Pulmonary gas exchange during exercise in highly trained cyclists with arterial hypoxemia.

The causes of exercise-induced hypoxemia (EIH) remain unclear. We studied the mechanisms of EIH in highly trained cyclists. Five subjects had no significant change from resting arterial PO(2) (Pa(O(2)); 92.1 +/- 2.6 Torr) during maximal exercise (C), and seven subjects (E) had a >10-Torr reduction in Pa(O(2)) (81.7 +/- 4.5 Torr). Later, they were studied at rest and during various exercise intensities by using the multiple inert gas elimination technique in normoxia and hypoxia (13.2% O(2)). During normoxia at 90% peak O(2) consumption, Pa(O(2)) was lower in E compared with C (87 +/- 4 vs. 97 +/- 6 Torr, P < 0.001) and alveolar-to-arterial O(2) tension difference (A-aDO(2)) was greater (33 +/- 4 vs. 23 +/- 1 Torr, P < 0. 001). Diffusion limitation accounted for 23 (E) and 13 Torr (C) of the A-aDO(2) (P < 0.01). There were no significant differences between groups in arterial PCO(2) (Pa(CO(2))) or ventilation-perfusion (VA/Q) inequality as measured by the log SD of the perfusion distribution (logSD(Q)). Stepwise multiple linear regression revealed that lung O(2) diffusing capacity (DL(O(2))), logSD(Q), and Pa(CO(2)) each accounted for approximately 30% of the variance in Pa(O(2)) (r = 0.95, P < 0.001). These data suggest that EIH has a multifactorial etiology related to DL(O(2)), VA/Q inequality, and ventilation.     

Effects of vitamin E and C supplementation either alone or in combination on exercise-induced lipid peroxidation in trained cyclists

Seven trained male cyclists (ate 22.3 +/- 2 years) participated in 4 separate supplementation phases. They ingested 2 capsules per day containing the following treatments: placebo (placebo plus placebo); vitamin C (1 g per day vitamin C plus placebo); vitamin C and E (1 g per day vitamin C plus 200 IU per kg vitamin E); and vitamin E (400 IU per kg vitamin E plus placebo). The treatment order (placebo, vitamin C, vitamin C and E, and vitamin E) was the same for all subjects. Performance trials consisting of a 60-minute steady state ride (SSR) and a 30-minute performance ride (PR) on Cybex 100 Metabolic cycles were performed after each trial. Workloads of 70% of the VO2max were set for the SSR and PR rides, with pedal rate maintained at 90 rpm (SSR) or self determined (PR). Blood samples (5 ml) were drawn pre- and postexercise and analyzed for malonaldehyde (MDA) and lactic acid. The results indicate that vitamin E treatment was more effective than vitamin C alone or vitamin C and E. Pre-exercise plasma levels of MDA in the vitamin E trial was 39% below the pre-exercise MDA levels of the placebo: 2.94 +/- 0.54 and 4.81 +/- 0.65 micromol per ml, respectively. Plasma MDA following exercise in the vitamin E group was also lower than teh placebo: 4.32 +/- 0.37 vs 7.89 +/- 1.0 micromol per ml, respectively. Vitamin C supplementation, on the other hand, elevated both the resting and exercise plasma levels of MDA. None of th supplemental phases had any significant effect on performance. In conclusion, the results indicate that 400 IU/day of vitamin E reduces membrane damage more effectively than vitamin C but does not enhance performance. Athletes are encouraged to include antioxidants, such as vitamin E and C, in their diet to counteract these detrimental effects of exercise. The data presented here suggests that 400 IU/day of vitamin E will provide adequate protection but supplementing the diet with 1 g per day of vitamin C may promote cellular damage. However neither of these vitamins, either alone or in combination, will enhance exercise performance.     

