Post-exercise dietary macronutrient composition modulates components of energy balance in young, physically active adults.

The effectiveness of exercise to reduce body mass is typically modest, partially due to energy compensation responses which may be linked to energy substrate availability around exercise. The present study aimed to investigate the effect of manipulating post-exercise energy substrate availability (high carbohydrate/low fat [HCLF] or low carbohydrate/high fat [LCHF] energy replacement) on energy balance components in the short-term (i.e., appetite, energy intake (EI) and energy expenditure (EE)). METHODS: Appetite, EI, activity- and total- EE were measured in twelve healthy, young (21.0 ± 2.3 years) physically active participants (10 men, 2 women) on two occasions across 4 days after a 75-min run and an isocaloric energy replacement drink (HCLF and LCHF). Appetite was measured daily by visual analogue scales, EI was calculated by subtracting the energy content of food leftovers from a provided food package, activity- and total- EE determined by heart-rate accelerometery. RESULTS: Composite appetite ratings between days were lower in HCLF (62.4 ± 12) compared to LCHF (68.3 ± 8.9 mm; p = 0.048). No differences between conditions were detected for EI. Cumulative activity-EE (HCLF=  20.9 ± 3.7, LCHF=  16.9 ± 3.1 MJ; p = 0.037), but not total-EE (HCLF=  44.6 ± 7.7, LCHF=  39.9 ± 4.7 MJ; p = 0.060), was higher for the HCLF condition than the LCHF across the measurement period. CONCLUSION: Compared with low carbohydrate/high fat, immediate post-exercise energy replacement with a high carbohydrate/low fat drink resulted in higher short-term activity energy expenditure and lower appetite ratings.

Effects of short-term cinnamon ingestion on in vivo glucose tolerance.

AIMS: Various spices display insulin-potentiating activity in vitro, and in particular, cinnamon spice and its phenolic extracts have been shown to exhibit these capabilities. In vivo study shows that cinnamon may have beneficial effects on glucose homeostasis; therefore the aim of this study was to further investigate this phenomenon in humans. METHODS: Seven lean healthy male volunteers, aged 26 +/- 1 years, body mass index 24.5 +/- 0.3 kg/m(2) (mean +/- s.e.m.), underwent three oral glucose tolerance tests (OGTT) supplemented with either a 5 g placebo (OGTT(control)), 5 g of cinnamon (OGTT(cin)), or 5 g of cinnamon taken 12 h before (OGTT(cin12hpre)) in a randomized-crossover design. RESULTS: Cinnamon ingestion reduced total plasma glucose responses (AUC) to oral glucose ingestion [-13% and -10% for OGTT(cin) (p < 0.05) and OGTT(cin12hpre) (p < 0.05), respectively], as well as improving insulin sensitivity as assessed by insulin sensitivity index measures based on Matsuda's model in both OGTT(cin) (p < 0.05) and OGTT(cin12hpre) (p < 0.05) trials compared with OGTT(control). CONCLUSIONS: These data illustrate that cinnamon spice supplementation may be important to in vivo glycaemic control and insulin sensitivity in humans, and not only are its effects immediate, they also appear to be sustained for 12 h.

Leukocyte heat shock protein expression before and after intensified training.

The purpose of the current research was to test the hypothesis that exercise induced leukocyte heat shock protein (HSP) expression is increased during periods of intensified exercise training. Seven male endurance cyclists carried out tests of maximal oxygen consumption and endurance capacity. These standard exercise tests were carried out prior to and following 6 days of prescribed intensified training. Sampled leukocytes were examined for Hsp27 and Hsp70 expression using a Fluorescence Activated Cell Scanner (EPICS XL, Coulter). During a period of overreaching, as signified by a drop in time to fatigue following the intensified training period (p = 0.02), the number of extracellular Hsp27 positive granulocytes increased in response to the VO(2)max test. Acute, intracellular HSP responses were observed in both baseline and overreached conditions. The present study showed that a period of intensified training caused adaptations in the acute heat shock protein exercise response, reflected by a greater increase of cell surface HSP positive leukocytes following heavy training.

