Influence of carbohydrate on immune function following 2 h cycling

The influence of carbohydrate compared with placebo ingestion on changes in immune cell counts and functions following 2 h intensive cycling was studied in 12 trained cyclists who functioned as their own controls. The subjects performed two tests 2 weeks apart where they cycled for 2 h at approximately 64% Watts(max) while receiving 4 mL x kg(-1) x 15 min(-1) carbohydrate (6%) (Cho) or placebo (Pla) beverages. Blood samples were collected 30 min preexercise, and immediately and 1 h postexercise. The samples were assayed for plasma cortisol and epinephrine, blood leukocyte subset counts, PHA-induced lymphocyte proliferation, and natural killer cell activity (NKCA). Compared with Pla ingestion, Cho attenuated exercise-induced changes in plasma cortisol, blood neutrophil, and monocyte counts, but not in total blood lymphocyte, T cell, and NK cell counts, PHA-induced lymphocyte proliferation, and NKCA. Thus despite a strong attenuating influence of carbohydrate ingestion on exercise-induced changes in plasma cortisol and blood neutrophil and monocyte counts, other immune measures related to lymphocyte subset counts, and function were unaffected.     

Influence of carbohydrate on cytokine and phagocytic responses to 2 h of rowing

PURPOSE: This study examined the influence of carbohydrate (C) versus placebo (P) beverage ingestion on the phagocytic and cytokine responses to normal rowing training by 15 elite female rowers. METHODS: Athletes received C or P before, during and after, two, 2-h bouts of rowing performed on consecutive days. Blood was collected before and 5-10 min and 1.5 h after rowing. Metabolic measures indicated that training was performed at moderate intensities, with some high-intensity intervals interspersed throughout the sessions. RESULTS: Concentrations of blood neutrophils and monocytes, phagocytic activity, and plasma IL-1ra were significantly lower postexercise after C versus P ingestion. No differences were observed for oxidative burst activity, IL-6, IL-8, or TNFalpha. Glucose was significantly higher after 2 h of rowing with C ingestion; however, cortisol, growth hormone, epinephrine, norepinephrine, and CRP were not affected by carbohydrate. CONCLUSIONS: These data indicate that carbohydrate compared with placebo ingestion attenuated the moderate rise in blood neutrophils, monocytes, phagocytosis, and plasma IL-1ra concentrations that followed 2-h bouts of training in elite female rowers. No changes in blood hormone concentrations were found.     

Effect of prolonged exercise and carbohydrate on total neutrophil elastase content

PURPOSE: The purpose of the present study was twofold: first, to assess the effect of prolonged intense exercise on total neutrophil elastase content in endurance-trained cyclists and to determine whether this is associated with postexercise falls in lipopolysaccharide (LPS)-stimulated neutrophil elastase release; and second, to determine the effect of carbohydrate (CHO) ingestion during exercise on these responses. METHODS: In a randomized design, nine trained male cyclists cycled for 2 h at 75% VO(2max) on two occasions with either CHO (6.4%, i.e., 64 g x L-1) or placebo (PLA) beverage ingestion before (5 mL x kg-1), during (2 mL x kg-1), and after (5 mL x kg-1) the exercise. Venous blood samples were obtained at rest, immediately postexercise, and at 1 h postexercise. RESULTS: After exercise, CHO ingestion was associated with a higher plasma glucose concentration (P < 0.05) and fewer numbers of circulating neutrophils compared with the PLA trial (P < 0.01). Neither exercise nor CHO ingestion affected total neutrophil elastase content, yet LPS-stimulated neutrophil elastase release fell postexercise by approximately 47% on the PLA trial (P < 0.01). Values did not change significantly from preexercise on the CHO trial. CONCLUSIONS: These findings suggest that neither exercise nor CHO-beverage ingestion influences the total elastase content of neutrophils. Therefore, changes in neutrophil elastase content cannot account for the fall in LPS-stimulated neutrophil elastase release after prolonged intense exercise or for the blunting of this response with CHO ingestion.     

