Understanding the Harvard Step Test and PEI Calculation

The Harvard Step Test is a type of cardiac stress test for detecting and diagnosing cardiovascular disease and for evaluating physical fitness. It measures your ability to recover after strenuous exercise. The test involves stepping up onto and down from a platform at a set rate for a set period.

The Physical Efficiency Index (PEI) is a score calculated based on the duration of the exercise and the heart rate during the recovery period. A higher PEI generally indicates better cardiovascular fitness.

Physical Efficiency Index (PEI) Long Form Formula

The formula for calculating the PEI using the long form of the Harvard Step Test is:

$$ \text{PEI} = \frac{\text{Duration of Exercise in Seconds} \times 100}{2 \times (\text{Sum of Pulse Counts in Recovery})} $$

The pulse counts in recovery are typically measured at three specific intervals:

• 1 to 1½ minutes after exercise stops.
• 2 to 2½ minutes after exercise stops.
• 3 to 3½ minutes after exercise stops.

Applying the Data from the Question

Let's take the data provided in the question and plug it into the formula to calculate the subject's Physical Efficiency Index.

• Duration of exercise = 5 minutes
• Duration of exercise in seconds = $5 \text{ minutes} \times 60 \text{ seconds/minute} = 300 \text{ seconds}$
• Recovery Pulse Count 1 (1‐1½ mins) = 75 beats
• Recovery Pulse Count 2 (2‐2½ mins) = 50 beats
• Recovery Pulse Count 3 (3‐3½ mins) = 35 beats

Sum of the three recovery pulse counts = Pulse 1 + Pulse 2 + Pulse 3

Sum of pulse counts = $75 + 50 + 35 = 160$ beats

Calculating the PEI

Now, using the long form PEI formula:

$$ \text{PEI} = \frac{\text{Duration of Exercise in Seconds} \times 100}{2 \times (\text{Sum of Pulse Counts})} $$

Substitute the values:

$$ \text{PEI} = \frac{300 \times 100}{2 \times 160} $$

$$ \text{PEI} = \frac{30000}{320} $$

$$ \text{PEI} = \frac{3000}{32} $$

$$ \text{PEI} = 93.75 $$

The calculated Physical Efficiency Index (PEI) is 93.75. When comparing this to the options, 94 is the closest value.

Interpreting the PEI Score

The PEI score provides an indication of cardiovascular fitness. While specific interpretation scales can vary slightly, a score around 90 or above generally suggests good to excellent fitness for the Harvard Step Test.

• Below 55: Poor
• 55 - 64: Low Average
• 65 - 79: High Average
• 80 - 89: Good
• 90 and above: Excellent

Based on this general scale, a PEI of 93.75 (or 94) indicates excellent cardiovascular fitness for the subject.

Revision Table: Harvard Step Test Key Points

Additional Information: Harvard Step Test Variations

Besides the long form, there is also a short form of the Harvard Step Test. The main difference lies in the PEI calculation formula and the number of recovery pulse measurements used.

Short Form PEI Formula:

$$ \text{PEI} = \frac{\text{Duration of Exercise in Seconds} \times 100}{5.5 \times (\text{Pulse Count at 1½ minutes recovery})} $$

This formula only uses the pulse count taken from 1 to 1½ minutes of recovery.

The long form is considered more accurate as it takes into account the recovery heart rate over a longer period, providing a more comprehensive picture of how quickly the heart rate returns to normal.