The effect of exercise training on the kinetics of the antibody response to influenza vaccination.

The significance of in vitro changes in immune function accompanying exercise training is unclear. To determine the effect of exercise on the response of the intact immune system to a challenge in vivo, we measured the speed and overall immunoglobulin G (IgG) response to influenza vaccination in humans engaged in different intensities of activity. Male participants (n = 21) were split into heavy and light training groups. Venous blood samples were collected 0, 2, 4, 7, 10 and 14 days after vaccination with trivalent influenza vaccine, and also 12 months after initial vaccination. Serum IgG was determined by enzyme-linked immunosorbant assay. There was a significant difference in baseline IgG between groups, but no difference in IgG concentration 14 days after vaccination. The IgG concentration remained elevated 12 months post-vaccination in the heavy training group. The results suggest a positive relationship between habitual physical activity and baseline antibody concentrations, which, in turn, affects the relative magnitude (fold or percentage increase) of the antibody response to vaccination. The training loads of the participants in this study had no effect on overall IgG measured 14 days after vaccination.

Carbohydrate beverage ingestion and neutrophil degranulation responses following cycling to fatigue at 75% VO2 max.

Carbohydrate (CHO) beverage ingestion appears to influence neutrophil functional responses to prolonged exercise of a fixed duration. The aim of this randomised study was to examine the effect of CHO (5% w/v) beverage ingestion on lipopolysaccharide (LPS)-stimulated neutrophil degranulation responses in nine recreationally active males who cycled at 75% VO2 max until fatigue. On two separate occasions, subjects ingested either placebo (PLA) or CHO beverages before and at 15 min intervals during the exercise. Subjects exercised for 31% longer on the CHO trial compared with the PLA trial (P < 0.05). At fatigue plasma glucose concentration was significantly lower on the PLA trial compared with the CHO trial (P < 0.05). Plasma cortisol concentrations had increased similarly on both trials at this time. A marked neutrophilia was evident at fatigue and throughout the 4 h recovery period, the magnitude of which was similar on both trials. At fatigue LPS-stimulated elastase release per neutrophil had fallen similarly on both trials compared with pre-exercise values (47% and 50% on the PLA and CHO trials, respectively). In conclusion, our results suggest that CHO beverage ingestion has negligible influence on the hormonal, circulating neutrophil and LPS-stimulated neutrophil degranulation responses when exercise is performed to fatigue.

Carbohydrate and fluid intake affect the saliva flow rate and IgA response to cycling.

PURPOSE: The purpose of this study was to examine the effect of regular CHO beverage ingestion and restricted fluid intake on various salivary parameters during prolonged cycle exercise. METHODS: In a randomized block design, 15 recreationally active men cycled for 2 h at 60% VO2max on three occasions, separated by 1 wk. On the CHO and placebo (PLA) treatments, subjects consumed either a glucose (60 g x L(-1)) or placebo drink before (400 mL), during (150 mL every 15 min), and after (400 mL) the exercise. On the restricted fluid intake (RFI) treatment subjects were given a total of 200 mL of placebo fluid to take as desired every 15-min during the exercise. Timed, unstimulated saliva samples were collected preexercise, at 1, 1.5, and 2 h of exercise and at 1 h postexercise. Blood samples were obtained from a subset of 8 subjects preexercise, postexercise, and at 1 h postexercise. RESULTS: Postexercise plasma glucose levels were 18% and 20% lower on the PLA and RFI treatments, respectively, compared with the CHO treatment (P < 0.01). Saliva flow rates were significantly higher on the CHO treatment compared with the RFI treatment at 1.5 h and 2 h of exercise (P < 0.01 and P < 0.05, respectively). Salivary IgA (s-IgA) concentration was significantly lower on the CHO treatment compared with the RFI treatment throughout the exercise (P < 0.05). No other differences were seen between treatments for either saliva flow rate or s-IgA concentration. Neither s-IgA secretion rate, alpha-amylase activity, nor alpha-amylase secretion rate were affected by treatment. CONCLUSIONS: These findings suggest that CHO and fluid intake influence the s-IgA and saliva flow rate response to prolonged submaximal exercise.

