Using the Karvonen formula, how do you calculate the Low end of the Target Heart Rate Zone (THRZ)?

To calculate the low end of the Target Heart Rate Zone (THRZ) using the Karvonen formula, the correct approach involves determining the Heart Rate Reserve (HRR) and then applying a percentage to it. Specifically, the formula considers both the HRR and the resting heart rate.

The HRR is calculated by subtracting the individual’s resting heart rate from their maximum heart rate (MHR). The MHR is typically estimated as 220 minus the person's age. After this, to find the low end of the THRZ, the formula takes 50% of the HRR and adds the resting heart rate back in. This step is crucial because it ensures that the calculated heart rate is above the resting level, effectively creating a personalized target zone that reflects both fitness level and resting physiological state.

Therefore, the correct calculation for the low end of the THRZ using the Karvonen formula is represented by multiplying the HRR by 0.50 and then adding the resting heart rate. This method ensures that the resulting target heart rate is both achievable and tailored to the individual.

In contrast, other options do not correctly apply the components of the Karvonen formula to derive the low end of the THRZ.