SUMMARY Adaptation to exercise was investigated in 14 men aged 34-69 years (mean 51) with stable exertional angina caused by occlusive coronary artery disease. All underwent exercise electrocardiography to symptom limitation according to the Bruce protocol (first effort), and exercise to the onset of angina (warm up) followed by four minutes' rest, followed by exercise to symptom limitation (second effort). This protocol was repeated after sequential treatment for one month each with nifedipine 10mg three times a day and with timolol 10mg twice a day. Warm up significantly increased walking time to the onset of angina by 34-5% and to maximal exercise by 29-5%. The heart rate and rate-pressure product were significantly higher on second effort both at the onset of angina (by 7 0 % and 11 1% respectively) and at maximal exercise (by 10 5 % and 15A4% respectively). ST segment displacement was not significantly different after warm up. The effect of warm up on walking time to the onset of angina was markedly reduced after treatment with nifedipine but little influenced by timolol. Mean (SE) walking time after warm up on no treatment was 10 1 (0 7) min; after treatment with nifedipine it was 10 0 (0-6) min and after treatment with timolol it was 9-7 (0-4) min.These data demonstrate a substantial improvement in exercise performance after warm up and are consistent with the hypothesis that submaximal exercise in angina pectoris facilitates myocardial oxygen uptake by coronary vasodilatation.Heberden first described the loss of symptoms with continued exercise in a patient experiencing angina.2 It has been variously described; by Osler as "walking through"3 and by Wenckebach as the "second wind".4 Gallavardin recorded the "warming up" effect of previous exercise in angina pectoris5 and Price described the phenomenon as "first effort angina".6 Gallavardin claimed it was not an uncommon phenomenon' but others have been unable to demonstrate it.7 Wayne and Gaybriel described two patients whose exercise performance was enhanced when they re-exercised between five and 30 minutes after an attack of angina, the effect being lost when the interval was one hour.
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