Exercise-induced hypoxaemia in highly trained cyclists at 40% peak oxygen uptake

A group of 15 competitive male cyclists [mean peak oxygen uptake, VO2peak 68.5 (SEM 1.5 ml x kg(-1) x min(-1))] exercised on a cycle ergometer in a protocol which began at an intensity of 150 W and was increased by 25 W every 2 min until the subject was exhausted. Blood samples were taken from the radial artery at the end of each exercise intensity to determine the partial pressures of blood gases and oxyhaemoglobin saturation (SaO2), with all values corrected for rectal temperature. The SaO2 was also monitored continuously by ear oximetry. A significant decrease in the partial pressure of oxygen in arterial blood (PaO2) was seen at the first exercise intensity (150 W, about 40% VO2peak). A further significant decrease in PaO2 occurred at 200 W, whereafter it remained stable but still significantly below the values at rest, with the lowest value being measured at 350 W [87.0 (SEM 1.9) mmHg]. The partial pressure of carbon dioxide in arterial blood (PaCO2) was unchanged up to an exercise intensity of 250 W whereafter it exhibited a significant downward trend to reach its lowest value at an exercise intensity of 375 W [34.5 (SEM 0.5) mmHg]. During both the first (150 W) and final exercise intensities (VO2peak) PaO2 was correlated significantly with both partial pressure of oxygen in alveolar gas (P(A)O2, r = 0.81 and r = 0.70, respectively) and alveolar-arterial difference in oxygen partial pressure (P(A-a)O2, r = 0.63 and r = 0.86, respectively) but not with PaCO2. At VO2peak PaO2 was significantly correlated with the ventilatory equivalents for both oxygen uptake and carbon dioxide output (r = 0.58 and r = 0.53, respectively). When both P(A)O2 and P(A-a)O2 were combined in a multiple linear regression model, at least 95% of the variance in PaO2 could be explained at both 150 W and VO2peak. A significant downward trend in SaO2 was seen with increasing exercise intensity with the lowest value at 375 W [94.6 (SEM 0.3)%]. Oximetry estimates of SaO2 were significantly higher than blood measurements at all times throughout exercise and no significant decrease from rest was seen until 350 W. The significant correlations between PaO2 and P(A)O2 with the first exercise intensity and at VO2peak led to the conclusion that inadequate hyperventilation is a major contributor to exercise-induced hypoxaemia.     

Patterns of leg muscle recruitment vary between novice and highly trained cyclists

This study compared patterns of leg muscle recruitment and coactivation, and the relationship between muscle recruitment, coactivation and cadence, in novice and highly trained cyclists. Electromyographic (EMG) activity of tibialis anterior (TA), tibialis posterior (TP), peroneus longus (PL), gastrocnemius lateralis (GL) and soleus (SOL) was recorded using intramuscular fine-wire electrodes. Four experimental conditions of varying cadence were investigated. Differences were evident between novice and highly trained cyclists in the recruitment of all muscles. Novice cyclists were characterized by greater individual variance, greater population variance, more extensive and more variable muscle coactivation, and greater EMG amplitude in periods between primary EMG bursts. Peak EMG amplitude increased linearly with cadence and was not different at individual preferred cadence in either novice or highly trained cyclists. However, EMG amplitude in periods between primary EMG bursts, as well as the duration of primary EMG bursts, increased with increasing cadence in novice cyclists but were not influenced by cadence in highly trained cyclists. Our findings suggest that muscle recruitment is highly skilled in highly trained cyclists and less refined in novice cyclists. More skilled muscle recruitment in highly trained cyclists is likely a result of neuromuscular adaptations due to repeated performance of the cycling movement in training and competition.     

Influence of inhaled nitric oxide on gas exchange during normoxic and hypoxic exercise in highly trained cyclists.

