Background: Although 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. Methods: Thirty-five trained male cyclists (age = 25.0 ± 7.3 yrs, height = 178.2 ± 8.8 cm, weight = 74.3 ± 8.8 kg, VO 2 max = 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. Results: Caffeine 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). Conclusions: Results suggest that individuals homozygous for the A allele of this polymorphism may have a larger ergogenic effect following caffeine ingestion.

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.

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; VO(2)peak = 57.9 +/- 7.0 ml x kg(-1) x min(-1)) completed two timed cycle-trials to volitional exhaustion at 75% of VO(2)peak. 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 x kg BW(-1); CHO+P = 0.15 g CHO + 0.038 g protein x 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 x L(-1)), but not the CHO+P trial (180 +/- 133; 222 +/- 141 U x 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.

December 19, 2007; doi:10.1152/ajpregu.00761.2007.-The soleus muscle has been consistently shown to atrophy more than other leg muscles during unloading and is difficult to protect using various exercise countermeasure paradigms. However, the efficacy of aerobic exercise, a known stimulus for oxidative adaptations, has not been tested in combination with resistance exercise (RE), a known hypertrophic stimulus. We hypothesized that a concurrent exercise program (AE ϩ RE) would preserve soleus fiber myosin heavy chain (MHC) I size and function during 60 days of bed rest. A secondary objective was to test the hypothesis that a leucine-enriched high protein diet would partially protect soleus single fiber characteristics. Soleus muscle biopsies were obtained before and after bed rest from a control (BR; n ϭ 7), nutrition (BRN; n ϭ 8), and exercise (BRE; n ϭ 6) group. Single muscle fiber diameter (Dia), peak force (Po), contractile velocity, and power were studied. BR decreased (P Ͻ 0.05) MHC I Dia (Ϫ14%), Po (Ϫ38%), and power (Ϫ39%) with no change in contractile velocity. Changes in MHC I size (Ϫ13%) and contractile function (ϳ30%) from BRN were similar to BR. BRE decreased (P Ͻ 0.05) MHC I Dia (Ϫ13%) and Po (Ϫ23%), while contractile velocity increased (P Ͻ 0.05) 26% and maintained power. These soleus muscle data show 1) the AE ϩ RE exercise program maintained MHC I power but not size and strength, and 2) the nutrition countermeasure did not benefit single fiber size and contractile function. The divergent response in size and functional MHC I soleus properties with the concurrent exercise program was a unique finding further highlighting the challenges of protecting the unloaded soleus. skeletal muscle; contractile properties; exercise; microgravity; spaceflight; Women's International Space Exploration (WISE) 2005 HUMAN BED REST STUDIES of 3-4 mo in duration have found the calf muscles to atrophy ϳ30%, which is ϳ10 -15% greater than the thigh muscles (2, 32, 43). Rodents subjected to hindlimb suspension consistently show that the soleus muscle atrophies more compared with other leg muscles (48). Numerous animal studies (17,24,30,58) have not been able to completely protect soleus muscle mass and function during unloading using a wide range of resistive-type muscle loading paradigms. In humans, slow-twitch muscle fiber size and contractile function are only partially protected (ϳ50%) with resistance exercise during long-term bed rest (52). Thus, leg muscles containing slow-twitch fibers, particularly the soleus, need to be targeted by an exercise prescription program beyond previous resistance exercise-related programs. Aerobic exercise is a potential candidate given the sustained involvement of slow-twitch muscle fibers during these types of activities (41). While aerobic activity during space travel has been extensively studied and proven to be beneficial for cardiovascular health dating back to Skylab experiments (14, 39, 40), it has not been systematically evaluated in combination with resistance exercise to as...

