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Medicina dello Sport 2017 March;70(1):61-8

DOI: 10.23736/S0025-7826.16.02800-3


language: English, Italian

The interaction of caffeine consumption and circadian rhythm in cardiovascular responses to exercise

Sakineh GHAEDI, Maryam K. JAHROMI, Aliasghar FALLAHI

Physical Education and Sport Science Department, School of Education and Psychology, Shiraz University, Shiraz, Iran


BACKGROUND: Caffeine is a widely used supplement which may interact with other environmental factors. The aim of this study was to determine the influence of caffeine consumption on cardiovascular response, following a session of morning and afternoon anaerobic exercises in active girls.
METHODS: The study was designed as double blind, cross over randomized, and placebo control. Fifteen active girls (age: 24±1 y, height: 160.75±4.95 cm, weight: 53.58±6.24 kg), participated in this study, voluntarily and purposefully. Participants carried out RAST test during four sessions including two morning sessions at 9:00 and two afternoon sessions at 17:00 with and without consuming caffeine separated by one week interval trials performed 60 minutes following ingesting 3 mg/kg caffeine or placebo. Afternoon systolic and diastolic blood pressure (BP) and heart rate (HR) were measured immediately and 5 minutes following exercise.
RESULTS: Caffeine caused significant increasing of afternoon systolic BP (63%), and HR (45%) immediately following exercise and morning and afternoon systolic (59% and 82%, respectively) and diastolic BP (81% and 94%, respectively) 5 min following exercise and HR 5 min following afternoon exercise (70%). However, statistically, caffeine consumption did not affect morning systolic and diastolic BP and HR, afternoon diastolic BP immediately following exercise, morning HR 5 min after exercise and morning and afternoon anaerobic performance.
CONCLUSIONS: The ingestion of low dose of caffeine did not improve anaerobic exercise performance but increased cardiovascular load to exercise especially during afternoon. So, caffeine consumption is not recommended especially to people with hypertension during afternoon exercise.

KEY WORDS: Circadian rhythm - Caffeine - Cardiovascular system - Anaerobic threshold

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