Caffeine ingestion acutely enhances muscular strength and power but not muscular endurance in resistance-trained men

doi:10.1080/17461391.2017.1330362

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Caffeine ingestion acutely enhances muscular strength and power but not muscular endurance in resistance-trained men

Journal Article•DOI•

Caffeine ingestion acutely enhances muscular strength and power but not muscular endurance in resistance-trained men

Jozo Grgic¹, Pavle Mikulic²•Institutions (2)

Victoria University, Australia¹, University of Zagreb²

24 May 2017-European Journal of Sport Science (Routledge)-Vol. 17, Iss: 8, pp 1029-1036

TL;DR: Individuals competing in events in which strength and power are important performance-related factors may consider taking 6 mg kg−1 of caffeine pre-training/competition for performance enhancement.

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Abstract: The goal of this randomized, double-blind, cross-over study was to assess the acute effects of caffeine ingestion on muscular strength and power, muscular endurance, rate of perceived exertion (RPE...

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Journal Article•DOI•

Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis.

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Jozo Grgic¹, Eric T. Trexler², Bruno Lazinica, Zeljko Pedisic¹•Institutions (2)

Victoria University, Australia¹, University of North Carolina at Chapel Hill²

05 Mar 2018-Journal of the International Society of Sports Nutrition

TL;DR: The meta-analyses showed significant ergogenic effects of caffeine ingestion on maximal muscle strength of upper body and muscle power and future studies should more rigorously control the effectiveness of blinding.

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Abstract: Caffeine is commonly used as an ergogenic aid. Literature about the effects of caffeine ingestion on muscle strength and power is equivocal. The aim of this systematic review and meta-analysis was to summarize results from individual studies on the effects of caffeine intake on muscle strength and power. A search through eight databases was performed to find studies on the effects of caffeine on: (i) maximal muscle strength measured using 1 repetition maximum tests; and (ii) muscle power assessed by tests of vertical jump. Meta-analyses of standardized mean differences (SMD) between placebo and caffeine trials from individual studies were conducted using the random effects model. Ten studies on the strength outcome and ten studies on the power outcome met the inclusion criteria for the meta-analyses. Caffeine ingestion improved both strength (SMD = 0.20; 95% confidence interval [CI]: 0.03, 0.36; p = 0.023) and power (SMD = 0.17; 95% CI: 0.00, 0.34; p = 0.047). A subgroup analysis indicated that caffeine significantly improves upper (SMD = 0.21; 95% CI: 0.02, 0.39; p = 0.026) but not lower body strength (SMD = 0.15; 95% CI: -0.05, 0.34; p = 0.147). The meta-analyses showed significant ergogenic effects of caffeine ingestion on maximal muscle strength of upper body and muscle power. Future studies should more rigorously control the effectiveness of blinding. Due to the paucity of evidence, additional findings are needed in the female population and using different forms of caffeine, such as gum and gel.

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191 citations

Cites background from "Caffeine ingestion acutely enhances..."

...Grgic J, Mikulic P. Caffeine ingestion acutely enhances muscular strength and power but not muscular endurance in resistance trained men....
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...Three studies [4, 12, 15] assessed both muscle strength and muscle power....
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...Recent work by Grgic and Mikulic [4], however, found a significant 3% increase in lower body strength with caffeine ingestion using the barbell back squat 1RM as a measure of maximal strength....
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...Two studies [4, 16] used a free weight exercise (barbell back squat), and both reported a significant increase in lower body strength....
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...[2], a number of experimental trials have been published [4, 11–16], presenting novel findings for females [14], trained [4, 16] and untrained men [11, 13], athletes [15], and adolescents [12]; as such, an updated review appears to be warranted....
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Journal Article•DOI•

Wake up and smell the coffee: caffeine supplementation and exercise performance—an umbrella review of 21 published meta-analyses

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Jozo Grgic¹, Ivana Grgic, Craig Pickering², Brad J. Schoenfeld³, David Bishop⁴, David Bishop¹, Zeljko Pedisic¹ - Show less +3 more•Institutions (4)

Victoria University, Australia¹, University of Central Lancashire², Lehman College³, Edith Cowan University⁴

01 Jun 2020-British Journal of Sports Medicine

TL;DR: It is suggested that caffeine ingestion improves exercise performance in a broad range of exercise tasks and the magnitude of the effect of caffeine is generally greater for aerobic as compared with anaerobic exercise.

