Effect of endurance training supplemented with green tea extract on substrate metabolism during exercise in humans

Endurance training and ingestion of green tea extract (GTE), composed mainly of tea catechins (TC), are well known to enhance fat metabolism. However, their synergistic effects remain to be fully elucidated. We tested the hypothesis that endurance training supplemented with GTE would further accelerate whole‐body fat utilization during exercise, compared with training alone, in humans. Twelve healthy male subjects [peak oxygen consumption (), 50.7 ± 1.3 (SEM) mL/kg/min] were divided into two groups: GTE and placebo (PLA) groups. Subjects in both groups performed a cycle ergometer exercise at 60% of for 60 min/day, 3 days/week, and daily ingested 572.8 or 0 mg TC in GTE and PLA groups for 10 weeks, respectively. Before and after training, respiratory gas exchange was measured during 90‐min exercise at pre‐training ～55% of . After training, the average respiratory exchange ratio during exercise remained unchanged in the PLA group (post‐training: 0.834 ± 0.008 vs pre‐training: 0.841 ± 0.004), whereas it was lower in the GTE group (post‐training: 0.816 ± 0.006 vs pre‐training: 0.844 ± 0.005, P<0.05). These results suggest that habitual GTE ingestion, in combination with moderate‐intense exercise, was beneficial to increase the proportion of whole‐body fat utilization during exercise.     

不同训练方法对士兵耐力素质训练的影响

目的 探求一种适合常规部队、能快速有效提高士兵有氧耐力素质、并可降低军事训练伤发生率的训练方法.方法 随机抽取某步兵团248名无军事训练史的汉族男性新兵,均分为实验组和对照组,每组124名.实验组采用以"循环训练法"为理念设计的强化耐力训练方法;对照组采用部队常用耐力训练方法,即以5000m跑为主的训练方法(每周5000m×3次,每日不超过1次).两组总共进行8周的耐力素质训练.训练开始前和训练8周后分别测试士兵的安静脉搏、肺活量、VO2max和5000m成绩等耐力素质指标,并于训练8周后对士兵进行体检,统计有小腿肿胀和按压痛、膝关节肿痛、下腰痛等军事训练伤症状的人数,计算军事训练伤发生率.结果 实验组训练后安静脉搏降低了8.0%,肺活量、VO2max、5000m成绩则分别提高了8.1%、20.0%、14.7%,与训练前及对照组比较差异均有统计学意义(P<0.01或P<0.05).实验组训练伤发生率(3.3%)显著低于对照组(8.1%,P<0.05).结论 以"循环训练法"为理念设计的强化耐力训练方法可有效提高部队士兵耐力素质并减少军事训练伤的发生.     

The effect of endurance training on parameters of aerobic fitness

Endurance exercise training results in profound adaptations of the cardiorespiratory and neuromuscular systems that enhance the delivery of oxygen from the atmosphere to the mitochondria and enable a tighter regulation of muscle metabolism. These adaptations effect an improvement in endurance performance that is manifest as a rightward shift in the 'velocity-time curve'. This shift enables athletes to exercise for longer at a given absolute exercise intensity, or to exercise at a higher exercise intensity for a given duration. There are 4 key parameters of aerobic fitness that affect the nature of the velocity-time curve that can be measured in the human athlete. These are the maximal oxygen uptake (VO2max), exercise economy, the lactate/ventilatory threshold and oxygen uptake kinetics. Other parameters that may help determine endurance performance, and that are related to the other 4 parameters, are the velocity at VO2max (V-VO2max) and the maximal lactate steady state or critical power. This review considers the effect of endurance training on the key parameters of aerobic (endurance) fitness and attempts to relate these changes to the adaptations seen in the body's physiological systems with training. The importance of improvements in the aerobic fitness parameters to the enhancement of endurance performance is highlighted, as are the training methods that may be considered optimal for facilitating such improvements.     

