Characterization of Spodoptera littoralis (Lepidoptera: Noctuidae) resistance to indoxacarb: inheritance mode, realized heritability, and fitness costs.

Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) is a major economic pest attacking a variety of crops in Egypt and other Mediterranean countries. S. littoralis has developed resistance to both traditional and novel insecticides. The current study investigated S. littoralis resistance to indoxacarb regarding inheritance mode, realized heritability (h2), and fitness costs. An indoxacarb-resistant strain (Indoxa-SEL) was obtained by selecting a field strain with indoxacarb. Indoxa-SEL strain outperformed the susceptible one (Indoxa-S) by 29.77-fold after 16 consecutive generations of selection. Based on the LC50 values of the progenies of reciprocal crosses F1 (R♂ × S♀) and F1' (R♀ × S♂), S. littoralis resistance to indoxacarb was found to be autosomal and partially recessive. Chi-square tests for goodness-of-fit between observed and expected mortalities of self-bred F1 and resistant strain reciprocal crosses revealed that the resistance was controlled by multiple genes. The resistant strain had a relative fitness of 0.80, with significantly increased total preovipositional period of females, egg, larvae, pupae, preadult, adult, and total longevity period. The estimated realized heritability value in the Indoxa-SEL strain was 0.21. The current study will contribute to sustaining indoxacarb efficacy and designing effective resistance management programs against S. littoralis.

Effect of dapagliflozin against NAFLD and dyslipidemia in type 2 diabetic albino rats: possible underlying mechanisms.

OBJECTIVE: The aim was to investigate the effect of dapagliflozin on non-alcoholic fatty liver disease and dyslipidemia in type 2 diabetic rats by studying the histopathological structure of the liver and detecting possible underlying mechanisms for this impact by evaluating the potential anti-inflammatory action of dapagliflozin. MATERIALS AND METHODS: 100 albino rats were used in this work and divided into five equal groups: group I (Control group), group II (Control diabetic group), group III (was administered dapagliflozin, 0.75 mg/kg, p.o.), group IV (was administered dapagliflozin, 1.5 mg/kg, p.o.), and group V (was administered dapagliflozin, 3 mg/kg, p.o.). RESULTS: In our study, the total body weight, liver weight, liver index, blood glucose level, insulin level, insulin resistance, total cholesterol, triglycerides, liver enzymes, IL-1 ß, and MDA were significantly higher in the control diabetic group than the normal group. The dapagliflozin reduced all the above variables significantly in a dose-dependent manner compared to the control diabetic group (p-value = 0.001 for all). CONCLUSIONS: Dapagliflozin may be a promising novel treatment strategy for treating T2DM-related non-alcoholic fatty liver disease (NAFLD), and dyslipidemia where it possesses anti-oxidative, anti-inflammatory and anti-dyslipidemic effects.

Prevalence of urinary incontinence among women in Saudi Arabia: a cross-sectional study.

OBJECTIVE: Urinary incontinence is defined as involuntary loss of urine, a common health condition that is more frequent in women. It disturbs the affected individuals and interferes with their daily activities. This study aimed to estimate the prevalence of urinary incontinence among Saudi women in the western area of the Kingdom of Saudi Arabia. SUBJECTS AND METHODS: A descriptive cross-sectional design was used for this study. A survey was administered to Saudi women in the western area of the Kingdom of Saudi Arabia ranging in age from 18 to 70 years. The data were collected using the Arabic version of the Questionnaire for Urinary Incontinence Diagnosis. Descriptive statistics were generated by calculating numbers and percentages of information on the prevalence of incontinence in women. p-values < 0.05 were considered statistically significant. RESULTS: The prevalence of urinary incontinence was 44.2%, with the urge type being the most reported. Stress urinary incontinence was reported by 155 women (15.4%), urgency urinary incontinence by 257 women (25.6%), and mixed urinary incontinence by 102 women (10.15%). CONCLUSIONS: Urinary incontinence is prevalent in women in Western Saudi Arabia. Age, multiparty obesity, and vaginal surgery are significant risk factors influencing its occurrence.

