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.     

Effects of 4 h preexercise carbohydrate feedings on cycling performance

This study determined the effects of consuming three different amounts of liquid carbohydrate 4 h before exercise on the metabolic responses during exercise and on exercise performance. Four hours before exercise subjects consumed either 45 (L) or 156 (M) g of carbohydrate in isocaloric feedings and either 0 (P) or 312 (H) g of carbohydrate. Interval cycling was undertaken for 95 min, followed by a performance trial. Blood glucose had reached basal 1 h after all feedings; blood insulin had reached basal 3 h after ingestion of P, L, and M but was still 84% higher for H at the start of exercise. During exercise insulin averaged 48% higher for H than P. Blood glucose decreased 16% during exercise for P, L, and M, whereas for H there was a transient drop the first 15 min of exercise, after which glucose increased and remained constant throughout exercise. More carbohydrate oxidation occurred during exercise for H vs P, whereas results were similar for L and M. Ingestion of H improved performance by 15% as compared with P, whereas performance was similar for L and M. These results indicate that, despite elevated insulin at the start of and during exercise, consumption of 312 g of carbohydrate 4 h before moderately intense prolonged exercise can improve performance, perhaps via an enhancement of carbohydrate oxidation.     

Immune changes: 2 h of continuous vs. intermittent cycling

Immune changes following 2 h of intensive cycling with or without rest intervals were measured in trained cyclists (n = 12) who functioned as their own controls during two test sessions that were separated by two weeks. Subjects cycled for 2.0 h at approximately 64 % Watts(max) continuously (C) or with 3-min rest intervals (R) interspersed every 10 min (2.6 h total time), with the order of the sessions randomized. Blood samples were collected 30-min pre-exercise, and immediately and 1-h postexercise, and assayed for blood leukocyte subset counts, plasma IL-6, IL-10, IL-1ra, IL-8, PHA-induced lymphocyte proliferation, and natural killer cell activity (NKCA). Significant time effects were measured for all immune measures, but no significant differences in the pattern of change were found between C and R exercise trials. In conclusion, immune changes induced by 2 h of intense and prolonged exercise paralleled those measured when athletes rested 3 min every 10 min of exercise.     

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.     

Muscle recruitment pattern in cycling: a review

Studies have indicated that the muscles work in a systematic and coordinated way to generate and direct power from the human body to the crank during cycling. Understanding of the muscle involvement or recruitment pattern during cycling will be useful for developing specific and effective muscle training and rehabilitation programs for cyclists. Moreover, it will also facilitate the use of the cycling ergometer for therapeutic purpose. This paper reviews the current literature on muscle recruitment pattern during cycling and the effects of muscle fatigue, cadence, riding posture and seat height on this recruitment pattern. In the power phase or ‘downstroke’, the hip, knee and ankle joints extend simultaneously for the pushing action, whilst in the recovery phase or ‘upstroke’, they flex together to pull the pedal back to the top dead center of the crank cycle. Recent studies have indicated that in this repeated sequence, the mono-articular muscles are mainly involved in the generation of positive work whereas the biarticular muscles are responsible for regulating force transmission. Some muscles co-activate during cycling to provide synergistic actions and other functional needs.Muscle fatigue is an important factor affecting cycling performance. It has been reported that muscle fatigue in the lower body would alter the cycling motion and muscle activation pattern. Therefore, studying the change of muscle activation pattern during cycling at the fatigued level may shed light on the sequel of local muscle fatigue. A muscle training program specifically for cycling can then be designed accordingly. Additionally, the change of cadence during cycling will affect the muscle recruitment pattern. There is a unique cadence that minimizes the muscle activation level at a specific level of power output. This cadence will increase as the power output increases. The change of riding posture from sitting to standing renders the pelvis unsupported and the body weight will assist the power phase of pedalling. Similarly, changes to the seat height will alter the posture which will affect the directions of muscle actions to the crank, thus changing the muscle recruitment pattern.     

Fluid replacement after dehydration: influence of beverage carbonation and carbohydrate content.

