Nicholas D. Luden

Consumption of an oral carbohydrate-protein gel improves cycling endurance and prevents postexercise muscle damage.

Investigators have reported improved endurance performance and attenuated post- exercise muscle damage with carbohydrate-protein beverages (CHO+P) versus carbohydrate-only beverages (CHO). However, these benefits have been demonstrated only when CHO+P was administered in beverage-form, and exclusively in male subjects. Thus, the purposes of this study were to determine if an oral CHO+P gel improved endurance performance and post-exercise muscle damage compared to a CHO gel, and determine if responses were similar between genders. Thirteen cyclists (8 men, 5 women; &OV0312;O2peak = 57.9 ± 7.0 ml·kg-1·min-1) completed two timed cycle-trials to volitional exhaustion at 75% of &OV0312;O2peak. At 15-minute intervals throughout these rides, subjects received CHO or CHO+P gels, which were matched for carbohydrate content (CHO = 0.15 g CHO·kg BW-1; CHO+P = 0.15 g CHO + 0.038 g protein·kg BW-1). Trials were performed using a randomly counterbalanced, double-blind design. Subjects rode 13% longer (p > 0.05) when utilizing the CHO+P gel (116.6 ± 28.5 minutes) versus the CHO gel (102.8 ± 25.0 minutes). In addition, men (101.8 ± 24.6; 114.8 ± 26.2) and women (104.4 ± 28.6; 119.6 ± 34.9) responded similarly to the CHO and CHO+P trials, with no significant treatment-by-gender effect. Postexercise creatine kinease (CK) was not significantly different between treatments. However, CK increased significantly following exercise in the CHO trial (183 ± 116; 267 ± 214 U·L-1), but not the CHO+P trial (180 ± 133; 222 ± 141 U·L-1). Therefore, to prolong endurance performance and prevent increases in muscle damage, it is recommended that male and female cyclists consume CHO+P gels rather than CHO gels during and immediately following exercise.

The influence of a CYP1A2 polymorphism on the ergogenic effects of caffeine

BackgroundAlthough caffeine supplementation improves performance, the ergogenic effect is variable. The cause(s) of this variability are unknown. A (C/A) single nucleotide polymorphism at intron 1 of the cytochrome P450 (CYP1A2) gene influences caffeine metabolism and clinical outcomes from caffeine ingestion. The purpose of this study was to determine if this polymorphism influences the ergogenic effect of caffeine supplementation.MethodsThirty-five trained male cyclists (age = 25.0 ± 7.3 yrs, height = 178.2 ± 8.8 cm, weight = 74.3 ± 8.8 kg, VO2max = 59.35 ± 9.72 ml·kg-1·min-1) participated in two computer-simulated 40-kilometer time trials on a cycle ergometer. Each test was performed one hour following ingestion of 6 mg·kg-1 of anhydrous caffeine or a placebo administered in double-blind fashion. DNA was obtained from whole blood samples and genotyped using restriction fragment length polymorphism-polymerase chain reaction. Participants were classified as AA homozygotes (N = 16) or C allele carriers (N = 19). The effects of treatment (caffeine, placebo) and the treatment × genotype interaction were assessed using Repeated Measures Analysis of Variance.ResultsCaffeine supplementation reduced 40 kilometer time by a greater (p < 0.05) magnitude in AA homozygotes (4.9%; caffeine = 72.4 ± 4.2 min, placebo = 76.1 ± 5.8 min) as compared to C allele carriers (1.8%; caffeine = 70.9 ± 4.3 min, placebo = 72.2 ± 4.2 min).ConclusionsResults suggest that individuals homozygous for the A allele of this polymorphism may have a larger ergogenic effect following caffeine ingestion.

Caffeine and 3-km cycling performance: Effects of mouth rinsing, genotype, and time of day.

We assessed the efficacy of caffeine mouth rinsing on 3‐km cycling performance and determined whether caffeine mouth rinsing affects performance gains influenced by the CYP1A2 polymorphism. Thirty‐eight recreational cyclists completed four simulated 3‐km time trials (TT). Subjects ingested either 6 mg/kg BW of caffeine or placebo 1 h prior to each TT. Additionally, 25 mL of 1.14% caffeine or placebo solution were mouth rinsed before each TT. The treatments were Placebo, caffeine Ingestion, caffeine Rinse and Ingestion+Rinse. Subjects were genotyped and classified as AA homozygotes or AC heterozygotes for the rs762551 polymorphism of the CYP1A2 gene involved in caffeine metabolism. Magnitude‐based inferences were used to evaluate treatment differences in mean power output based on a predetermined meaningful treatment effect of 1.0%. AC heterozygotes (4.1%) and AA homozygotes (3.4%) benefited from Ingestion+Rinse, but only AC performed better with Ingestion (6.0%). Additionally, Rinse and Ingestion+Rinse elicited better performance relative to Placebo among subjects that performed prior to 10:00 h (Early) compared with after 10:00 h (Late). The present study provides additional evidence of genotype and time of day factors that affect the ergogenic value of caffeine intake that may allow for more personalized caffeine intake strategies to maximize performance.

