title: Enhancing performance during inclined loaded walking with a powered ankle-foot exoskeleton.
abstract: OBJECTIVE
  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 VO₂ 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.
  
  
  CONCLUSIONS
  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.
authors: Department of Movement and Sport Sciences, Ghent University, Watersportlaan 2, 9000, Ghent, Belgium, samuel.galle@ugent.be.
authors: Samuel
authors: S
authors: Galle
authors: Philippe
authors: P
authors: Malcolm
authors: Wim
authors: W
authors: Derave
authors: Dirk
authors: D
authors: De Clercq
mesh_terms: D000328:Adult; D000842:Ankle / Q000502:physiology*; D000843:Ankle Joint / Q000502:physiology; D005260:Female; D005528:Foot / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D009989:Orthotic Devices; D010101:Oxygen Consumption; D011897:Random Allocation; D016138:Walking / Q000502:physiology*
chemical_list: D019344:Lactic Acid