Effect of testosterone and endurance training on glycogen metabolism in skeletal muscle of chronic hyperglycaemic female rats

OBJECTIVES: To investigate in glycolytic and oxidative muscles of trained (nine weeks) and untrained hyperglycaemic female rats the effect of hyperandrogenicity and/or endurance training on energy metabolic properties. METHODS: Glycogen content and activity of muscle enzymes with regulatory functions in glycogen synthesis were examined. RESULTS: Testosterone treatment increased glycogen content of extensor digitorum longus (EDL) and soleus muscles of hyperglycaemic sedentary (18% and 84% respectively) and hyperglycaemic trained (7% and 16% respectively) rats. In both types of muscle of the hyperglycaemic testosterone treated exercised subgroup, less depletion of glycogen was found than in the untreated group (38% and 87% for EDL and soleus respectively). CONCLUSIONS: The mechanisms by which training and/or hyperandrogenism alone or in combination elicits their specific effects are complex. Differences in sex, surgery, levels of hormones administered, and exercise model used may be the main reasons for the observed discrepancies. Conclusions from the results: (a) hyperandrogenism is not a primary cause of the development of insulin resistance; (b) glycogen content of slow and fast twitch muscle is increased by training through increased glycogen synthase activity. The most plausible explanation for differences between different muscle fibre types is the different levels of expression of androgen receptors in these fibres. Hyperandrogenicity therefore acts on energy metabolic variables of hyperglycaemic animals by different mechanisms in glycolytic and oxidative muscle fibres.     

Resting echocardiographic parameters after cessation of regular endurance training

Resting echocardiograms were examined in nonathletic healthy young men (controls, n = 16), in highly trained endurance athletes (n = 20), and in endurance athletes who stopped regular training (n = 40). The relative muscular wall thickness (Rel. MWTd), left ventricular internal diameters both in diastole and in systole (LVIDd, LVIDs), thus also the end-diastolic and end-systolic volumes (LVEDV, LVESV), and the stroke volume index (SVI) were greater in the endurance athletes still in training than in the nonathletes. The ejection fraction (EF), heart rate (HR), cardiac index (CI), and mean circumferential shortening velocity (Vcf) were significantly lower in the athletes. During the 60 days of detraining no change was seen in the Rel. MWTd, LVEDV, LVESV, and HR. The SVI became even greater; EF and Vcf rose up to the control level while CI exceeded it. The cardiovascular regulation is therefore assumed to undergo a peculiar shift during detraining in that a persisting cardiac enlargement and bradycardia is associated with a temporarily unstable autonomous control. This imbalance often leads to a hyperkinesis-like syndrome when an athlete stops endurance training abruptly.     

Effects of iron supplementation on total body hemoglobin during endurance training at moderate altitude

The aim of the study was to test the hypothesis that iron supplementation in well-trained non-iron-depleted athletes leads to an enhanced increase of total body hemoglobin (TBH) during training at moderate altitude. Therefore, the members of the national German boxing team were randomly assigned to treatment with ferrous-glycine-sulfate (1335 mg equivalent to 200mg elementary iron daily) or with placebo during 18 days of endurance training at moderate altitude (1800 m). Before and after altitude training TBH was determined by CO-rebreathing, measures of exercise performance were determined with an incremental treadmill test. Before, during and after the stay at moderate altitude erythropoietin (Epo), reticulocytes (Retics) and parameters of iron metabolism were measured in venous blood. The results show that TBH did not change significantly in the placebo-group and even slightly, but significantly decreased in the iron-treated group. However, there was a significant increase of Epo and Retics in both groups during training at moderate altitude whereas parameters of iron metabolism remained unchanged. VO2max did not change either. To test whether a training-induced hemolysis, an increased urinary iron excretion or gastrointestinal blood loss could explain the unexpected drop of TBH we tested most of the boxers again during a similar training camp at low altitude (400-1000 m) to obtain measures of hemolysis, urinary iron excretion and occult hemoglobin loss with the stools. Although there were signs of an increased erythrocyte turnover no iron loss could be observed. We conclude that 18 days of endurance training at an altitude of 1800 m does not lead to an increase of TBH in non-iron-depleted athletes with and without iron supplementation.     

Effects of tennis training on lipid metabolism and lipoproteins in recreational players.