Effect of oral glutamine supplementation on human neutrophil lipopolysaccharide-stimulated degranulation following prolonged exercise.

Recent studies have shown that neutrophils can utilize glutamine and that glutamine supplementation can improve neutrophil function in postoperative and burn patients. The present study investigated the influence of oral glutamine supplementation on stimulated neutrophil degranulation and oxidative burst activity following prolonged exercise. Subjects, 7 well-trained men, reported to the laboratory following an overnight fast and cycled for 2 hrs at 60% VO2max on two occasions a week apart. They were randomly assigned to either a glutamine or placebo treatment. For both trials, subjects consumed a sugar-free lemon drink at 15-min intervals until 90 minutes, then a lemon flavored glutamine drink (GLN) or sugar-free lemon drink (PLA) was consumed at 15-min intervals for the remaining exercise and the 2-hr recovery period. Venous blood samples were taken pre-, during, and postexercise. Glutamine supplementation had no effect on the magnitude of postexercise leukocytosis, the plasma elastase concentration following exercise (which increased in both trials), or the plasma elastase release in response to bacterial stimulation (which fell in both trials). Neutrophil function assessed by oxidative burst activity of isolated cells did not change following exercise in either trial. These findings therefore suggest that the fall in plasma glutamine concentration does not account for the decrease in neutrophil function (degranulation response) following prolonged exercise.

The effects of carbohydrate supplementation on immune responses to a soccer-specific exercise protocol.

The aim of this study was to determine the effect of carbohydrate (CHO) versus placebo (PLA) beverage consumption on the immune and plasma cortisol responses to a soccer-specific exercise protocol in 8 university team soccer players. In a randomized, counterbalanced design, the players received carbohydrate or placebo beverages before, during and after two 90 min soccer-specific exercise bouts (3 days apart) designed to mimic the activities performed and the distance covered in a typical soccer match. Blood and saliva samples were collected before, during and after the exercise protocol. Plasma lactate concentration increased to approximately 4 mmol x l(-1) at 45 and 90 min of exercise in both treatments (P<0.01). Plasma glucose concentration was significantly lower after 90 min of exercise with ingestion of the placebo than the carbohydrate (PLA: 4.57+/-0.12 mmol x l(-1); CHO: 5.49+/-0.11 mmol x l(-1); P<0.01). The pattern of change in plasma cortisol, circulating lymphocyte count and saliva immunoglobulin A secretion did not differ between the carbohydrate and placebo trials. Blood neutrophil counts were 14% higher 1 h after the placebo trial than the carbohydrate trial (PLA: 4.8+/-0.5x10(9) cells x l(-1); CHO: 4.2+/-0.5x10(9) cells x l(-1); P = 0.06), but the treatment had no effect on the degranulation response of blood neutrophils stimulated by bacterial lipopolysaccharide. We conclude that, although previous studies have shown that carbohydrate feeding is effective in attenuating immune responses to prolonged continuous strenuous exercise, the same cannot be said for a soccer-specific intermittent exercise protocol. When overall exercise intensity is moderate, and changes in plasma glucose, cortisol and immune variables are relatively small, it would appear that carbohydrate ingestion has only a minimal influence on the immune response to exercise.

Nutritional aspects of immunosuppression in athletes.

