Lower-extremity kinetic response to activity program dosing in older adults

The purpose of this investigation was to determine the effects of two doses of a weighted vest on acute lower-extremity gait kinetics in older adults. Peak ankle, knee, and hip net joint moments were quantified in 56 men and women volunteers (73.8 +/- 6.9 years old) enrolled in a B-month physical ac tivity study. At the initial study visit, participants underwent 6 walking trials (3 with vest, 3 without vest) at their normal pace. During the vest- wearing trials, participants wore a vest loaded with either 0% of body weig ht (BW) (n = 19), 3% of BW (n = 16), or 5% of BW (n = 21). With acute appli cation of the vests, maxi mum peak plantarflexion moments increased by 5.7% in the 5% BW group compared to the 0% BW group, p < 0.01. Compared to the 0% vest-weight group, knee extension moments increased by 13.8% when 5% BW was applied, p < 0.01: a marginally significant treatment effect was eviden t in the 3% BW group, p = 0.04. Despite these acute alterations, knee stren gth and physical performance did not improve when subjects wore the vests 2 hours a day, 4 days a week for 27 weeks, without additional exercise presc ription. These findings suggest that: (a) the acute changes in vest-mediate d lower-extremity kinetics are not systemic but joint specific and load dep endent, and (b) weighted vest prescription should be greater than 5% BW wit hout pre scribed exercise, or should include prescribed exercises, to invok e long-term strength and physical performance gains in older adults.