OBJECTIVE: To investigate the short term effects of tennis training on lipid metabolism and to find out if a typical tennis training programme has positive longitudinal effects on cardiovascular risk factors in recreational players. METHODS: The experimental design consisted of an exercise study and a subsequent longitudinal study. In the exercise study the short term metabolic effects of a two hour technically orientated tennis training (TT) session and a running intensive tennis training (RIT) session were investigated in 16 recreational tennis players (eight men: 46 (SD 7) years, 177 (6) cm, 81 (10) kg; and eight women: 44 (5) years, 165 (5) cm, 64 (6) kg). In the longitudinal study the long term effects of a six week RIT programme in 22 players (11 men and 11 women) of similar characteristics were compared with those in 16 control subjects (eight men and eight women). The results of the exercise study (higher lipolytic activity and cardiopulmonary demand, as well as acceptance by the players) led to the RIT method being chosen for all training sessions in the longitudinal study. RESULTS: In RIT, significantly higher values for heart rate (148 (SD 10) v 124 (11) beats/minute) and lactate (2.8 (1.1) v 1.5 (0.6) mmol/l), significantly higher post exercise concentrations of serum glycerol (0.37 (0.15) v 0.29 (0.14) mmol/l) and high density lipoprotein cholesterol (1.31 (0.55) v 1.20 (0.50) mmol/l) and a higher acceptance than in TT (15 of the 16 players preferred RIT) were found. During the six week tennis training programme the changes in body weight (-1.41 (1.56) v 0.00 (1.50) kg) and anaerobic threshold (1.04 (0.84) v -0.08 (0.92) km/h) were significantly different between the training and control group. In the training group several parameters of the lipoprotein profile tended to change in an antiatherosclerotic direction. CONCLUSIONS: The results indicate that typical regular tennis training influences cardiovascular risk factors in a positive manner and can be suggested as an attractive alternative to other current health orientated sports programmes. A more frequent use of running intensive exercises during tennis training is recommended.     

Effect of hyperoxic-supplemented interval training on endurance performance in trained cyclists

The aim of this study was to determine the effect of hyperoxic-supplemented interval training on endurance performance. Using a single-blind, randomised control-trial design, 16 well-trained cyclists were randomly assigned to either hyperoxic or normoxic training. Participants visited the laboratory twice per week, for 4 weeks, to perform high-intensity interval training sessions. A 20 km TT, incremental exercise test and 60s all-out test were conducted pre- and post-intervention. Smaller effects for most physiological measures, including VO 2peak (1.9 ± 4.3%) and lactate threshold (0.3 ± 8.3%), were observed after training in hyperoxia compared to normoxia. There was a small increase in mean power during the 20 km TT after hyperoxia [2.1 ± 3.7%; effect size (ES): - 0.30 ± 0.39] but this was less than that observed after normoxia (4.9 ± 3.9%; ES: - 0.44 ± 0.60). During the 60 s all-out test, the peak relative power was relatively unchanged, whereas mean relative power was increased in normoxia (2.3 ± 3.4%) but not hyperoxia (0.3 ± 1.2%; ES: - 0.34 ± 0.49). Hyperoxic-supplemented interval training in the competitive season had less effect on endurance and high-intensity performance and physiology in trained endurance cyclists compared to interval training in normoxia. Therefore hyperoxic-supplemented training at sea level appears to be not worthwhile for maximising performance in competitive endurance athletes.     

Effects of endurance training on tissue glutathione homeostasis and lipid peroxidation in streptozotocin-induced diabetic rats

