Changes

It is often suggested that HR_max varies with the mode of exercise. If you consider HR_max to be the highest [[Heart Rate ]] that the heart is capable of achieving, then this makes no sense. However, some sports do not use sufficient amounts of muscle to max out the heart rate. If you consider an extreme example, doing bicep curls would not demand enough oxygen to raise the heart rate to HR_max. This means that sports like cycling, which use a smaller number of muscles than running, will not raise the heart rate to HR_max. However, there will be a highest heart rate for that sport, and using that value as HR_max may be useful as the sport specific HR_max will reflect how hard the working muscles are being used. So if you have a HR_max of 200 while running, but 180 while cycling, then it is appropriate to use a 'HR_max' of 180 for cycling activities. So exercising at 75% of HR_max would be 150 when running and 135 while cycling. The lower [[Heart Rate ]] when cycling will reflect the fact that the heart and lungs are not working as hard when running as when cycling, but the active muscles should be performing at a similar level.