Influence of protocols and criteria in ventilatory and lactate thresholds - Abstract

The relationship between ventilatory (VTs) and lactic threshold (LTs) has been the main subject of numerous investigations in literature. The type of treadmill protocol test, the criteria utilized in the determination of the thresholds, as well as the subjectivity of the evaluator's determination, are among the various factors that may influence the relationship between VTs and LTs. The purpose of the present study was to determine the relationship between the VT and LT using three criteria for the determination of VT (1. minimum value of VEO2 before its systematic increase without an increase of VECO2; 2. the linearity break in the increase in VCQ2 versus V02; and 3. an abrupt and systematic increase of RER); and two criteria for LV2 (1. smaller VE CO2, before its systematic increase; 2. the linearity break in the increase of VE versus VCO2) with the LTs determined by the interpretation of the lactate curve, as suggested by Skinner & McLellan (Res. Q. Exerc. Sports, 5l (l):234-248, 1980). The VTs for each criterion were determined by the average of the evaluators that presented a high intra-evaluator reliability. The LTs were determined by two evaluators working together, as suggested by Aunola & Rusko (Eur. J. Appl. Physiol., 53:260-266,1984). Ten long-distance runners (age = 29 ± 4 years; body fat determined by hydrostatic weighing = 6.2 ± 3.5; and VO2peak = 72.9 ±5.4 ml.kg-1 .min-1) after being exposed to an adaptation session, were randomly submitted to two maximum progressive tests on a treadmill with different protocols in two separate days (Protocol A - 4-min warm-up at 3.5 mph and 0% slope; followed by 5.0 mph at a 2% slope, with subsequent increases in speed by 1,1 mph every 2 min until volitional fatigue; Protocol B - 6 min warm up at 0% slope, being 3 min at 3.5 mph and 3 min at half way between 3.5 mph and 60% of VO2peak, followed by an increase in 2% in the slope with a speed equivalent to 60% VO2peak for two min; thereafter the speed was increased every 2 minutes until volitional fatigue with increments based on the formula - Increment = [(Max Vel + 15%) -(Speed at 60% Max) 9]. Throughout the test, all subjects were continuously monitored for respiratory gas exchange measurements, as well as for blood lactate variables, at regular intervals. ANOVA results did not show any significant interactions (p < 0.05) for criteria (LTs and VTs) and protocols. Student t test showed no significant differences (p < 0.05) in the determination of the thresholds for both protocols used. All correlation coefficients were significantly high (p<0.05) for LT and VT, with the exception of criterion #4 and LT2. Based on the present results, within the limitations of the present study, it was concluded that: a) in long-distance runners, when tested under the same procedures as the present ones, the relationship between VTL and LTL was shown to be satisfactory and not dependent on the protocol used; and b) it is recommended that the determination of the VTs should be done by using criterion # 3 (VT 1 ) and # 5 (VT2) and protocol B.