The literature suggests that a heavy schedule of training and competition leads to immunosuppression in athletes, placing them at a greater risk of opportunistic infection. There are many factors which influence exercise-induced immunosuppression, and nutrition undoubtedly plays a critical role. Misinterpretation of published data and misleading media reports have lead many athletes to adopt an unbalanced dietary regimen in the belief that it holds the key to improved performance. Some sports have strict weight categories, whilst in others low body fat levels are considered to be necessary for optimal performance or seen as an aesthetic advantage. This leads some athletes to consume a diet extremely low in carbohydrate content which, whilst causing rapid weight loss, may have undesirable results which include placing the athlete at risk from several nutrient deficiencies. Complete avoidance of foods high in animal fat reduces the intake of protein and several fat-soluble vitamins. On the other hand, diets with a very high carbohydrate content are usually achieved at the expense of protein. In addition, anecdotal and media reports have often promoted the supposed performance benefits of certain vitamins and minerals, yet most athletes do not realise that micronutrient supplementation is only beneficial when correcting a deficiency, and to date there is little scientific evidence to substantiate claims that micronutrients act as an ergogenic aid. Moreover, excessive intakes of micronutrients can be toxic. Deficiencies or excesses of various dietary components can have a substantial impact on immune function and may further exacerbate the immunosuppression associated with heavy training loads. This review examines the role of nutrition in exercise-induced immunosuppression and the effect of both excessive and insufficient nutrient intake on immunocompetence. As much of the present literature concerning nutrition and immune function is based on studies with sedentary participants, the need for future research which directly investigates the relationship between exercise, training, immunity and nutrition is highlighted.

Effects of exercise intensity, duration and recovery on in vitro neutrophil function in male athletes.

The aim of the present study was to compare the effects of exercise at 80% VO2max (resulting in fatigue within 1 h) with more prolonged exercise at a lower work rate (55% VO2max for up to 3 h) on blood neutrophil function and plasma concentrations of cortisol, glutamine and glucose. Eighteen healthy male subjects (mean+/-SD age 22.5+/-3.7 yrs, VO2max 60.1+/-6.6 ml x kg(-1) x min(-1)) cycled on an electrically braked ergometer at 80% VO2max to fatigue (37+/-19 min). On another occasion, separated by at least one week, subjects performed exercise on the same ergometer at 55% VO2max for 3 h or to fatigue, whichever was the sooner. Mean exercise time was 164+/-23 min. The order of the trials was randomised. Both exercise bouts caused significant (p<0.05) elevations of the blood leucocyte count and plasma cortisol concentration and reductions in the in vitro neutrophil degranulation response to bacterial lipopolysaccharide and oxidative burst activity. After exercise at the lower work rate for a longer duration, plasma cortisol concentration was higher, blood leucocyte and neutrophil counts were higher, blood lymphocytes, plasma glucose and indices of neutrophil function were lower than those observed at 80% VO2max. Plasma glutamine only fell significantly during recovery after the more prolonged exercise. We conclude that when exercise is very prolonged, the diminution of innate immune function is greater, or at least as great as that observed after fatiguing exercise at higher work rates. Furthermore, reductions in neutrophil function after exercise at 80% VO2max were not related to changes in the plasma glutamine concentration, although both plasma glutamine and neutrophil function were decreased at 1 and 2.5 h post-exercise in the long duration exercise trial.

The effects of high-intensity intermittent exercise on saliva IgA, total protein and alpha-amylase.

The aim of this study was to assess the effect of an acute bout of high-intensity intermittent exercise on saliva IgA concentration and alpha-amylase activity, since this type of training is commonly incorporated into the training programmes of endurance athletes and games players. Eight well-trained male games players took part in the study. They reported to the laboratory after an overnight fast and performed a 60-min cycle exercise task consisting of twenty 1-min periods at 100% VO2max, each separated by 2 min recovery at 30% VO2max. Unstimulated whole saliva was collected over a 5-min period into pre-weighed tubes and analysed for total protein, saliva IgA and alpha-amylase. The saliva flow rate ranged from 0.08 to 1.40 ml x min(-1) at rest and was not significantly affected by the exercise. The performance of the intermittent exercise bout did not affect the saliva IgA concentration, but caused a five-fold increase in alpha-amylase activity (P<0.01 compared with pre-exercise) and a three-fold increase in total protein concentration (P<0.01). These returned to pre-exercise values within 2.5 h post-exercise. It has been suggested that IgA concentration should be expressed as the ratio to total protein concentration, to correct for any concentrating effect due to evaporative loss of saliva water when breathing through the mouth (as in strenuous exercise). The present study clearly demonstrates that this is not appropriate, since there is an increase in salivary protein secretion rate immediately after exercise (571+/-77 microg x min(-1) compared with 218+/-71 microg x min(-1) pre-exercise; P<0.05). The increased saliva alpha-amylase activity after exercise may improve the protective effect of saliva, since this enzyme is known to inhibit bacterial attachment to oral surfaces. The saliva alpha-amylase secretion rate was lower immediately pre-exercise than at any other instant, which may have been due to anticipatory psychological stress, although the subjects were all familiar with interval exercise. This emphasizes the need for true resting non-stressed control conditions in future studies of the effects of exercise on saliva constituents.

