Insufficient control of exercise intensity by heart rate monitoring in cardiac patients.

OBJECTIVES: To test the reliability of heart rate (HR) recommendations for cardiac rehabilitation training obtained from different treadmill tests. BACKGROUND: For training in cardiac rehabilitation, HR recommendations are derived from cardio-pulmonary tests. Exercise intensity is often controlled through self-monitoring HR by the cardiac patients. DESIGN: Non-randomized clinical trial. METHODS: 25 patients of a cardiac sports group (six women, 19 men, age 68.3 ± 5 years, height 171 ± 10 cm, weight 82 ± 12.8 kg) performed a stepwise increasing treadmill test according to a modified Stanford protocol (S) and a ramp treadmill test according to the Balke-Ware protocol (B) until volitional exhaustion. In 16 patients, HR was assessed with a HR monitor and compared with HR obtained by self-monitoring through pulse palpation during three training sessions. RESULTS: Similar peak cardiopulmonary responses were obtained with the two exercise protocols of significantly (p < 0.001) different duration (S 22:05 ± 7:11 min, B 13:31 ± 4:20 min). During the training sessions, HR exceeded the upper HR limit set at 85% HR(peak) in 15 patients and in nine patients, higher HR(peak) than in the exercise tests was observed. Five participants did not accurately measure their HR by pulse palpation. CONCLUSIONS: All but one patient of the cardiac sports group did not adhere to the HR recommendations derived from incremental treadmill testing, most likely because volitional exhaustion occurred in both treadmill tests before maximal cardiopulmonary responses were reached. In about 30% of the patients, training intensity could not be controlled by self-monitoring because of inaccurate pulse palpation.

Effects of acute moderate hypoxia on anaerobic capacity in endurance-trained runners.

While there is some controversy whether anaerobic capacity might be improved after altitude training little is known about changes in anaerobic capacity during hypoxic exposure in highly trained athletes. In order to analyze the effects of acute moderate normobaric hypoxia on anaerobic capacity, 18 male competitive triathletes, middle- and long-distance runners VO2max 67.4 +/- 3.8 ml kg min(-1) performed 2 supra-VO2max treadmill runs with the same speed, one in normoxia and one after 4 h exposure to normobaric hypoxia (FiO(2) 0.15), for estimation of their maximal accumulated oxygen deficit (MAOD) and measurement of peak capillary lactate and peak capillary ammonia concentration. MAOD was not significantly different in normoxia and in moderate hypoxia while time to exhaustion and accumulated O(2) uptake were significantly (P < 0.001) reduced in hypoxia compared to normoxia by 28 and 45%, respectively. The reduction in time to exhaustion was significantly correlated to the decrement in accumulated O(2) uptake (R = 0.730, P = 0.001). In hypoxia, there was a tendency for peak capillary lactate concentration to be decreased compared to normoxia (12.9 +/- 2.1 vs. 13.8 +/- 2.2 mmol l(-1), P = 0.082); peak capillary ammonia concentration was significantly decreased in hypoxia (97 +/- 52 vs. 121 +/- 44 micromol l(-1), P = 0.032). In conclusion, anaerobic capacity is not significantly changed during acute exposure to moderate hypoxia in endurance-trained athletes. The performance reduction during all-out exercise of short duration has to be attributed to the decrement in aerobic capacity.