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Abstract: Objective To systematically review, summarise and appraise findings of published meta-analyses that examined the effects of caffeine on exercise performance. Design Umbrella review. Data sources Twelve databases. Eligibility criteria for selecting studies Meta-analyses that examined the effects of caffeine ingestion on exercise performance. Results Eleven reviews (with a total of 21 meta-analyses) were included, all being of moderate or high methodological quality (assessed using the Assessing the Methodological Quality of Systematic Reviews 2 checklist). In the meta-analyses, caffeine was ergogenic for aerobic endurance, muscle strength, muscle endurance, power, jumping performance and exercise speed. However, not all analyses provided a definite direction for the effect of caffeine when considering the 95% prediction interval. Using the Grading of Recommendations Assessment, Development and Evaluation criteria the quality of evidence was generally categorised as moderate (with some low to very low quality of evidence). Most individual studies included in the published meta-analyses were conducted among young men. Summary/conclusion Synthesis of the currently available meta-analyses suggest that caffeine ingestion improves exercise performance in a broad range of exercise tasks. Ergogenic effects of caffeine on muscle endurance, muscle strength, anaerobic power and aerobic endurance were substantiated by moderate quality of evidence coming from moderate-to-high quality systematic reviews. For other outcomes, we found moderate quality reviews that presented evidence of very low or low quality. It seems that the magnitude of the effect of caffeine is generally greater for aerobic as compared with anaerobic exercise. More primary studies should be conducted among women, middle-aged and older adults to improve the generalisability of these findings.

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176 citations

Journal Article•DOI•

Test–Retest Reliability of the One-Repetition Maximum (1RM) Strength Assessment: a Systematic Review

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Jozo Grgic¹, Bruno Lazinica, Brad J. Schoenfeld², Zeljko Pedisic¹•Institutions (2)

Victoria University, Australia¹, Lehman College²

17 Jul 2020-Sports Medicine - Open

TL;DR: The 1RM test generally has good to excellent test–retest reliability, regardless of resistance training experience, number of familiarization sessions, exercise selection, part of the body assessed (upper vs. lower body), and sex or age of participants.

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Abstract: The test–retest reliability of the one-repetition maximum (1RM) test varies across different studies. Given the inconsistent findings, it is unclear what the true reliability of the 1RM test is, and to what extent it is affected by measurement-related factors, such as exercise selection for the test, the number of familiarization trials and resistance training experience. The aim of this paper was to review studies that investigated the reliability of the 1RM test of muscular strength and summarize their findings. The PRISMA guidelines were followed for this systematic review. Searches for studies were conducted through eight databases. Studies that investigated test–retest reliability of the 1RM test and presented intra-class correlation coefficient (ICC) and/or coefficient of variation (CV) were included. The COSMIN checklist was used for the assessment of the methodological quality of the included studies. After reviewing 1024 search records, 32 studies (pooled n = 1595) on test–retest reliability of 1RM assessment were found. All the studies were of moderate or excellent methodological quality. Test–retest ICCs ranged from 0.64 to 0.99 (median ICC = 0.97), where 92% of ICCs were ≥ 0.90, and 97% of ICCs were ≥ 0.80. The CVs ranged from 0.5 to 12.1% (median CV = 4.2%). ICCs were generally high (≥ 0.90), and most CVs were low (< 10%) for 1RM tests: (1) among those without and for those with some resistance training experience, (2) conducted with or without familiarization sessions, (3) with single-joint or multi-joint exercises, (4) for upper- and lower-body strength assessment, (5) among females and males, and (6) among young to middle-aged adults and among older adults. Most studies did not find systematic changes in test results between the trials. Based on the results of this review, it can be concluded that the 1RM test generally has good to excellent test–retest reliability, regardless of resistance training experience, number of familiarization sessions, exercise selection, part of the body assessed (upper vs. lower body), and sex or age of participants. Researchers and practitioners, therefore, can use the 1RM test as a reliable test of muscular strength.

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102 citations

Journal Article•DOI•

The Influence of Caffeine Supplementation on Resistance Exercise: A Review.