This study tested the effects of inhaled nitric oxide [NO; 20 parts per million (ppm)] during normoxic and hypoxic (fraction of inspired O(2) = 14%) exercise on gas exchange in athletes with exercise-induced hypoxemia. Trained male cyclists (n = 7) performed two cycle tests to exhaustion to determine maximal O(2) consumption (VO(2 max)) and arterial oxyhemoglobin saturation (Sa(O(2)), Ohmeda Biox ear oximeter) under normoxic (VO(2 max) = 4.88 +/- 0.43 l/min and Sa(O(2)) = 90.2 +/- 0.9, means +/- SD) and hypoxic (VO(2 max) = 4.24 +/- 0.49 l/min and Sa(O(2)) = 75.5 +/- 4.5) conditions. On a third occasion, subjects performed four 5-min cycle tests, each separated by 1 h at their respective VO(2 max), under randomly assigned conditions: normoxia (N), normoxia + NO (N/NO), hypoxia (H), and hypoxia + NO (H/NO). Gas exchange, heart rate, and metabolic parameters were determined during each condition. Arterial blood was drawn at rest and at each minute of the 5-min test. Arterial PO(2) (Pa(O(2))), arterial PCO(2), and Sa(O(2)) were determined, and the alveolar-arterial difference for PO(2) (A-aDO(2)) was calculated. Measurements of Pa(O(2)) and Sa(O(2)) were significantly lower and A-aDO(2) was widened during exercise compared with rest for all conditions (P < 0.05). No significant differences were detected between N and N/NO or between H and H/NO for Pa(O(2)), Sa(O(2)) and A-aDO(2) (P > 0.05). We conclude that inhalation of 20 ppm NO during normoxic and hypoxic exercise has no effect on gas exchange in highly trained cyclists.     

Protein metabolism and strength performance after bovine colostrum supplementation

Summary. This study was designed to determine the responses of muscle protein, serum amino acids, and strength performance to bovine colostrum supplementation in physically active men. The rest (R) group (n=6) and the exercise (E) group (n=6) carried out twice a 2-week experiment randomly assigned in a double-blind fashion with either placebo (PLA; consuming daily 20g maltodextrin) or bovine colostrum (COL; consuming daily 20g colostrum supplement) treatment with one month between. On the test day after the treatment period the measurements were carried out in fasting conditions and E carried out a strength training session (STS). The methods involved the infusion of ring-²H₅-phenylalanine, femoral arterial and venous blood sampling, and biopsies from the vastus lateralis muscle. Serum concentration of essential amino acids during recovery was greater (p<0.05) in the COL groups compared with the PLA groups. Both muscle protein synthesis and breakdown increased (p<0.05) with COL. There were no differences in phenylalanine net balance or strength performance between the PLA and COL groups. It was concluded that a 2-week supplementation with bovine colostrum in physically active men increases serum concentration of essential amino acids but has no effect either on strength performance or protein net balance in fasting conditions during recovery after STS.     

Effect of creatine supplementation on intermittent sprint running performance in highly trained athletes

This study examined the impact of short-term (7-day), high-dose (0.35 g.kg(-1).d(-1)) oral creatine monohydrate supplementation (CrS) on single sprint running performance (40 m, <6 seconds) and on intermittent sprint performance in highly trained sprinters. Nine subjects completed the double-blind cross-over design with 2 supplementation periods (placebo and creatine) and a 7-week wash-out period. A test protocol consisting of 40-m sprint runs was performed, and running velocity was continuously recorded over the total distance. The maximal sprint performance, the relative degree of fatigue at the end of intermittent sprint exercise (6 x 40 m, 30-second rest interval), as well as the degree of recovery (120-second passive rest) remained unchanged following CrS. There were no significant changes related to CrS in absolute running velocity at any distance between start and finish (40 m). It was concluded that no ergogenic effect on single or repeated 40-m sprint times with varying rest periods was observed in highly trained athletes.     

IGF-I, IgA, and IgG responses to bovine colostrum supplementation during training.

This study examined the effect of bovine colostrum (Dynamic colostrum) supplementation on blood and saliva variables (study 1) and the absorption of orally administered human recombinant insulin-like growth factor (IGF)-I (rhIGF-I) labeled with 123I (123I-rhIGF-I) (study 2). In study 1, adult male and female athletes were randomly assigned in a double-blind fashion to either an experimental (Dynamic; n = 19) or a control (Placebo; n = 11) group. The former consumed daily 20 g of Dynamic supplement, and the latter 20 g of maltodextrin during a 2-wk training period. After bovine colostrum supplementation, significant increases were noticed in serum IGF-I (P < 0.01) and saliva IgA (P < 0.01) in Dynamic compared with Placebo. In study 2, gel electrophoresis was carried out in 12 adult subjects with serum samples taken 60 min after ingestion of 123I-rhIGF-I and showed peaks at 0.6 and at 40-90 kDa, with the former inducing 96% and the latter 4% of the total radioactivity. It was concluded that a long-term supplementation of bovine colostrum (Dynamic) increases serum IGF-I and saliva IgA concentration in athletes during training. Absorption data show that ingested 123I-rhIGF-I is fragmented in circulation and that no radioactive IGF-I is eluted at the positions of free, or the IGF, binding proteins, giving no support to the absorption of IGF-I from bovine colostrum.     

