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Study Title and Description

Effects of acute exercise on the soleus H-reflex and self-reported anxiety after caffeine ingestion.



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on behavior*?
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Primary Publication Information
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TitleData
Title Effects of acute exercise on the soleus H-reflex and self-reported anxiety after caffeine ingestion.
Author RW Motl,RK Dishman,
Country
Year 2004
Numbers

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Extraction Form: Behavior - Design Details - INCLUDED Studies
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Design Details
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Refid 14741244
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What outcome is being evaluated in this paper? Behavior
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What is the objective of the study (as reported by the authors)? The present study was designed to provide a stronger test of the relationships among exercise, anxiety, and the Hreflex by experimentally increasing and then decreasing anxiety and measuring the concurrent effects on the Hreflex. We examined the effects of acute cycling exercise on changes in the soleus H-reflex and self-reported state anxiety in individuals whose anxiety was increased by consumption of a high dose of caffeine.
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Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods) 2.1. Participants Participants (N = 16) were male nonsmoking college students of average body weight who reported low daily caffeine consumption (i.e., < 100 mg/d), average or less than average trait anxiety scores, and no hypersensitivity to caffeine. Only males were recruited because caffeine clearance is slowed during the luteal phase of the menstrual cycle [31] and with the use of oral contraceptives [32]. Only nonsmokers of average body weight were recruited to avoid the effects of cigarette smoking [33] and obesity [34] on the rate of caffeine metabolism. Participants who reported low daily caffeine consumption were recruited to minimize tolerance to the effects of caffeine among habitual consumers of caffeine [35]. Those participants who reported average or less than average trait anxiety scores [36] and no previous hypersensitivity to a large dose of caffeine were recruited to minimize the potential for extreme anxiety reactions to caffeine ingestion [28]. Selected participant characteristics are provided in Table 1. 2.2. Measures 2.2.1. State–Trait Anxiety Inventory The 40-item State–Trait Anxiety Inventory (STAI) was used to measure state and trait anxiety [36]. Twenty items measured state anxiety and 20 items measured trait anxiety. The items were rated on a four-point scale anchored by ‘‘not at all’’ (1), ‘‘somewhat’’ (2), ‘‘moderately so’’ (3), and ‘‘very much so’’ (4). The STAI has acceptable internal consistency and test–retest reliability [36]. An abundance of correlational and experimental evidence supports the validity of the inference that scores on the STAI reflect anxiety [36]. 2.3. Procedures The procedures were approved by the University of Georgia Institutional Review Board. Participants completed 1 day of preliminary testing and 4 days of experimental testing. The 4 days of experimental testing were separated by approximately 1 week. Experimental testing was conducted in the morning (0700 h) and the time of day was standardized within and between subjects (F1 h). Before the experimental testing, participants were asked to abstain from caffeine consumption for 1 week; alcohol consumption for 24 h; and eating and exercising for 12 h. 2.3.1. Preliminary testing day On the day of preliminary testing, participants signed an informed consent document and completed a preexercise medical history questionnaire, 7-day recall of daily caffeine consumption [39], and the measure of trait anxiety. The researcher performed a 7-day physical activity recall interview. Participants then performed the incremental exercise test. After the exercise test, participants were prepared for recording the H-reflex and moved to an environmental chamber and positioned on a custom-designed chair. Participants completed the measure of state anxiety, and then underwent measurements of the H-reflex in the soleus muscle. The data from the baseline day were not analyzed, and testing only was performed to familiarize subjects with the protocol. 2.3.2. Experimental days On the experimental days, participants underwent one of four, 30-min conditions: (1) cycling at 60% V˙ O2peak after consuming caffeine; (2) cycling at 60% V˙ O2peak after consuming placebo; (3) quiet rest after consuming caffeine; and (4) quiet rest after consuming placebo. Caffeine and placebo were delivered in gelatin capsules (No. 1, Lilly, Eli Lilly & Company, Indianapolis, IN). The dose of caffeine (Caffeine Anhydrous, USP/NF, Gallipot, St. Paul, MN) was 10 mg/kg body weight based on consistent observations of elevated anxiety [28,41,42]. The dose of placebo was an equal number of gelatin capsules containing white, allpurpose flour. The order of the conditions was counterbalanced and drug administration was double-blind; otherwise the procedures were identical. Subjects consumed the gelatin capsules containing either caffeine or placebo with 500 ml of water, and sat and read quietly in the environmental chamber. One hour after ingesting the capsules, which has been reported to coincide with peak plasma caffeine concentrations [34,43], participants again completed the measure of state anxiety. Beginning 10 min after exercise or quiet rest, participants completed the measure of state anxiety and underwent measurements of the H-reflex. 2.4. Data analysis The data were analyzed with 2 (drug: caffeine and placebo)_x0001_2 (activity: exercise and quiet rest)_x0001_3 (time: predrug, postdrug/precondition, postcondition) repeatedmeasures ANOVAs based on the multivariate F statistic (Pillai-Bartlett) [44]. Effect sizes associated with F statistics were expressed as eta-squared (g2). Effect sizes based on mean differences were expressed as Cohen’s d [45]. The Greenhouse–Geisser epsilon (e) was reported when the sphericity assumption was violated (i.e., if Mauchly’s test of sphericity was statistically significant at P < .05). The family-wise error rate was controlled using the Bonferroni adjustment when tests of simple effects were conducted [44]. The relationship between changes in the H/M ratio and state anxiety was examined using a Drug_x0001_Activity repeated- measures ANCOVA on H/M ratio change scores with state anxiety change scores as a time varying covariate [46]. The result of that analysis was compared with a Drug_x0001_ Activity repeated-measures ANOVA on only H/M ratio change scores. Changes in the univariate F statistic and g2 were indicative of a difference between models, and hence an effect of state anxiety on the H-reflex; the univariate F statistic was compared across models [46] as the multivariate F statistic was unavailable with the repeated measures ANCOVA that included the time varying covariate. Those analyses were performed on change scores computed for pre–post drug and then pre–post condition
