(46) The Validity of the PACER Test for Predicting Maximal Oxygen Consumption

Background: Indirect calorimetry has been a staple and criterion measure for estimating maximal oxygen consumption (VO_2max) in athletes. However, equipment to perform this test is costly and requires training and personnel. The Progressive Aerobic Capacity Endurance Run (PACER), was developed in 1982 and is designed to estimate VO_2max using a 20-meter shuttle run and is traditionally used to evaluate youth, although it is used in adult populations. Little evidence currently exists validating the PACER test in adult athletes, specifically highly trained aerobic endurance athletes who participate in continuous exercise events.

Purpose: To determine the validity of the PACER test when compared to the criterion measure of indirect calorimetry using a graded exercise test (GET).

Methods: 7 collegiate cross country male athletes were recruited (Age: 20.4 ± 1.3, Height: 1.74 ± 0.08, Weight: 65.2 ± 14.3). A randomized experimental design was utilized to compare the criterion measure for VO_2max with the VO_2max as estimated by the PACER test. Subjects completed two testing sessions separated by no less than 24 hours. In one session, subjects completed the PACER test as described in the FitnessGram protocol. This consists of a 20-meter shuttle run that progressively increases the pace of running at set intervals until the subject cannot maintain the pace or voluntarily ends the test. The GET consisted of running on a treadmill using the Bruce treadmill protocol, which is a progressive staged exercise that increases in speed or grade every three minutes until volitional failure. A Parvomedics metabolic cart was utilized to measure oxygen consumption of the participants. All tests were taken to volitional failure. For the day of testing, subjects were asked to monitor their food with a food log, and replicate their meals between the two days of testing. Upon arrival, subjects completed a hydration USG test, food, sleep, footwear, and caffeine questionnaire. Subjects did a 10-minute dynamic warm up. They then performed their test until volitional failure. To compare the validity of the PACER test, we used Bland-Altman analysis to calculate the bias and limits of agreements between the two tests and performed a linear regression analysis.

Results: Figure 1 shows the results of the Bland-Altman analysis. The results of the Bland-Altman analysis shows that PACER has a bias of -4.3 ± 8.1 ml/kg/min and the limits of agreement (LOA) were -20.2 and 11.5. The results of the regression analysis showed VO_2max is not significantly predicted by the PACER.

Conclusions: The PACER test is not a valid way to test VO_2max in endurance athletes. When interpreting the bias and LOA, we see that on average the PACER test underestimated VO_2max by 4.3 ml/kg/min.  The LOA show that the true mean difference is quite wide and the PACER test may not meaningfully predict VO_2max in this population. One explanation could be that elite endurance runners rarely need to stop their forward momentum and acceleration in the opposite direction, as done in the PACER.  This may lead to a reduce overall performance in the shuttle run, as excess energy is used in the deceleration and acceleration phase during change of direction.  PRACTICAL APPLICATION: The PACER test should not be used to estimate VO_2max in endurance athletes. However, studies suggest that the PACER test is valid within the average population, adolescents, and explosive athletes. 

Acknowledgements: None