Incidence of Guillain-Barré Syndrome post COVID-19: a systematic review of case reports and case series.

OBJECTIVE: The purpose of this systematic review was to study the incidence, risk factors and patients subjected to Guillain-Barré syndrome (GBS) after COVID-19. MATERIALS AND METHODS: For qualitative assessment and assessing the methodological quality, the Cochrane Handbook for Systematic Reviews of Interventions and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) checklist were utilized. Data from PubMed, Cochrane, Embase, CINAHIL, Medline, ResearchGate, and Scopus were searched. The relevant studies involved patients with confirmed COVID-19 diagnosis by RT-PCR, and GBS diagnosis based on typical clinical symptoms and/or confirmatory diagnostic results. A total of 12 English relevant articles (6 papers were case reports and 8 were case series with a total of 32 patients) published in a peer-reviewed journal from 2019 to 2021 were included. Following the review methodology, two independent raters were responsible for retrieving, extracting and checking for data eligibility. Demographic characteristics are presented as frequencies and percentages. Based on distribution of values, continuous data were expressed as median and interquartile range (IQR). RESULTS: Out of 32 patients, 26 patients reported neurological symptoms, 6 cases went unnoticed, 7 cases showed involvement of the cranial nerves, 12 cases did not, and 13 cases went unreported. CONCLUSIONS: It is too early to draw any conclusions concerning a potential relationship between SARS-CoV-2 infection and GBS. More large-scale observational studies are required to understand the pathogenesis of SARS-CoV-2-associated GBS and to demonstrate a definite causal relationship between GBS and SARS-CoV-2 infection.

Flupyradifurone induces transgenerational hormesis effects in the cowpea aphid, Aphis craccivora.

With low-dose stimulation and high-dose inhibition, insecticide-induced hormesis, a biphasic phenomenon, can contribute to pest resurgence. The cowpea aphid, Aphis craccivora (Koch) (Homoptera: Aphididae), is a vital insect that infests legume crops. Its hormesis of flupyradifurone has not been previously established. Age-stage two-sex life analysis is used to investigate the sublethal and transgenerational effects of flupyradifurone on two successive generations of A. craccivora. A leaf-dip bioassay method revealed high toxicity of flupyradifurone against A. craccivora, with lethal concentration 50% value (LC50) of 1.82 mg L-1 after 48 h exposure. Treatment of parent generation (F0) with LC10 and LC25 of flupyradifurone significantly increased the longevity and fecundity of the directly exposed adults. The results of transgenerational effects showed that the treatment of (F0) with LC25 induced significant hormetic effects in progeny generation (F1). Furthermore, flupyradifurone at LC25 significantly enhanced the biological traits, such as intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R0) compared with the control. Similarly, both LC10 and LC25 induced a significant increase in the mean generation time T (d). Conversely, both treatments caused a significant decrease in the doubling time (DT). Data in the present study demonstrate that the exposure of (F0) to flupyradifurone at LC10 and LC25 enhanced longevity and fecundity in the directly exposed adults of A. craccivora, and induced transgenerational hormesis across the subsequent (F1) generation. These results should be taken into consideration when using flupyradifurone for controlling cowpea aphid.

Role of exogenous-applied salicylic acid, zinc and glycine betaine to improve drought-tolerance in wheat during reproductive growth stages.

