title: Effect of time of day on the relationship between lactate and ventilatory thresholds: a brief report.
abstract: The purpose of this investigation was to study the effect of time of day on the relationship between lactate (LT) and ventilatory thresholds (VT) of pulmonary oxygen uptake (VO2). Seven moderately active male volunteers (26.3 ± 3.0 years, 1.74 ± 0.08 m, 76 ± 5 kg) performed a maximal incremental test (increases of 30 W every 2 min) on a cycle ergometer on consecutive days at 0900 h, 1400h and 1900 h in a randomized fashion. The anaerobic threshold was determined using both ventilatory gas analysis and blood lactate measures. Each of the following variables was recorded both at VT and the LT; heart rate (HR, beats.min(-1)), minute ventilation (VE, L.min(-1)), respiratory exchange ratio (RER), time to threshold (Time, sec), oxygen uptake (VO2, ml·kg(-1).min(-1)) and VO2 as a percentage of maximal oxygen uptake (%VO2max). The correlations between VT and LT variables analyzed by Pearson product moment correlations for each time of day. ANOVA was used to compare the data obtained at different times of the day. There were no significant differences for the data related to time of day either for ventilatory gas analysis or lactate measurements. The correlation coefficients between VT and LT variables were moderate to high (r=0.56-0.94) for time of day. However, the correlations for HR, VO2, and %VO2max (r=0.81-0.94) were slightly stronger compared with Time, VE and RER (r=0.56-0.88). It was concluded that, the data at VT and LT were not influenced by time of day.
authors.affiliation: Medical Faculty of Uludag University , Department of Sports Medicine, Bursa, Turkey.
authors.forename: Ufuk
authors.initials: U
authors.lastname: Sekir
authors.affiliation: Medical Faculty of Uludag University , Department of Physiology, Bursa, Turkey.
authors.forename: Fadil
authors.initials: F
authors.lastname: Ozyener
authors.affiliation: Medical Faculty of Uludag University , Department of Sports Medicine, Bursa, Turkey.
authors.forename: Hakan
authors.initials: H
authors.lastname: Gür
keywords: Anaerobic threshold; circadian rhythm
references.citation: J Appl Physiol (1985). 1985 Apr;58(4):1115-21
references.pmid: 3988668
references.citation: Chronobiol Int. 1990;7(1):59-67
references.pmid: 2372852
references.citation: Respiration. 1979;38(1):36-42
references.pmid: 493728
references.citation: Am J Cardiol. 1964 Dec;14:844-52
references.pmid: 14232808
references.citation: Adv Cardiol. 1986;35:47-64
references.pmid: 3551516
references.citation: Ergonomics. 1982 Nov;25(11):1093-107
references.pmid: 7173159
references.citation: J Sports Med Phys Fitness. 1996 Sep;36(3):155-60
references.pmid: 8979644
references.citation: J Appl Physiol (1985). 1985 Dec;59(6):1936-40
references.pmid: 4077801
references.citation: Pediatr Cardiol. 1999 Jan-Feb;20(1):12-5; discussion 16
references.pmid: 9861065
references.citation: J Sports Med Phys Fitness. 1997 Jun;37(2):117-21
references.pmid: 9239989
references.citation: J Appl Physiol (1985). 1986 Jun;60(6):2020-7
references.pmid: 3087938
references.citation: Br J Nutr. 1974 Jul;32(1):77-97
references.pmid: 4843734
references.citation: Crit Rev Biomed Eng. 1990;18(3):165-80
references.pmid: 2286092
references.citation: J Appl Physiol. 1976 Oct;41(4):544-50
references.pmid: 985399
references.citation: Sports Med. 1993 Feb;15(2):104-15
references.pmid: 8446822
references.citation: Eur J Appl Physiol Occup Physiol. 1998 Feb;77(3):249-56
references.pmid: 9535586
references.citation: Ergonomics. 1980 Jun;23(6):591-5
references.pmid: 7202402
references.citation: Br J Sports Med. 1994 Mar;28(1):18-21
references.pmid: 8044486
references.citation: Eur J Appl Physiol Occup Physiol. 1985;54(1):104-8
references.pmid: 4018043
references.citation: J Appl Physiol (1985). 1986 Sep;61(3):999-1004
references.pmid: 3759786
references.citation: JAMA. 2000 Dec 20;284(23):3043-5
references.pmid: 11122593