Relation between duration and intensity of first exercise and "warm up" in ischaemic heart disease

OBJECTIVE: To determine the importance of the duration and intensity of "warm up" exercise for reducing ischaemia during second exercise in patients with exertional angina. DESIGN: Randomised crossover comparison of three warm up exercise protocols. PATIENTS: 18 subjects with stable ischaemic heart disease and > 0.1 mV ST segment depression on treadmill exercise testing. INTERVENTIONS: The warm up protocols were 20 minutes of slow exercise at 2.7 km/h, symptom limited graded exercise for a mean of 7.4 (range 5.0 to 10.5) minutes, and three minutes of symptom limited fast exercise of similar maximum intensity. MAIN OUTCOME MEASURES: ST segment depression during graded treadmill exercise undertaken 10 minutes after each warm up protocol or no warm up exercise. RESULTS: Compared with exercise with no warm up, the duration of graded exercise after earlier slow warm up increased by 4.9% (95% confidence interval (CI), -3.3% to 13.7%), after graded warm up by 10.3% (95% CI, 5.6% to 15.2%), and after fast warm up by 16% (95% CI, 6.2% to 26.7%). ST segment depression at equivalent submaximal exercise decreased after slow warm up by 27% (95% CI, 5% to 44%), after graded warm up by 31% (95% CI, 17% to 44%), and after fast warm up by 47% (95% CI, 27% to 61%). Compared with slow warm up exercise, the more intense graded and fast warm up protocols significantly increased the duration of second exercise (p = 0.0072) and reduced both peak ST depression (p = 0.0026) and the rate of increase of ST depression (p = 0.0069). CONCLUSIONS: In patients with exertional angina the size of the warm up response is related to the maximum intensity rather than the duration of first exercise.