The aims of our study were to assess whether endurance training strengthens glutathione-dependent antioxidant defenses and decreases oxidative stress in experimental diabetes. Streptozotocin-induced diabetic rats were divided into trained and untrained groups, which were further divided into resting and acute exercise groups. Endurance training consisted of treadmill running for 8 weeks. For acute exhaustive exercise, graded treadmill running was conducted until exhaustion. Eight weeks' treadmill training increased the endurance, favorably decreased lipid peroxidation as measured by thiobarbituric acid reactive substances but not conjugated dienes levels in kidney and vastus lateralis muscle and upregulated glutathione peroxidase in red gastrocnemius muscle. However, it adversely decreased total glutathione level and glutathione peroxidase activity in kidney. Acute exhaustive exercise up-regulated glutathione peroxidase activity in liver. Endurance training did not prevent the increase in thiobarbituric acid reactive substances level in liver due to acute exhaustive exercise. Activities of glutathione disulfide reductase and glutathione S-transferase were not affected. Even though endurance training appeared to upregulate glutathione dependent antioxidant defense in skeletal muscle and to decrease lipid peroxidation in kidney and vastus lateralis muscle as measured by TBARS, our results suggests that beneficial effects of 8 weeks of endurance training are limited in this rat model of uncontrolled diabetes mellitus.     

Impact of reduced training on performance in endurance athletes.

Many endurance athletes and coaches fear a decrement in physical conditioning and performance if training is reduced for several days or longer. This is largely unfounded. Maximal exercise measures (VO2max, maximal heart rate, maximal speed or workload) are maintained for 10 to 28 days with reductions in weekly training volume of up to 70 to 80%. Blood measures (creatine kinase, haemoglobin, haematocrit, blood volume) change positively or are maintained with 5 to 21 days of reduced training, as are glycogen storage and muscle oxidative capacities. Submaximal or improved with a 70 to 90% reduction in weekly volume over 6 to 21 days, provided that or improved with a 70 to 90% reduction in weekly volume over 6 to 21 days, provided that exercise frequency is reduced by no more than 20%. Athletic performance is improved or maintained with a 60 to 90% reduction in weekly training volume during a 6 to 21 day reduced training period, primarily due to an enhanced ability to exert muscular power. These findings suggest that endurance athletes should not refrain from reduced training prior to competition in an effort to improve performance, or for recovery from periods of intense training, injury, or staleness.     

Effect of endurance training on myocardial myosin adenosine triphosphatase activity of the dog.

Endurance exercise training has been found to enhance the functional capacity of the myocardium in several animal models. The sub-cellular phenomena accompanying the augmented function are yet to be explained. The present study sought to determine if the myosin ATPase activity of cardiac muscle increased as a result of endurance conditioning. Five beagles trained by running on a motor driven treadmill (T) and five control (NT) animals were studied. Follwoing 10 weeks of training the T group had a significantly (P less than .05) lower heart rate than the NT while performing the same submaximal exercise and the gastrocnemius cytochrome oxidase activity was significantly greater (P less than .005) in the T than in the NT. These two measurements established that the exercised animals were physically trained. Myosin was isolated from the left ventricular myocardium and activated in a medium containing K-EDTA. No significant (P less than .05) difference in maximum myosin ATPase activity was observed between the NT and T groups in cardiac muscle. It was concluded that cardiac muscle myosin ATPase activity was not affected by 10 weeks of endurance conditioning induced by treadmill running in dogs.     

Effect of reduced training on muscular strength and endurance in competitive swimmers

Following 5 months of competitive training (approximately 9,000 yards.d-1, 6 d.wk-1), three groups of eight male swimmers performed 4 wk of either reduced training (3,000 yard.session-1) or inactivity. Two groups reduced their training to either 3 sessions.wk-1 (RT3) or 1 session.wk-1 (RT1), whereas the third group (IA) did no training. Measurement of muscular strength (biokinetic swim bench) showed no decrement in any group over the 4 wk. In contrast, swim power (tethered swim) was significantly decreased (P less than 0.05) in all groups, reaching a mean change of -13.6% by week 4. Blood lactate measured after a standard 200-yard (183 m) front crawl swim increased by 1.8, 3.5, and 5.5 mM over the 4 wk in groups RT3, RT1 and IA, respectively. In group RT1, stroke rate measured during the 200-yard swim significantly increased (P less than 0.05) from 0.54 +/- 0.03 to 0.59 +/- 0.03 strokes.-1 while stroke distance significantly decreased (P less than 0.05) from 2.50 +/- 0.08 to 2.29 +/- 0.13 m.stroke-1 during the 4-wk period. Both stroke rate and stroke distance were maintained in group RT3 over the 4 wk of reduced training. Group IA was not tested for stroke mechanics. Whereas maximal oxygen uptake decreases significantly (P less than 0.05) over the 4 wk in group RT1 (4.75 to 4.62 l.min-1), no change in maximal oxygen uptake was observed in group RT3. These results suggest that aerobic capacity is maintained over 4 wk of moderately reduced training (3 sessions.wk-1) in well-trained swimmers. Muscular strength was not diminished over 4 wk of reduced training or inactivity, but the ability to generate power during swimming was significantly reduced in all groups.     