Leukocyte subset responses during exercise under heat stress with carbohydrate or water intake

PURPOSE: This study investigated leukocyte subset responses to moderate-intensity exercise under heat stress, with water (W) or carbohydrate (CHO) drink ingestion. METHODS: In repeated trials, 13 soldiers consumed either a W or CHO drink during 3 h of walking at 4.4 km x h(-1) with a 5% gradient (15 min rest per hour) under heat stress (35 degrees C and 55% relative humidity). The soldiers wore combat uniforms and carried water bottles and dummy rifles and ammunition, altogether weighing about 11.5 +/- 1.0 kg. RESULTS: Plasma glucose concentration was significantly higher with CHO than W ingestion during exercise (p < 0.01). There were no significant differences between W and CHO conditions in exercise performance, plasma cortisol concentration, heart rate, or core temperature. CHO ingestion significantly moderated the increases in leukocyte (83% in W, 28% in CHO; p < 0.001), monocyte (60% in W, 34% in CHO; p < 0.05), and granulocyte counts (120% in W, 30% in CHO; p < 0.001), but not in lymphocyte count (41% in W, 25% in CHO). CONCLUSIONS: The increases in leukocyte and subset counts during moderate-intensity exercise under heat stress may be comparable to those observed during intense exercise in cool conditions. The response of immune cell counts is blunted by CHO intake during moderate-intensity exercise in the heat, and may not occur through the cortisol pathway.     

Anaerobic exercise induces moderate acute phase response

PURPOSE: It was intended to compare the immune reaction after single and repeated short bouts of anaerobic exercise. METHODS: Twelve unspecifically trained male subjects (27 +/- 2 yr, 75 +/- 2 kg, VO(2peak) 52 +/- 2 mL x min(-1) x kg(-1)) performed one 60-s all-out test (SMT) on a cycling ergometer and the same test followed by eight 10-s all-out tests every 5 min (AN-TS). These tests and one control day (Co-Day) were applied in randomized order. At rest and 15 min, 2 h, and 24 h after cessation of exercise the following venous blood parameters were determined: concentration of neutrophils and (CD16(+ -)) premacrophages (both flow-cytometrically), interleukin 6 and 8 (IL-6, IL-8), C-reactive protein (CRP) and cortisol. RESULTS: Two hours after cessation of exercise the neutrophils increased stronger after AN-TS than after SMT (P < 0.01). The peak in the number of premacrophages occurred earlier after SMT (15 min post; P < 0.01 to Co-Day) than after AN-TS (2 h post; P < 0.05 to Co-Day). IL-6 was elevated at 15 min and 2 h after AN-TS (P < 0.01 to SMT and Co-Day) but only slightly 2 h after SMT (P < 0.01 to Co-Day). There were no significant changes in IL-8. CRP was the only elevated parameter 24 h postexercise exclusively after AN-TS (P < 0.05 to Co-Day). CONCLUSIONS Repeated short anaerobic bouts of cycling lead to an acute phase response, which is more pronounced than after a single bout. Athletes should take care in performing such training sessions several times a week because signs of inflammation are detectable even 24 h after cessation of exercise.     

Effect of an isocaloric carbohydrate-protein-antioxidant drink on cycling performance