Glutamine, exercise and immune function. Links and possible mechanisms.

Glutamine is the most abundant free amino acid in human muscle and plasma and is utilised at high rates by rapidly dividing cells, including leucocytes, to provide energy and optimal conditions for nucleotide biosynthesis. As such, it is considered to be essential for proper immune function. During various catabolic states including surgical trauma, infection, starvation and prolonged exercise, glutamine homeostasis is placed under stress. Falls in the plasma glutamine level (normal range 500 to 750 mumol/L after an overnight fast) have been reported following endurance events and prolonged exercise. These levels remain unchanged or temporarily elevated after short term, high intensity exercise. Plasma glutamine has also been reported to fall in patients with untreated diabetes mellitus, in diet-induced metabolic acidosis and in the recovery period following high intensity intermittent exercise. Common factors among all these stress states are rises in the plasma concentrations of cortisol and glucagon and an increased tissue requirement for glutamine for gluconeogenesis. It is suggested that increased gluconeogenesis and associated increases in hepatic, gut and renal glutamine uptake account for the depletion of plasma glutamine in catabolic stress states, including prolonged exercise. The short term effects of exercise on the plasma glutamine level may be cumulative, since heavy training has been shown to result in low plasma glutamine levels (< 500 mumol/L) requiring long periods of recovery. Furthermore, athletes experiencing discomfort from the overtraining syndrome exhibit lower resting levels of plasma glutamine than active healthy controls. Therefore, physical activity directly affects the availability of glutamine to the leucocytes and thus may influence immune function. The utility of plasma glutamine level as a marker of overtraining has recently been highlighted, but a consensus has not yet been reached concerning the best method of determining the level. Since injury, infection, nutritional status and acute exercise can all influence plasma glutamine level, these factors must be controlled and/or taken into consideration if plasma glutamine is to prove a useful marker of impending overtraining.

The effect of severe eccentric exercise-induced muscle damage on plasma elastase, glutamine and zinc concentrations.

The aim of this study was to determine if severe exercise-induced muscle damage alters the plasma concentrations of glutamine and zinc. Changes in plasma concentrations of glutamine, zinc and polymorphonuclear elastase (an index of phagocytic cell activation) were examined for up to 10 days following eccentric exercise of the knee extensors of one leg in eight untrained subjects. The exercise bout consisted of 20 repetitions of electrically stimulated eccentric muscle actions on an isokinetic dynamometer. Subjects experienced severe muscle soreness and large increases in plasma creatine kinase activity indicative of muscle fibre damage. Peak soreness occurred at 2 days post-exercise and peak creatine kinase activity [21714 (6416) U x l(-1) mean (SEM)] occurred at 3 days post-exercise (P < 0.01 compared with pre-exercise). Plasma elastase concentration was increased at 3 days post-exercise compared with pre-exercise (P < 0.05), and is presumably indicative of ongoing phagocytic leucocyte infiltration and activation in the damaged muscles. There were no significant changes in plasma zinc and glutamine concentrations in the days following eccentric exercise. We conclude that exercise-induced muscle damage does not produce changes in plasma glutamine or zinc concentrations despite evidence of phagocytic neutrophil activation.