This investigation evaluated the effects of beverage carbonation and carbohydrate (CHO) content on fluid replacement following exercise/thermal dehydration. On four occasions separated by at least 7 days, eight healthy men cycled at 50% of VO2max in a hot environmental chamber (40 degrees C, 40% relative humidity) until a weight loss of 4.12 +/- 0.22% was attained. In the subsequent four hours, subjects ingested one of four solutions at 15-min intervals. The total volume ingested equalled that lost during dehydration. The solutions were administered in randomized order and varied in their carbonation and carbohydrate (CHO) content: 1. CK: carbonated 10% glucose-fructose solution, 2. NCK: non-carbonated 10% glucose-fructose solution, 3. CNK: carbonated non-caloric solution, and 4. NCNK: non-carbonated non-caloric solution. Plasma volume changes, total plasma protein concentration, plasma osmolality, and the plasma glucose concentration were determined at rest before and after dehydration, and at 30, 90, 150, and 240 min of recovery. Plasma volume changes and the plasma protein concentration were not different (p greater than 0.05) between treatments. Values for the plasma glucose concentration and the change in plasma osmolality were significantly elevated when CHO beverages were ingested when compared with non-CHO beverage ingestion. Five-min cycling bouts were performed at 70% of VO2max before and after dehydration and at 60, 120, 180, and 240 min of rehydration. The respiratory exchange ratio was elevated in both of the CHO treatments when compared with both of the non-CHO treatments at 60, 120, 180 and 240 min of rehydration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of pre-exercise carbohydrate feedings on endurance cycling performance

Six men were studied to compare the effects of pre-exercise carbohydrate feedings on endurance performance and muscle glycogen utilization during prolonged exercise. Trials consisted of a cycling ride to exhaustion at 75% maximal oxygen uptake preceded by the ingestion of either 75 g of glucose in 350 ml of water (GLU), 75 g of fructose in 350 ml of water (FRU), or 350 ml of an artificially sweetened and flavored placebo (CON). No differences were observed between trials for oxygen uptake, respiratory exchange ratio, heart rate, or exercise time to exhaustion (CON = 92.7 +/- 5.2 min, FRU = 90.6 +/- 12.4, and GLU = 92.8 +/- 11.3, mean +/- SE). Blood glucose was elevated as a result of the GLU feeding, but fell rapidly with the onset of exercise, reaching a low of 4.02 +/- 0.34 mmol X l-1 at 15 min of exercise. Serum insulin also increased following the GLU feeding but had returned to pre-drink levels by 30 min of exercise. No differences in blood glucose and insulin were observed between FRU and CON. Muscle glycogen utilization during the first 30 min of exercise (CON = 46.3 +/- 8.2 mmol X kg-1 wet weight, FRU = 56.3 +/- 3.0 mmol X kg-1 wet weight, GLU = 50.0 +/- 4.9 mmol X kg-1 wet weight) and total glycogen use (CON = 93.4 +/- 11.1, FRU = 118.8 +/- 10.9, and GLU = 99.5 +/- 4.3) were similar in the three trials.(ABSTRACT TRUNCATED AT 250 WORDS)     

Alterations in running economy and mechanics after maximal cycling in triathletes: influence of performance level

The effects of the triathlon performance level on the metabolic and mechanical alterations in running after an exhaustive cycling exercise were studied. Eight elite and 18 middle-level triathletes completed two 7 min runs on a treadmill at a velocity corresponding to that sustained during a triathlon before and after maximal cycling exercise. Energy cost of running was quantified during the last minute of each run from the net oxygen uptake. External mechanical cost was quantified during the last minute of each run from displacements of the centre of mass using a kinematic arm. The effect of cycling on the running energy cost differed when comparing the elite (from 4.01+/-0.46 to 3.86+/-0.34J x kg(-1) x m(-1)) and the middle-level triathletes (from 3.67+/-0.37 to 3.76+/-0.39 x kg(-1) x m(-1) (P<0.01). The effect of cycling on the respiratory muscle O2 was more important (P<0.05) for the middle-level (from 120.1+/-27.2 to 166.4+/-47.8 ml x min(-1)) than for elite triathletes (from 124.5 +/- 24.5 to 143.7 +/- 28.9 ml x min(-1)). A tendency to a decrease of the mechanical cost and of the vertical displacement of the centre of mass during the braking phase was observed for the elite triathletes, suggesting a better leg stiffness regulation than for their less successful counterparts.     

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.     

用脉图方法观察2.5h头低位15°倾斜期间心血管系统的变化

为了解航天员航天初期心血管功能的动态变化，用脉图方法观察了１９名被试者在２．５ｈ头低位１５°倾斜期间的心血管功能。结果表明，ＨＤＴ期间心血管指标变化可分为现时期：急性反应期和反应期。     

Time- and dose-dependent changes of intracellular cytokine and cytokine receptor profile of Ewing tumour subpopulations under the influence of ionizing radiation