Adiposity, lipid levels, and brief endurance training in nonobese adolescent males

Physical activity during childhood and adolescence may influence the development of childhood obesity and cardiovascular disease later in life. Research focused prospectively on the effects of training on lipid levels in nonobese subjects, and studies using noninvasive measurements of subcutaneous and intraabdominal fat are lacking. It was hypothesized in nonobese sedentary adolescent males that a brief endurance-type exercise training intervention would reduce body fat and improve lipid profiles. Thirty-eight healthy, nonobese sedentary adolescent males (mean age 16 +/- 0.7 years old; 18 controls, 20 trained) completed a 5-week prospective, randomized, controlled study. Adiposity was measured using magnetic resonance images of the thigh and abdomen (subcutaneous abdominal adipose tissue [SAAT] and intraabdominal adipose tissue [IAAT]). Lipid measurements included serum triglycerides (TG), total cholesterol (TC), HDL and LDL cholesterol. There was no change in body weight in either control or training groups. Training led to small but significant reductions in thigh fat (-4.6 +/- 1.5%, p < 0.03) and SAAT% (1.7 +/- 0.8%, p < 0.02). There was no change in IAAT%. Unexpectedly in the control group there were significant increases in thigh fat (5.2 +/- 1.7%, p<0.01), SAAT% (1.8 +/- 0.6, p < 0.007) and IAAT% (4.5 +/- 1.1, p < 0.0007). Training-induced changes in adiposity were not accompanied by changes in circulating lipids. In nonobese adolescent males a brief period of endurance training led to reductions in body fat depots without weight change while body fat increased rapidly in the control group. Exercise training did not change lipid levels, the latter may require more sustained alterations in patterns of physical activity.     

Effect of endurance training on cardiovascular response to static exercise performed with untrained muscles

Eighteen male volunteers (20-23 years) were submitted to 13 weeks of training consisting of 30 min of exercise (at 50%-75% VO2max) on a bicycle ergometer, performed three times a week. Every 4 weeks the heart rate (HR), blood pressure (BP), and systolic time interval (STI) responses to the static handgrip (at 30% MVC) were examined. Before and after 13 weeks of training echocardiograms were recorded in seven subjects at rest and during the handgrip. Significant decreases in HR and BP responses to static exercise were found already after 4 weeks of training. Resting STI and left ventricular dimensions were not affected by training, but during the static exercise the pre-ejection period (PEP) and isovolumic contraction time interval (ICT) at the corresponding HR were significantly shortened after 8 weeks of training. The values of echocardiographic indices of left ventricular function obtained during exercise after training did not differ significantly from those found before training. It is concluded that endurance training of moderate intensity improves cardiac function during static exercise performed with untrained muscles.     

Effect of sodium bicarbonate on muscle metabolism during intense endurance cycling