Effects of bovine colostrum supplementation on serum IGF-I, IgG, hormone, and saliva IgA during training

Mero, Antti, Heidi Miikkulainen, Jarmo Riski, RaimoPakkanen, Jouni Aalto, and Timo Takala. Effects of bovinecolostrum supplementation on serum IGF-I, IgG, hormone, and saliva IgAduring training. J. Appl. Physiol.83(4): 1144-1151, 1997.The purpose of this study was to examinethe effects of bovine colostrum supplementation (Bioenervi) on seruminsulin-like growth factor I (IGF-I), immunoglobulin G, hormone, andamino acid and saliva immunoglobulin A concentrations during a strengthand speed training period. Nine male sprinters and jumpersunderwent three randomized experimental training treatments of 8 daysseparated by 13 days. The only difference in the treatments was thedrink of 125 ml consumed per day. Posttraining increases were noticedfor serum IGF-I in the 25-ml Bioenervi treatment (125 ml contained 25 ml Bioenervi) and especially in the 125-ml Bioenervi treatment (125 mlcontained 125 ml Bioenervi) compared with the placebo (normal milkwhey) treatment (P < 0.05). The change in IGF-I concentration during the 8-day periods correlated positively with the change in insulin concentration during the sameperiods with 25-ml Bioenervi treatment(r = 0.68;P = 0.045) and with 125-ml Bioenervitreatment (r = 0.69;P = 0.038). Serum immunoglobulin G,hormone, and amino acid and saliva immunoglobulin A responses weresimilar during the three treatments. It appears that a bovine colostrumsupplement (Bioenervi) may increase serum IGF-I concentration inathletes during strength and speed training.

     

Effects of trehalose supplementation on cell viability and oxidative stress variables in frozen-thawed bovine calf testicular tissue

Trehalose is widely used for cryopreservation of various cells and tissues. Until now, the effect of trehalose supplementation on cell viability and antioxidant enzyme activity in frozen-thawed bovine calf testicular tissue remains unexplored. The objective of the present study was to compare the effect of varying doses of trehalose in cryomedia on cell viability and key antioxidant enzymes activities in frozen-thawed bovine calf testicular tissue. Bovine calf testicular tissue samples were collected and cryopreserved in the cryomedias containing varying doses (0, 5, 10, 15, 20 and 25%; v/v) of trehalose, respectively. Cell viability, total antioxidant capacity (T-AOC) activity, catalase (CAT) activity, superoxide dismutase (SOD) activity, glutathione (GSH) content and malondialdehyde (MDA) content were measured and analyzed. The results showed that cell viability, T-AOC activity, SOD activity, CAT activity and GSH content of frozen-thawed bovine calf testicular tissue was decreased compared with that of fresh group (P < 0.05). MDA content in frozen-thawed bovine calf testicular tissue was significantly increased compared with that of fresh group (P < 0.05). The cryomedia added 15% trehalose exhibited the greatest percentage of cell viability and antioxidant enzyme activity (SOD and CAT) among frozen-thawed groups (P < 0.05). Meanwhile, GSH content was the lowest among frozen-thawed groups (P < 0.05). However, there were no significance differences in MDA content among the groups added 10, 15 and 20% trehalose (P > 0.05). In conclusion, the cryomedia added 15% trehalose reduced the oxidative stress and improved the cryoprotective effect of bovine calf testicular tissue. Further studies are required to obtain more concrete results on the determination of antioxidant capacity of trehalose in frozen-thawed bovine calf testicular tissue.     

Leptin in bovine colostrum and milk.

