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Effect of acute calcium slow-channel antagonism on the cardiorespiratory response to graded exercise testing
Abstract:
The effect of acute calcium slow-channel antagonism on the cardiorespiratory responses of 12 healthy males was studied during multistage maximal exercise testing. Oral diltiazem (60 mg), nifedipine (10 mg), verapamil (80 mg), and placebo were administered in a randomized double-blind crossover fashion 1.5 h before an intermittent multistage cycle ergometer exercise test. At peak effort, heart rate, pulmonary ventilation, CO2 production, and respiratory exchange ratio were not significantly modified by drug ingestion. In contrast, maximal O2 consumption (2.6% reduction, P less than 0.02) and performance time (6.4% reduction, P less than 0.02) were reduced by nifedipine. During submaximal exercise, the chronotropic response was accentuated by nifedipine but not by diltiazem or verapamil. Furthermore, nifedipine altered the relationship of percentage of maximal O2 consumption to percentage of maximal heart rate, and both the relative and absolute O2 consumption corresponding to 70% and 85% of the maximal heart rate were significantly reduced after nifedipine ingestion. The results indicated that in persons without symptomatic coronary artery disease exercise performed at a given percentage of the maximal heart rate will yield a lower than expected relative and absolute intensity in the presence of acute nifedipine-induced calcium slow-channel antagonism.
Insights
Nifedipine, a calcium channel blocker, reduced exercise performance and altered heart rate responses in healthy males. Exercise intensity may be overestimated when using heart rate during nifedipine use.
Area of Science:
- Cardiology
- Exercise Physiology
Background:
- Calcium channel blockers are widely used for cardiovascular conditions.
- Their effects on exercise capacity in healthy individuals require further elucidation.
Purpose of the Study:
- To investigate the impact of acute calcium slow-channel antagonism on cardiorespiratory responses during maximal exercise.
- To compare the effects of diltiazem, nifedipine, and verapamil on exercise performance.
Main Methods:
- A randomized, double-blind, crossover study involving 12 healthy males.
- Administration of oral diltiazem (60 mg), nifedipine (10 mg), verapamil (80 mg), or placebo 1.5 hours before exercise testing.
- Multistage maximal cycle ergometer exercise testing to assess cardiorespiratory parameters.
Main Results:
- Nifedipine significantly reduced maximal oxygen consumption and performance time.
- Nifedipine accentuated the heart rate response during submaximal exercise.
- Drug ingestion did not significantly alter peak heart rate, ventilation, or CO2 production.
- Nifedipine altered the relationship between maximal oxygen consumption and maximal heart rate percentage.
Conclusions:
- Acute nifedipine use can lead to an underestimation of exercise intensity when using heart rate as a measure in individuals without coronary artery disease.
- Diltiazem and verapamil did not show significant effects on exercise performance or heart rate response in this context.