This study examined the effects of β-hydroxy-β-methylbutyrate (HMB) and α-ketoisocaproic acid (KIC) supplementation on signs and symptoms of exercise-induced muscle damage following a single bout of eccentrically biased resistance exercise. Six non-resistance trained male subjects performed an exercise protocol designed to induce muscle damage on two separate occasions, performed on the dominant or non-dominant arm in a counter-balanced crossover design. Subjects were assigned to an HMB/KIC (3 g HMB and 0.3 g α-ketoisocaproic acid, daily) or placebo treatment for 14 d prior to exercise in the counter-balanced crossover design. One repetition maximum (1RM), plasma creatine kinase activity (CK), delayed onset muscle soreness (DOMS), limb girth, and range of motion (ROM) were determined pre-exercise, at 1h, 24 h, 48 h, and 72 h post-exercise. DOMS and the percentage changes in 1RM, limb girth, and ROM all changed over the 72 h period (P < 0.05). HMB/KIC supplementation attenuated the CK response, the percentage decrement in 1RM, and the percentage increase in limb girth (P < 0.05). In addition, DOMS was reduced at 24 h post-exercise (P < 0.05) in the HMB/KIC treatment. In conclusion, 14 d of HMB and KIC supplementation reduced signs and symptoms of exercise-induced muscle damage in non-resistance trained males following a single bout of eccentrically biased resistance exercise.
Ken A. van Someren, Adam J. Edwards and Glyn Howatson
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.
Eric P. Plaisance, J. Kyle Taylor, Sofiya Alhassan, Asheber Abebe, Michael L. Mestek and Peter W. Grandjean
Inflammatory markers such as C-reactive protein (CRP), fibrinogen, and white-blood-cell (WBC) count are strongly associated with cardiovascular disease. The authors’ purpose was to compare the inflammatory response to a single aerobic-exercise session between individuals of high and moderate fitness. Ten apparently healthy highly ft and 11 moderately ft men expended 500 kcal at 70% of VO2peak. Fasting blood samples were obtained on 2 consecutive days before and again at 24, 72, and 120 h post exercise. Blood samples were analyzed for CRP, fibrinogen, and WBC count. CRP was 76% lower at baseline in the highly ft group than in the moderately ft group (P = 0.03). CRP, fibrinogen, and WBC count remained unaltered, however, in the days after exercise (P > 0.05 for all). These findings suggest that markers of inflammation are stable in the days after a single session of moderate-intensity aerobic exercise in apparently healthy men of at least average fitness.
Emma Stevenson, Clyde Williams, Gareth McComb and Christopher Oram
This study examined the effects of the glycemic index (GI) of post-exercise carbohydrate (CHO) intake on endurance capacity the following day. Nine active males participated in 2 trials. On day 1, subjects ran for 90 min at 70% VO2max (R1). Thereafter, they were supplied with either a high GI (HGI) or low GI (LGI) CHO diet which provided 8 g CHO/kg body mass (BM). On day 2, after an overnight fast, subjects ran to exhaustion at 70% VO2max (R2). Time to exhaustion during R2 was longer in the LGI trial (108.9 ± 7.4 min) than in the HGI trial (96.9 ± 4.8 min) (P < 0.05). Fat oxidation rates and free fatty acid concentrations were higher in the LGI trial than the HGI trial (P < 0.05). The results suggest that the increased endurance capacity was largely a consequence of the increased fat oxidation following the LGI recovery diet.
Michael L. Mestek, John C. Garner, Eric P. Plaisance, James Kyle Taylor, Sofiya Alhassan and Peter W. Grandjean
The purpose of this study was to compare blood lipid responses to continuous versus accumulated exercise. Nine participants completed the following conditions on separate occasions by treadmill walking/jogging at 70% of VO2max : 1) one 500-kcal session and 2) three 167 kcal sessions. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) concentrations were measured from serum samples obtained 24 h prior to and 24 and 48 h after exercise. All blood lipid responses were analyzed in 2 (condition) × 3 (time) repeated measures ANOVAs. HDL-C increased by 7 mg/dL over baseline at 48 h post-exercise with three accumulated sessions versus 2 mg/dL with continuous exercise (P < 0.05). Triglyceride concentrations were unchanged in both conditions. These findings suggest that three smaller bouts accumulated on the same day may have a modestly greater effect for achieving transient increases in HDL-C compared to a continuous bout of similar caloric expenditure.
Richard R. Rosenkranz, Chad M. Cook and Mark D. Haub
To illustrate the effects of low-carbohydrate (LC) and grain-based (GB) diets on body composition, biomarkers, athletic training, and performance in an elite triathlete.
The athlete followed 2 dietary interventions for 14 d while maintaining a prescheduled training program. Pre- and post intervention measurements for each diet included plasma and serum samples, resting energy expenditure, body composition, and a performance bike ride.
