Jo. Judge et al., STEP LENGTH REDUCTIONS IN ADVANCED AGE - THE ROLE OF ANKLE AND HIP KINETICS, The journals of gerontology. Series A, Biological sciences and medical sciences, 51(6), 1996, pp. 303-312
Background. Aging is associated with a reduction in gait velocity, whi
ch is due to a shortened step length. This study investigated the rela
tionship between joint kinetics and step length. Methods. Three-dimens
ional gait kinematics and kinetics were measured during usual pace gai
t in 26 older subjects (average age 79) and in 32 young subjects (aver
age age 26). Gait measures were obtained at maximal velocity in five o
lder subjects. Lower extremity strength was measured in the older subj
ects on an isokinetic dynamometer. Results. Older persons had a 10% sh
orter step length during usual gait, when corrected for leg length (.6
5 +/- .07, .74 +/- .04/leg length, respectively, p < .001). Older pers
ons had reduced ankle plantarflexion during late stance (13 +/- 5 degr
ees, 17 +/- 5 degrees, p = .02) and lower ankle plantarflexor power (2
.9 +/- 0.9 W kg(-1), 3.5 +/- 0.9 W kg(-1), respectively, p = .007). An
kle strength was associated with plantarflexor power developed during
late stance (r = .49, p < .001). When gait kinetics were corrected for
step length, the older subjects developed 16% greater hip flexor powe
r during late stance than younger subjects (estimate of effect: .15 W
kg(-1), p = .002). Older subjects were unable to increase ankle planta
rflexor power at maximal pace, but increased hip flexor power 72% (1.1
+/- 0.3 W kg(-1) to 1.9 +/- 1.0 W kg(-1), p = .02). Conclusions. Olde
r subjects had lower ankle plantarflexor power during the late stance
phase of gait and appeared to compensate for reductions in plantarflex
or power by increasing hip flexor power. Appropriate training of ankle
plantarflexor muscles may be important in maintaining step length in
advanced age.