BACKGROUND: Drought has become a dangerous threat to reduce crop productivity throughout the world. Exogenous applications of regulators, micronutrients, and/or osmoprotectants for inducing drought-tolerance in field crops have been effectively adopted. A controlled pot study was performed to investigate the relative efficacy of salicylic acid (SA), zinc (Zn), and glycine betaine (GB) as foliar applications on the growth, tissues pigments content, relative water content (RWC), leaf gas-exchange, antioxidant enzymes activity, reactive oxygen species (ROS) accumulation, osmolytes contents, and the yield parameters of wheat plants subjected to two soil water conditions (85% field capacity: well-watered, 50% field capacity: water-deficient) during reproductive growth stages. RESULTS: Water deficient conditions significantly decreased the growth, yield parameters, RWC, photosynthesis pigment, and gas-exchange attributes except for intercellular CO2 concentration. However, foliar applications remarkably improved the growth and yield parameters under water deficit conditions. Under drought condition, exogenous applications of SA, Zn, and GB increased the grain yield pot- 1 by 27.99, 15.23 and 37.36%, respectively, as compared to the control treatment. Drought stress statistically increased the contents of hydrogen peroxide (H2O2), superoxide anion radical (O2 •-), and malonaldehyde (MDA), and elevated the harmful oxidation to cell lipids in plants, however, they were considerably reduced by foliar applications. Foliar applications of SA, Zn, and GB decreased MDA content by 29.09, 16.64 and 26.51% under drought stress, respectively, as compared to the control treatment. Activities of all antioxidant enzymes, proline content, and soluble sugar were increased in response to foliar applications under water deficit conditions. CONCLUSIONS: Overall, foliar application of GB, SA, and Zn compounds improved the drought-tolerance in wheat by decreasing the ROS accumulation, promoting enzymatic antioxidants, and increasing osmolytes accumulation. Finally, GB treatment was most effective in thoroughly assessed parameters of wheat followed by SA and Zn applications to alleviate the adverse effects of drought stress.

Risk of acute pulmonary embolism in COVID-19 pneumonia compared to community-acquired pneumonia: a retrospective case-control study.

AIM: To compare the incidence of pulmonary embolism (PE) in COVID-19 pneumonia and non-COVID-19-related community-acquired pneumonia (CAP) in hospitalised patients. MATERIALS AND METHODS: A retrospective case-control study was conducted. This included patients hospitalised with pneumonia and investigated for suspected PE with computed tomography pulmonary angiogram (CTPA). Cases were defined as patients with COVID-19 pneumonia from 1 March 2020 to 17 May 2020; controls were patients with CAP from 5 July 2019 to 31 January 2020. The primary outcome was to determine the risk of developing PE in both groups. Multivariable logistic regression was used to calculate the adjusted odds ratio for PE. RESULTS: One hundred and forty-four patients were included; 72 cases (47% male; mean age 59 (±15) years), and 72 controls (56% male; mean age 58 (±20) years). PE was diagnosed in 23.6% of the cases versus 6.9% of the controls. The adjusted odds ratio for PE in hospitalised patients with COVID-19 pneumonia compared with those with CAP was 3.23 (95% confidence interval [CI] 1.04-10.04, p=0.04). CONCLUSION: The odds of developing PE in hospitalised patients with COVID-19 pneumonia are three-times higher than in those with CAP. The results provide a quantitative assessment of the risk of PE in COVID-19 pneumonia, a condition new to healthcare, compared to other forms of pneumonia with a well-established scientific basis.

Effects of salicylic acid, zinc and glycine betaine on morpho-physiological growth and yield of maize under drought stress.