PURPOSE: Fourteen male cyclists were studied to compare the effect of carbohydrate-protein-antioxidant beverage (CHOPA) to an isocaloric carbohydrate-only (CHO) beverage on time to fatigue and muscle damage. METHODS: Subjects performed two sets of rides to exhaustion on a cycle ergometer. In each set, the first ride was performed at 70% VO2peak, and the second was performed 24 h later at 80%. CHO or CHOPA was consumed every 15 min during exercise and immediately afterward. Plasma CK and LDH and muscle soreness were measured pre- and postexercise. RESULTS: Time to fatigue was not different between CHO and CHOPA at 70% VO2peak (95.8 +/- 29.7 vs 98.1 +/- 28.7 min), 80% VO2peak (42.3 +/- 18.6 vs 42.9 +/- 21.8 min), or total performance time (138.1 +/- 39.3 vs 140.9 +/- 43.7 min). Postexercise CK was increased (P < 0.05) from baseline in CHO (203 +/- 120 vs 582 +/- 475 U.L(-1)) but not with CHOPA (188 +/- 119 vs 273 +/- 169 U.L(-1)). Similarly, LDH values increased over baseline in CHO (437 +/- 46 vs 495 +/- 64 U.L(-1)) but not with CHOPA (432 +/- 40 vs 451 +/- 43 U.L(-1)). Postexercise CPK and LDH were higher after the CHO trial than after the CHOPA trial. Median postexercise muscle soreness was higher in CHO (3.0 +/- 5.0) than with CHOPA (1.0 +/- 3.0). CONCLUSION: No differences in time to fatigue were observed between the beverages, despite lower total carbohydrate content in the CHOPA beverage. The CHOPA beverage attenuated postexercise muscle damage, as evidenced by CK and LDH values, compared with an isocaloric CHO beverage.     

Delayed leukocytosis and cytokine response to high-force eccentric exercise

PURPOSE: Delayed leukocytosis after strenuous exercise is well documented, but the underlying mechanisms are not clear. In this study, we investigated the relationship between exercise-induced muscle damage and delayed leukocytosis, by utilizing an extreme eccentric exercise protocol. METHODS: We obtained blood samples from 11 healthy men before and after 300 maximal eccentric actions with m. quadriceps. Maximal force-generating capacity was tested before and regularly during the 7 d after exercise. Blood was analyzed for leukocytes, growth hormone (GH), cortisol, granulocyte colony-stimulating factor (G-CSF), macrophage colony-stimulating factor (M-CSF), interleukin (IL)-6, IL-8, monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1beta (MIP-1beta), creatine kinase (CK), C-reactive protein (CRP), complement activation products (C3bc and the terminal complement complex (TCC)), and chemotactic activity in plasma. RESULTS: The force-generating capacity was reduced by 47 +/- 5% (mean +/- SEM) immediately after exercise. Blood concentration of neutrophils and monocytes and the plasma concentration of G-CSF, IL-6, and MCP-1 peaked 6 h after exercise, whereas M-CSF peaked immediately after exercise. Serum concentration of GH and cortisol also peaked immediately after exercise, whereas the serum concentration of CRP and CK peaked after 2 and 4 d, respectively. At 1 h after exercise, chemotactic activity in plasma was increased; at the same time, concentration of C3bc and TCC were decreased. A positive correlation was found between the acute loss of force and the delayed leukocytosis (r = 0.66; P < 0.05), between peak G-CSF and the delayed neutrophilia (r = 0.65, P < 0.05), between acute loss of force and changes in CK (r = 0.65, P < 0.05), between acute loss of force and changes in CRP (r = 0.65, P < 0.05), and between changes in GH and monocyte blood concentrations (r = 0.68, P < 0.05). CONCLUSION: The degree of exercise-induced muscle damage seems to be reflected by the magnitude of the subsequent delayed leukocytosis. The signal between the exercised muscle and bone marrow must be investigated further, but G-CSF and GH are putative mobilizing factors.     