INTRODUCTION: Sodium bicarbonate (NaHCO3) ingestion has been shown to increase both muscle glycogenolysis and glycolysis during brief submaximal exercise. These changes may be detrimental to performance during more prolonged, exhaustive exercise. This study examined the effect of NaHCO3 ingestion on muscle metabolism and performance during intense endurance exercise of approximately 60 min in seven endurance-trained men. METHODS: Subjects ingested 0.3 g.kg-1 body mass of either NaHCO3 or CaCO3 (CON) 2 h before performing 30 min of cycling exercise at 77 +/- 1% .VO(2peak) followed by completion of 469 +/- 21 kJ as quickly as possible (approximately 30 min, approximately 80% .VO(2peak)). RESULTS: Immediately before, and throughout exercise, arterialized-venous plasma HCO3- concentrations were higher (P < 0.05) whereas plasma and muscle H+ concentrations were lower (P < 0.05) in NaHCO3 compared with CON. Blood lactate concentrations were higher (P < 0.05) during exercise in NaHCO3, but there was no difference between trials in muscle glycogen utilization or muscle lactate content during exercise. Reductions in PCr and ATP and increases in muscle Cr during exercise were also unaffected by NaHCO3 ingestion. Accordingly, exercise performance time was not different between treatments. CONCLUSION: NaHCO3 ingestion resulted in a small muscle alkalosis but had no effect on muscle metabolism or intense endurance exercise performance in well-trained men.     

Thyroidal changes associated with endurance training in women

The associations between endurance training, body composition, and the pituitary-thyroid axis were studied in 17 healthy, young women. Body composition and plasma concentrations of T4, T3, rT3, resin T3 uptake, TSH, and TRH-stimulated TSH were examined at baseline and after each subject's weekly distance had increased 48 km (delta 48) and 80 km (delta 80) above baseline. Total body weight did not change at delta 48 or delta 80. Mean (+/- SE) lean weight in kg increased from 42.9 +/- 1.2 at baseline to 44.8 +/- 1.2 at delta 80 (P = 0.002). We have reported previously that at delta 48 the subjects had evidence of mild thyroidal impairment, which consisted of decreased T3 and rT3, and an exaggerated TSH response to TRH. With more prolonged training (delta 48 to delta 80) there were significant increases in T4, rT3, and unstimulated TSH, while the ratios of T4/rT3 and T3/rT3 and the TSH response to TRH decreased significantly. Some of the thyroidal changes that occurred between delta 48 and delta 80 are similar to those seen in other stressful non-thyroidal conditions.     

The effect of endurance running training on asthmatic adults.

Nine mild to moderate asthmatic adults (three males, six females) and six non-asthmatics (one male, five females) underwent endurance running training three times per week for five weeks, at self selected running speeds on a motorized treadmill. After training, the asthmatic group had a significantly higher maximum oxygen uptake, significantly lower blood lactate and heart rate in submaximal running, and significantly reduced time to complete a two mile treadmill run, partly attributable to the ability to exercise at a higher % VO2 max after training. These training induced changes of the asthmatic group were generally of a greater magnitude than those shown by the non-asthmatic group. Although seven of the nine asthmatics did show a reduction in the post-exercise fall in FEV1 after the five week training period, this was not statistically significant for the asthmatic group as a whole. The results of this study therefore suggest that endurance running training can improve the aerobic fitness of asthmatic adults, and may reduce the severity of exercise-induced asthma.     

Effect of endurance training on dental erosion,caries, and saliva

The aim of this investigation was to give insights into the impact of endurance training on oral health, with regard to tooth erosion, caries, and salivary parameters. The study included 35 triathletes and 35 non‐exercising controls. The clinical investigation comprised oral examination, assessment of oral status with special regard to caries and erosion, saliva testing during inactivity, and a self‐administered questionnaire about eating, drinking, and oral hygiene behavior. In addition, athletes were asked about their training habits and intake of beverages and sports nutrition. For saliva assessment during exercise, a subsample of n = 15 athletes volunteered in an incremental running field test (IRFT). Athletes showed an increased risk for dental erosion (P = 0.001). No differences were observed with regard to caries prevalence and salivary parameters measured during inactivity between athletes and controls. Among athletes, a significant correlation was found between caries prevalence and the cumulative weekly training time (r = 0.347, P = 0.04). In athletes after IRFT and at maximum workload, saliva flow rates decreased (P = 0.001 stimulated; P = 0.01 unstimulated) and saliva pH increased significantly (P = 0.003). Higher risk for dental erosions, exercise‐dependent caries risk, and load‐dependent changes in saliva parameters point out the need for risk‐adapted preventive dental concepts in the field of sports dentistry.