Drought is one of the major environmental stresses that negatively affect the maize (Zea mays L.) growth and production throughout the world. Foliar applications of plant growth regulators, micronutrients or osmoprotectants for stimulating drought-tolerance in plants have been intensively reported. A controlled pot experiment was conducted to study the relative efficacy of salicylic acid (SA), zinc (Zn), and glycine betaine (GB) foliar applications on morphology, chlorophyll contents, relative water content (RWC), gas-exchange attributes, activities of antioxidant enzymes, accumulations of reactive oxygen species (ROS) and osmolytes, and yield attributes of maize plants exposed to two soil water conditions (85% field capacity: well-watered, 50% field capacity: drought stress) during critical growth stages. Drought stress significantly reduced the morphological parameters, yield and its components, RWC, chlorophyll contents, and gas-exchange parameters except for intercellular CO2 concentration, compared with well water conditions. However, the foliar applications considerably enhanced all the above parameters under drought. Drought stress significantly (p < 0.05) increased the hydrogen peroxide and superoxide anion contents, and enhanced the lipid peroxidation rate measured in terms of malonaldehyde (MDA) content. However, ROS and MDA contents were substantially decreased by foliar applications under drought stress. Antioxidant enzymes activity, proline content, and the soluble sugar were increased by foliar treatments under both well-watered and drought-stressed conditions. Overall, the application of GB was the most effective among all compounds to enhance the drought tolerance in maize through reduced levels of ROS, increased activities of antioxidant enzymes and higher accumulation of osmolytes contents.

Lipid profiles are influenced by arm cranking exercise and training in individuals with spinal cord injury.

STUDY DESIGN: A prospective, two-group comparative intervention study. OBJECTIVE: To determine the acute and training effects of arm cranking exercise on blood lipid profiles in wheel chair bound individuals with spinal cord injury (SCI) and normal able-bodied subjects. SETTING: Faculty of Science, School of Sport and Exercise Science, Liverpool John Moores University, England. METHODS: Total cholesterol, triglyceride and high-density lipoprotein cholesterol (HDL-C) at rest and in response to arm cranking exercise before and after 12 weeks of training were compared between individuals with SCI (N = 5) and able-bodied subjects (N = 7). Following the determination of peak oxygen consumption (VO2peak), all subjects performed a submaximal arm cranking exercise at an intensity corresponding to 60-65% VO2peak for 30 min. Venous blood samples were obtained before and after submaximal exercise and measured for total cholesterol, triglycerides and HDL-C concentrations. These lipid parameters were remeasured in all subjects at rest and in response to the same submaximal arm cranking exercise after 12 weeks of individually supervised arm cranking training programme. RESULTS: Before training, the resting mean value of triglyceride in individuals with SCI was significantly (P < 0.05) higher than that found in able-bodied persons. Acute arm cranking exercise did not change total cholesterol or triglyceride concentrations in either the SCI or the able-bodied groups. However, HDL-C increased significantly following exercise in the able-bodied subjects. Following training, the resting mean value of total cholesterol in the group with SCI was significantly (P < 0.05) higher compared with able-bodied individuals. Furthermore, the resting and post submaximal arm cranking exercise mean values of total cholesterol in the able-bodied group, but not in the group with SCI, were significantly lower than those observed before training. While the resting mean value of HDL-C before training in the group with SCI was lower than that found in the able-bodied, this difference did not reach the designated level of significance (P > 0.05). Submaximal arm cranking exercise was followed by a significant increase in HDL-C only in the able-bodied individuals. Compared to pretraining, the resting and post arm cranking exercise levels of HDL-C in the group with SCI increased significantly (P < 0.05) after training. CONCLUSION: It is concluded that acute arm cranking exercise and training in individuals with SCI is associated with favourable effects on HDL-C, whereas total cholesterols and triglycerides were not altered. The mechanism responsible for the increase in HDL-C with training in individuals with SCI is not known, but it is likely to be related to increased activity of cholesterol transport enzymes lipoprotein lipase and acyltransferase.

Adverse effects of alcohol ingestion post exercise on blood rheological variables during recovery.