Compared with the GB diet, the LC diet elicited more disruptions to training and unfavorable subjective experiences. Total cholesterol, HDL cholesterol, LDL cholesterol, ratings of perceived exertion, and heart rate were elevated on the LC diet. Blood insulin, resting lactate, post exercise lactate, and C-reactive protein were lowest on the LC diet.
The LC diet resulted in both favorable and unfavorable outcomes. The primary observation was a disruption to scheduled training on the LC diet. Researchers should consider how the potential mediating effect of disruptions to training could influence pretest–posttest designs.
Kazunori Nosaka, P.▀ Sacco and K.▀ Mawatari
This study investigated the effect of a supplement containing 9 essential and 3 non-essential amino acids on muscle soreness and damage by comparing two endurance exercise bouts of the elbow fexors with amino acid or placebo supplementation in a double blind crossover design. The supplement was ingested 30 min before (10 h post-fasting) and immediately after exercise (Experiment 1), or 30 min before (2-3 h after breakfast), immediately post, and 8 more occasions over 4-day post-exercise (Experiment 2). Changes in muscle soreness and indicators of muscle damage for 4 days following exercise were compared between supplement conditions using two-way ANOVA. No significant differences between conditions were evident for Experiment 1; however, plasma creatine kinase, aldolase, myoglobin, and muscle soreness were significantly lower for the amino acid versus placebo condition in Experiment 2. These results suggest that amino acid supplementation attenuates DOMS and muscle damage when ingested in recovery days.
Dylan Thompson, Clyde Williams, Stephen J. McGregor, Ceri W. Nicholas, Frank McArdle, Malcolm J. Jackson and Jonathan R. Powell
The aim of the present study was to investigate whether 2 weeks of vitamin C supplementation affects recovery from an unaccustomed bout of exercise. Sixteen male subjects were allocated to either a placebo (P; n = 8) or vitamin C group (VC; n = 8). The VC group consumed 200 mg of ascorbic acid twice a day, whereas the P group consumed identical capsules containing 200 mg of lactose. Subjects performed a prolonged (90-min) intermittent shuttle-running test 14 days after supplementation began. Post-exercise serum creatine kinase activities and myoglobin concentrations were unaffected by supplementation. However, vitamin C supplementation had modest beneficial effects on muscle soreness, muscle function, and plasma concentrations of malondialdehyde. Furthermore, although plasma interleukin-6 increased immediately after exercise in both groups, values in the VC group were lower than in the P group 2 hours after exercise (p < .05). These results suggest that prolonged vitamin C supplementation has some modest beneficial effects on recovery from unaccustomed exercise.
William J. Kraemer, Scott E. Gordon, James M. Lynch, Mariana E.M.V. Pop and Kristine L. Clark
The purpose of this investigation was to determine the effects of a 3.5-day dietary multibuffer supplement (containing predominantly inorganic phosphate, or Pj, along with bicarbonate and carnosine, i.e., PhosFuel™) on repetitive (four trials separated by 2 min rest) Wingate test (WT) performances and whole blood 2,3-diphosphoglycerate (2,3-DPG) concentrations in 10 recreationally trained road cyclists (T) and 10 normally active but untrained (UT) men. A 2-week washout period was utilized between experimental sessions. Venous blood samples were obtained via cannula once before exercise (baseline), immediately post each WT, and 3 min after the final WT (recovery). The data indicate that this supplement does not affect acid-base status with following intense anaerobic exercise and does not improve repetitive WT performance. However, the supplement does enhance post-exercise levels of 2,3-DPG and the 2,3-DPG/Hb ratio in recreationally trained cyclists while improving acute recovery of peak power in these men.
Michael J. Saunders
Endurance athletes commonly consume carbohydrate-electrolyte sports beverages during prolonged events. The benefits of this strategy are numerous—sports-beverage consumption during exercise can delay dehydration, maintain blood glucose levels, and potentially attenuate muscle glycogen depletion and central fatigue. Thus, it is generally agreed that carbohydrate-electrolyte beverages can improve endurance performance. A controversy has recently emerged regarding the potential role of protein in sports beverages. At least 3 recent studies have reported that carbohydrate-protein ingestion improves endurance performance to a greater extent than carbohydrate alone. In addition, carbohydrate-protein ingestion has been associated with reductions in markers of muscle damage and improved post exercise recovery. Although many of these muscle damage and recovery studies examined post exercise nutritional intake, recent evidence suggests that these benefits may be elicited with carbohydrate-protein consumption during exercise. These findings are intriguing and suggest that the importance of protein for endurance athletes has been underappreciated. However, 2 studies recently reported no differences in endurance performance between carbohydrate and carbohydrate-protein beverages. The varied outcomes may have been influenced by a number of methodological differences, including the amounts and types of carbohydrate or protein in the beverages, the exercise protocols, and the relative statistical power of the studies. In addition, although there are plausible mechanisms that could explain the ergogenic effects of carbohydrate-protein beverages, they remain relatively untested. This review examines the existing research regarding the efficacy of carbohydrate-protein consumption during endurance exercise. Limitations of the existing research are addressed, as well as potential areas for future study.