Effect of carbohydrate and prolonged exercise on affect and perceived exertion

INTRODUCTION: It has been reported that perceptions of exertion are attenuated during prolonged cycle exercise, following CHO ingestion. However, no studies to date have examined the influence of such feedings on psychological affect during prolonged exercise, even though affect and perceived exertion are different constructs. PURPOSE: To examine the influence of regular CHO beverage ingestion on affect (pleasure-displeasure) and perceived exertion during prolonged cycle exercise. METHODS: In a randomized, double-blind, counterbalanced design, nine endurance trained males cycled for 2 h at 70% VO2max on two occasions, separated by 1 wk. On each occasion, they consumed either a water placebo (PLA) or a 6.4% carbohydrate-electrolyte solution (CHO) immediately before they cycled (5 mL x kg(-1) body mass) and every 15 min thereafter (2 mL x kg(-1) body mass). Pleasure-displeasure was assessed before, during, and after the prolonged bout of cycling. RESULTS: During exercise, reported pleasure initially improved and was subsequently maintained in the CHO trial, in contrast to a decline reported in the PLA trial. Ratings of pleasure-displeasure were more positive during recovery in the CHO trial compared with the PLA trial (P < 0.05) and the only significant increase (P < 0.05) in pleasure occurred 15 min postexercise in the CHO trial only. RPE increased (P < 0.05) over the course of the bout of cycling and was lower (P < 0.05) 75 min into exercise in the CHO trial. Immediately postexercise, plasma glucose concentration was higher in the CHO compared with the PLA trial (P < 0.05). A main effect of trial was found for plasma cortisol concentration, with higher values reported in PLA trial. CONCLUSION: Results suggest that CHO ingestion enhanced feelings of pleasure during and following prolonged cycling and highlighted the importance of assessing not only "what," but also "how" a person feels.     

Postexercise muscle glycogen recovery enhanced with a carbohydrate-protein supplement

PURPOSE: This study assessed whether liquid carbohydrate-protein (C+P) supplements, ingested early during recovery, enhance muscle glycogen resynthesis versus isoenergetic liquid carbohydrate (CHO) supplements, given early or an isoenergetic solid meal given later during recovery (PLB). METHODS: Two hours after breakfast (7.0 kcal.kg; 0.3 g.kg P, 1.2 g.kg C, 0.1 g.kg F), six male cyclists performed a 60-min time trial (AMex). Pre- and postexercise, vastus lateralis glycogen concentrations were determined using nMRS. Immediately, 1 h, and 2 h postexercise, participants ingested C+P (4.8 kcal.kg; 0.8 g.kg C, 0.4 g.kg P), CHO (4.8 kcal.kg; 1.2 g.kg C), or PLB (no energy). Four hours postexercise, a solid meal was ingested. At that time, C+P and CHO received a meal identical to breakfast, whereas PLB received 21 kcal.kg (1 g.kg P, 3.6 g.kg C, 0.3 g.kg F); energy intake during 6 h of recovery was identical among treatments. After 6 h of recovery, measurement and cycling protocols (PMex) were repeated. RESULTS: Absolute muscle glycogen utilization was 18% greater (P 相似文献   

Effects of increasing insulin secretion on acute postexercise blood glucose disposal

BACKGROUND: Coingestion of protein and/or free amino acids with carbohydrate has been reported to accelerate postexercise muscle glycogen synthesis due to an increase in the insulin response. PURPOSE: To determine the extent to which the combined ingestion of carbohydrate and a casein protein hydrolysate with or without additional free leucine can increase insulin levels during postexercise recovery in endurance-trained athletes. To determine how this affects whole-body plasma glucose disposal during postexercise recovery. METHODS: Fourteen male athletes (age: 24.3 +/- 0.8 yr; VO2max: 62.9 +/- 1.4 mL.kg.min) were subjected to three randomized crossover trials in which they performed 2 h of exercise (55% Wmax). Thereafter, subjects were studied for 3.5 h during which they ingested carbohydrate (CHO: 0.8 g.kg.h), carbohydrate and a protein hydrolysate (CHO-PRO: 0.8 and 0.4 g.kg.h, respectively), or carbohydrate, a protein hydrolysate, and free leucine (CHO-PRO-LEU: 0.8, 0.4, and 0.1 g.kg.h, respectively) in a double-blind fashion. Continuous infusions with [6,6-H2] glucose were applied to quantify plasma glucose appearance (Ra) and disappearance rates (Rd). RESULTS: Plasma insulin responses were 108 +/- 17 and 190 +/- 33% greater in the CHO-PRO and CHO-PRO-LEU trial, respectively, compared with the CHO-trial (P < 0.01). Plasma glucose responses were lower in the CHO-PRO and CHO-PRO-LEU trial compared with the CHO-trial (35 +/- 5 and 42 +/- 11% lower, respectively; P < 0.01). Plasma glucose Ra and Rd were greater in the CHO versus the CHO-PRO and CHO-PRO-LEU trials (P < 0.05). Glucose Rd represented 100 +/- 0.03% of Ra in all trials. CONCLUSIONS: The combined ingestion of a protein hydrolysate and/or free leucine with carbohydrate (0.8 g.kg.h) substantially augments insulin secretion, but does not affect plasma glucose disposal during the first 3.5 h of postexercise recovery in trained athletes.     