The present study examined the influence of ingesting a moderate dose of alcohol on the main determinants of blood rheology namely: plasma viscosity, plasma fibrinogen concentration, plasma total protein concentration, and haematocrit. Eleven moderately active young men were studied immediately after a standardised cycle ergometer test and during the 24 h period of recovery. Alcohol (0.7 g/kg body mass) was given 1 h after exercise on one test occasion, while an equal volume of alcohol-free solution was administered on the other. Venous blood samples were obtained at baseline, post exercise, and at 1, 5, and 22 h post alcohol ingestion. A significant reduction in plasma volume was observed immediately after exercise, but this decrease was restored 1-h post drink ingestion. Blood alcohol level increased significantly 1 h after the ingestion of alcohol, but decreased and returned to the resting baseline level at 5 h during recovery. Exercise induced significant changes (P<0.05) in blood rheology as manifested by a significant increase (P<0.05) in plasma viscosity and plasma fibrinogen. Parallel increase (P<0.05) in haematocrit and total protein was also observed after exercise. The increase in these rheological variables immediately after exercise was mainly due to exercise-induced plasma volume loss. During recovery, while the increase in haematocrit post-exercise returned to the baseline level in both control and alcohol trials, plasma viscosity and plasma fibrinogen remained significantly high during recovery in the alcohol trial compared with control condition. It is concluded that exercise induces significant changes in the main determinants of blood rheology and the consumption of alcohol after physical exercise delays the normal return of plasma viscosity, plasma fibrinogen to the resting baseline levels during recovery. Although the mechanism responsible for these findings is not, as yet known, it might be linked with alcohol induce dehydration.

Effects of alcohol ingestion following exercise on postprandial lipemia.

The study determined the effect of alcohol ingestion postexercise on postprandial lipemia during recovery. The mean values were compared with those obtained in a control experiment during which no alcohol was given. Nineteen normolipidemic subjects (11 males and 8 females) performed two exercise trials at an intensity corresponding to 70% VO2max for 35 min. In a random order, alcoholic (0.7 g/kg) or alcohol-free drinks were given 1 h after the completion of exercise. Venous blood samples were obtained pre- (before breakfast) and postexercise and pre- and postprandially during recovery. Total cholesterol and high-density lipoprotein cholesterol showed no change with exercise or alcohol ingestion. In the control trial, when subjects consumed a standardized lunch, triglycerides showed no significant change, but when alcohol was consumed postexercise triglyceride concentration increased substantially 5 h during recovery in both males and females. The mechanism responsible for the rise in triglyceride concentration during recovery when alcohol was ingested following exercise is not known, but this appears to be a late phenomenon.

The effect of alcohol ingestion on the exercise-induced changes in fibrin and fibrinogen degradation products in man.

The present study examined the influence of ingesting a moderate dose of alcohol on plasminogen activator activity (t-PA), plasma fibrinogen (Fb), total degradation products (TDP) and the degradation products of fibrin (FbDP) and fibrinogen (FgDP) at rest and in response to exercise. Eleven male subjects performed two separate experimental trials at an exercise intensity corresponding to 70% maximal oxygen consumption for 35 min. Prior to trials, subjects were either given 0.5 g/kg alcohol in orange-flavoured drink or an equal volume of non-caloric non-alcoholic drink 45 min before exercise. Comparison of the levels of t-PA, Fb, TDP, FbDP, and FgDP at rest, before and 45 min after the ingestion of alcohol revealed no significant differences between alcohol and control experiments. Exercise resulted in a marked increase in t-PA, TDP, and FgDP, with no appreciable change in FbDP. Although plasma fibrinogen level showed significant decrease post-exercise when subjects ingested alcohol, this difference was small and its biological significance is questionable. While t-PA level increased similarly in response to exercise during alcohol and control trials, a significantly higher response of TDP was found during the control trial compared with alcohol trial. It was concluded that exercise with and without alcohol ingestion is followed by a substantial increase in t-PA, which coincided with an increase in TDP. The increase in TDP was mainly due to an increase in FgDP, but not to FbDP. These findings support the hypothesis that a significant fibrinogenolysis occurs in response to exercise, and moderate intoxication with alcohol prior to exercise reduced this response.

Blood hemostasis in exercise and training.