The effects of high-intensity intermittent exercise on the plasma concentrations of glutamine and organic acids.

Glutamine is an essential substrate for the proper functioning of cells of the immune system. Falls in plasma glutamine concentration after exercise may have deleterious consequences for immune cell function and render the individual more susceptible to infection. The purpose of the present study was to examine changes in plasma glutamine concentration (measured using a validated enzymatic spectrophotometric method) following an acute bout of intermittent high-intensity exercise. Eight well-trained male games players took part in the study. Subjects reported to the laboratory following an overnight fast and performed a 1-h cycle exercise task consisting of 20 1-min periods at 100% maximal O2 consumption (VO2max) each separated by 2 min of recovery at 30% VO2max. Venous blood samples were taken before exercise and at 5 min, 1 h, 2.5 h, 5 h and 24 h post-exercise. Glutamine was measured by enzymatic spectrophotometric determination of the ammonia concentration before and after treatment of the plasma with glutaminase (EC 3.5.1.2). Plasma glutamine concentration did not fall in the immediate post-exercise period [pre-exercise 681 (23) microM compared with 663 (46) microM at 5 min post-exercise, mean (SEM)], but fell to 572 (35) microM at 5 h post-exercise (P < 0.05 compared with pre-exercise). Plasma lactate concentration rose to 8.8 (1.0) mM at the end of exercise and fell to 1.8 (0.4) mM at 1 h post-exercise, but plasma concentrations of free fatty acids and beta-hydroxybutyrate both rose substantially in the post-exercise period (to 240% and 400% of pre-exercise levels, respectively). The circulating leucocyte count increased significantly during exercise (P < 0.01), continued to increase in the hours following exercise and peaked at 2.5 h post-exercise (mainly due to a neutrophilia). The fall in the plasma glutamine concentration at 5 h post-exercise could be due to increased renal uptake of glutamine, which generally occurs in conditions of metabolic acidosis or due to a greater removal of glutamine from the plasma resulting from the elevated circulating leucocyte count.

Effect of low- and high-carbohydrate diets on the plasma glutamine and circulating leukocyte responses to exercise.

We examined the effects of a low-carbohydrate (CHO) diet on the plasma glutamine and circulating leukocyte responses to prolonged strenuous exercise. Twelve untrained male subjects cycled for 60 min at 70% of maximal oxygen uptake on two separate occasions, 3 days apart. All subjects performed the first exercise task after a normal diet; they completed the second exercise task after 3 days on either a high-CHO diet (75 +/- 8% CHO, n = 6) or a low-CHO diet (7 +/- 4% CHO, n = 6). The low-CHO diet was associated with a larger rise in plasma cortisol during exercise, a greater fall in the plasma glutamine concentration during recovery, and a larger neutrophilia during the postexercise period. Exercise on the high-CHO diet did not affect levels of plasma glutamine and circulating leukocytes. We conclude that CHO availability can influence the plasma glutamine and circulating leukocyte responses during recovery from intense prolonged exercise.

Effect of exercise-induced muscle damage on the blood lactate response to incremental exercise in humans.

