![]() Performance depends on morphology, behavior and motor control ( Aerts et al., 2003 Alexander, 2002 Carrier et al., 2001 Dial et al., 2008 Eilam, 1994 Jindrich et al., 2006 Jindrich and Full, 1999 Jindrich et al., 2007 Van Damme and van Dooren, 1999). Animals must maneuver to forage, negotiate uneven terrain or escape predation, with direct impacts on fitness ( Demes et al., 1999 Dunbar, 1988 Howland, 1974 Losos and Irschick, 1996). Maneuvers involve behaviourally generated changes to speed, direction and/or body orientation. Maneuverability is necessary for locomotion in natural environments ( Jindrich and Qiao, 2009). These results suggest that in submaximal effort turning, legged systems may be robust to changes in morphological parameters, and that compensations can involve relatively minor adjustments between steps to change initial stance conditions. Increasing inertia revealed that the opposing effects of several turning parameters, including rotation due to symmetrical anterior–posterior forces, result in a system that can compensate for fourfold changes in rotational inertia with less than 50% changes to rotational velocity. Contrary to our prediction, braking forces remained consistent at different rotational inertias, facilitated by anticipatory changes to body rotational speed. We recorded ground reaction force and body kinematics from seven participants performing 45 deg sidestep cutting turns and straight running at five levels of body rotational inertia, with increases up to fourfold. We tested this hypothesis by increasing body rotational inertia and testing whether braking forces during stance decreased. Previous studies have argued that because humans have small yaw rotational moments of inertia relative to body mass, deceleratory forces in the initial velocity direction that occur during the turning step, or ‘braking’ forces, could function to prevent body over-rotation during turns. ![]() We investigated the strategies used by humans to perform sidestep cutting turns when running. Locomotion in a complex environment is often not steady state, but unsteady locomotion (stability and maneuverability) is not well understood.
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