versus 1.4 +/- 3.0 minutes per day. CONCLUSIONS: These results indicate that the amount of physical activity was generally adequate on CRP days, but failed to reach target levels on non-CRP days. Thus CRP participants, when it is medically appropriate, should be encouraged to incorporate lifestyle physical activity, additional exercise, or both on non-CRP days to supplement their caloric expenditure from CRP exercise sessions.

The use of uniaxial accelerometry for the assessment of physical-activity-related energy expenditure: a validation study against whole-body indirect calorimetry.

Assessing the total energy expenditure (TEE) and the levels of physical activity in free-living conditions with non-invasive techniques remains a challenge. The purpose of the present study was to investigate the accuracy of a new uniaxial accelerometer for assessing TEE and physical-activity-related energy expenditure (PAEE) over a 24 h period in a respiratory chamber, and to establish activity levels based on the accelerometry ranges corresponding to the operationally defined metabolic equivalent (MET) categories. In study 1, measurement of the 24 h energy expenditure of seventy-nine Japanese subjects (40 (SD 12) years old) was performed in a large respiratory chamber. During the measurements, the subjects wore a uniaxial accelerometer (Lifecorder; Suzuken Co. Ltd, Nagoya, Japan) on their belt. Two moderate walking exercises of 30 min each were performed on a horizontal treadmill. In study 2, ten male subjects walked at six different speeds and ran at three different speeds on a treadmill for 4 min, with the same accelerometer. O2 consumption was measured during the last minute of each stage and was expressed in MET. The measured TEE was 8447 (SD 1337) kJ/d. The accelerometer significantly underestimated TEE and PAEE (91.9 (SD 5.4) and 92.7 (SD 17.8) % chamber value respectively); however, there was a significant correlation between the two values (r 0.928 and 0.564 respectively; P<0.001). There was a strong correlation between the activity levels and the measured MET while walking (r(2) 0.93; P<0.001). Although TEE and PAEE were systematically underestimated during the 24 h period, the accelerometer assessed energy expenditure well during both the exercise period and the non-structured activities. Individual calibration factors may help to improve the accuracy of TEE estimation, but the average calibration factor for the group is probably sufficient for epidemiological research. This method is also important for assessing the diurnal profile of physical activity.

Effect of moderate exercise training on peripheral glucose effectiveness, insulin sensitivity, and endogenous glucose production in healthy humans estimated by a two-compartment-labeled minimal model.

For examining the effects of moderate exercise training on peripheral glucose effectiveness (S(g)(2)*), insulin sensitivity (S(i)(2)*), and endogenous glucose production (EGP), seven men and one woman (24.8 +/- 1.8 years) participated in cycle ergometer training at lactate threshold intensity for 60 min/day, 5 days/week for 12 weeks. Stable-labeled frequently sampled intravenous glucose tolerance tests were performed before and 16 h and 1 week after the last training session. S(g)(2)* (pre 0.71 +/- 0.03 x 10(-2), 16 h 0.85 +/- 0.02 x 10(-2) dl. kg(-1). min(-1)) and S(i)(2)* (pre 12.6 +/- 2.6 x 10(-4), 16 h 19.7 +/- 3.3 x 10(-4) dl. kg(-1). min(-1). [ micro U/ml](-1)), analyzed using the two-compartment minimal model, were significantly elevated 16 h after the last training session. The elevated S(g)(2)* remained higher despite the cessation of exercise training for 1 week (1.00 +/- 0.03 x 10(-2) dl. kg(-1). min(-1)). EGP was suppressed within 20 min after glucose bolus, and the suppression of EGP was followed by their overshoot. The time course of EGP during the intravenous glucose tolerance test remained similar after the training period. In conclusion, moderate exercise training at lactate threshold improves not only peripheral insulin sensitivity but also peripheral glucose effectiveness with no change in the effect of glucose and/or insulin to suppress EGP in healthy humans.

The difference between the basal metabolic rate and the sleeping metabolic rate in Japanese.

Previous studies have demonstrated the difference between the basal metabolic rate (BMR) and the sleeping metabolic rate (SMR): however, the difference in the Japanese population has not yet been explored. This study examined the relationship between the BMR and SMR in ninety-four healthy Japanese subjects (37 males and 57 females, 39 +/- 12 y of age and 22.0 +/- 7.4% body fat) in a respiratory chamber. The SMR was significantly lower than the BMR (1416 +/- 245 vs. 1492 +/- 256 kcal/d): however, there was a highly significant correlation between the two (r = 0.867; p < 0.001). The ratio of SMR/BMR largely varied among individuals (0.95 +/-0.08, 8.4% of the coefficient of variation). The ratio was significantly lower in males than in females (0.93 +/- 0.10 vs. 0.97 +/- 0.06, p < 0.05). None of the anthropometric measures (age, weight, body mass index, body surface area or percent body fat) correlated with the ratio. These results showed that SMR was 95%, of BMR on average in a healthy Japanese group. However, when applied over a longer time period (24 h or more), the difference tends to become negligible for most analyses in a group. Although the difference between SMR and BMR will induce a 5% gap of physical activity level defined as the total energy expenditure divided by the BMR or SMR, this factor seems to have little practical importance in epidemiological research.