Recovery from Cycling Exercise: Effects of Carbohydrate and Protein Beverages

The effects of different carbohydrate-protein (CHO + Pro) beverages were compared during recovery from cycling exercise. Twelve male cyclists (VO2peak: 65 ± 7 mL/kg/min) completed ~1 h of high-intensity intervals (EX1). Immediately and 120 min following EX1, subjects consumed one of three calorically-similar beverages (285–300 kcal) in a cross-over design: carbohydrate-only (CHO; 75 g per beverage), high-carbohydrate/low-protein (HCLP; 45 g CHO, 25 g Pro, 0.5 g fat), or low-carbohydrate/high-protein (LCHP; 8 g CHO, 55 g Pro, 4 g fat). After 4 h of recovery, subjects performed subsequent exercise (EX2; 20 min at 70% VO2peak + 20 km time-trial). Beverages were also consumed following EX2. Blood glucose levels (30 min after beverage ingestion) differed across all treatments (CHO > HCLP > LCHP; p < 0.05), and serum insulin was higher following CHO and HCLP ingestion versus LCHP. Peak quadriceps force, serum creatine kinase, muscle soreness, and fatigue/energy ratings measured pre- and post-exercise were not different between treatments. EX2 performance was not significantly different between CHO (48.5 ± 1.5 min), HCLP (48.8 ± 2.1 min) and LCHP (50.3 ± 2.7 min). Beverages containing similar caloric content but different proportions of carbohydrate/protein provided similar effects on muscle recovery and subsequent exercise performance in well-trained cyclists.

Inter-Study Examination of Physiological Variables Associated with Improved Endurance Performance with Carbohydrate/Protein Administration: 1067

PURPOSE: Previous studies from our laboratory reported improvements in endurance performance when athletes consumed carbohydrate/protein (CHO+P) beverages or gels compared to carbohydrate-only (CHO) treatments. However, relatively small sample sizes in these studies precluded the ability to examine correlations between physiological variables that may have been associated with performance benefits. Therefore, the purpose of this study was to examine data across multiple studies to determine if improvements in performance were related to alterations in physiological measures during exercise.

Time of Day and Training Status Both Impact the Efficacy of Caffeine for Short Duration Cycling Performance

This project was designed to assess the effects of time of day and training status on the benefits of caffeine supplementation for cycling performance. Twenty male subjects (Age, 25 years; Peak oxygen consumption, 57 mL·kg−1·min−1) were divided into tertiles based on training levels, with top and bottom tertiles designated as ‘trained’ (n = 7) and ‘untrained’ (n = 7). Subjects completed two familiarization trials and four experimental trials consisting of a computer-simulated 3-km cycling time trial (TT). The trials were performed in randomized order for each combination of time of day (morning and evening) and treatment (6mg/kg of caffeine or placebo). Magnitude-based inferences were used to evaluate all treatment effects. For all subjects, caffeine enhanced TT performance in the morning (2.3% ± 1.7%, ‘very likely’) and evening (1.4% ± 1.1%, ‘likely’). Both untrained and trained subjects improved performance with caffeine supplementation in the morning (5.5% ± 4.3%, ‘likely’; 1.0% ± 1.7%, ‘likely’, respectively), but only untrained subjects rode faster in the evening (2.9% ± 2.6%, ‘likely’). Altogether, our observations indicate that trained athletes are more likely to derive ergogenic effects from caffeine in the morning than the evening. Further, untrained individuals appear to receive larger gains from caffeine in the evening than their trained counterparts.

Fiber Type-Specific Satellite Cell Content in Cyclists Following Heavy Training with Carbohydrate and Carbohydrate-Protein Supplementation

