Balance control in stepping down expected and unexpected level changes

Leg adjustments during running across visible and camouflaged incidental changes in ground level

“…In contrast to such an expected situation, the time between expected and actual ground contact in unexpected stepping down appears to be too short to substantially adjust the movement of the leading leg [according to van Dieën et al (van Dieën et al, 2007) and Shinya et al (Shinya et al, 2009)]. This is even more valid during running.…”

“…Such a visually guided pre-adaptation is not possible in experiments where the changes in ground level are invisible because of camouflage and occur by chance. Experiments on humans walking along a walkway with an unexpected loss of ground support have shown that in the unexpected lowered contact the absence of expected heel contact triggered responses in the ipsilateral antigravity muscles and contralateral flexor muscles (Shinya et al, 2009;van der Linden et al, 2007), and that after touchdown humans reset the gait rhythm to permit continued walking by delaying the subsequent take-off (Shinya et al, 2009;van Dieën et al, 2007). Compared with walking, during running the duration of the stance phase is shorter and thus adjustments may be necessary prior to contact.…”

“…When walking down a visible step of 10cm, humans control their forward horizontal and angular momentum by increasing step length (van Dieën et al, 2007). In contrast to such an expected situation, the time between expected and actual ground contact in unexpected stepping down appears to be too short to substantially adjust the movement of the leading leg [according to van Dieën et al (van Dieën et al, 2007) and Shinya et al (Shinya et al, 2009)].…”

Longitudinal changes in transtibial amputee gait characteristics when negotiating a change in surface height during continuous gait

“…Although stepping gait may be executed by young able-bodied indi-58 viduals without apparent difficulty (Barbieri et al, 2013;Begg and 59 Sparrow, 2000;Buckley et al, 2011;van Dieen et al, 2007van Dieen et al, , 2008, it is 60 more mechanically challenging compared to level gait (Nadeau et al, 61 2003 (Aldridge et al, 2012;Alimusaj et al, 2009;Jones et al, 73 2006; Powers et al, 1997;Ramstrand and Nilsson, 2009;Schmalz 74 et al, 2007;Vanicek et al, 2010;Winter and Sienko, 1988). When…”

Hitting a support surface at unexpected height during walking induces loading transients

“…Such a yield of the leg has been observed after landing on an unexpectedly stiff surface during hopping as well [23], but not following an unexpected step-down [20,30].…”