Eccentric muscle actions are known to induce temporary muscle damage, delayed onset muscle soreness (DOMS) and muscle weakness that may persist for several days. The purpose of the present study was to determine whether DOMS-inducing exercise affects blood lactate responses to subsequent incremental dynamic exercise. Physiological and metabolic responses to a standardised incremental exercise task were measured two days after the performance of an eccentric exercise bout or in a control (no prior exercise) condition. Ten healthy recreationally active subjects (9 male, 1 female), aged 20 (SD 1) years performed repeated eccentric muscle actions during 40 min of bench stepping (knee high step; 15 steps x min[-1]). Two days after the eccentric exercise, while the subjects experienced DOMS, they cycled on a basket loaded cycle ergometer at a starting work rate of 150 W, with increments of 50 W every 2 min until fatigue. The order of the preceding treatments (eccentric exercise or control) was randomised and the treatments were carried out 2 weeks apart. Two days after the eccentric exercise, all subjects reported leg muscle soreness and exhibited elevated levels of plasma creatine kinase activity (P < 0.05). Endurance time and peak VO2 during cycling were unaffected by the prior eccentric exercise. Minute volume, respiratory exchange ratio and heart rate responses were similar but venous blood lactate concentration was higher (P < 0.05) during cycling after eccentric exercise compared with the control condition. Peak blood lactate concentration, observed at 2 min post-exercise was also higher [12.6 (SD 1.4) vs 10.9 SD (1.3) mM; P < 0.01]. The higher blood lactate concentration during cycling exercise after prior eccentric exercise may be attributable to an increased rate of glycogenolysis possibly arising from an increased recruitment of Type II muscle fibres. It follows that determination of lactate thresholds for the purpose of fitness assessment in subjects experiencing DOMS is not appropriate.

The effect of exercising to exhaustion at different intensities on saliva immunoglobulin A, protein and electrolyte secretion.

The quality and quantity of saliva may be important in defending against pathogens transmitted via the buccal cavity. The aim of the present study was to examine the effect of cycling to exhaustion at moderate and high intensity on various salivary parameters and the time course of recovery. Eighteen male subjects of mixed physical fitness took part in the study. Subjects performed two bouts of exercise on separate occasions at least one week apart. Following an overnight fast, subjects cycled on an electrically braked cycle ergometer at a work rate equivalent to 80% VO2max until exhaustion. On another occasion they cycled on the same ergometer at 55% VO2max for 3 h or to fatigue (whichever was sooner). The order of the rides was randomised. Timed, unstimulated saliva samples were collected pre-exercise, during exercise, at cessation of exercise and at 1, 2.5, 5 and 24 h post-exercise. Saliva samples were analysed for IgA, total protein and osmolality. Saliva flow rate was significantly reduced by exercise (P < 0.01). Saliva IgA concentration, secretion rate and ratio to osmolality increased during exercise (P < 0.01). IgA to protein ratio did not change significantly during exercise. Since saliva protein secretion rate increased during exercise (P < 0.01) it appears that correcting for loss of saliva water by expressing IgA relative to protein is misleading. IgA secretion rate and IgA to osmolality ratio are more appropriate measures and neither parameter was lowered by exercise. The results of this study indicate that exercise may detrimentally affect the quantity of saliva produced, but not the quality of saliva. Furthermore, when exercise is to exhaustion, the intensity of the bout does not appear to influence the saliva response. Neither exercise protocol had any long term effect on saliva as all variables recovered within 1 h post-exercise.

Effects of submaximal cycling and long-term endurance training on neutrophil phagocytic activity in middle aged men.

OBJECTIVE: To investigate the effects of long term (> 10 years) endurance training and submaximal exercise on the phagocytic activity of circulating neutrophil granulocytes. METHODS: The ability of stimulated blood neutrophils isolated from well trained cyclists [n = 8; VO2max 61.0(SD 8.8) ml.kg-1.min-1; age 38(4) years] and age matched sedentary controls [n = 8; VO2max 37.4 (6.6) ml.kg-1.min-1] to ingest nitroblue tetrazolium was assessed at rest and following a standardised submaximal bout of exercise on a cycle ergometer. RESULTS: Trained subjects had a lower resting blood neutrophil count (P < 0.01). Acute exercise caused a rise (P < 0.01) in the blood neutrophil count irrespective of training status, but the magnitude of the rise was smaller in the trained subjects (P < 0.05). The circulating neutrophil phagocytic capacity was approximately 70% lower in trained individuals at rest compared with the control subjects (P < 0.01). Acute submaximal exercise increased this variable in both groups, but phagocytic capacity remained substantially lower in the trained subjects compared with the controls (P < 0.05) despite the observation that a higher proportion of the circulating neutrophils were stimulated to undergo phagocytosis in the trained subjects [57(14)% v 32(7)%; P < 0.01). CONCLUSIONS: Although neutrophil phagocytic activity is only one variable that contributes to immunological status, prolonged periods of endurance training may lead to increased susceptibility to opportunistic infections by diminishing this activity at rest.