The authors investigated the effects of postexercise carbohydrate-protein-antioxidant (CHO+P+A) ingestion on plasma creatine kinase (CK), muscle soreness, and subsequent cross-country race performance. Twenty-three runners consumed 10 mL/kg body weight of CHO or CHO+P+A beverage immediately after each training session for 6 d before a cross-country race. After a 21-d washout period, subjects repeated the protocol with the alternate beverage. Postintervention CK (223.21 +/- 160.71 U/L; 307.3 +/- 312.9 U/L) and soreness (medians = 1.0, 2.0) were significantly lower after CHO+P+A intervention than after CHO, despite no differences in baseline measures. There were no overall differences in running performance after CHO and CHO+P+A interventions. There were, however, significant correlations between treatment differences and running mileage, with higher mileage runners having trends toward improved attenuations in CK and race performance after CHO+P+A intervention than lower mileage runners. We conclude that muscle damage incurred during training was attenuated with postexercise CHO+P+A ingestion, which could lead to performance improvements in high-mileage runners.

This study examined whether a carbohydrate + casein hydrolysate (CHO+ProH) beverage improved time-trial performance vs. a CHO beverage delivering approximately 60 g CHO/hr. Markers of muscle disruption and recovery were also assessed. Thirteen male cyclists (VO2peak = 60.8 +/- 1.6 ml . kg-1 . min-1) completed 2 computer-simulated 60-km time trials consisting of 3 laps of a 20-km course concluding with a 5-km climb (approximately 5% grade). Participants consumed 200 ml of CHO (6%) or CHO+ProH beverage (6% + 1.8% protein hydrolysate) every 5 km and 500 ml of beverage immediately postexercise. Beverage treatments were administered using a randomly counterbalanced, double-blind design. Plasma creatine phosphokinase (CK) and muscle-soreness ratings were assessed immediately before and 24 hr after cycling. Mean 60-km times were 134.4 +/- 4.6 and 135.0 +/- 4.0 min for CHO+ProH and CHO beverages, respectively. All time differences between treatments occurred during the final lap, with protein hydrolysate ingestion explaining a significant (p < .05) proportion of between-trials differences over the final 20 km (44.3 +/- 1.6, 45.0 +/- 1.6 min) and final 5 km (16.5 +/- 0.6, 16.9 +/- 0.6 min). Plasma CK levels and muscle-soreness ratings increased significantly after the CHO trial (161 +/- 53, 399 +/- 175 U/L; 15.8 +/- 5.1, 37.6 +/- 5.7 mm) but not the CHO+ProH trial (115 +/- 21, 262 +/- 88 U/L; 20.9 +/- 5.3, 32.2 +/- 7.1 mm). Late-exercise time-trial performance was enhanced with CHO+ProH beverage ingestion compared with a beverage containing CHO provided at maximal exogenous oxidation rates during exercise. CHO+ProH ingestion also prevented increases in plasma CK and muscle soreness after exercise.

No abstract

The purpose of this study was to examine the effects of a 3-wk taper on the physiology of competitive distance runners. We studied seven collegiate distance runners (20+/-1 yr, 66+/-1 kg) before and after a 3-wk taper. The primary measures included 8-km cross-country race performance, gastrocnemius single muscle fiber size and function (peak force, shortening velocity, and power), baseline and exercise-induced gene expression 4 h after a standardized 8-km run, citrate synthase activity, and maximal and submaximal cardiovascular physiology (oxygen consumption, ventilation, heart rate, and respiratory exchange ratio). Race performance improved by 3% following taper (P<0.05). Myosin heavy chain (MHC) IIa fiber diameter (+7%, P<0.05), peak force (+11%, P=0.06), and absolute power (+9%, P<0.05) increased following taper. In addition to the MHC IIa adaptations, taper elicited a distinct postexercise gene response. Specifically, the induction of MuRF-1 was attenuated following taper, whereas MRF4, HSP 72, and MT-2A displayed an exaggerated response (P<0.05). No changes were observed in MHC I size or function, baseline gene expression, citrate synthase activity, or cardiovascular function. Our findings show that tapered training in competitive runners promoted MHC IIa fiber remodeling and an altered transcriptional response following the same exercise perturbation, with no adverse affects on aerobic fitness. Together, these results provide a myocellular basis for distance runners to taper in preparation for peak performance.