The purpose of this study was to compare fluid retention of carbohydrate plus protein, a carbohydrate-only, and water following 2.5% body weight (BW) loss. Thirteen subjects dehydrated to 2.5% of BW, then ingested a CHO (6%) plus protein drink (1.5%; CP), a 6% CHO drink, or water (WA) at a volume equal to BW loss during a 3-h recovery. Fluid retention was significantly greater for CP (88 ± 4.7%) than CHO (75 ± 14.6%), which was greater than WA (53 ± 16.1%). Serum and urine osmolalities were greater for CP (284.7 ± 5.0; 569.4 ± 291.4 mOsm/kg) than CHO (282.6 ± 5.2; 472.9 ± 291.5 mOsm/kg) which were greater than WA (280.6 ± 5.9, 303.7 ± 251.5 mOsm/kg). Results indicate that fluid retention for CP was 15% greater than CHO and 40% greater than WA. Water ingestion led to a dilution of the serum and resulted in only 53% fluid retention.
John Seifert, Joseph Harmon and Patty DeClercq
Kristen L. MacKenzie-Shalders, Neil A. King, Nuala M. Byrne and Gary J. Slater
Increasing the frequency of protein consumption is recommended to stimulate muscle hypertrophy with resistance exercise. This study manipulated dietary protein distribution to assess the effect on gains in lean mass during a rugby preseason. Twenty-four developing elite rugby athletes (age 20.1 ± 1.4 years, mass 101.6 ± 12.0 kg; M ± SD) were instructed to consume high biological value (HBV) protein at their main meals and immediately after resistance exercise while limiting protein intake between meals. To manipulate protein intake frequency, the athletes consumed 3 HBV liquid protein supplements (22 g protein) either with main meals (bolus condition) or between meals (frequent condition) for 6 weeks in a 2 × 2 crossover design. Dietary intake and change in lean mass values were compared between conditions by analysis of covariance and correlational analysis. The dietary manipulation successfully altered the protein distribution score (average number of eating occasions containing > 20 g of protein) to 4.0 ± 0.8 and 5.9 ± 0.7 (p < .01) for the bolus and frequent conditions, respectively. There was no difference in gains in lean mass between the bolus (1.4 ± 1.5 kg) and frequent (1.5 ± 1.4 kg) conditions (p = .91). There was no clear effect of increasing protein distribution from approximately 4–6 eating occasions on changes in lean mass during a rugby preseason. However, other dietary factors may have augmented adaptation.
Paolo C. Colombani, Eva Kovacs, Petra Frey-Rindova, Walter Frey, Wolfgang Langhans, Myrtha Arnold and Caspar Wenk
A field study was performed to investigate the acute influence of a milk protein hydrolysate supplemented drink (CHO+PRO) on metabolism during and after a marathon run compared to the same drink without protein (CHO). Carbohydrate metabolites and hormones were not influenced by CHO+PRO. Levels of plasma free fatty acids were significantly lower and levels of urea and most amino acids were significantly higher with CHO+PRO. Sweat urea and ammonia nitrogen excretion during the run as well as urinary 3-methylhistidine excretion during the entire exercise day was similar with both treatments. Urinary total nitrogen was significantly increased and urinary pH decreased with CHO+PRO. It was concluded that the supplemented protein was absorbed and probably at least partially oxidized during the run and that no obvious negative metabolic effects occurred. CHO+PRO did not acutely affect myofibrillar protein breakdown as assessed by the 3-methylhistidine method: however, total body protein breakdown was not measured.
Ryan D. Andrews, David A. MacLean and Steven E. Riechman
Variability in protein consumption may influence muscle mass changes induced by resistance exercise training (RET). We sought to administer a post-exercise protein supplement and determine if daily protein intake variability affected variability in muscle mass gains. Men (N = 22) and women (N = 30) ranging in age from 60 to 69 y participated in a 12-wk RET program. At each RET session, participants consumed a post-exercise drink (0.4 g/kg lean mass protein). RET resulted in significant increases in lean mass (1.1 ±1.5 kg), similar between sexes (P > 0.05). Variability in mean daily protein intake was not associated with change in lean mass (r < 0.10, P > 0.05). The group with the highest protein intake (1.35 g · kg−1 · d−1, n = 8) had similar (P > 0.05) changes in lean mass as the group with the lowest daily protein intake (0.72 g · kg−1 · d−1, n = 9). These data suggest that variability in total daily protein intake does not affect variability in lean mass gains with RET in the context of post-exercise protein supplementation.
