A step in the right direction: Assessing exercise tolerance in cystic fibrosis

Abstract

Summary. Exercise tolerance may be reduced in patients with cystic fibrosis, but it is not always possible to predict this from standard lung function measurements. Formal exercise testing may, therefore, be necessary, and the test should be simple and readily available. We have developed a ''3-minute step test'' and compared it with the standard 6-minute walking test. Subjects stepped up and down a 15-cm-high single step at a rate of 30 steps per minute for 3 minutes. The effect of the step test on spirometry was tested first in 31 children with CF (mean age, 12.0 years), who had a mean (range) baseline forced expired volume in 1 second (FEV 1 ) of 64% (18-94%) of predicted values. The step test was then compared with the standard 6-minute walk in a further 54 patients with cystic fibrosis (mean age, 12.5 years), with mean (range) baseline FEV 1 of 61% (14-103%) of predicted values. Outcome measures were minimum arterial oxygen saturation (SaO 2 ), maximum pulse rate, and the modified Borg dyspnea score.Post-step test spirometry showed mean (95% CI) changes of −1.1% (−6.0+3.9%) for forced vital capacity, of −1.6% (−4.2+1.1%) for FEV 1 , and +0.25% (−2.8+3.3%) for peak expiratory flow, although 5/31 children showed >15% drop in one or more parameters. The step and walk tests both produced significant changes (P < 0.0001) in all outcomes, with a mean (range) minimum SaO 2 of 92% (75-98%) versus 92% (75-97%), a maximum pulse rate of 145 b.p.m. (116-189) versus 132 (100-161), and a Borg score of 2.5 (0-9) versus 1.0 (0-5), respectively. Comparison of the two tests showed that the step test increased breathlessness (mean change Borg score, 2.3 vs. 0.8; P < 0.0001) and pulse rate (mean change, 38% vs. 24%, P < 0.0001) significantly more than the walk, whereas the decrease in SaO 2 was similar (mean change, −2.9% vs. −2.6%; P = 0.12). Some patients with a significant drop in SaO 2 (>4%) would not have the decrease predicted from their baseline lung function. Reproducibility for the two tests was similar. The step test is quick, simple and portable, and is not dependent on patient motivation. Although the step test is more tiring, its effect on SaO 2 is similar to the 6-minute walking test. It is a safe test that may prove to be a valuable measure of exercise tolerance in children with pulmonary disease, although longitudinal studies are now needed. Pediatr Pulmonol. 1998; 25:278-284.

Reliability of health-related physical fitness tests in European adolescents. The HELENA Study

“…10,35 When the search was extended to healthy or unhealthy people of any age, only eight additional studies using the Bland-Altman approach were found. [36][37][38][39][40][41][42][43] Given that physical fitness can already be considered a marker of health in this period of life, 3,6,44 information about the reliability of health-related physical fitness tests in young people is of interest. In addition, the review also shows that both cardiorespiratory fitness and muscular strength were the most studied physical fitness qualities (in 41 and 50%, respectively, of the reviewed studies), whereas data about speed-agility, coordination and flexibility in young people are lacking (used in 4-14% of the reviewed studies).…”

Reproducibility of step tests in patients with bronchiectasis

“…The reliability of the different step tests has been studied among patients with idiopathic pulmonary fibrosis 23 , COPD 16 , asthma 24 , or cystic fibrosis 25 . Although Swinburn et al 26 observed great variation between the four step tests conducted on patients with COPD, most studies have found the opposite (i.e., little variation between the step tests among patients with chronic lung disease 16,[23][24][25] ). In patients with COPD, the CST was highly reliable for tests conducted on the same day 16 , with an ICC of 0.99 (95% CIs=0.97 to 0.99) for NOSs.…”

“…In patients with COPD, the CST was highly reliable for tests conducted on the same day 16 , with an ICC of 0.99 (95% CIs=0.97 to 0.99) for NOSs. Balfour-Lynn et al 25 evaluated an externally dictated (30 steps/min) 3-min step test (15-cm steps) among a subgroup of individuals with cystic fibrosis (n=12) on different days. They found that this test was reliable with regard to the evaluation of SpO 2 , HR, dyspnea perception, and NOSs in 11 of 12 individuals.…”

3-Min step test and treadmill exercise for evaluating exercise-induced asthma

“…For this reason, a simple, standardised and reproducible challenge test is needed to assess the diagnosis of asthma and EIA. The step test, a reproducible test in healthy children and cystic fibrosis patients [7,8], is used with various protocols, to evaluate physical efficiency in healthy subjects and sportsmen [9][10][11][12]. It is legally compulsory in Italy for all persons wishing to engage in competitive sports [13].…”

“…It is legally compulsory in Italy for all persons wishing to engage in competitive sports [13]. The 3-min step test is also used to assess exercise capacity in children with cystic fibrosis [8,14,15], to evaluate the effect of a course of intravenous antibiotics on exercise tolerance [16], to study candidates for lung transplantation [17], and to determine the risk of oxygen desaturation during exercise [18].…”