In order to determine the ventilatory threshold (VT) and the lactate threshold (LT) in a reliable way, a new method is proposed and compared with conventional methods. The new method consists of calculating the point that yields the maximal distance from a curve representing ventilatory and metabolic variables as a function of oxygen uptake (VO2) to the line formed by the two end points of the curve (Dmax method). Male cyclists (n = 8) performed two incremental exercise tests a week apart. Ventilatory/metabolic variables were measured and blood was sampled for later lactate measurement during each workload and immediately after exercise. No statistical differences were observed in the threshold values (expressed as absolute oxygen uptake; VO2) determined by the Dmax method and the conventional linear regression method (according to O2 equivalent; EqO2) and venous blood at the onset of blood lactate (OBLA), while VT assessed with the conventional linear method (according to the slope of CO2 output; Vslope) yielded significantly lower threshold values. Similar results were obtained from the reproducibility test. Thus, the Dmax method appears to be an objective and reliable method for threshold determination, which can be applied to various ventilatory or metabolic variables yet yield similar results. The results also showed that breathing frequency can be used to determine VT.

A B S T R A C TThe aim of the present study was to establish whether gastro-intestinal (GI) complaints observed during and after ultra-endurance exercise are related to gut ischaemia-associated leakage of endotoxins [lipopolysaccharide (LPS)] into the circulation and associated cytokine production. Therefore we collected blood samples from 29 athletes before, immediately after, and 1, 2 and 16 h after a long-distance triathlon for measurement of LPS, tumour necrosis factor-α and interleukin-6 (IL-6). As the cytokine response would trigger an acute-phase response, characteristic variables of these responses were also measured, along with creatine kinase (CK) to obtain an indicator of muscle damage. There was a high incidence (93 % of all participants) of GI symptoms ; 45 % reported severe complaints and 7 % of the participants abandoned the race because of severe GI distress. Mild endotoxaemia (5-15 pg/ml) was evident in 68 % of the athletes immediately after the race, as also indicated by a reduction in IgG anti-LPS levels. In addition, we observed production of IL-6 (27-fold increase immediately after the race), leading to an acutephase response (20-fold increase in C-reactive protein and 12 % decrease in pre-albumin 16 h after the race). The extent of endotoxaemia was not correlated with the GI complaints or the IL-6 response, but did show a correlation with the elevation in C-reactive protein (r s 0.389 ; P l 0.037). Creatine kinase levels were increased significantly immediately post-race, and increased further in the follow-up period. Creatine kinase levels did not correlate with those of either IL-6 or C-reactive protein. It is therefore concluded that LPS does enter the circulation after ultra-endurance exercise and may, together with muscle damage, be responsible for the increased cytokine response and hence GI complaints in these athletes.

995.Accepted aftel revision: 0ctober 30, 1994 &t+J*$Bãi The effect of dlfferent dosa ges of caffelne (0 -5 -9 -13 mg 'l

Carbohydrate-electrolyte (CE) feedings have been shown to improve endurance performance at moderate intensities (60-75% VO2max) and or more than 2 h duration. The effects of CE feedings during high intensity exercise (i.e. > or = 80% VO2 max) of shorter duration (approximately 1 h) are less clear. Therefore the purpose of the present study was to investigate the effect of the ingestion of a 7.6% CE solution during exercise on time trial cycling performance of approximately 1 h. This type of performance testing has been shown to be more reproducible (coefficient of variation 3.35%) than the traditional exercise test to exhaustion. On two occasions and in random order nineteen endurance trained cyclists completed an exercise test requiring the accomplishment of a set amount of work as fast as possible (time trial) under strictly standardized conditions. As the start and during the trials they drank in total 14 ml/kg of either a 7.6% CE solution or artificially flavored and colored water (placebo). Time to complete the set amount of work was significantly reduced and thus performance was significantly increase (p < 0.001) with the CE drink by 2.3%. Time to complete the set amount of work was 58.74 +/- 0.52 min with CE and 60.15 +/- 0.65 min with placebo (p < 0.001). Average workload during the time trials was 297.5 +/- 1.4W and 291.0 +/- 10.3 W, respectively. Subjects exercised at 76.4 +/- 0.7% of their maximal work rate (Wmax) with CE and at 74.8% Wmax with placebo (p < 0.001). It was concluded tht also in relative short term (1h) high intensity (75% Wmax) cycling exercise ingestion of a carbohydrate-electrolyte solution compared to placebo improves performance.