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How many outcome-specific endpoints are evaluated? 1
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Anxiety
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List additional health endpoints (separately).
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List additional health endpoints (separately)
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Notes state anxiety
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Clinical
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Physiological
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Other
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What is the study design? Controlled Trial
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Randomized or Non-Randomized? RCT
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What were the diagnostics or methods used to measure the outcome? Subjective
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Optional: Name of Method or short description State Trait Anxiety Inventory (STAI)
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Caffeine (general) Caffeine (general)
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Coffee
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Chocolate
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Energy drinks
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Gum
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Medicine/Supplement
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Soda
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Tea
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Measured Measured
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Self-report
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Children
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Adolescents
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Adults Adults
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Pregnant Women
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) placebo (flour, 0 mg caffeine) vs 800 mg caffeine
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What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models.  Copy from methods) Trait anxiety was considered as a confounder
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Provide a general description of results (as reported by the authors). There was a significant Drug_x0001_Activity_x0001_Time interaction on state anxiety scores, F(2,14) = 5.12, P < .05, g2=.42, e =.68. As illustrated in Fig. 3, state anxiety scores were significantly increased from before to after consumption of caffeine in both the exercise (d = 0.67) and quiet rest (d = 1.36) conditions; scores were unchanged from before to after consumption of placebo in the exercise (d =_x0002_0.07) and quiet rest (d =_x0002_0.04) conditions. State anxiety scores were significantly decreased from before to after cycling exercise in the caffeine condition (d =_x0002_0.34), but were unchanged after quiet rest in the caffeine condition (d = 0.05). There were no changes in anxiety scores from before to after cycling exercise (d = 0.04) or quiet rest (d = 0.04) in the placebo condition. There was not a statistically significant Group_x0001_Drug_x0001_ Activity _x0001_Time interaction on state anxiety scores [F(2,13) = 0.66, P=.53, g2=.09]. There still was a statistically significant and virtually identical in magnitude Drug_x0001_Activity_x0001_Time interaction on state anxiety scores [ F(2,13) = 5.14, P < .05, g2=.44, e =.70. Hence, trait anxiety did not moderate the interactive effects of caffeine ingestion and acute exercise on state anxiety scores in this study.
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Did the authors perform a dose-response analysis (or trend/related analysis)? No
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What were the authors's observations re: trend analysis?
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What were the author's conclusions? Consumption of caffeine did not influence the amplitude of the soleus H-reflex, but it resulted in a large increase of state anxiety. As expected, consumption of a large dose of caffeine (10 mg/kg body weight) was effective for increasing precondition anxiety scores. Similar to previous research [30], we observed a large effect of caffeine on precondition state anxiety scores (d = 1.04) in the present study. Also, similar to previous results [30], we found that 30 min of moderate intensity cycling exercise resulted in a reduction of state anxiety, but only after consuming caffeine; there was no effect of exercise on anxiety in the placebo condition. For example, there were no consistent effects of exercise on the rate of caffeine absorption, peak plasma caffeine concentration, volume of caffeine distribution, the half-life of caffeine, elimination rate constant, or caffeine clearance compared with rest in a small sample of three lean college-aged males. Hence, those findings strengthen our conclusion that the anxiolytic effects of exercise are not mediated by altered caffeine pharmacokinetics, which is consistent with previous research [30], though we did not measure caffeine pharmacokinetics
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What were the sources of funding? None listed
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What conflicts of interest were reported? N/A
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Does the exposure (dose) need to be standardized to the SR? Multiple metrics
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Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest). subjects were administered 10 mg/kg 10 mg/kg x (80 kg) = 800 mg caffeine
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List all the endpoint(s) followed by the dose (mg) which will be used in comparison to Nawrot.  Characterize value as LOAEL/NOAEL, etc. if possible.  Anxiety - LOAEL = 800 mg/day
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Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot. single dose Increase in anxiety above levels seen in Nawrot.
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What is the importance of the study with respect to the adverseness of the outcome? Important
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