Formation of the blood clot is a slow but normal physiological process occurring as a result of the activation of blood coagulation pathways. Nature's guard against unwanted blood clots is the fibrinolytic enzyme system. In healthy people, there is a delicate dynamic balance between blood clot formation and blood clot dissolution. Available evidence suggests that exercise and physical training evoke multiple effects on blood hemostasis in normal healthy subjects and in patients. A single bout of exercise is usually associated with a transient increase in blood coagulation as evidenced by a shortening of activated partial thromboplastin time (APTT) and increased Factor VIII (FVIII). The rise in FVIII is intensity dependent and continues into recovery. The effects of acute exercise on plasma fibrinogen have yielded conflicting results. Thus, the issue of whether exercise-induced blood hypercoagulability in vitro mirrors an in vivo thrombin generation and fibrin formation remains disputable. Exercise-induced enhancement of fibrinolysis has been repeatedly demonstrated using a wide range of exercise protocols incorporating various exercise intensities and durations. Moderate exercise appears to enhance blood fibrinolytic activity without a concomitant activation of blood coagulation mechanisms, whereas, very heavy exercise induces simultaneous activation of blood fibrinolysis and coagulation. The increase in fibrinolysis is due to a rise in tissue-type plasminogen activator (tPA) and decrease in plasminogen activator inhibitor (PAI). The mechanism of exercise-induced hyperfibrinolysis is poorly understood, and the physiological utility of such activation remains unresolved. Strenuous exercise elicits a transient increase in platelet count, but there are conflicting results concerning the effect of exercise on platelet aggregation and activation. Few comprehensive studies exist concerning the influence of exercise training on blood hemostasis, making future investigation necessary to identify whether there are favorable effects of exercise training on blood coagulation, fibrinolysis, and platelet functions.

The effect of moderate alcohol ingestion on blood coagulation and fibrinolysis at rest and in response to exercise.

The effect of alcohol ingestion before exercise on blood haemostasis is not known. The present study examined the effects of moderate alcohol ingestion on blood haemostatic variables at rest and in response to exercise. Eleven normal healthy individuals randomly performed two tests separated by 7 days. A moderate dose of ethanol (0.5 g.kg-1) was administered before one test, whereas an equal volume of an alcohol-free drink was administered before the other. Forty-five minutes after the ingestion of either drink, the participants cycled at 65% VO2max for 30 min followed by a 5-min all-out performance. Venous blood samples were obtained before and 45 min after the ingestion of both drinks, and also immediately after exercise. Exercise induced a significant increase in tissue-type plasminogen activator activity and antigen, and factor VIII procoagulant activity. The post-exercise data also showed a significant decrease in plasminogen activator inhibitor activity and soluble fibrin, with a significant shortening in prothrombin time and activated partial thromboplastin time, but not thrombin time. No significant changes were observed in antithrombin III. Although no significant differences were found between trials in the haemostatic and fibrinolytic variables at rest, a significant decrease in fibrinogen concentration was observed after exercise in the alcohol trial. This suggests that ingesting a moderate dose of alcohol does not alter blood coagulation and fibrinolysis at rest. Apart from fibrinogen concentration, which was significantly decreased after exercise in the alcohol trial, most of the haemostatic and fibrinolytic variables were not affected by alcohol. The mechanism responsible for the decrease in fibrinogen following exercise in the alcohol trial remains unknown, but might be related to inhibition of fibrinogen synthesis by the liver or an enhanced rate of its catabolism.

Activation and disturbance of blood haemostasis following strenuous physical exercise.