The central purpose of this study was to evaluate the fiber type-specific satellite cell and myonuclear responses of endurance-trained cyclists to a block of intensified training, when supplementing with carbohydrate (CHO) vs. carbohydrate-protein (PRO). In a crossover design, endurance-trained cyclists (n = 8) performed two consecutive training periods, once supplementing with CHO (de facto “control” condition) and the other with PRO. Each training period consisted of 10 days of intensified cycle training (ICT–120% increase in average training duration) followed by 10 days of recovery (RVT–reduced volume training; 33% volume reduction vs. normal training). Skeletal muscle biopsies were obtained from the vastus lateralis before and after ICT and again following RVT. Immunofluorescent microscopy was used to quantify SCs (Pax7+), myonuclei (DAPI+), and myosin heavy chain I (MyHC I). Data are expressed as percent change ± 90% confidence limits. The 10-day block of ICTCHO increased MyHC I SC content (35 ± 28%) and myonuclear density (16 ± 6%), which remained elevated following RVTCHO (SC = 69 ± 50% vs. PRE; Nuclei = 17 ± 15% vs. PRE). MyHC II SC and myonuclei were not different following ICTCHO, but were higher following RVTCHO (SC = +33 ± 31% vs. PRE; Nuclei = 15 ± 14% vs. PRE), indicating a delayed response compared to MyHC I fibers. The MyHC I SC pool increased following ICTPRO (37 ± 37%), but without a concomitant increase in myonuclei. There were no changes in MyHC II SC or myonuclei following ICTPRO. Collectively, these trained endurance cyclists possessed a relatively large pool of SCs that facilitated rapid (MyHC I) and delayed (MyHC II) satellite cell proliferation and myonuclear accretion under carbohydrate conditions. The current findings strengthen the growing body of evidence demonstrating alterations in satellite cell number in the absence of hypertrophy. Satellite cell pool expansion is typically viewed as an advantageous response to exercise. However, when coupled with our previous report that PRO possibly enhanced whole muscle recovery and increased MyHC I and II fiber size, the limited satellite cell/myonuclear response observed with carbohydrate-protein seem to indicate that protein supplementation may have minimized the necessity for satellite cell involvement, thereby suggesting that protein may benefit skeletal muscle during periods of heavy training.

Erratum to: The influence of a CYP1A2 polymorphism on the ergogenic effects of caffeine

[This corrects the article DOI: 10.1186/1550-2783-9-7.].

Time of Day, but not Sleep Restriction, Affects Markers of Hemostasis Following Heavy Exercise

We sought to determine the effects of sleep restriction on markers of hemostasis the morning after an exercise session. Seven subjects performed evening exercise followed by an exercise session the next morning, both with and without sleep restriction. Evening exercise included a 20-min submaximal cycling trial (10 min at 50% maximal power (Wmax), 10 min at 60% Wmax), a 3-km cycling time trial, 60 min of cycling intervals, and 3 sets of leg press. Subsequent morning exercise was the same, excluding intervals and leg press. Blood samples were collected at rest and following the 20-min submaximal trial for factor VIII antigen, tissue plasminogen activator (tPA) activity, and plasminogen activator inhibitor-1 (PAI-1) activity. Sleep restriction had no effect on the variables. Factor VIII antigen was higher and tPA activity lower in the morning versus evening, respectively (P < 0.05). There were larger (P < 0.05) exercise responses for tPA activity in the evening (pre-exercise = 0.32 ± 0.14, postexercise = 1.89 ± 0.60 AU/mL) versus morning (pre-exercise = 0.27 ± 0.13 AU/mL, postexercise = 0.69 ± 0.18 AU/mL). PAI-1 exhibited lower (P < 0.05) responses in the evening (pre-exercise = 0.78 ± 0.26 AU/mL, postexercise = 0.69 ± 0.29 AU/mL) versus morning (pre-exercise = 7.06 ± 2.66, postexercise = 5.40 ± 2.31 AU/mL). Although a prothrombotic environment was observed the morning following an evening exercise session, it was not exacerbated by sleep restriction.

Arterial adaptations to training among first time marathoners

BackgroundExercise training favorably alters arterial anatomy in trained limbs, though the simultaneous effects on passively trained arteries are unclear. Thus, brachial (non-trained limb), popliteal (trained limb) and carotid total wall thickness (TWT), wall-to-lumen ratios (W:L), intima-media thickness (IMT) and lumen diameters (LD) were compared between experimental (n = 14) and control (n = 11) participants before and after the experimental participants participated in marathon training.MethodsArterial dimensions were measured with B-mode ultrasonography. Initial and final testing of VO2max and running speed at 3.5 mmol lactate were measured in the experimental group.ResultsVO2max was unchanged by training, but running speed at 3.5 mmol lactate increased by 5 % (p = .008). Time by group interactions were observed for the brachial and popliteal measures (p < 0.05), but not the carotid. No changes were observed in the control group. Prior to the intervention the experimental group had larger LD in the brachial (p = .002) and popliteal arteries (p = .007) than controls; no other pre-testing differences were found. Following training, TWT declined in the brachial (pre = .99 ± .16 mm; post = .84 ± .10 mm; p = .007) and popliteal (pre = .96 ± .09 mm; post = .86 ± .11 mm; p = .005) arteries, characterized by a 0.07 mm decrease in brachial IMT (p = .032) and a non-significant 0.03 mm reduction in popliteal IMT. LD increased in the brachial (pre = 3.38 ± .35 mm; post = 3.57 ± .41 mm; p = .015) and popliteal (pre = 4.73 ± .48 mm; post = 5.11 ± .72 mm; p = .002) arteries.ConclusionsThese data suggest that exercise-induced alterations in arterial dimensions occur in trained and non-trained limbs, and that adaptations may be dose dependent.