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Jozo Grgic¹, Pavle Mikulic², Brad J. Schoenfeld³, David Bishop⁴, David Bishop¹, Zeljko Pedisic¹ - Show less +2 more•Institutions (4)

Victoria University, Australia¹, University of Zagreb², Lehman College³, Edith Cowan University⁴

01 Jan 2019-Sports Medicine

TL;DR: The emerging evidence suggests that coffee might be at least equally ergogenic as caffeine alone when the caffeine dose is matched, and in general, caffeine seems to be safe when taken in the recommended doses.

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Abstract: This paper aims to critically evaluate and thoroughly discuss the evidence on the topic of caffeine supplementation when performing resistance exercise, as well as provide practical guidelines for the ingestion of caffeine prior to resistance exercise. Based on the current evidence, it seems that caffeine increases both maximal strength and muscular endurance. Furthermore, power appears to be enhanced with caffeine supplementation, although this effect might, to a certain extent, be caffeine dose- and external load-dependent. A reduction in rating of perceived exertion (RPE) might contribute to the performance-enhancing effects of caffeine supplementation as some studies have observed decreases in RPE coupled with increases in performance following caffeine ingestion. However, the same does not seem to be the case for pain perception as there is evidence showing acute increases in resistance exercise performance without any significant effects of caffeine ingestion on pain perception. Some studies have reported that caffeine ingestion did not affect exercise-induced muscle damage, but that it might reduce perceived resistance exercise-induced delayed-onset muscle soreness; however, this needs to be explored further. There is some evidence that caffeine ingestion, compared with a placebo, may lead to greater increases in the production of testosterone and cortisol following resistance exercise. However, given that the acute changes in hormone levels seem to be weakly correlated with hallmark adaptations to resistance exercise, such as hypertrophy and increased muscular strength, these findings are likely of questionable practical significance. Although not without contrasting findings, the available evidence suggests that caffeine ingestion can lead to acute increases in blood pressure (primarily systolic), and thus caution is needed regarding caffeine supplementation among individuals with high blood pressure. In the vast majority of studies, caffeine was administered in capsule or powder forms, and therefore the effects of alternative forms of caffeine, such as chewing gums or mouth rinses, on resistance exercise performance remain unclear. The emerging evidence suggests that coffee might be at least equally ergogenic as caffeine alone when the caffeine dose is matched. Doses in the range of 3–9 mg·kg−1 seem to be adequate for eliciting an ergogenic effect when administered 60 min pre-exercise. In general, caffeine seems to be safe when taken in the recommended doses. However, at doses as high as 9 mg·kg−1 or higher, side effects such as insomnia might be more pronounced. It remains unclear whether habituation reduces the ergogenic benefits of caffeine on resistance exercise as no evidence exists for this type of exercise. Caution is needed when extrapolating these conclusions to females as the vast majority of studies involved only male participants.

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100 citations

Journal Article•DOI•

Effects of acute ingestion of caffeine on team sports performance: a systematic review and meta-analysis.

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Juan José Salinero¹, Beatriz Lara¹, Juan Del Coso¹•Institutions (1)

Universidad Camilo José Cela¹

01 Apr 2019-Research in Sports Medicine

TL;DR: The acute ingestion of a moderate dose of caffeine had a small but significant positive effect on several aspects related to physical performance in team sports.

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Abstract: The aim of this investigation was to perform a systematic review and meta-analysis to determine the efficacy of the acute ingestion of caffeine (from 3 to 6 mg/kg) to increase performance on variab...

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97 citations

Cites background from "Caffeine ingestion acutely enhances..."

...However, recent investigations have shown that not all individuals experience enhanced physical performance after the ingestion of moderate doses of caffeine (Doherty, Smith, Davison, & Hughes, 2002; Grgic & Mikulic, 2017; Lara et al., 2015; Skinner, Jenkins, Coombes, Taaffe, & Leveritt, 2010)....
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References

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Book•

Statistical Power Analysis for the Behavioral Sciences

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Jacob Cohen¹•Institutions (1)

University of North Carolina at Chapel Hill¹

01 Dec 1969

TL;DR: The concepts of power analysis are discussed in this paper, where Chi-square Tests for Goodness of Fit and Contingency Tables, t-Test for Means, and Sign Test are used.