Physical exercise activates blood coagulation and enhances fibrinolytic activity. To investigate whether these activations of blood coagulation and fibrinolysis are balanced post-exercise and during the period of recovery, 11 moderately active young men were examined immediately after a standardised cycle ergometer test and during the 24 h period of recovery. Blood samples were obtained at rest, immediately after exercise, and 2, 6 and 24 h after exercise. All post-exercise values were corrected for any change in plasma volume. Exercise induced a significant increase in factor VIII activity and this occurred with a significant shortening of activated partial thromboplastin time. A concomitant enhancement of tissue plasminogen activity resulted in significant increases in tissue plasminogen activity antigen and total fibrin/fibrinogen degradation products, and a significant decrease in tissue plasminogen activator inhibitor-1 activity. Increases in coagulation and fibrinolytic activity changed in parallel during exercise. However, during recovery, while the increase in factor VIII activity post-exercise persisted 2 and 6 h into recovery, fibrinolytic activity demonstrated a sharp fall. It is concluded that whereas the enhanced fibrinolytic activity during exercise appears to counterbalance the increase in blood coagulability, this haemostatic balance is not maintained during recovery. This perturbed blood haemostasis could constitute an enhanced risk for coronary artery thrombosis and may contribute to exercise-related cardiovascular events.

Exercise induces a change in plasma fibrinogen concentration: fact or fiction?

This study examined the effect of exercise on plasma fibrinogen concentrations with simultaneous measurements of plasma volume changes. Eight moderately active males aged 26.6+/-3.6 years (mean +/- SD) completed maximal (VO2max) and submaximal (75% VO2max for 30 minutes) exercise trials separated by 7 days. Venous blood samples were obtained at rest, immediately postexercise, and following 30 minutes of recovery. Whole blood was analysed for haematocrit and haemoglobin, while citrated plasma was assayed for fibrinogen levels. Values of haematocrit and haemoglobin before and after exercise were utilised for the estimation of plasma volume changes. Plasma volume decreased (p<0.05) immediately following both maximal (-17.7+/-5.1%) and submaximal (-14.3+/-4.1%) exercise. Exercise resulted in decreased plasma fibrinogen levels (maximal exercise: from 266.3+/-14.5 to 222.2+/-23.9 mg x dL(-1); submaximal exercise: from 239.5+/-45.4 to 209.7+/-42.4 mg x dL(-1)) only when postexercise raw data were corrected for the contraction of plasma volume. It is concluded therefore that changes in plasma volume in response to exercise should be taken into account when interpreting exercise effects on plasma fibrinogen concentration.

Effects of exercise and training on blood rheology.

The effects of exercise on the rheological properties of blood have not received much research attention. Recent, limited evidence indicates that the viscosities of whole blood and plasma increase in response to a variety of exercise protocols. The increase in whole blood viscosity is mainly attributed to an increase in haematocrit and plasma viscosity, whereas the deformability and aggregability of red blood cells remain unaltered. The increases in plasma viscosity and haematocrit have been ascribed to exercise-induced haemoconcentration as a result of fluid transfer from the blood to the interstitial spaces. Although the long term effects of endurance training on blood rheology have been very briefly examined, the exact effect of training has not as yet been determined. However, available cross-sectional and longitudinal studies indicate that the blood of endurance athletes is more dilute and this has been attributed to an expansion of plasma volume as a result of training. It has been suggested that this blood dilutional effect of endurance training may be advantageous in delivering oxygen to the exercising muscles because of a reduced resistance to blood flow. The increase in plasma volume may also contribute to the body water pool and help offset dehydration. The influence of strength and power training on blood rheology is not known.

Exogenous carbohydrate utilisation: effects on metabolism and exercise performance.