PURPOSE: Cytokines and their corresponding cell surface receptors are involved in intercellular signalling pathways and in the radioresistance of normal and malignant cells. The aim was the characterization of the expression of intracellular cytokines, their receptors and apoptosis-associated markers under the influence of radiation. MATERIAL AND METHODS: Two Ewing tumours were characterized in vitro before and 4, 24 and 72 h after radiation with 5 and 10 Gy, and in vivo 4, 6 and 15 days after radiation with 5 and 30 Gy by five parameter flow cytometry. Direct fluorescence-conjugated antibodies directed against intracellular cytokines (interferon-gamma, tumour necrosis factor [TNF]-alpha, interleukin 1) and their receptors (CD119, CD120a, CD121a) were used. Annexin V and 7-amino-actinomycin D were used to identify radiation-induced apoptosis. RESULTS: Inter- and intra-individual heterogeneities were identified by the expression of cytokine receptors and the intracellular cytokine profile before radiation. Time- and dose-dependent up-regulation of the cytokines TNF-alpha and interleukin 1 were found in vitro. In vivo, an up-regulation of CD120a and CD121a was detectable on tumour cell subpopulations. For interferon-gamma and CD119, no changes were seen. CONCLUSIONS: The observed radiation-induced changes of cytokine and receptor profile are an indication for complex intercellular interactions in view of radioresistance-associated mechanisms between cell populations within one individual tumour. The observed heterogeneous response on radiation might have therapeutic implications for an individualized therapy based on combined radiation and cytokine modulation, defined by flow cytometric characterization of markers potentially informative for radioresistance.     

Effects of graded carbohydrate supplementation on the immune response in cycling

PURPOSE: This study examined the acute immune response after three standardized cycling sessions of 4-h duration in the field with varying carbohydrate (CHO) supplementation in a randomized, double-blind, placebo-controlled fashion. We hypothesized that the ingestion of carbohydrate (6 or 12% CHO beverages; placebo (P) without CHO) during exercise attenuates the exercise-induced immune response in a dose-dependent manner. METHODS: A total of 14 male competitive cyclists and triathletes (age: 25 +/- 5 yr; height: 180 +/- 7 cm; weight: 72 +/- 9 kg; VO2max: 67 +/- 6 mL.min(-1).kg(-1)) cycled for 4 h on a 400-m track at a given workload of 70% of the individual anaerobic threshold (198 +/- 21 W). Leukocyte and lymphocyte subpopulations were measured by flow cytometry before, immediately, and 1 and 19 h after exercise. In addition, C-reactive protein (CRP) interleukin 6 (IL-6), and cortisol were determined. RESULTS: The exercise-induced increase in leukocytes, neutrophils, and monocytes was significantly attenuated to the same extent by 6 and 12% CHO (P < 0.001). No differences could be demonstrated for lymphocytes and natural killer cells. The increase in CRP was attenuated significantly by 12% CHO only (P < 0.05), whereas the increase in cortisol and IL-6 was significantly reduced by 6 and 12% CHO (P < 0.001). The postexercise neutrophilia, which dominated the exercise-induced leukocytosis, was strongly related to the postexercise concentration of cortisol (r = 0.72; P < 0.001). CONCLUSIONS: Because of the lacking dose-dependent difference, the ingestion of at least 6% CHO beverages can sufficiently attenuate the exercise-induced immune response and stress, especially in phagocytizing cells (neutrophils and monocytes) by the reduced release of cortisol.     

The effect of fluid and carbohydrate feedings during intermittent cycling exercise

The purpose of this study was to determine the effect of ingesting water or carbohydrates solutions on physiologic function and performance during 1.6 h of intermittent cycling exercise in the heat (dry bulb temperature = 33 degrees C). Thirteen male subjects (24 to 35 yr) completed four separate rides. Each ride consisted of intermittent steady-state cycling (at 55 and 65% VO2max) interspersed with five rest periods. A timed 480 revolution cycling task completed each experimental session. During each rest period, subjects consumed 2 ml.kg-1 body weight of water placebo or solutions of 5% glucose polymer, 6% sucrose/glucose, or 7% glucose polymer/fructose. Beverages were administered in double-blind, counter-balanced order. No differences were observed among subjects in response to beverage treatments for changes in plasma concentrations of total proteins, sodium, potassium, lactate, or in osmolality, percent change in plasma volume, heart rate, oxygen uptake, respiratory exchange ratio, rating of perceived exertion, sweat rate, rectal temperature, or mean skin temperature. Compared to water placebo, the carbohydrate treatments produced higher plasma glucose values following 1 h cycling (P less than 0.01). Mean (SD) times for the 480 revolution cycling task: water placebo = 432 (43) s; glucose polymer = 401 (52) s; *sucrose/glucose = 384 (39) s; and *glucose polymer/fructose = 375 (30) s, where = P less than 0.001 compared to water placebo. Physiologic function was similarly maintained during exercise by all beverage treatments, while ingestion of sucrose/glucose and glucose polymer/fructose resulted in improved end-exercise cycling performance.     

