Enhancing performance during inclined loaded walking with a powered ankle–foot exoskeleton

Samuel Galle, Philippe Malcolm, Wim Derave, Dirk De Clercq

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Purpose: A simple ankle–foot exoskeleton that assists plantarflexion during push-off can reduce the metabolic power during walking. This suggests that walking performance during a maximal incremental exercise could be improved with an exoskeleton if the exoskeleton is still efficient during maximal exercise intensities. Therefore, we quantified the walking performance during a maximal incremental exercise test with a powered and unpowered exoskeleton: uphill walking with progressively higher weights.

Methods: Nine female subjects performed two incremental exercise tests with an exoskeleton: 1 day with (powered condition) and another day without (unpowered condition) plantarflexion assistance. Subjects walked on an inclined treadmill (15 %) at 5 km h−1 and 5 % of body weight was added every 3 min until exhaustion.

Results: At volitional termination no significant differences were found between the powered and unpowered condition for blood lactate concentration (respectively, 7.93 ± 2.49; 8.14 ± 2.24 mmol L−1), heart rate (respectively, 190.00 ± 6.50; 191.78 ± 6.50 bpm), Borg score (respectively, 18.57 ± 0.79; 18.93 ± 0.73) and (Formula presented.) peak (respectively, 40.55 ± 2.78; 40.55 ± 3.05 ml min−1 kg−1). Thus, subjects were able to reach the same (near) maximal effort in both conditions. However, subjects continued the exercise test longer in the powered condition and carried 7.07 ± 3.34 kg more weight because of the assistance of the exoskeleton.

Conclusion: Our results show that plantarflexion assistance during push-off can increase walking performance during a maximal exercise test as subjects were able to carry more weight. This emphasizes the importance of acting on the ankle joint in assistive devices and the potential of simple ankle–foot exoskeletons for reducing metabolic power and increasing weight carrying capability, even during maximal intensities.

Original languageEnglish (US)
Pages (from-to)2341-2351
Number of pages11
JournalEuropean Journal of Applied Physiology
Issue number11
StatePublished - Oct 16 2014
Externally publishedYes


  • Ankle–foot exoskeleton
  • Exercise test
  • Exhaustion
  • Loaded walking
  • Locomotion
  • Maximal exercise
  • Performance
  • Uphill walking

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Public Health, Environmental and Occupational Health
  • Physiology (medical)


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