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Abstract: Contents: Prefaces. The Concepts of Power Analysis. The t-Test for Means. The Significance of a Product Moment rs (subscript s). Differences Between Correlation Coefficients. The Test That a Proportion is .50 and the Sign Test. Differences Between Proportions. Chi-Square Tests for Goodness of Fit and Contingency Tables. The Analysis of Variance and Covariance. Multiple Regression and Correlation Analysis. Set Correlation and Multivariate Methods. Some Issues in Power Analysis. Computational Procedures.

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115,069 citations

"Caffeine ingestion acutely enhances..." refers background or methods in this paper

...An effect size (ES; Cohen (1988)) was calculated for all differences. All results are presented as mean ± SD. The following scale, proposed by Hopkins (2002), was observed to determine the magnitude of an effect: 0–0....
[...]
...These acute increases in strength performance may probably be attributed to better motor unit recruitment; however, discussing the physiological effects of caffeine is beyond the scope of this article (for a review, see Graham, 2001; Tarnopolsky, 2008). Improvements in lower-body strength performance were accompanied by a reduction in RPE. By contrast, the perception of pain did not change significantly among conditions in the 1RM back squat exercise, while it was significantly lower for the caffeine condition in the 1RM bench press exercise. No differences in RPE were noted for the bench press exercise, possibly because the bench press exercise is a less complex and less demanding exercise than the squat; however, this remains unclear. It has been suggested by Warren et al. (2010) that smaller muscles, such as muscles of the upper arm, have a limited ability for increased motor unit recruitment with caffeine ingestion. Differences in the effects of caffeine on upper and lower body were also noted in a recent study by Black, Waddell, and Gonglach (2015). These authors (Black et al....
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...These acute increases in strength performance may probably be attributed to better motor unit recruitment; however, discussing the physiological effects of caffeine is beyond the scope of this article (for a review, see Graham, 2001; Tarnopolsky, 2008). Improvements in lower-body strength performance were accompanied by a reduction in RPE. By contrast, the perception of pain did not change significantly among conditions in the 1RM back squat exercise, while it was significantly lower for the caffeine condition in the 1RM bench press exercise. No differences in RPE were noted for the bench press exercise, possibly because the bench press exercise is a less complex and less demanding exercise than the squat; however, this remains unclear. It has been suggested by Warren et al. (2010) that smaller muscles, such as muscles of the upper arm, have a limited ability for increased motor unit recruitment with caffeine ingestion....
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...An effect size (ES; Cohen (1988)) was calculated for all differences....
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Journal Article•

Perceived exertion as an indicator of somatic stress.

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Gunnar Borg¹•Institutions (1)

Stockholm University¹

01 Jan 1970-Scandinavian Journal of Rehabilitation Medicine

4,336 citations

"Caffeine ingestion acutely enhances..." refers methods in this paper

...During the first session, the participants were also introduced to the Borg scale (Borg, 1970) for estimation of the RPE, and to the PP scale (described in Cook, O’Connor, Oliver, & Lee, 1998) which ranged from 0 to 10, with 0 marking “no pain at all” and 10 marking “extremely intense pain”....
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Journal Article•DOI•

Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue

[...]

Matt Brzycki¹•Institutions (1)

Princeton University¹

01 Jan 1993-The Journal of Physical Education, Recreation & Dance

TL;DR: Predicting a One-Rep Max from Reps-to-Fatigue from Reps toFatigue using strength testing data is shown to be a good predictor of fatigue.

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Abstract: (1993). Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue. Journal of Physical Education, Recreation & Dance: Vol. 64, No. 1, pp. 88-90.

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913 citations

"Caffeine ingestion acutely enhances..." refers methods in this paper

...The estimation of 1RM was then calculated using the equation proposed by Brzycki (1993), where W stands for weight and R for repetitions: 1RM = W × (36/(37− R))....
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...The estimation of 1RM was then calculated using the equation proposed by Brzycki (1993), where W stands for weight and R for repetitions:...
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Journal Article•DOI•

Caffeine and exercise: metabolism, endurance and performance

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Terry E. Graham¹•Institutions (1)

University of Guelph¹

01 Jan 2001-Sports Medicine

TL;DR: The limited information available suggests that caffeine non-users and users respond similarly and that withdrawal from caffeine may not be important, and caffeine may act synergistically with other drugs including ephedrine and anti-inflammatory agents.