Serial analysis of gene expression in the skeletal muscle of endurance athletes compared to sedentary men.

Physical exercise produces several adaptive changes in skeletal muscle. However, the molecular mechanisms of these effects are poorly understood. We performed serial analysis of gene expression (SAGE) to quantify the global gene expression profile in sedentary and endurance-trained muscle. A total of 10869 SAGE tags was sequenced and represented 4727 genes. The genes most expressed in muscle are mainly involved in contraction and energy metabolism. Thirty-three genes were differentially expressed between endurance athletes and sedentary individuals. Four genes such as myosin binding protein C fast-type, glycogen phosphorylase, and pyruvate kinase were expressed less in endurance athletes, whereas eight genes coding for expressed sequence tag similar to (EST) crystallin alpha B, EST myosin light chain 2, EST surfactant pulmonary-associated protein A1, EST thrombospondin, EST fructose-bisphosphate aldolase A, EST cytochrome oxidase 1, NADH dehydrogenase 3, and G8 protein were up-regulated. Most of the up-regulated tags corresponded to novel genes. On the other hand, different isoforms of fructose-bisphosphate aldolase A were also differentially expressed. The current study underlying the most highly expressed genes allows a better understanding of global muscle characteristics in normal and endurance-trained individuals. Moreover, the current data suggest novel candidate genes that may be responsible for enhanced endurance performance.

Cardiorespiratory fitness and cancer mortality in Japanese men: a prospective study.

PURPOSE: Limited data are available on the relationship between cardiorespiratory fitness and cancer mortality. We evaluated the cardiorespiratory fitness and risk of cancer mortality in Japanese men. METHODS: A total of 9039 men (19-59 yr) who were given a submaximal exercise test and a health examination between 1982 and 1988 and were followed for mortality up to 1999. Cardiorespiratory fitness was measured using a cycle ergometer test, and maximal oxygen uptake was estimated. RESULTS: The mean follow-up period was slightly more than 16 yr, producing a total of 148,491 person-years of observation. There were 231 deaths, with 123 deaths due to cancer. Relative risk (RR) and 95% confidence interval (95%CI) for cancer mortality were obtained using the Cox proportional hazards model. Taking into consideration age, systolic blood pressure, body mass index, smoking habit, and alcohol habit and using the lowest physical fitness group as the reference, the RR (95% CI) for increasing quartiles of fitness were 0.75(0.48-1.16), 0.43(0.25-0.74) and 0.41(0.23-0.74); P < 0.001 for trend. CONCLUSION: Low cardiorespiratory fitness is associated with cancer mortality in Japanese men.

Multivariate analysis of the prognostic determinants of the depressor response to exercise therapy in patients with essential hypertension.

This study investigated the contribution of hemodynamic and humoral factors to the variation in the depressor responses to exercise therapy and the significance of the baseline values of these factors in predicting the depressor response of essential hypertensives to mild exercise therapy. Patients with mild to moderate essential hypertension (n=122, F/M: 97/25) performed a bicycle ergometer exercise at a workload equivalent to the lactate threshold for 10 weeks. In all of the patients, systolic and diastolic blood pressures (BP) significantly decreased after 1 week of exercise, continued to decrease until 4 weeks, and were stable from 4 weeks to 10 weeks. Changes in the plasma volume and humoral factors during the study did not differ significantly between responders and non-responders. A multiple logistic regression analysis showed that higher baseline mean BP (MBP) was significantly associated with a poor depressor response (odds ratio 1.84, p=0.002). A variance component analysis indicated that baseline MBP accounted for only 11.2% of the total variance of the depressor response. In conclusion, these summarized results showed that variations in the depressor response to mild exercise therapy were partly determined by baseline MBP, but not by humoral factors, suggesting the possible involvement of other factors, including genetic factors.

Relationship between exercise training-induced increase in insulin sensitivity and adiponectinemia in healthy men.