We studied leptin content in bovine colostrum, milk and plasma during the first month of lactation, and investigated relationships between selected milk components and milk leptin in five multiparous dairy cows. Colostrum/milk yield and composition were measured on days 0, 10, 20, and 30 of lactation. Leptin was assayed using a multi-species leptin RIA kit. Leptin concentration was 56 % lower in mature milk (day 10) than colostrum (13.90 vs. 6.14 microg/l; p < 0.001), but remained steady over the twenty days afterwards. Daily secretion of leptin into mature milk was 28 % lower than into colostrum (173.2 microg/d vs. 220.0 microg/d; p = 0.09) notwithstanding an 80 % increase in production. Colostrum and milk leptin levels correlated with fat (0.90; p < 0.001) and choline phospholipid (0.76; p < 0.05). Plasma and milk leptin decreased during the first month, but remained higher in milk, and highest in colostrum. Thus, leptin is present in large quantities in colostrum, less so and more variably in untreated milk, and is likely to be decreased in skimmed milk. These findings have implications for the use of untreated milk and colostrum-based (functional) food products.     

Muscle oxygenation trends after tapering in trained cyclists

BACKGROUND: This study examined muscle deoxygenation trends before and after a 7-day taper using non-invasive near infrared spectroscopy (NIRS). METHODS: Eleven cyclists performed an incremental cycle ergometer test to determine maximal oxygen consumption (VO2max = 4.68 +/- 0.57 L.min-1) prior to the study, and then completed two or three high intensity (85-90% VO2max) taper protocols after being randomly assigned to a taper group: T30 (n = 5), T50 (n = 5), or T80 (n = 5) [30%, 50%, 80% reduction in training volume, respectively]. Physiological measurements were recorded during a simulated 20 km time trials (20TT) performed on a set of wind-loaded rollers. RESULTS AND DISCUSSION: The results showed that the physiological variables of oxygen consumption (VO2), carbon dioxide (VCO2) and heart rate (HR) were not significantly different after tapering, except for a decreased ventilatory equivalent for oxygen (VE/VO2) in T50 (p 相似文献   

Effect of a bovine colostrum whey supplementation on growth performance, faecal Escherichia coli population and systemic immune response of piglets at weaning

This study examined the effect of a bovine colostrum whey supplementation on growth performance, feed intake, faecal Escherichia coli population and systemic immune response of piglets at weaning. A total of 96 piglets weaned at 26 ± 2 days of age were assigned for 4 weeks to one of the two treatments: (1) the control (commercial diet with bovine milk whey powder) and (2) the colostrum (commercial diet with freeze-dried bovine colostrum whey) treatments. The two supplements were incorporated in the diet at a level of 20 g/kg during the first 2 weeks after weaning and lowered to a level of 10 g/kg for the next 2 weeks. BW and feed intake were measured weekly. Faecal E. coli counts were determined weekly on specific culture media. Blood samples were collected weekly and submitted to a cell counter analyser for their main components (red and white blood cells, platelets) and flow cytometry was used to determine the lymphocyte population (B, T, Th and Tc). Finally, total seric immunoglobulin (IgM, IgG and IgA) concentrations were determined by the ELISA method. During the first week of the trial, the piglets from the colostrum treatment had improved average daily gain (170 g/day v. 81 g/day, P < 0.001), average daily feed intake (346 g/day v. 256 g/day, P = 0.03) and feed efficiency (BW gain/feed intake) (0.48 v. 0.31, P = 0.04). The pigs fed the colostrum treatment had also a 25% increase in circulating IgA (P = 0.03) compared with the control treatment the first week. It is concluded that a distribution of bovine colostrum whey (20 g/kg diet) during the first week post-weaning induces a systemic IgA response and has a beneficial action on growth performances and feed efficiency.     

Modulation of human humoral immune response through orally administered bovine colostrum

Eighteen healthy volunteers were randomized into two treatment groups and consumed liquid prepackaged bovine colostrum whey and placebo for 7 days. On days 1, 3 and 5, an attenuated Salmonella typhi Ty21a oral vaccine was given to all subjects to mimic an enteropathogenic infection. The circulating antibody secreting cells and the expression of phagocytosis receptors of the subjects before and after oral immunization were measured with the ELISPOT assay and flow cytometry. All subjects responded well to the vaccine. No significant differences were observed in ELISPOT values for IgA, IgG, IgM, Fcgamma and CR receptor expression on neutrophils and monocytes between the two groups. There was a trend towards greater increase in specific IgA among the subjects receiving their vaccine with bovine colostrum. These results suggest that bovine colostrum may possess some potential to enhance human special immune responses.     

