The influence of carbohydrate and protein ingestion during recovery from prolonged exercise on subsequent endurance performance

Abstract

Ingesting carbohydrate plus protein following prolonged exercise may restore exercise capacity more effectively than ingestion of carbohydrate alone. The objective of the present study was to determine whether this potential benefit is a consequence of the protein fraction per se or simply due to the additional energy it provides. Six active males participated in three trials, each involving a 90-min treadmill run at 70% maximal oxygen uptake (run 1) followed by a 4-h recovery. At 30-min intervals during recovery, participants ingested solutions containing: (1) 0.8 g carbohydrate · kg body mass (BM)^?1 · h^?1 plus 0.3 g · kg^?1 · h^?1 of whey protein isolate (CHO-PRO); (2) 0.8 g carbohydrate · kg BM^?1 · h^?1 (CHO); or (3) 1.1 g carbohydrate · kg BM^?1 · h^?1 (CHO-CHO). The latter two solutions matched the CHO-PRO solution for carbohydrate and for energy, respectively. Following recovery, participants ran to exhaustion at 70% maximal oxygen uptake (run 2). Exercise capacity during run 2 was greater following ingestion of CHO-PRO and CHO-CHO than following ingestion of CHO (P ≤ 0.05) with no significant difference between the CHO-PRO and CHO-CHO treatments. In conclusion, increasing the energy content of these recovery solutions extended run time to exhaustion, irrespective of whether the additional energy originated from sucrose or whey protein isolate.     

Optimization of insulin-mediated creatine retention during creatine feeding in humans

Abstract

The aim of this study was to determine whether creatine ingested in combination with relatively small quantities of essential amino acids, simple sugars, and protein would stimulate insulin release and augment whole-body creatine retention to the same extent as a large bolus of simple sugars. Seven young, healthy males underwent three randomized, 3-day experimental trials. Each day, 24-h urine collections were made, and on the second day participants received 5 g creatine + water (creatine trial), 5 g creatine + ～95 g dextrose (creatine + carbohydrate) or 5 g creatine + 14 g protein hydrolysate, 7 g leucine, 7 g phenylalanine, and 57 g dextrose (creatine + protein, amino acids, and carbohydrate) via naso-gastric tube at three equally spaced intervals. Blood samples were collected at predetermined intervals after the first and third naso-gastric bolus. After administration of the first and third bolus, serum insulin concentration was increased by 15 min (P < 0.05) in the creatine + carbohydrate and creatine + protein, amino acids, and carbohydrate trials compared with creatine alone, and plasma creatine increased more following creatine alone (15 min, P < 0.05) than in the creatine + carbohydrate and creatine + protein, amino acids, and carbohydrate trials. Urinary creatine excretion was greater with creatine alone (P < 0.05) than with creatine + carbohydrate and creatine + protein, amino acids, and carbohydrate. Administration of creatine + protein, amino acids, and carbohydrate can stimulate insulin release and augment whole-body creatine retention to the same extent as when larger quantities of simple sugars are ingested.     

射箭运动员在不同训练时期血液氨基酸变化的研究

目的：观察射箭运动员在不同运动负荷状态时的血液氨基酸的变化。方法：用高效液相法测定射箭运动员冬训期间不同的训练时期血液中四种氨基酸——门冬氨酸（Asp）、谷氨酸（Glu）、甘氨酸（（Gly）和r-氨基丁酸（GABA）的含量。结果：在进行中等强度训练期和大强度训练期运动后1h血浆中谷氨酸的血浆浓度明显升高（P〈0．01）。而在大强度训练期后明显下降,甚至低于安静值;门冬氨酸在中等强度训练后血浆浓度也升高（P〈0．05）,在疲劳期则呈下降趋势,但仍高于安静值;在进行中等强度训练期和大强度训练期运动1h后血浆中r-氨基丁酸、甘氨酸均上升。大强度训练期明显升高,与训练前期安静值相比有显著意义（P〈0．01）。结论：射箭运动员在长时间大强度大运动量训练后,血液中的氨基酸会发生变化,中枢疲劳可能从血浆氨基酸的变化反映出来。     

模拟不同海拔高原训练对大鼠骨骼肌蛋白质与糖原含量的影响

用低压氧舱模拟海拔２０００米、３０００米高度进行１周耐力训练,观察对骨骼肌细胞蛋白质和肌糖原含量的影响,验证１周时间高原训练的效果,同时观察各高度训练１周后平原效应期２周间的变化。结果表明：高原耐力训练可导致骨骼肌蛋白质分解代谢增强,蛋白质净降解,并有随高度升高而加剧的趋势,同时可提高骨骼肌中肌糖原贮量;不同海拔高度１周耐力训练后的平原效应期间,骨骼肌蛋白质含量第１周即可完全恢复,第２周保持稳定水平,肌糖原含量第１周下降,第２周显著回升。本研究支持高原训练的高度应在２０００～３０００米之间,回平原参赛时间应选择在下高原３天以内或２周以后的观点