Pre-exercise carbohydrate status influences carbohydrate-mediated attenuation of post-exercise cytokine responses

Most studies investigating the effects of acute carbohydrate (CHO) ingestion on post-exercise cytokine responses have involved fasted athletes. This study characterised the effects of acute CHO beverage ingestion preceded by consumption of a CHO-containing pre-exercise meal. Sixteen highly-trained male cyclists/triathletes (age: 30.6 +/- 5.6 y; V O (2max): 64.8 +/- 4.7 ml . kg . min (-1) [mean +/- SD]) undertook two cycle ergometry trials involving randomised consumption of a 10 % CHO beverage (15 mL . kg (-1) . hr (-1)) or water (H (2)O). Trials were undertaken 2 h after a breakfast providing 2.1 g CHO . kg (-1) body mass (BM) (48 kJ . kg (-1) BM) and consisted of 100 min steady state cycle ergometry at 70 % V O (2max) followed by a time trial of approximately 30 min duration. Blood samples were collected pre-, post- and 1 h post-exercise for measurement of Interleukin (IL)-6, IL-8, IL-10 and IL-1ra. Time-trial performance was not substantially different between CHO and H (2)O trials (4.5 %, p = 0.42). Neither IL-6 nor IL-8 responses were substantially reduced in the CHO compared to the H (2)O trial. There was a substantial reduction in IL-10 (32 %, p = 0.05) and IL-1ra (43 %, p = 0.02) responses at 1 h post-exercise with CHO compared to H (2)O ingestion. In conclusion, the previously shown attenuating effects of CHO ingestion during exercise on cytokine responses appear reduced when athletes consume a CHO-containing pre-exercise meal.     

Gastric emptying: influence of prolonged exercise and carbohydrate concentration

Gastric emptying: influence of prolonged exercise and carbohydrate concentration, Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 269-274, 1989. The purpose of this study was to examine the effects of serial feedings of different concentrations of carbohydrate (CHO) on gastric emptying and to compare the rates of gastric emptying at rest and during prolonged exercise. Solutions of 0, 6, 12, and 18 g. 100 ml-1 (WP, CHO-6, CHO-12, and CHO-18, respectively) were tested. Ten trained male cyclists performed five trials involving 120 min of cycling. The first 105 min were at 70% of VO2max, and the final 15 min were an all-out self-paced performance ride. In one of the five trials, the subjects rode intermittently, completing seven 15-min rides at 70% of VO2max, with 3 min of rest between each ride. Every 15 min, approximately 150 ml (8.5 ml.kg-1.h-1) of one of the four test solutions were consumed. (In the intermittent trial, the CHO-12 solution was used.) Subjects were also tested during 120 min of seated rest using the above feeding schedule (6% solution). Gastric residue was determined by stomach aspiration following the performance ride. The volumes emptied during the CHO-12 and CHO-18 trials (1,049.8 and 889.2 ml) were significantly different from each other and were less than during the WP and CHO-6 trials (1,210.3 and 1,185.6 ml) (P less than 0.05). CHO delivery was significantly higher in the CHO-12 and CHO-18 trials (126 and 160 g) compared to the CHO-6 trial (71.1 g).(ABSTRACT TRUNCATED AT 250 WORDS)     

Placebo effect of carbohydrate feedings during a 40-km cycling time trial

PURPOSE: The placebo effect, a favorable outcome from belief that one has received a beneficial treatment, may be an important phenomenon in athletic performance. We have therefore investigated the placebo effect of a carbohydrate supplement on endurance performance. METHODS: Forty-three competitive endurance cyclists (2 female, 41 male) performed two simulated 40-km time trials on an air-braked ergometer. In the first trial they ingested water to establish baseline performance (mean power 265 +/- 46 W for 58 +/- 4 min, mean +/- SD). For the second trial 6-8 d later they were randomized to two groups: one group ingested 16 mL x kg(-1) of a drink containing 7.6 g x 100 mL(-1) carbohydrate; the other ingested an indistinguishable noncaloric placebo drink. Cyclists in each group were further randomized to three subgroups according to whether they were told the drink contained carbohydrate, placebo, or either (not told). RESULTS: Changes in mean power in the second trial were: told carbohydrate, 4.3 +/- 4.8%; told placebo, 0.5 +/- 5.8%; and not told, -1.1 +/- 8.5%. The difference between the told-carbohydrate and told-placebo groups was 3.8% (95% likely range 7.9 to -0.2%). The change in performance in the not-told group was more variable than that of the told groups by a factor of 1.6 (2.6 to 1.0). The real effect of carbohydrate was a slight reduction in power of 0.3% (4.4 to -3.8%). CONCLUSIONS: (a) The placebo effect of a potentially ergogenic treatment during unblinded laboratory time trials lasting approximately 1 h is probably a small but worthwhile increase in endurance power. (b) Blinding subjects to the treatment increases individual differences in endurance effort, which may reduce precision of performance outcomes in controlled trials.     

