Background: Isokinetic testing imposes severe cardiovascular stress which must be taken into consideration particularly when at risk patients are involved. Objective: To assess the effects of isokinetic tests on heart rate (HR) in stable chronic heart failure (CHF) patients. Subjects: Twenty five CHF patients, 23 men, 2 women. Intervention: After a 10-min warm-up on a cycle ergometer, one lower limb was tested isokinetically using 3 successive repetitions of knee flexion-extension at 60 and 180 • /s and 20-repetitions at 240 • /s. Heart rate was recorded on average over 5 sec and was analyzed at the start and end of each exercise. PeakV O2 was assessed during maximal incremental test on the ergometer. Results: Maximal values (117.6 ± 22.0 bpm) of HR were obtained during incremental exercise testing which corresponded to 97.6 ± 14.0 % of maximal HR noted at peakV O2. Conclusion: Isokinetic muscle strength testing in CHF patients must be performed under the supervision of an experienced clinician who should judge the value and feasibility of the endurance test.