It is generally recognized that a decrease in carbohydrate availability can lead to the development of fatigue during prolonged exercise in humans. Administration of glucose or other carbohydrates before or during exercise has been shown to postpone fatigue, conserve muscle glycogen and improve performance. Carbohydrates can be categorised according to their ability to increase blood glucose concentration (known as glycaemic index) and by the extent they stimulate the release of insulin. The glycaemic index is reflected in the rate at which consumed carbohydrate is made available in the blood. Glucose is the only type of carbohydrate that can readily be oxidised by skeletal muscle for energy production. Gastric emptying is the primary factor limiting the rate of carbohydrate delivery to the blood and therefore influences the utilisation of exogenous carbohydrate ingested before or during exercise. Various methods have been used to assess the oxidation of exogenous carbohydrates during exercise. Peak rates of CHO oxidation during exercise have been reported between 0.4 and 1.0 g/min, and the rates of oxidation do not appear to be influenced to a major extent by the use of multiple drinking schedule in comparison with a single bolus schedule. Previous studies also suggest that the ingestion of fructose during exercise does not offer any additional benefits over ingestion of glucose or glucose polymer solutions of similar concentration. The hormones insulin, glucagon and adrenaline together with cortisol and growth hormone play key roles in the regulation of carbohydrate metabolism during exercise. Ingestion of moderately concentrated carbohydrate solutions (4-8%) enhances prolonged exercise performance and is appropriate for optimising energy and fluid delivery without causing adverse effects. The ergogenic effects of carbohydrate ingestion on performance during intermittent exercise such as competitive sports are less well established, although the evidence to date suggests diminished performance when carbohydrate are limiting.

Carbohydrate ingestion improves endurance performance during a 1 h simulated cycling time trial.

This study examined the effect of carbohydrate ingestion on metabolic and performance-related responses during and after a simulated 1 h cycling time trial. Eight trained male cyclists (VO2 peak = 66.5 ml kg-1 min-1) rode their own bicycles mounted on a windload simulator to imitate real riding conditions. At a self-selected maximal pace, the cyclists performed two 1 h rides (separated by 7 days) and were fed either an 8% carbohydrate or placebo solution. The beverages were administered 25 min before (4.5 ml kg-1) and at the end (4.5 ml kg-1) of the ride. With carbohydrate feeding, plasma glucose tended (P = 0.21) to rise before the time trial. Compared with rest, the plasma glucose concentration decreased significantly (P < 0.05) at the end of both rides, with no statistically significant difference being observed between treatments. Thereafter, plasma glucose increased significantly (P < 0.05) at 15 and 30 min into recovery and was significantly higher at 30 min during the carbohydrate trial compared with the placebo trial. No significant changes in plasma free fatty acids were observed during the ride. However, a significant increase (P < 0.05) in free fatty acids was found at 15 and 30 min into recovery, with no difference between trials. Mean power output was significantly (P < 0.05) greater during the carbohydrate compared with the placebo trial (mean +/- S.E.: 277 +/- 3 and 269 +/- 3 W, respectively). The greater distance covered in the carbohydrate compared with the placebo trial (41.5 +/- 1.06 and 41.0 +/- 1.06 km, respectively; P < 0.05) was equivalent to a 44 s improvement. We conclude that pre-exercise carbohydrate ingestion significantly increases endurance performance in trained cyclists during a 1 h simulated time trial. Although the mechanism for this enhancement in performance with carbohydrate ingestion cannot be surmised from the present results, it could be related to a higher rate of carbohydrate oxidation, or to favourable effects of carbohydrate ingestion on the central component of fatigue.

Effects of active warm-down and carbohydrate feeding on free fatty acid concentrations after prolonged submaximal exercise.

We examined the effects of active warm-down (AWD) and carbohydrate ingestion on plasma levels of free fatty acids (FFAs) and glucose changes into recovery following prolonged submaximal exercise. Subjects in Group 1 cycled at 70% of maximal oxygen uptake (VO2max); carbohydrate (CHO) or placebo (PLA) was ingested 15 min before and 45 min during exercise. In the AWD experiment, exercise was followed immediately by an AWD and subjects were given a placebo solution. Group 2 subjects consumed CHO or PLA at 75 min during and after exercise at 70% VO2max. ANOVA revealed a significant decrease in blood glucose levels only in Group 1, with a concomitant increase in FFA concentrations during exercise in both groups. Carbohydrate ingestion in Groups 1 and 2 significantly decreased the normal response of FFAs during exercise and markedly reduced the normal elevation of FFAs in recovery. AWD following submaximal exercise had no effect on plasma FFA elevations in recovery. These results suggest that carbohydrate ingestion, but not active warm-down, attenuates FFA elevations in recovery.