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First published online April 18, 2008
Journal of Experimental Biology 211, 1368-1375 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.014589

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Lower-limb biomechanics during stair descent: influence of step-height and body mass

M. Spanjaard^1,2,*, N. D. Reeves¹, J. H. van Dieën², V. Baltzopoulos¹ and C. N. Maganaris¹

¹ Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Alsager, UK
² Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands

View larger version (12K): [in this window] [in a new window]   Fig. 1. Mean ankle joint moment (A) and knee joint moment (B) of 10 subjects of one full descending stride cycle for all four step-heights: decreased 50% (dotted lines), standard (thin lines), increased 50% (thick lines) and increased 75% (thick broken lines). Vertical lines indicate foot-contact times [lift-off (LO) right, touch-down (TD) right and lift-off left] for all four step-heights, whereas 0 and 100% of the stride cycle indicate TD of the left (analyzed) foot. For clarity, standard deviations (s.d.) are omitted. The s.d. for the standard step-height can be viewed in Fig. 5.

View larger version (12K): [in this window] [in a new window]   Fig. 2. Mean locomotory power (ground reaction force x centre of mass velocity) of 10 subjects over one full descending stride cycle for all four step-heights: decreased 50% (dotted lines), standard (thin lines), increased 50% (thick lines) and increased 75% (thick broken lines). Vertical lines indicate foot-contact times [lift-off (LO) right, touch-down (TD) right and LO left] for both conditions, whereas 0 and 100% of the stride cycle indicate TD of the left (analyzed) foot. For clarity, only positive standard deviations of the standard step-height are presented.

View larger version (12K): [in this window] [in a new window]   Fig. 3. Mean ankle joint power (A) and knee joint power (B) of 10 subjects of one full descending stride cycle for all four step-heights: decreased 50% (dotted lines), standard (thin lines), increased 50% (thick lines) and increased 75% (thick broken lines). Vertical lines indicate foot-contact times [lift-off (LO) right, touch-down (TD) right and LO left] for all four step-heights, whereas 0 and 100% of the stride cycle indicate TD of the left (analyzed) foot. For clarity, standard deviations are omitted.

View larger version (15K): [in this window] [in a new window]   Fig. 4. Mean fascicle length change (A), muscle–tendon complex (MTC) length change (B) and smoothed GM EMG (C) of 10 subjects of one full descending stride cycle for all four step-heights: decreased 50% (dotted lines), standard (thin lines), increased 50% (thick lines) and increased 75% (thick broken lines). The fascicular behaviour was analyzed during touch-down (from 0 to 14% stride cycle). Vertical lines indicate foot-contact times [lift-off (LO) right, touch-down (TD) right and LO left] for all four step-heights, whereas 0 and 100% of the stride cycle indicate TD of the left (analyzed) foot. Standard deviations (s.d.) were similar for all step-heights. For clarity, only positive s.d. of fascicle length change are plotted for the decreased 50% step-height.

View larger version (11K): [in this window] [in a new window]   Fig. 5. Mean ankle joint moment (A) and knee joint moment (B) of 10 subjects of one full descending stride cycle for standard stair descent (solid lines) and stair descent with 20% extra body weight (dotted lines). Vertical lines indicate foot-contact times [lift-off (LO) right, touch-down (TD) right and LO left] for both conditions, whereas 0 and 100% of the stride cycle indicate TD of the left (analyzed) foot. For clarity, only the negative s.d. of standard stair mass condition are presented.

View larger version (13K): [in this window] [in a new window]   Fig. 6. Mean fascicle length change (A) of 4 subjects, mean muscle–tendon complex (MTC) length change (B) and smoothed GM EMG (C) data of 10 subjects of one full descending stride cycle for standard stair descent (solid lines) and stair descent with 20% extra body weight (dotted lines). The fascicular behaviour was analyzed during touch-down (from 0 to 14% stride cycle). Vertical lines indicate foot-contact times [lift-off (LO) right, touch-down (TD) right and LO left] for both conditions, whereas 0 and 100% of the stride cycle indicate TD of the left (analyzed) foot. For clarity, only the positive standard deviations of the standard mass condition are presented.

View larger version (11K): [in this window] [in a new window]   Fig. 7. Mean tendon length change of 10 subjects, relative to the tendon length calculated when standing still, of one full descending stride cycle for all four step-heights: decreased 50% (dotted lines), standard (thin lines), increased 50% (thick lines) and increased 75% (thick broken lines). Vertical lines indicate foot-contact times [lift-off (LO) right, touch-down (TD) right and LO left] for both conditions, whereas 0 and 100% of the stride cycle indicate TD of the left (analyzed) foot. For clarity, standard deviations are omitted.

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