Encouraged 6-min walking test indicates maximum sustainable exercise in COPD patients

Alejandro Casas, Jordi Vilaro, Roberta Rabinovich, Anamaria Mayer, Joan Albert Barberà, Robert Rodriguez-Roisin, Josep Roca

Research output: Indexed journal article Articlepeer-review

109 Citations (Scopus)


Study objectives: In patients with moderate-to-severe COPD, an encouraged 6-min walking test (6MWT) is a high-intensity submaximal exercise protocol that shows an oxygen uptake (V̇O2) plateau after the third minute of the test. This last feature prompted the hypothesis that self-paced walking speed is set to achieve "maximal" sustainable V̇O2, namely "critical power" or "critical speed." Patients and methods: Eight patients with moderate-to-severe COPD (mean age, 68 ± 7 years [± SD]; FEV1,50 ± 13% predicted; PaO 2,69 ± 8 mm Hg) underwent the following tests on different days in order: (1) encouraged 6MWT; (2) standard incremental shuttle test to identify peak walking speed; (3) four different high-intensity, constant walking speed tests to exhaustion to calculate critical walking speed; and (4) timed walking test at critical walking speed (CWS) to examine sustainability of the exercise. Results: 6MWT and CWS showed similar results (mean of last 3 min): V̇O2 (1,605 ± 304 mL/min vs 1,584 ± 319 mL/min), minute ventilation (47 ±12 L/min vs 48 ± 11 L/min), respiratory exchange ratio (0.89 ± 0.1 vs 0.90 ± 0.1), heart rate (130 ± 18 beats/min vs 131 ± 16 beats/min), Borg dyspnea score (5.4 ± 1.3 vs 5.5 ± 2.4), and walking speed (1.49 ± 0.1 m/s vs 1.44 ± 0.1 m/s, respectively). Conclusion: This study supports that 6MWT indicates maximum sustainable exercise that might be related with its predictive value in COPD patients.

Original languageEnglish
Pages (from-to)55-61
Number of pages7
Issue number1
Publication statusPublished - Jul 2005


  • 6-min walking test
  • COPD
  • Critical power
  • Exercise testing
  • Exercise tolerance
  • Sustainable submaximal exercise


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