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Study Title and Description

Influence of caffeine ingestion on autonomic nervous activity during endurance exercise in humans.



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on cardiovascular outcomes?
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Primary Publication Information
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TitleData
Title Influence of caffeine ingestion on autonomic nervous activity during endurance exercise in humans.
Author Y Nishijima,T Ikeda,M Takamatsu,Y Kiso,H Shibata,T Fushiki,T Moritani,
Country
Year 2002
Numbers

Secondary Publication Information
There are currently no secondary publications defined for this study.


Extraction Form: Cardiovascular Design
Design Details
Question... Follow Up Answer Follow-up Answer
What outcome is being evaluated in this paper? Cardiovascular
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What is the objective of the study (as reported by the authors)? The effects of caffeine ingestion on the activities of the autonomic nervous system (ANS) during endurance exercise at low intensity were investigated using a power spectrumanalysis of heart rate variability.
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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) Subjects A group of eight healthy young Japanese men [mean (SEM)] [age 25.5 (0.8) years, body mass 68.3 (1.7) kg, height 172.2 (4.3) cm] participated in this study. They were physically active, but none were engaged in regular athletic training. They were habitual users of caffeine and normally consumed less than 500 mg/day. Study Design On the day preceding the exercise test, the subjects were instructed to refrain from strenuous physical exercise, tobacco and alcohol. They were instructed not to take any food or beverages except water during the 10 h prior to the commencement of exercise. The next morning at 2 h and 5 min before the exercise, they consumed a standardized breakfast of boiled rice (energy content 300 kcal or approximately 1,254 kJ). At 2 h before exercise, placebo capsules or caffeine capsules (300 mg of caffeine, Takasago-kohryoh Co., Osaka, Japan) were ingested with 100 ml of water. The order of the experimental treatments was chosen at random, separated by a week. To avoid the influences of circadian rhythm, each test was made between 0800 and 1100 hours. After taking the capsules the subjects rested in a sitting position in a quiet and relaxing atmosphere at a temperature of 23–24oC, and the baseline electrocardiogram (ECG) and BP parameters were recorded for 5 min (rest). Following this, the subjects cycled for 30 min at an intensity corresponding to 40%–50% of that at the VT of each individual, ranging from 60 to 80 W. Measurements were made at the following times: 5–10 min, 15–20 min and 25–30 min after the start of exercise. During rest, the subjects were instructed to breathe at a frequency of 1 breath every 4 s (0.25 Hz) in synchrony with the sound of an electric metronome, so that respiratory-linked HRV would not overlap with fluctuations in low-frequency heart rate. During exercise, the subject was instructed that they could breathe freely as the respiratory rate would easily exceed the 0.25 Hz, so that low frequency HRV frequency components would not be affected by the respiration. Data Acquisition The ECG was obtained using a CM5 lead. The analogue output of the ECG was connected to an ECG amplifier (Multi-channel Amplifier MEG-6100, Nihon Kohden Co., Japan) and digitized using a 13 bit analogue-to-digital converter (HTB410) at a sampling rate of 1 kHz, using a 0.5 Hz–100 Hz band pass filter at rest and a 1.5 Hz–100 Hz filter during exercise. The BP was recorded using an automated sphygmomanometer (FINAPRES 2300, Ohmeda, USA) connected to a finger cuff containing a plethysmotransducer. Analogue output of the BP was digitized using a 13 bit analogue-to-digital converter at a sampling rate of 1 kHz. Beat-by-beat systolic blood pressure (BPs) and diastolic blood pressure (BPd) values were calculated later using computer software developed in our laboratory. R-R Interval Power Spectrum Analysis The heart acts in a discrete fashion with successive heartbeats leading to a series of fluctuating values of R-R intervals. Power spectrum analysis of HRV has shown two major distinct regions of periodicity in R-R intervals: the high frequency, respiration-linked component (HI, greater than 0.15 Hz) and the low frequency component (LO, less than 0.15 Hz). The HI is associated solely with activity in the parasympathetic nervous system while LO reflects mainly activity in the sympathetic nervous system, and partly activity in the vagus. In the actual analysis, the derived R-R interval time series was aligned in 2 Hz sequences for power spectrum analysis. The DC component and linear trends were completely eliminated by digital filtering for band pass between 0.03–0.5 Hz in rest and 0.03–0.8Hz during exercise. After passing through a Hamming-type data window, power spectrum analysis using a fast Fourier transform was performed on consecutive 240 s time series of the data for R-R intervals obtained during the experiments. We analysed LO (0.03–0.15 Hz), HI (at rest: 0.15–0.4 Hz, during exercise: 0.15–0.8Hz), and total power (TOTAL, at rest: 0.03–0.4 Hz, during exercise: 0.03–0.8Hz) by integrating the spectrum for the appropriate bandwidth. Because integrated values of the basal spectrum differ greatly among individuals, the value of each placebo trial was standardized as 100%, and the other values were compared to this. Statistical Analyses All statistical analyses were performed using a commercial software package (SPSS version 7.5 for Windows, SPSS Inc., Chicago, Ill.). The effects of time, treatment and time·treatment were evaluated using 2-way ANOVA for repeated measurements; for comparisons between the trials at certain times, we used Student’s paired t-test. P values of less than 0.05 were considered to be statistically significant. Data are expressed as mean +/- SEM.
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How many outcome-specific endpoints are evaluated? 3
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Blood pressure (SBP, DBP)
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List additional health endpoints (separately). 2 Heart rate
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List additional health endpoints (separately).3 Heart rate variability (low frequency, high frequency, and total power power)
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List additional health endpoints (separately).4
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List additional health endpoints (separately).5
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List additional health endpoints (separately).6
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Clinical, physiological, other Physiological
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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? Objective
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Optional: Name of Method or short description The ECG was obtained using a CM5 lead. The analogue output of the ECG was connected to an ECG amplifier (Multi-channel Amplifier MEG-6100, Nihon Kohden Co., Japan) and digitized using a 13 bit analogue-to-digital converter (HTB410) at a sampling rate of 1 kHz, using a 0.5 Hz–100 Hz band pass filter at rest and a 1.5 Hz–100 Hz filter during exercise. The BP was recorded using an automated sphygmomanometer (FINAPRES 2300, Ohmeda, USA) connected to a finger cuff containing a plethysmotransducer. Analogue output of the BP was digitized using a 13 bit analogue-to-digital converter at a sampling rate of 1 kHz. Beat-by-beat systolic blood pressure (BPs) and diastolic blood pressure (BPd) values were calculated later using computer software developed in our laboratory.
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Caffeine (general) Caffeine (general)
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Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other?
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Measured or self reported? Measured
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Children, adolescents, adults, or pregnant included? Adults
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) Subjects served as their own controls
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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) None
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What conflicts of interest were reported? No information provided
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Refid 12355185
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What were the sources of funding? This work was supported in part by grants from the Institute for Health Care Science, Suntory Ltd. to T. Moritani.
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Results & Comparisons

No Results found.