Development of the A-STEP: A new incremental maximal exercise capacity step test in cystic fibrosis

Exercise testing is important in people with cystic fibrosis (pwCF). The aim was to develop an incremental maximal step test to assess exercise capacity across the range of pwCF, without floor or ceiling effects, within restrictions of space, and infection prevention.

The step test was developed in adults with stable CF. Subjects assisted in selecting: step height, start rate, increments, stage and test duration parameters. Equipment to externally pace and time the test and measure exercise parameters were selected. Reasons for stopping, criteria for achieving a maximal test, and key outcome measures were determined. Documentation to record and standardize the test and instructions to set up the metronome and timer App were developed. Infection control practices were considered.

Eight subjects were recruited to develop the Alfred Step Test Exercise Protocol (A-STEP) on a 20 cm portable step. The A-STEP package included a pretest information sheet, clinical assessment and instructions, recording worksheet, and the metronome/timer instructions. The test started at 18 steps/min. Each level increased by two steps/min to a maximum of 48 steps (Level 16). Results were presented as mean (SD) [range] for: age 30.63 (5.89) [21-39] years; FEV₁ 58.13 (18.33) [32-89]%; levels: 10.31 (3.29) [6-15.5]. The A-STEP required space of 2 m² and complied with current infection control guidelines.

The A-STEP is a new incremental maximal step test to assess exercise capacity in pwCF, without floor or ceiling effects. It addresses the issues of space restrictions and the need for strict infection prevention in the clinical setting.