Attenuation of increase in circulating cortisol and enhancement of the acute phase protein response in vitamin C-supplemented ultramarathoners

Supplementary vitamin C (2 x 500 mg tablets daily) or a matched placebo was administered to 10 and 6 ultramarathon athletes respectively for 7 days prior to participation in a 90 kilometer running event, as well as on the day of the race and for 2 days after its completion. Circulating concentrations of vitamins A, C and E, as well as those of leukocytes and platelets, myeloperoxidase, C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF), cortisol, and creatine kinase were measured 16 hours before the race and at 30 min, 24 hours, and 48 hours after completion. Pre-race vitamin C concentrations in the supplemented group were unchanged after the race (118.2 +/- 15.9 and 115.9 +/- 11.9 micromol/l) while an increase was observed in the placebo group immediately post-race (85.8 +/- 11.9 to 107.4 +/- 18.8 micromol), with a return to pre-race values after 24 hours. Immediately on completion of the race transient elevations occurred in the concentrations of circulating neutrophils, monocytes and platelets, IL-6, cortisol, CRP, and creatine kinase in both groups. In the supplemented group the concentrations of CRP were significantly higher (p < 0.01) at each of the post-race time-points while those of cortisol were 30% lower immediately post-race. These observations provide evidence that supplementation with vitamin C may blunt the adaptive mobilization of this vitamin from the adrenals during exercise-induced oxidative stress and may be associated with an enhancement of the acute phase protein response and attenuation of the exercise-induced increase in serum cortisol.     

Dose-response effects of ingested carbohydrate on exercise metabolism in women

PURPOSE: The effect of different quantities of carbohydrate (CHO) intake on CHO metabolism during prolonged exercise was examined in endurance-trained females. METHOD: On four occasions, eight females performed 2 h of cycling at approximately 60% .VO2max with ingestion of beverages containing low (LOW, 0.5 g.min(-1)), moderate (MOD, 1.0 g.min(-1)), or high (HIGH, 1.5 g.min(-1)) amounts of CHO, or water only (WAT). Test solutions contained trace amounts of [U-13C] glucose. Indirect calorimetry combined with measurement of expired 13CO2 and plasma 13C enrichment enabled calculation of exogenous CHO, liver-derived glucose, and muscle glycogen oxidation during the last 30 min of exercise. RESULTS: The highest rates of exogenous CHO oxidation were observed in MOD, with no further increases in HIGH (peak rates of 0.33 +/- 0.02, 0.50 +/- 0.03, and 0.48 +/- 0.05 g.min(-1) for LOW, MOD, and HIGH, respectively; P < 0.05 for LOW vs MOD and HIGH). Endogenous CHO oxidation was lowest in MOD (0.99 +/- 0.06, 0.82 +/- 0.08, 0.70 +/- 0.07, and 0.89 +/- 0.09 g.min(-1); P < 0.05 for MOD vs all other trials). Compared with WAT, CHO ingestion reduced liver glucose oxidation during exercise by approximately 30% (P < 0.05 for WAT vs all CHO). Differential rates of muscle glycogen oxidation were observed with different CHO doses (0.57 +/- 0.07, 0.53 +/- 0.08, 0.41 +/- 0.07, and 0.60 +/- 0.09 g.min(-1) for WAT, LOW, MOD, and HIGH respectively; P < 0.05 for MOD vs HIGH). CONCLUSION: In endurance-trained women, the highest rates of exogenous CHO oxidation and greatest endogenous CHO sparing was observed when CHO was ingested at moderate rates (1.0 g.min(-1), 60 g.h(-1)) during exercise.     

