Predictability of predicted HRmax in Black Africans

HRmax is the heart rate that can be attained after maximum exertion. It is an index of the amount of stress the heart can take during exercise. For safety reason, it is usually predicted and reduced to a certain percentage when prescribing exercise. 220
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age and 208
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0.7 x age are the common formulae used to predict HRmax. This study, using 40 young adults (22 male & 18 female) between the ages of 18-30 years, aims to validate the predictability of these formulae. They were subjected to maximum exertion on bicycle ergometer and the maximum heart rate measured. We then calculated the predicted HRmax and compare with the measured HRmax. The findings revealed that the measured HRmax is 135.70 ±3.80, Predicted HRmax using 220
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age is197.83 ±0.45 and using 208
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0.7 x age is 192.48 ±0.31. The 85% of Predicted HRmax, commonly used as submaximal HRmax was found to be 168.15 ±0.38. All these are significantly raised above the HRmax. The prediction error was found to be between 32 and 62 beats/minute (b/min) which is far above the acceptable 11 b/min. We then used 70% of Predicted HRmax and got means of 138.23 ±0.39 and prediction error of 3 b/min.In conclusion, caution should be taken in using these predictions and if we must, then we recommend values much below 85% Predicted HRmax; most especially in the elderly black Africans.