中药对大鼠急性骨骼肌拉伤后骨骼肌α-actinmRNA表达的影响

本研究建立了急性骨骼肌拉伤的动物实验模型 ,观察了不同治疗措施对拉伤后动物骨骼肌α -actinmRNA表达的影响。结果表明 :(1)急性拉伤后即刻 ,动物骨骼肌α-actinmRNA表达量显著增高 ,伤后第 1天、第 2天保持显著性高水平 ,至第 5天恢复至正常水平 ,但第 14天又显著增高 ;(2 )舒筋活血类中药抑制骨骼肌拉伤后α -actinmRNA表达的第 2次升高。研究提示 ,舒筋活血类中药能更有效地促进急性骨骼肌拉伤后α -actinmRNA表达的恢复。     

Exogenous carbohydrate spares muscle glycogen in men and women during 10 h of exercise

PURPOSE: The purpose of the study was to evaluate the effects of carbohydrate (CHO) supplementation on whole-body and net muscle substrate use during 10 h of discontinuous exercise, simulating occupational settings in men and women. METHODOLOGY: Recreationally trained subjects (N = 7 males, N = 6 females) performed a graded exercise test on a treadmill (TM) and cycle ergometer (CE) to determine ventilatory threshold (VT) and V O2peak. In a double-blind, randomized crossover design, subjects received either CHO [20% maltodextrin (0.6 g.kg FFM.h)] or flavored placebo (PLA) drink each hour across 10 h of exercise. Exercise intensity was 71.3 +/- 3% and 72.4 +/- 4% VT for TM and CE, respectively. Hourly exercise included 9 min of upper-body ergometery, 19 min of cycling, and 20 min of treadmill walking, with a 1-min transition between modes, followed by a 10-min rest and feeding period. The protocol was selected to simulate arduous occupational settings. Vastus lateralis biopsies were obtained before and after exercise. Expired gases were collected every other hour to establish average rates of whole-body CHO and fat oxidation. Blood glucose (BG) was measured continuously. RESULTS: Whole-body CHO oxidation was maintained during CHO trial compared with the PLA trial. Net muscle glycogen use was 52% higher for the PLA trial (176.0 +/- 16.7, 117.0 +/- 20.9 and 164.5 +/- 11.0, 133.8 +/- 10.9 mmol.kg w.w. for PLA and CHO, respectively, P < 0.05). There were no significant sex-specific differences in glycogen use, whole-body substrate oxidation, or BG values. CONCLUSION: The ingestion of CHO during long-duration exercise decreases net muscle glycogen use while better maintaining whole-body carbohydrate oxidation, and potentially increasing performance in field settings. There are limited differences in sex-specific substrate oxidation.     

Gastric emptying during 1 h of cycling and running at 75% VO2max

The purpose of this study was to compare gastric emptying (GE) responses during intense, prolonged cycling and running. It is important to discern whether gastric emptying (GE) responses are exercise-mode specific, since the findings of cycling and running studies are often compared and applied to one another. Ten male biathletes cycled (CY) and ran (R) for 1 h at 75% of their mode-specific VO2max or rested (S) and consumed water (SW, CYW, RW) or a 7% carbohydrate solution (SC, CYC, RC) at a rate of 10 ml.kg-1.h-1 (approximately 180 ml at 0, 15, 30, and 45 min). No differences were found between CYW, CYC, RW, RC, and SC for volume of drink emptied (mean +/- SE) (522.8 +/- 47.9 ml) and GE rate (range, 8.2 +/- 0.9 (RC) to 9.3 +/- 0.6 ml.min-1 (SC]. A mean of 72.7 +/- 5.7% of the total consumed volume was emptied. The GE rate during SW was significantly (P less than 0.05) greater than the other conditions (11.3 +/- 0.4 ml.min-1, 94.0 +/- 1.9% of total consumed volume emptied). Substantial volumes of water and a 7% carbohydrate solution are thus emptied from the stomach during prolonged, intense running and cycling, with no differences in GE between these exercise modes. These data suggest that recommendations concerning GE are reciprocal between running and cycling bouts similar to those in the current study.