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Abstract: Caffeine is a common substance in the diets of most athletes and it is now appearing in many new products, including energy drinks, sport gels, alcoholic beverages and diet aids. It can be a powerful ergogenic aid at levels that are considerably lower than the acceptable limit of the International Olympic Committee and could be beneficial in training and in competition. Caffeine does not improve maximal oxygen capacity directly, but could permit the athlete to train at a greater power output and/or to train longer. It has also ben shown to increase speed and/or power output in simulated race conditions. These effects have been found in activities that last as little as 60 seconds or as long as 2 hours. There is less information about the effects of caffeine on strength; however, recent work suggests no effect on maximal ability, but enhanced endurance or resistance to fatigue. There is no evidence that caffeine ingestion before exercise leads to dehydration, ion imbalance, or any other adverse effects. The ingestion of caffeine as coffee appears to be ineffective compared to doping with pure caffeine. Related compounds such as theophylline are also potent ergogenic aids. Caffeine may act synergistically with other drugs including ephedrine and anti-inflammatory agents. It appears that male and female athletes have similar caffeine pharmacokinetics, i.e., for a given dose of caffeine, the time course and absolute plasma concentrations of caffeine and its metabolites are the same. In addition, exercise or dehydration does not affect caffeine pharmacokinetics. The limited information available suggests that caffeine non-users and users respond similarly and that withdrawal from caffeine may not be important. The mechanism(s) by which caffeine elicits its ergogenic effects are unknown, but the popular theory that it enhances fat oxidation and spares muscle glycogen has very little support and is an incomplete explanation at best. Caffeine may work, in part, by creating a more favourable intracellular ionic environment in active muscle. This could facilitate force production by each motor unit.

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760 citations

Journal Article•DOI•

Human cytochrome P-450PA (P-450IA2), the phenacetin O-deethylase, is primarily responsible for the hepatic 3-demethylation of caffeine and N-oxidation of carcinogenic arylamines

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Mary Ann Butler¹, M Iwasaki, F P Guengerich, Fred F. Kadlubar•Institutions (1)

National Center for Toxicological Research¹

01 Oct 1989-Proceedings of the National Academy of Sciences of the United States of America

TL;DR: Estimation of caffeine 3-demethylation activity in humans may be useful in the characterization of arylamine N-oxidation phenotypes and in the assessment of whether or not the hepatic levels of cytochrome P-450PA, as affected by environmental or genetic factors, contribute to interindividual differences in susceptibility to arieslamine-induced cancers.

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Abstract: Aromatic amines are well known as occupational carcinogens and are found in cooked foods, tobacco smoke, synthetic fuels, and agricultural chemicals. For the primary arylamines, metabolic N-oxidation by hepatic cytochromes P-450 is generally regarded as an initial activation step leading to carcinogenesis. The metabolic activation of 4-aminobiphenyl, 2-naphthylamine, and several heterocyclic amines has been shown recently to be catalyzed by rat cytochrome P-450ISF-G and by its human ortholog, cytochrome P-450PA. We now report that human hepatic microsomal caffeine 3-demethylation, the initial major step in caffeine biotransformation in humans, is selectively catalyzed by cytochrome P-450PA. Caffeine 3-demethylation was highly correlated with 4-aminobiphenyl N-oxidation (r = 0.99; P less than 0.0005) in hepatic microsomal preparations obtained from 22 human organ donors, and both activities were similarly decreased by the selective inhibitor, 7,8-benzoflavone. The rates of microsomal caffeine 3-demethylation, 4-aminobiphenyl N-oxidation, and phenacetin O-deethylation were also significantly correlated with each other and with the levels of immunoreactive human cytochrome P-450PA. Moreover, a rabbit polyclonal antibody raised to human cytochrome P-450PA was shown to inhibit strongly all three of these activities and to inhibit the N-oxidation of the carcinogen 2-naphthylamine and the heterocyclic amines, 2-amino-6-methyldipyrido-[1,2-a:3',2'-d]imidazole and 2-amino-3-methylimidazo[4,5-f]-quinoline. Human liver cytochrome P-450PA was also shown to catalyze caffeine 3-demethylation, 4-aminobiphenyl N-oxidation, and phenacetin O-deethylation. Thus, estimation of caffeine 3-demethylation activity in humans may be useful in the characterization of arylamine N-oxidation phenotypes and in the assessment of whether or not the hepatic levels of cytochrome P-450PA, as affected by environmental or genetic factors, contribute to interindividual differences in susceptibility to arylamine-induced cancers.

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656 citations