Systematic Review and Meta-analysis on the Relationship Between Lactate and Ventilatory Thresholds and Fatmax: an Interim Analysis

BACKGROUND: The relationship between lactate threshold (LT), ventilatory threshold (VT) and the exercise-intensity associated with maximal fat oxidation (Fatmax) is unclear. Despite this, the three measures are commonly utilised widely and interchangeably within both athletic sporting environments and clinical settings to enhance fuel utilisation and address disturbed fat metabolism respectively. A clearer understanding of their potential relationship and capacity to improve both athlete performance and patient outcomes is necessary. PURPOSE: To synthesise existing literature and determine the relationship between LT and/or VT and Fatmax during exercise within apparently healthy participants. METHODS: PubMed, MEDLINE, Embase and Scopus were systematically searched from inception to 9th July 2022. Studies were included if they reported measures of the LT and/or VT, and Fatmax in apparently healthy participants. Pooled effect sizes were analysed for studies comparing the relative intensities (i.e., % of maximal oxygen uptake (VO2max)) between LT/VT and Fatmax using a random-effects meta-analysis with mean differences (MD). A meta-regression is planned to examine the relationship between LT/VT and Fatmax, after accounting for differences in mean age, sex, training history, diet, and testing protocols. RESULTS: After screening the title and abstracts of 2,331 studies, 264 full texts were screened, and only 56 studies were included in the analysis. Of that, 23 studies reported % VO2max for LT/VT, and Fatmax which were deemed eligible for inclusion in this meta-analysis. Of the included studies, there was a total of 900 participants. There were 8 studies that measured LT, while 14 measured VT and only 1 measured both LT and VT. The average exercise intensity associated with the LT/VT and Fatmax was 60.2 ± 9.9% and 54.54 ± 10.76% VO2max, respectively. The meta-analysis showed that the relative exercise intensity that LT/VT occurred at was not significantly different to that observed for Fatmax (Z = 0.84, P = 0.40, MD = 1.29 % VO2max (-1.73, 4.32)). CONCLUSION: Our interim findings show that LT/VT occurred on average at the same relative exercise intensity as Fatmax, thus suggesting the interchangeable use of LT, VT and Fatmax when considering exercise prescription. REGISTRATION: PROSPERO ID CRD42022346457.