Sharon L. Miller, Carl M. Maresh, Lawrence E. Armstrong, Cara B. Ebbeling, Shannon Lennon and Nancy R. Rodriguez
The interaction of substrates and hormones in response to ingestion of intact proteins during endurance exercise is unknown. This study characterized substrate and hormone responses to supplementation during endurance exercise. Nine male runners participated in 3 trials in which a non-fat (MILK), carbohydrate (CHO), or placebo (PLA) drink was consumed during a 2-hour treadmill >· run at 65% V̇O2max. Circulating levels of insulin, glucagon, epinephrine, norepi-nephrine, growth hormone, testosterone, and cortisol were measured. Plasma substrates included glucose, lactate, free fatty acids, and select amino acids. Except for insulin and cortisol, hormones increased with exercise. While post-exercise insulin concentrations declined similarly in all 3 trials, the glucagon increase was greatest following MILK consumption. CHO blunted the post-exercise increase in growth hormone compared to levels in MILK. Free fatty acids and plasma amino acids also were responsive to nutritional supplementation with both CHO and MILK attenuating the rise in free fatty acids compared to the increase observed in PLA. Correspondingly, respiratory exchange ratio increased during CHO. Essential amino acids increased significantly only after MILK and were either unchanged or decreased in CHO. PLA was characterized by a decrease in branched-chain amino acid concentrations. Modest nutritional supplementation in this study altered the endocrine response as well as substrate availability and utilization following and during an endurance run, respectively.
Alba Reguant-Closa, Margaret M. Harris, Tim G. Lohman and Nanna L. Meyer
·kg −1 BM·day −1 ). Because we only had three categories (E, M, H) in this study, the hard and very hard categories were combined (H). Therefore, the recommendations for carbohydrate intake were defined as E (4 g·kg −1 BM·day −1 ), M (6 g·kg −1 BM·day −1 ), and H (8 g·kg −1 BM·day −1 ). Protein The
Mark Messina, Heidi Lynch, Jared M. Dickinson and Katharine E. Reed
For a variety of reasons, dietary protein has gained increased research attention in recent years. Evidence shows that consuming protein in excess of the U.S. recommended dietary allowance has health benefits and that for many population groups, the recommended dietary allowance of protein (0.8 g
Liam Anderson, Graeme L. Close, Matt Konopinski, David Rydings, Jordan Milsom, Catherine Hambly, John Roger Speakman, Barry Drust and James P. Morton
– – 2.7 7.4 – 12 ± 14 Lunch (g) 58 34 66 21 55 62 77 53 ± 19 Afternoon snack (g) 22 48 75 28 – 29 29 39 ± 20 Dinner (g) 105 58 14.2 179 83 19.5 8 67 ± 62 Evening snack (g) – – – – – – 27 27 ± 0 Protein (g) 242 245 192 210 128 205 182 201 ± 40 Protein (g/kg) 3.3 3.2 2.5 2.8 1.7 2.7 2.4 2.7 ± 0
Luc J.C. van Loon, Arie K. Kies and Wim H.M. Saris
With the increasing knowledge about the role of nutrition in increasing exercise performance, it has become clear over the last 2 decades that amino acids, protein, and protein hydrolysates can play an important role. Most of the attention has been focused on their effects at a muscular level. As these nutrients are ingested, however, it also means that gastrointestinal digestibility and absorption can modulate their effcacy significantly. Therefore, discussing the role of amino acids, protein, and protein hydrolysates in sports nutrition entails holding a discussion on all levels of the metabolic route. On May 28–29, 2007, a small group of researchers active in the field of exercise science and protein metabolism presented an overview of the different aspects of the application of protein and protein hydrolysates in sports nutrition. In addition, they were asked to share their opinions on the future progress in their fields of research. In this overview, an introduction to the workshop and a short summary of its outcome is provided.
Amy J. Hector and Stuart M. Phillips
restriction, strategies to promote high-quality weight loss (i.e., the loss of fat mass while maintaining LBM) are of importance for elite athletes. The normal maintenance of LBM is determined by continuously opposing and fluctuating rates of muscle protein synthesis (MPS) and muscle protein breakdown (MPB