[Aims] In the present study, we examined effects of exercise training (TR) on high fat diet (HFD)-induced expression changes of prothymosin α (ProTα) and its functions in white adipose tissue (WAT). [Methods] Eight-week-old male C57BL/6J mice were divided randomly into three groups: 1) C mice: control mice; 2) HFD mice: mice fed HFD (60% fat) for 4 months; 3) HFD-TR mice: mice fed HFD with voluntary TR on a running wheel for 4 months. We then investigated the expression of ProTα in WAT. Moreover, to investigate the function of ProTα in adipocytes, ProTα siRNA or recombinant lentivirus containing ProTα cDNA was infected into mouse 3T3-L1 adipocytes. [Results] Although the levels of body and WAT mass in HFD mice were significantly higher than those of C mice, TR inhibited such HFD-induced increases. Moreover, although expression of ProTα in WAT was upregulated by HFD, TR markedly attenuated HFD-induced expression of ProTα. The reduction of ProTα in 3T3-L1 cells resulted in inhibition of adipocyte differentiation with decreased expression of CCAAT-enhancer-binding proteinα (C/EBPα) gene. Conversely, overexpression of ProTα in 3T3-L1 cells enhanced expression of genes for C/EBPα and peroxi-some proliferator-activated receptor γ. [Conclusions] These results suggest that ProTα involves in adipocyte differentiation. Further, TR attenuates HFD-induced increases in expression of ProTα, which is speculated to be implicated in anti-obesity effects of TR. [Aims] Maximal fat oxidation (MFO) in the graded exercise test is considered to be an indicator of the capacity to oxidize fat during exercise. MFO varies widely based on cardiorespiratory fitness and body composition. Fat oxidation at rest (FO rest) positively correlated with MFO in overweight and healthy untrained people. However, it is unclear whether this positive correlation applies to all people with various levels of cardiorespiratory fitness and body composition. The current study examined the correlations between FO rest and MFO in trained, healthy inactive normal weight and overweight men. [Methods] This study included 8 trained, 6 healthy inactive normal weight, and 7 overweight men. All participants rested for 30 min in the supine position and performed a graded exercise test on a treadmill in the morning after a 12 h overnight fast. FO rest , maximal oxygen consumption (V ・ O 2 max), and MFO were measured by indirect calorimetry. Pearson's correlation coefficient was calculated between V ・ O 2 max and FO rest or MFO, FO rest and MFO. [Results] V ・ O 2 max significantly positively correlated with FO rest and MFO (R = 0.51, 0.72; P < 0.05, 0.01, respectively). FO rest significantly positively correlated with MFO (R = 0.71, P < 0.01). [Conclusions] FO rest positively correlated with MFO in trained, healthy inactive normal weight and overweight men. [Aims] Various clinical and epidemiological studies have shown an inverse association between serum high-density lipoprotein (HDL) cholesterol and cardiovascular events. Exercise is an effective treatment for increasin...

This is the first part in a series of three articles about fat metabolism during exercise. In this part the mobilization of fatty acids and their metabolism will be discussed as well as the possible limiting steps of fat oxidation. It is known for a long time that fatty acids are an important fuel for contracting muscle. After lipolysis, fatty acids from adipose tissue have to be transported through the blood to the muscle. Fatty acids derived from circulating TG may also be used as a fuel but are believed to be less important during exercise. In the muscle the IMTG stores may also provide fatty acids for oxidation after stimulation of hormone sensitive lipase. In the muscle cell, fatty acids will be transported by carrier proteins (FABP), and after activation, fatty acyl CoA have to cross the mitochondrial membrane through the carnitine palmytoyl transferase system, after which the acyl CoA will be degraded to acetyl CoA for oxidation. The two steps that are most likely to limit fat oxidation are fatty acid mobilization from adipose tissue and transport of fatty acids into the mitochondria along with mitochondrial density and the muscles capacity to oxidize fatty acids.

The aim of this study was to investigate the effect of medium-chain triacylglycerol (MCT) ingestion during exercise on subsequent time-trial cycling performance. Seven well-trained cyclists performed four exercise trials consisting of 2 h at 60% of maximal oxygen uptake followed by a simulated time trial (ie, completion of a preset amount of work as fast as possible) of approximately 15 min duration. During the trials, subjects ingested 1) a 10% carbohydrate solution (CHO; 170 +/- 6 g glucose), 2) a 10% carbohydrate electrolyte with 5% MCT solution (CHO + MCT; 85 +/- 3 g MCT), 3) a 5% MCT solution, or 4) artificially colored and flavored water (placebo). Neither CHO nor CHO + MCT ingestion had any effect on performance compared with placebo ingestion, whereas ingestion of MCT had a negative effect on performance. Average work rates during the time trial were 314 +/- 19, 314 +/- 13, and 312 +/- 18 with CHO, CHO + MCT, and placebo, respectively, and was 17-18% lower in the MCT trial (263 +/- 22 W). In addition, compared with placebo ingestion, MCT ingestion had no effect on total rates of fat or carbohydrate oxidation, nor did it affect exogenous or endogenous carbohydrate utilization. The negative effect of MCT ingestion was associated with increased gastrointestinal complaints (ie, intestinal cramping). These data suggest that large amounts of MCTs (85 g) ingested during prolonged submaximal exercise may provoke gastrointestinal problems leading to decreased exercise performance.

This part discusses the complex regulation of fat metabolism. Catecholamines as a stimulator of lipolysis and insulin as a suppressor play very important roles in the regulation of fat oxidation. The interaction of carbohydrate and fat metabolism has been extensively studied in the past decennia but the understanding of this multifactorial regulation is complex and still incompletely understood. In 1963, Randle et al. proposed the glucose-fatty acid cycle as a possible mechanism, and more recently, regulation through malonyl-CoA has been put forward as a possible way to explain shifts in carbohydrate and fat metabolism at rest and during exercise. The exercise intensity affects fat oxidation mainly by increasing lipolysis and fatty acid availability during exercise of low to moderate intensity. At high exercise intensities, both a reduction in fatty acid availability (decreased RaFa) and intramuscular factors reduce fat oxidation. These intramuscular factors are largely unknown. The increased mitochondrial density after training and increased oxidative enzymes may partly explain the increased fatty acid oxidation during exercise as observed after training. However, also supply of fatty acids to the mitochondria may be important. The available evidence suggests that the additional fatty acids oxidized after training are primarily derived from intramuscular triacylglycerols and not from adipose tissue derived fatty acids or circulating triacylglycerols.