title: Improvements on neuromuscular performance with caffeine ingestion depend on the time-of-day.
abstract: OBJECTIVE
  To determine whether the ergogenic effects of caffeine ingestion on neuromuscular performance are similar when ingestion takes place in the morning and in the afternoon.
  
  
  METHODS
  Double blind, cross-over, randomized, placebo controlled design.
  
  
  METHODS
  Thirteen resistance-trained males carried out bench press and full squat exercises against four incremental loads (25%, 50%, 75% and 90% 1RM), at maximal velocity. Trials took place 60 min after ingesting either 6 mg kg(-1) of caffeine or placebo. Two trials took place in the morning (AMPLAC and AMCAFF) and two in the afternoon (PMPLAC and PMCAFF), all separated by 36-48 h. Tympanic temperature, plasma caffeine concentration and side-effects were measured.
  
  
  RESULTS
  Plasma caffeine increased similarly during AMCAFF and PMCAFF. Tympanic temperature was lower in the mornings without caffeine effects (36.7±0.4 vs. 37.0±0.5°C for AM vs. PM; p<0.05). AMCAFF increased propulsive velocity above AMPLAC to levels similar to those found in the PM trials for the 25%, 50%, 75% 1RM loads in the SQ exercise (5.4-8.1%; p<0.05). However, in the PM trials, caffeine ingestion did not improve propulsive velocity at any load during BP or SQ. The negative side effects of caffeine were more prevalent in the afternoon trials (13 vs. 26%).
  
  
  CONCLUSIONS
  The ingestion of a moderate dose of caffeine counteracts the muscle contraction velocity declines observed in the morning against a wide range of loads. Caffeine effects are more evident in the lower body musculature. Evening caffeine ingestion not only has little effect on neuromuscular performance, but increases the rate of negative side-effects reported.
authors.affiliation: Exercise Physiology Laboratory at Toledo, University of Castilla-La Mancha, Spain. Electronic address: Ricardo.Mora@uclm.es.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Mora-Rodríguez
authors.affiliation: Exercise Physiology Laboratory at Toledo, University of Castilla-La Mancha, Spain.
authors.forename: Jesús G
authors.initials: JG
authors.lastname: Pallarés
authors.affiliation: Faculty of Sport Sciences, University of Murcia, Spain.
authors.forename: José María
authors.initials: JM
authors.lastname: López-Gullón
authors.affiliation: Exercise Physiology Laboratory at Toledo, University of Castilla-La Mancha, Spain.
authors.forename: Álvaro
authors.initials: Á
authors.lastname: López-Samanes
authors.affiliation: Exercise Physiology Laboratory at Toledo, University of Castilla-La Mancha, Spain.
authors.forename: Valentín E
authors.initials: VE
authors.lastname: Fernández-Elías
authors.affiliation: Exercise Physiology Laboratory at Toledo, University of Castilla-La Mancha, Spain.
authors.forename: Juan F
authors.initials: JF
authors.lastname: Ortega
mesh_terms: D001831:Body Temperature / Q000187:drug effects; D002110:Caffeine / Q000008:administration & dosage* / Q000009:adverse effects / Q000097:blood; D000697:Central Nervous System Stimulants / Q000008:administration & dosage* / Q000009:adverse effects / Q000097:blood; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005080:Exercise Test; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D053580:Muscle Strength / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects*; D013997:Time Factors; D014891:Weight Lifting / Q000502:physiology*; D055815:Young Adult
chemical_list: D000697:Central Nervous System Stimulants; D002110:Caffeine
keywords: Body temperature; Chronobiology; Circadian rhythm; Ergogenic aid; Maximal voluntary contraction; Muscle strength