Introduction. The objective of this paper was to verify hart rate values for the anaerobic threshold in cross-country skiers during long-term submaximal intensity training effort. Material and methods. Stress tests were conducted for 6 athletes (4 female and 2 male members of the Polish National Team). The first test involved a graded-intensity laboratory stress test on a mechanical treadmill which consisted of 5-minute exercising periods and enable determining the anaerobic threshold values. The subsequent test (performed within 2-7 days after the first test) involved a submaximal intensity run test based on the determined heart rate (HR) ranges for 400 m on a tartan track. The test involved a 10-minute run done three times at a given intensity based on the HR values for blood lactate level at 4 mmol/l (HRppa), previously determined during the laboratory tests. First exercise: a run at a speed corresponding to HRppa minus 10 bpm, second exercise: HRppa minus 5 bpm and third exercise: HRppa. Results. The verification of the HRppa values recorded in the laboratory tests on a mechanical treadmill confirmed that this indicator is moderately useful for the purpose of selecting the exercise load during race trainings in natural conditions. Conclusion. The race speeds determined on a mechanical treadmill for the anaerobic threshold need to be corrected (increased speed) for the purpose of finding similar exercise load for race trainings in natural conditions.