Cardiorespiratory, hormonal and haematological responses to submaximal cycling performed 2 days after eccentric or concentric exercise bouts.

Eccentric muscle actions are known to induce delayed-onset muscle soreness (DOMS) and muscle weakness (reduced static strength and dynamic peak power output) that may persist for several days. The aim of the present study was to determine whether DOMS-inducing exercise affects physiological responses to subsequent submaximal dynamic exercise. Physiological and metabolic responses to a standardized exercise task were measured 2 days after the performance of an eccentric or concentric exercise bout. Six healthy, untrained male subjects aged 30 +/- 7 years (mean +/- S.D.) performed repeated eccentric contractions during 30 min of bench stepping (47-cm step, 15 steps min-1). On another occasion, they performed concentric contractions by walking uphill (8% incline) for 30 min at 5 km h-1, which elicited a similar heart rate response to bench stepping. Two days after the eccentric or concentric exercise, the subjects cycled for 15 min on an electrically braked cycle ergometer at a work rate (172 +/- 37 W) equivalent to 80% VO2 max. The order of the preceding treatments was randomized and the treatments were carried out 2 weeks apart. Two days after the eccentric exercise, all subjects reported leg muscle soreness and exhibited elevated levels of serum creatine kinase activity (P < 0.01) and plasma cortisol concentration (P < 0.05). After uphill walking, the subjects were not sore and serum creatine kinase activity was unchanged. Minute volume, breathing frequency, respiratory exchange ratio, heart rate, rating of perceived exertion, venous blood lactate concentration and plasma cortisol concentration were all higher (P < 0.05) during cycling after eccentric exercise compared with after uphill walking. Increases in plasma catecholamine concentrations and numbers of circulating leucocytes after cycling at 80% VO2 max for 15 min were similar under both experimental conditions, but the delayed leucocytosis (at 150 min post-exercise) was significantly greater (P < 0.01) for the post-eccentric exercise condition. We conclude that dynamic submaximal exercise performed 2 days following exercise with a large eccentric component produces physiological responses that are indicative of a higher relative exercise stress. It is likely that such effects will significantly limit the level and duration of exercise that can be achieved in subsequent training bouts over several days.

Short-term changes in the blood leucocyte and platelet count following different durations of high-intensity treadmill running.

Short-term changes in the blood leucocyte count after exercise are known to be dependent on the intensity of exercise performed. The aim of the present study was to investigate the effects of the duration of high-intensity exercise on changes in the leucocyte and platelet count during the early recovery period. On separate occasions following a standard warm-up, eight healthy subjects (six males, two females) ran at a constant speed of 5.6 m s-1 (20 km h-1) on a level treadmill for 30, 60, 90, 120 or 150 s or to fatigue. Heart rates were increased to near maximal levels within 30 s of exercise. Significant increases in the blood leucocyte count occurred after all exercise durations compared with baseline (pre-exercise) levels. Running for 30 s increased the blood leucocyte count by 35 +/- 10% (x +/- S.D.). Running for 60 s increased the blood leucocyte count by 57 +/- 16%, but running for longer durations did not produce any further significant increase in the immediately post-exercise blood leucocyte count. After exercise to exhaustion, the leucocyte count had increased by 63 +/- 17%. This was mainly due to an increase of lymphocytes (114 +/- 20%) rather than neutrophils (34 +/- 7%). At exhaustion, plasma volume had decreased by 15.9 +/- 2.6% compared with pre-exercise. During 5 min of recovery from exercise, the leucocyte count fell significantly (after 30 and 60 s of running), remained unchanged (90 and 120 s) or increased significantly (150 s and fatigue) compared with immediately post-exercise.(ABSTRACT TRUNCATED AT 250 WORDS)