Circulating concentrations of adiponectin, an adipocyte-derived protein, are increased by thiazolidinediones and by weight reduction, accompanied with improvement in insulin sensitivity. The effect of exercise training, another therapy to increase insulin sensitivity (SI), on adiponectinemia is currently unclear. The present study was undertaken to clarify whether exercise training-induced increase in SI is related to changes in adiponectinemia in healthy men. Twelve healthy non-obese men underwent ergometer training at lactate threshold (LT) intensity for 60 min/day for 5 days/week for 6 weeks. An insulin-modified intravenous glucose tolerance test was performed before and at 16 h and 1 week after the last training session to determine SI using a minimal-model approach. Serum levels of adiponectin were determined at the same time. After the exercise training, VO2max and LT were significantly increased by 7.2% and 22.3% (P<0.01), while BMI and body fat mass remained unchanged. SI was significantly increased at 16 h after the last training session (from 7.0 +/- 3.1 to 9.6 +/- 3.6 [x 10(-4) x (microU/ml)(-1) x min(-1)], P<0.01), but returned toward the basal levels at 1 week after the cessation of the training. Serum adiponectin concentrations before the training (20.9 +/- 7.4 microg/ml) were positively correlated with SI. The concentrations were slightly but significantly decreased at 16 h (17.2 +/- 6.6 microg/ml, P<0.05), and returned to the basal values at 1 week after the training. From these results, it can be concluded that exercise training-induced increase in SI is not dependent on the increase in adiponectinemia in healthy men.

Effects of low intensity aerobic training on skeletal muscle capillary and blood lipoprotein profiles.

The effects of low intensity endurance training on skeletal muscle capillary density and serum lipoprotein levels were studied in 11 non-obese men (18-25 years). The subjects performed a 6-week training regimen (60 min, 5 times per week) at the lactate threshold (LT). Capillary density was determined in biopsy specimens obtained from the vastus lateralis muscle before and after the training. The number of capillaries per fiber (cap/fiber ratio) before training was 1.97 +/- 0.47, and increased to 2.49 +/- 0.69 after training (p < 0.05). The maximal oxygen uptake (VO2 max) and LT- VO2 increased significantly by 5% (p < 0.01) and 27% (p < 0.01), respectively, whereas no change was observed in body weight. Low density lipoprotein cholesterol (LDL-C) tended to decrease (p = 0.06). The change in the cap/fiber ratio correlated inversely with the change in the ratio of LDL-C to high density lipoprotein cholesterol (HDL-C) (r = -0.61, p < 0.05). It was also, positively associated with the change in HDL2-C (r = 0.82, p < 0.01) and inversely associated with the change in HDL3-C (r = -0.63, p < 0.05). The change in LT- VO2 was inversely associated with the change in LDL-C (r = -0.62, r < 0.05). These results indicate that low intensity training increases capillary density in skeletal muscle, which may explain in part the changes in the lipoprotein profiles.

S(G), S(I), and EGP of exercise-trained middle-aged men estimated by a two-compartment labeled minimal model.

To examine the effects of physical training on glucose effectiveness (S(G)), insulin sensitivity (S(I)), and endogenous glucose production (EGP) in middle-aged men, stable-labeled frequently sampled intravenous glucose tolerance tests (FSIGTT) were performed on 11 exercise-trained middle-aged men and 12 age-matched sedentary men. The time course of EGP during the FSIGTT was estimated by nonparametric stochastic deconvolution. Glucose uptake-specific indexes of glucose effectiveness (S(2*)(G) x 10(2): 0.81 +/- 0.08 vs. 0.60 +/- 0.05 dl. min(-1). kg(-1), P < 0.05) and insulin sensitivity [S(2*)(I) x 10(4): 24.59 +/- 2.98 vs. 11.89 +/- 2.36 dl. min(-1). (microU/ml)(-1). kg(-1), P < 0.01], which were analyzed using the two-compartment minimal model, were significantly greater in the trained group than in the sedentary group. Plasma clearance rate (PCR) of glucose was consistently greater in the trained men than in sedentary men throughout FSIGTT. Compared with sedentary controls, EGP of trained middle-aged men was higher before glucose load. The EGP of the two groups was similarly suppressed by approximately 70% within 10 min, followed by an additional suppression after insulin infusion. EGP returned to basal level at approximately 60 min in the trained men and at 100 min in the controls, followed by its overshoot, which was significantly greater in the trained men than in the controls. In addition, basal EGP was positively correlated with S(2*)(G) . The higher basal EGP and greater EGP overshoot in trained middle-aged men appear to compensate for the increased insulin-independent (S(2*)(G)) and -dependent (S(2*)(I)) glucose uptake to maintain glucose homeostasis.