Effects of sodium butyrate supplementation on reproductive performance and colostrum composition in gilts

Nutrients are essential for the health and survival of human beings and animals. Also, they play a major role in enhancing reproductive efficiency. The aim of the current study was to investigate the effects of sodium butyrate (SB) on reproductive performance and colostrum composition in gilts. A total of 40 Large White×Landrace replacement gilts (at the age of 160 to 175 days) were fed either a standard diet (control group, n=20) or standard diet top dressed with encapsulated SB at the level of 500 mg/kg (SB group, n=20) from 1 month before mating to 7 days after farrowing. The rate of gilts regular return to estrus after insemination was lower in SB group than the control group. The total number of piglets born (P=0.179) and the litter weight at birth (P=0.063) did not differ between the two treatment groups. However, the mean BW at day 7 tended to be greater in SB group (P=0.051) and average daily gain of piglets was greater (P=0.011) compared with control group. Colostrum samples were collected at parturition and the concentrations of total protein (P=0.197), cholesterol (P=0.161) and lactose (P=0.923) were not influenced by SB supplementation. However, compared with control gilts, colostrum from SB-treated gilts contained lower triglyceride (P=0.050). Moreover, colostrum concentrations of prolactin (P=0.005) and leptin (P=0.006) were significantly lower in SB group. No significant differences were noted for the colostral concentrations of cortisol (P=0.899), thyroxine (P=0.891) or triiodothyronine (P=0.194). The concentration of lipopolysaccharide in colostrum was not influenced by SB supplementation (P=0.972). However, colostrum from SB-treated gilts had significantly lower tumor necrosis factor α (TNFα) (P=0.030) and higher immunoglobulin A (IgA) (P=0.042). Collectively, SB supplementation could reduce the rate of gilts return to estrus, alter the composition of colostrum and enhance the growth rate of piglets. Moreover, SB could alter the immune function of newborn piglets through decreased production of TNFα and increased IgA concentration in colostrum.     

Effects of prolonged exercise in highly trained traumatic paraplegic men

This study investigated the cardiovascular and metabolic responses to prolonged wheelchair exercise in a group of highly trained, traumatic paraplegic men. Six endurance-trained subjects with spinal cord lesions from T10 to T12/L3 underwent a maximal incremental exercise test in which they propelled their own track wheelchairs on a motor-driven treadmill to exhaustion to determine maximal O2 uptake (VO2max) and related variables. One week later each subject exercised in the same wheelchair on a motorized treadmill at 60-65% of VO2max for 80 min in a thermoneutral environment (dry bulb 22 degrees C, wet bulb 17 degrees C). Approximately 10 ml of venous blood were withdrawn both 20 min and immediately before exercise (0 min), after 40 and 80 min of exercise, and 20 min postexercise. Venous blood was analyzed for hematocrit (Hct), hemoglobin (Hb), and lactate, and the separated plasma was analyzed for glucose, K+, Na+, Cl-, free fatty acid (FFA), and osmolality. VO2, CO2 production (VCO2), minute ventilation (VE), respiratory exchange ratio (R), net efficiency, and wheelchair strike rate were determined at four intervals throughout the exercise period. Data were analyzed with an analysis of variance repeated-measures design and a Scheffé post hoc test. VO2max was 47.5 +/- 1.8 (SE) ml.min-1.kg-1 with maximal VE BTPS and maximal heart rate (HR) being 100.1 +/- 3.8 l/min and 190 +/- 1 beats/min, respectively. During prolonged exercise there were no significant changes in VO2, VCO2, VE, R, net efficiency, wheelchair strike rate, and lactate, glucose, and Na+ concentrations. Significant increases occurred in HR, FFA, K+, Cl-, osmolality, Hb, and Hct throughout exercise.(ABSTRACT TRUNCATED AT 250 WORDS)