Do Recreational Endurance Athletes Fulfill Exhaustion Criteria in Endurance Performance Diagnostics Sufficiently?

Background: To determine individual maximum oxygen uptake (VO_2max) during incremental tests it is necessary that subjects reach exhaustion. The literature describes different exhaustion criteria.

Aims: To assess the percentage of recreational endurance athletes fulfilling different levels of exhaustion criteria.

Methods: Two hundred and seventeen male (36.0±15.6 years; 77.3±10.1 kg; 180.3±7.1 cm) and 90 female (48.2±17.7 years; 66.7±11.3 kg; 166.0±6.5 cm) recreational endurance athletes performed an incremental cycling test (50 W/min^-1 increasing linearly each 2 min^-1 by 25 W/min^-1) until volitional exhaustion. Breath-by-breath respiratory parameters were measured permanently; heart rate and blood lactate concentration were determined at exhaustion. In order to analyze the percentage of participants fulfilling exhaustion criteria, two levels were used. Level one: 1) Levelling off in oxygen uptake (VO_2LO); 2) Predicted maximum heart rate (HR_max) 210-age [years]; 3) Respiratory exchange ratio (RER) 1.1; 4) Ventilatory equivalent (VE) 35; 5) Blood lactate concentration (La) ≥ 9 mmol/l; and Level two: 1) VO_2LO; 2) HR_max 200-age [years]; and 3) RER ≥ 1.0; 4) VE 30; 5) La ≥ 8 mmol/l.

Results: Concerning exhaustion, criteria level one 71.3% of the participants reached VO_2LO, 71.9% HR_max, 65.8% RER, 41.4% VE, and 50.4% La; level two 71.3% VO_2LO, 91.1% HR_max, 94.1%, RER, 76.6% VE, and 62.4% La.

Discussion: Regarding both levels, a considerable number of participants did not meet the exhaustion criteria. Therefore, a general statement of reaching VO_2max via an incremental cycling test should be treated with caution. A distinction between VO_2max and VO_2peak will be conducted in the future.