Influence of weight training exercise and modification of hormonal response on skeletal muscle growth

To investigate the influence of carbohydrate (CHO) consumption on the acute hormonal response, and chronic adaptation to weight lifting exercise, two studies were conducted. Following a four-hour fast, seven young men (21.3 +/- 3.5 y) performed (on two occasions) a nine-station weight lifting protocol, completing 3 sets of 10 repetitions at 75% of 1RM (series 1). Randomly assigned, one session included the ingestion of a non-caloric placebo, and the other, a 6% CHO solution. For series 2, two groups of young men (21.3 +/- 1.5 y) participated in 12 weeks of progressive resistance weight training. Training for one group included the ingestion of a non-caloric placebo, and the other, a 6% CHO solution. In series 1, weight lifting exercise with CHO ingestion significantly (p < 0.05) elevated blood glucose and plasma insulin levels above baseline, as well as that occurring with the placebo. This resulted in a significant blunting of the cortisol response (7% with CHO compared to 99% with placebo). These findings indicate that CHO consumption during weight lifting exercise can modify the acute hormonal response to exercise. With series 2, CHO consumption continued to blunt the cortisol response to exercise during the twelve weeks of training. This is in contrast to significantly elevated cortisol levels observed for the placebo control group. Corresponding with the modified response patterns were differences in muscle growth. Weight training exercise with CHO ingestion resulted in significantly greater gains in both type I (19.1%) and type II (22.5%) muscle fibre area than weight training exercise alone. The difference in the cortisol response accounted for 74% of the variance (r = 0.8579, p = 0.006) of change in type I muscle fibre area, and 52.3% of the variance (r = 0.7231, p = 0.043) of change in type II muscle fibre area. These findings suggest that the modification of the cortisol response associated with CHO ingestion can positively impact the skeletal muscle hypertrophic adaptation to weigh training.     

Immunoendocrine response to cycling following ingestion of caffeine and carbohydrate

PURPOSE: This study investigated the effect of caffeine consumed with and without carbohydrate (CHO) on immunoendocrine responses after exercise. METHODS: On four occasions, 12 recreational male cyclists cycled for 2 h at 65% V O2max. Sixty minutes before exercise, participants ingested 6 mg.kg(-1) body mass of caffeine (CAF) or placebo (PLA), then during exercise they consumed a 6% CHO or placebo (PLA) drink, providing CAF/CHO, PLA/CHO, CAF/PLA, and PLA/PLA conditions. RESULTS: f-MLP-stimulated neutrophil oxidative burst responses were significantly higher after exercise on CAF/CHO and PLA/CHO (both P<0.05) than PLA/PLA when expressed as a percentage of baseline value. The response on CAF/PLA tended to be higher than PLA/PLA at this point (P=0.056). No significant differences between CAF/CHO, PLA/CHO, and CAF/PLA were observed after exercise; however, only PLA/CHO showed no significant postexercise decline. Coingestion of CAF/CHO significantly attenuated epinephrine (P<0.05) and IL-6 (P<0.05) responses that occurred after ingestion of CAF alone (CAF/PLA) and significantly attenuated the transient alterations in circulating leukocyte (P<0.05) and neutrophil (P<0.01) counts. Plasma cortisol concentration was significantly lower on PLA/CHO than CAF/PLA and PLA/PLA after exercise (P<0.05). Perceived exertion during exercise was significantly lower on CAF/CHO than the other three trials (P<0.05). CONCLUSION: Taken together, this suggests that coingestion of caffeine and CHO has greater influence on immunoendocrine responses than neutrophil functional responses to prolonged exercise.     

Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage

INTRODUCTION: The purpose of this study was to determine whether endurance cycling performance and postexercise muscle damage were altered when consuming a carbohydrate and protein beverage (CHO+P; 7.3% and 1.8% concentrations) versus a carbohydrate-only (CHO; 7.3%) beverage. METHODS: Fifteen male cyclists (mean (.-)VO(2peak) = 52.6 +/- 10.3 mL x kg x min) rode a cycle ergometer at 75% (.-)VO(2peak) to volitional exhaustion, followed 12 - 15 h later by a second ride to exhaustion at 85% (.-)VO(2peak). Subjects consumed 1.8 mL x kg BW of randomly assigned CHO or CHO+P beverage every 15 min of exercise, and 10 mL x kg BW immediately after exercise. Beverages were matched for carbohydrate content, resulting in 20% lower total caloric content per administration of CHO beverage. Subjects were blinded to treatment beverage and repeated the same protocol seven to 14 d later with the other beverage. RESULTS: In the first ride (75% (.-)VO(2peak)), subjects rode 29% longer (P < 0.05) when consuming the CHO+P beverage (106.3 +/- 45.2 min) than the CHO beverage (82.3 +/- 32.6 min). In the second ride (85% (.-)VO(2peak)), subjects performed 40% longer when consuming the CHO+P beverage (43.6 +/- 12.5 min) than when consuming the CHO beverage (31.2 +/- 8.7 min). Peak postexercise plasma CPK levels, indicative of muscle damage, were 83% lower after the CHO+P trial (216.3 +/- 122.0 U x L) than the CHO trial (1318.1 +/- 1935.6 U x L). There were no significant differences in exercising levels of (.-)VO(2), ventilation, heart rate, RPE, blood glucose, or blood lactate between treatments in either trial. CONCLUSION: A carbohydrate beverage with additional protein calories produced significant improvements in time to fatigue and reductions in muscle damage in endurance athletes. Further research is necessary to determine whether these effects were the result of higher total caloric content of the CHO+P beverage or due to specific protein-mediated mechanisms.     

Impact of a competitive marathon race on systemic cytokine and neutrophil responses

PURPOSE: To investigate whether cytokines and neutrophils mediate exercise-related pathogenesis, we examined their responses and possible association after exhaustive exercise. METHODS: Plasma and urine samples were obtained from 10 male runners before and after a 42.195-km marathon race. Major cytokines and neutrophil activation markers [myeloperoxidase (MPO) and lactoferrin (LTF)] were measured by enzyme-linked immunosorbent assays. Functional modulation of standard neutrophils and monocytes by plasma was determined on their luminol-dependent chemiluminescence responses. RESULTS: The race induced peripheral neutrophilia accompanied by an increase in band neutrophils and monocytosis. Plasma MPO and LTF concentrations increased significantly by 1.8 and 1.4 times after the race. There was a greater increase in urine concentrations of MPO and LTF, 12.3 and 3.5 times after exercise, respectively, suggesting that neutrophil activation occurred and that renal clearance exceeded the increase in plasma concentrations. Plasma interleukin (IL)-6, IL-8, IL-10, granulocyte colony-stimulating factor (G-CSF), macrophage CSF (M-CSF), and monocyte chemotactic protein 1 (MCP-1) increased significantly after the race, and urine IL-1beta, IL-6, G-CSF, M-CSF, and MCP-1 increased significantly. The plasma IL-6 responses correlated with the increases of band neutrophil count (r = 0.860, P < 0.01), suggesting IL-6-mediated bone marrow release of neutrophils. Furthermore, the increases in urine MPO concentration were correlated with increases in urine IL-6 (r = 0.868, P < 0.01) and G-CSF (r = 0.875, P < 0.01), suggesting that these cytokines promoted neutrophil activation. However, preincubation of neutrophils and monocytes with postexercise plasma could not cause priming responses, possibly because of the exercise-induced enhancement of plasma antioxidant activity. CONCLUSION: Although many cytokines recruiting and priming neutrophils and monocytes were secreted and functional after exhaustive exercise, overwhelming antioxidant and antiinflammatory defenses were induced, preventing exercise-induced oxidative stress.     

