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

<p>Abstract</p> <p>Background</p> <p>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.</p> <p>Methods</p> <p>Thirty-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^-1of 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.</p> <p>Results</p> <p>Caffeine supplementation reduced 40 kilometer time by a greater (<it>p </it>< 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).</p> <p>Conclusions</p> <p>Results suggest that individuals homozygous for the A allele of this polymorphism may have a larger ergogenic effect following caffeine ingestion.</p

Physiological adaptations to taper in competitive distance runners.

Access to thesis permanently restricted to Ball State community onlyAccess to abstract permanently restricted to Ball State community onlyThesis (Ph. D.)School of Physical Education, Sport, and Exercise Scienc

The efficacy of a verification stage for determining V˙O2max and the impact of sampling intervals

It is unknown whether oxygen uptake (V̇O2) sampling intervals influence the efficacy of a verification stage following a graded exercise test (GXT). Fifteen females and 14 males (18–25 years) completed a maximal treadmill GXT. After a 5 ​min recovery, the verification stage began at the speed and grade corresponding with the penultimate stage from the GXT. Maximal oxygen consumption (V̇O2max) from the incremental GXT (iV̇O2max) and V̇O2max from the verification stage (verV̇O2max) were determined using 10 seconds (s), 30 ​s, and 60 ​s from breath ​× ​breath averages. There was no main effect for V̇O2max measure (iV̇O2maxvs. verV̇O2max) 10 ​s ([47.9 ​± ​8.31] ml∙kg−1∙min−1 vs [48.85 ​± ​7.97] ml∙kg−1∙min−1), 30 ​s ([46.94 ​± ​8.62] ml∙kg−1∙min−1 vs [47.28 ​± ​7.97] ml∙kg−1∙min−1), and 60 ​s ([46.17 ​± ​8.62] ml∙kg−1∙min−1 vs [46.00 ​± ​8.00] ml∙kg−1∙min−1]. There was a stage ​× ​sampling interval interaction as the difference between (verV̇O2max−iV̇O2max) was greater for 10-s than 60-s sampling intervals. The verV̇O2max was > 4% higher than iV̇O2maxin 31%, 31%, and 17% of the tests for the 10-s, 30-s, and 60-s sampling intervals respectively. Sensitivity for the plateau was 90% for all sampling intervals; while specificity was < 25%. Findings from the present study suggest that the efficacy of verification stages for eliciting a higher V̇O2max may be influenced by the sampling interval utilized

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 with CHO. The current findings strengthen the growing body of evidence demonstrating alterations in SC number without hypertrophy. SC 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 was beneficial and may have minimized the necessity for satellite cell involvement

Protein Supplementation During or Following a Marathon Run Influences Post-Exercise Recovery

The effects of protein supplementation on the ratings of energy/fatigue, muscle soreness [ascending (A) and descending (D) stairs], and serum creatine kinase levels following a marathon run were examined. Variables were compared between recreational male and female runners ingesting carbohydrate + protein (CP) during the run (CPDuring, n = 8) versus those that were consuming carbohydrate (CHODuring, n = 8). In a second study, outcomes were compared between subjects who consumed CP or CHO immediately following exercise [CPPost (n = 4) versus CHOPost (n = 4)]. Magnitude-based inferences revealed no meaningful differences between treatments 24 h post-marathon. At 72 h, recovery [Δ(72 hr-Pre)] was likely improved with CPDuring versus CHODuring, respectively, for Physical Energy (+14 ± 64 vs −74 ± 70 mm), Mental Fatigue (−52 ± 59 vs +1 ± 11 mm), and Soreness-D (+15 ± 9 vs +21 ± 70 mm). In addition, recovery at 72 h was likely-very likely improved with CPPost versus CHOPost for Physical Fatigue, Mental Energy, and Soreness-A. Thus, protein supplementation did not meaningfully alter recovery during the initial 24 h following a marathon. However, ratings of energy/fatigue and muscle soreness were improved over 72 h when CP was consumed during exercise, or immediately following the marathon

Protein Supplementation During or Following a Marathon Run Influences Post-Exercise Recovery

The effects of protein supplementation on the ratings of energy/fatigue, muscle soreness [ascending (A) and descending (D) stairs], and serum creatine kinase levels following a marathon run were examined. Variables were compared between recreational male and female runners ingesting carbohydrate + protein (CP) during the run (CPDuring, n = 8) versus those that were consuming carbohydrate (CHODuring, n = 8). In a second study, outcomes were compared between subjects who consumed CP or CHO immediately following exercise [CPPost (n = 4) versus CHOPost (n = 4)]. Magnitude-based inferences revealed no meaningful differences between treatments 24 h post-marathon. At 72 h, recovery [Δ(72 hr-Pre)] was likely improved with CPDuring versus CHODuring, respectively, for Physical Energy (+14 ± 64 vs −74 ± 70 mm), Mental Fatigue (−52 ± 59 vs +1 ± 11 mm), and Soreness-D (+15 ± 9 vs +21 ± 70 mm). In addition, recovery at 72 h was likely-very likely improved with CPPost versus CHOPost for Physical Fatigue, Mental Energy, and Soreness-A. Thus, protein supplementation did not meaningfully alter recovery during the initial 24 h following a marathon. However, ratings of energy/fatigue and muscle soreness were improved over 72 h when CP was consumed during exercise, or immediately following the marathon

Supplemental Protein during Heavy Cycling Training and Recovery Impacts Skeletal Muscle and Heart Rate Responses but Not Performance

The effects of protein supplementation on cycling performance, skeletal muscle function, and heart rate responses to exercise were examined following intensified (ICT) and reduced-volume training (RVT). Seven cyclists performed consecutive periods of normal training (NT), ICT (10 days; average training duration 220% of NT), and RVT (10 days; training duration 66% of NT). In a crossover design, subjects consumed supplemental carbohydrate (CHO) or an equal amount of carbohydrate with added protein (CP) during and following each exercise session (CP = +0.94 g/kg/day protein during ICT; +0.39 g/kg/day during RVT). A 30-kilometer time trial performance (following 120 min at 50% Wmax) was modestly impaired following ICT (+2.4 ± 6.4% versus NT) and returned to baseline levels following RVT (−0.7 ± 4.5% versus NT), with similar responses between CHO and CP. Skeletal muscle torque at 120 deg/s benefited from CP, compared to CHO, following ICT. However, this effect was no longer present at RVT. Following ICT, muscle fiber cross-sectional area was increased with CP, while there were no clear changes with CHO. Reductions in constant-load heart rates (at 50% Wmax) following RVT were likely greater with CP than CHO (−9 ± 9 bpm). Overall it appears that CP supplementation impacted skeletal muscle and heart rate responses during a period of heavy training and recovery, but this did not result in meaningful changes in time trial 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 (VO&lt;sub&gt;2peak&lt;/sub&gt;: 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% VO&lt;sub&gt;2peak&lt;/sub&gt; + 20 km time-trial). Beverages were also consumed following EX2. Blood glucose levels (30 min after beverage ingestion) differed across all treatments (CHO &gt; HCLP &gt; LCHP; &lt;em&gt;p&lt;/em&gt; &lt; 0.05), and serum insulin was higher following CHO and HCLP ingestion &lt;em&gt;versus&lt;/em&gt; 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