Fig 1.
Stair and force plate configuration.
Two different configurations of force plates (FP) were used to investigate on the four types of transitions in between level walking and stair ambulation. Setup a) covers most of the transition on the lower end of the stairs and setup b) covers most of the transition at the upper end. Both setups were used for the stair ascent (strides A1 to A11) and stair descent (strides D1 to D11). Due to size, FP1 and FP2 can not be placed on the staircase.
Fig 2.
Biomechanics of level walking to stair ascent.
Mean values of the hip, knee, and ankle angle and moment. For reference, the level walking stride D11 (thick, solid, dark gray) and the stair ascent stride A6 (thick, solid, light gray) are shown. Solid lines represent the left leg, dashed lines the right leg.
Fig 3.
Biomechanics of stair ascent to level walking.
Mean values of the hip, knee, and ankle angle and moment. For reference, the level walking stride D11 (thick, solid, dark gray) and the stair ascent stride A6 (thick, solid, light gray) are shown. Solid lines represent the left leg, dashed lines the right leg.
Fig 4.
Biomechanics of level walking to stair descent.
Mean values of the hip, knee, and ankle angle and moment. For reference, the level walking stride D11 (thick, solid, dark gray) and the stair ascent stride D6 (thick, solid, light gray) are shown. Solid lines represent the left leg, dashed lines the right leg.
Fig 5.
Biomechanics of stair descent to level walking.
Mean values of the hip, knee, and ankle angle and moment. For reference, the level walking stride D11 (thick, solid, dark gray) and the stair ascent stride D6 (thick, solid, light gray) are shown. Solid lines represent the left leg, dashed lines the right leg.
Fig 6.
Joint power in the stair ascent transitions.
Mean values of the hip, knee, and ankle power for the transition from level walking to stair ascent (left) and from stair ascent to level walking (right). For reference, the level walking stride D11 (thick, solid, dark gray) and the stair ascent stride A6 (thick, solid, light gray) are shown. Solid lines represent the left leg, dashed lines the right leg.
Fig 7.
Joint power in the stair descent transitions.
Mean values of the hip, knee, and ankle power for the transition from level walking to stair ascent (left) and from stair ascent to level walking (right). For reference, the level walking stride D11 (thick, solid, dark gray) and the stair ascent stride A6 (thick, solid, light gray) are shown. Solid lines represent the left leg, dashed lines the right leg.
Fig 8.
Center of mass height for the level to ascend, ascend to level, level to descent, and descent to level transition. For reference, the level walking stride D11 (thick, solid, dark gray) and the stair ascent stride A6 (thick, solid, light gray) are shown. Solid lines represent the left leg, dashed lines the right leg. For visualization reasons, the center of mass height of D11 of the ascent to level and the level to descent transition was shifted to the height of the top level.
Fig 9.
Statistical analysis of the ascent transitions.
Joint specific (hip, knee, ankle) transitions from level walking to stair ascent and back to level walking for the strides A1 to A11. Individual stride phases that are not different from level walking (A1, D1, and D11) are indicated in gray. Phases that are not different from stair ascent (A5 and A6) are indicated in dark red. White areas are significantly different from level walking and from stair ascent.
Fig 10.
Statistical analysis of the descent transitions.
Joint specific (hip, knee, ankle) transitions from level walking to stair descent and back to level walking for the strides D1 to D11. Individual stride phases that are not different from level walking (A1, D1, or D11) are indicated in gray. Phases that are not different from stair descent (D5 and D6) are indicated in dark red. White areas are significantly different from the level walking and from stair descent.
Fig 11.
Joint specific timing of the transition start, the transition end, and the transition duration of the leading and the trailing limb for all analyzed types of transitions. Circle colors indicate the lower limb joint (hip in red, knee in blue, ankle in green). The numbers in the circles indicate the gait percent (in percent of the stride time) of the start and the end of the transition, and the total duration from the start to the end (sum of the passed gait percent in percent of the stride time).
Fig 12.
Relative time delay in between the hip (red), the knee (blue), and the ankle (green) for the leading and the trailing limb of all transitions. The analyses was performed for the start (left) and the end (right) of the transition. The start occurs when leaving a state (e.g., level walking), and the end occurs when entering a new state (e.g., ascending stairs). The joint with the earliest transition is set to zero, and the other joints are placed relative to it based on their delay.
Table 1.
Grand means of the horizontal CoM velocity in forward walking direction, stride duration, stance duration and duty factor for the strides of the stair ascent (A) and the stair descent (D) trials.