Effects of dietary protein on enzyme activity following exercise-induced muscle injury

PURPOSE: The objective of this investigation was to determine the effects of varying levels of dietary protein on the postexercise increase in serum and muscle enzyme activity normally observed following exercise-induced muscle injury. METHODS: Serum creatine kinase (CK), serum aspartate aminotransferase (AST), and muscle glucose-6-phosphate dehydrogenase (G-6-PD) activities were measured in rats fed for 10 d on high (50%), normal (12%), or low (4%) protein diets following a single bout of eccentric exercise (treadmill running at 16 m.min(-1), -16 degrees incline, 90 min). RESULTS: The exercise intervention resulted in significant increases in serum CK and AST activities in all diet groups. Serum CK demonstrated peak activity immediately postexercise with increases reaching 910+/-94, 594+/-53, and 283+/-52 IU.L(-1) for animals on high, normal, and low protein diets, respectively. Similarly, peak postexercise AST activity for high, normal, and low protein diets reached 193+/-10, 147+/-3, and 162+/-9 IU.L(-1), respectively. The exercise intervention resulted in increases in muscle G-6-PD activity for all diet groups; however, LP rats demonstrated significantly lower values than NP or HP rats. CONCLUSIONS: These data show that dietary protein intake can significantly effect both serum and muscle enzyme activity following acute exercise-induced muscle injury.     

Immune response to a 30-minute walk

PURPOSE: To measure several components of immune changes related to walking 30 min with or without an exercise assist device compared with sitting. METHODS: Fifteen healthy and nonobese female subjects (37.5 +/- 3.1 yr of age) accustomed to regular walking were recruited and tested for aerobic power (VO(2max) 34.4 +/- 1.4 mL.kg(-1).min(-1)). During three randomly assigned 30-min test sessions, subjects functioned as their own controls and either sat in the laboratory, walked at approximately 60% VO(2max), or walked at the same treadmill speed using the BODY BAT Aerobic Exerciser. This exercise assist device resembles a pair of baseball bats seamlessly joined together and is held with both hands and swung to shoulder height across the body in a natural side to side pendulum motion. Saliva and blood samples were collected pre- and postexercise, and 1 h postexercise, with the data statistically analyzed using a 3 x 3 repeated measures ANOVA. RESULTS: Walking with the exercise assist device increased oxygen consumption 11 +/- 2% and heart rate 8 +/- 2 beats.min(-1). The pattern of increase in blood counts for neutrophils, lymphocytes, monocytes, and natural killer cells, plasma interleukin-6 concentration, and PHA-induced lymphocyte proliferation differed significantly when comparing walking with sitting, but no differences were found between walking with or without the exercise assist device. No significant increases over time or interaction effects were measured for plasma cortisol concentration, salivary IgA output, or plasma interleukin-1 receptor antagonist concentration. CONCLUSIONS: The use of an exercise assist device increased oxygen consumption 11% during walking, but did not alter the pattern of change in several components of immunity measured during walking alone in comparison to sitting. Walking caused modest and short-lived changes in immune parameters, most notably for neutrophil and natural killer blood cell counts.     

Relationships between leptin levels and carbohydrate intake during rowing training

AIM: This study was designed to determine the relationship between diet and leptin levels during rowing training. METHODS: Dietary intakes using 3-day food records, training volume and leptin responses to a 90-min exercise (measurement before, at the end and after 2 and 24 h of recovery) were assessed at the beginning and at the end of an 8-month training season for heavyweight rowers. RESULTS: During the training, we observed increases in energy intake and in training volume (12.1+/-1.8 and 14+/-1.4 MJ/day, and 3.8+/-1.1 and 6.5+/-1.8 sessions/week, respectively at the beginning and at the end of the season). Carbohydrate (CHO) and protein intakes were increased (P<0.001 and P<0.05, respectively), whereas those of lipid were unchanged (P=0.08). Leptin levels at rest were unchanged, while delayed decreases occurred (at 2 h postexercise) in response to the 90-min exercise (P<0.01). At the end of the season, postexercise and 24 h postexercise leptin levels were positively correlated to CHO intake (r=0.62 and r=0.69, respectively; P<0.05). CONCLUSION: There is an increase in CHO intake over a training season for rowers. Our results suggested that repeated hypoleptinemia in response to acute exercise triggered the particular choice of CHO in order to insure the energy homeostasis.