STEPPING OUTSIDE THE BOX: TAILORING EXERCISE TEST PROTOCOLS & PROCEDURES
Authors: Brawner Clinton A. , Pasztor Samantha A. , Keteyian Steven J. , Ehrman Jonathan K. , Gindi Ryan 
Published: February 2025

https://youtu.be/r8yQKiNeJWc

INTRODUCTION

The most frequently used exercise test protocol in the United States is the Bruce treadmill protocol. Using this standard protocol enables clinicians to report clinically useful information beyond myocardial ischemia, hemodynamic response, and rhythm, such as estimating prognosis with the Duke Treadmill Score and categorizing fitness by age and sex. However, some patients, especially highly fit aerobic-type athletes, might be better served with tailored exercise test procedures.

CASE PRESENTATION

A 22-year-old, apparently healthy male, collegiate track athlete complained of lightheadedness and profound fatigue after repeated intervals of 400-800 m. The referring physician ordered a cardiopulmonary exercise test in order to replicate his training regimen and symptoms.

MANAGEMENT

A plan was developed to perform a graded exercise test (GXT) on a treadmill with measurement of expired air, followed by a 3-min active cooldown, then up to 4 run/walk intervals of 1- and 2-min duration, respectively. Spirometry was performed before the GXT and repeatedly up to 20 min after the last run interval. The GXT protocol was based on the athlete’s self-reported pace during warmup (8:00/mile [4:58/km]) and a 10 km run (6:00/mile [3:44/km]) with a target duration of 10 min. The run intervals were based on his self-reported target time to complete 400 m (~65 s) during training. That time was converted to speed (13.8 miles/h [22.2 km/h]) and the associated metabolic equivalents of task (METs) were estimated (22 METs). Because the maximum speed of the laboratory treadmill is 12 miles/h (19.3 km/h), a 3% incline was used to achieve the target METs during the run intervals. A 12-lead ECG and pulse oximetry were monitored continuously during the GXT, the run/walk intervals, and through 6 min of recovery. Blood pressure (BP) was monitored via auscultation every 2 min through the initial 6 min of the GXT and recovery. BPs could not be obtained at higher running speeds. He did not use the handrail for support during testing. He reported that the run intervals were a similar level of exertion as during training. No abnormalities were noted during the GXT or the spirometry. His symptoms were reproduced during the 4th run interval. Total time in the laboratory was 1.5 hours.

DISCUSSION

Exercise testing on this patient could have been limited to a GXT (Bruce protocol or other), but the probability of reproducing his symptoms would have been low. As a young athlete, staff were confident that he could tolerate a GXT and several running intervals during the same encounter. Knowledge of METs allowed for an equivalent workload to be identified for the intervals despite limitations of the treadmill speed. It is not uncommon for laboratories to limit testing protocols to a few options (e.g. Bruce or modified Bruce). However, it can be beneficial to tailor procedures for select patients to increase the likelihood of reproducing patient-specific complaints or responses.