LEG EXTENSION POWER AND WALKING SPEED IN VERY OLD-PEOPLE LIVING INDEPENDENTLY

Background. Leg extension power can be determined as the product of th e force and velocity of movement. Its association with maximal walking speed was studied in 131 80- and 85-year-old men and women. Methods. Leg extension power was measured with the help of a sledge ergometer i n a sitting position using a facilitated ''jump test.'' The participan t was attached by belts to a sliding chair on rails inclined at 12.6 d egrees to the floor. The feet were placed on the force plate attached perpendicularly to the rails, and the knee angle was 90 degrees at the starting position. The participant was advised to extend his or her l egs powerfully. The highest value of five to eight attempts was accept ed as the result. The results were adjusted for body mass and expresse d as watts.kiloogram(-1). Maximal walking speed was measured in the la boratory corridor over a distance of 10 m. Results. Men and 80-year-ol d subjects exhibited greater leg extension power and were faster walke rs than women and 85-year-old persons. Leg extension power correlated positively with maximal walking speed in all groups: the correlation c oefficients were .412 in the 80-year-old men (n = 41, p = .007), .619 in the 80-year-old women (n = 56, p < .001), .939 in the 85-year-old m en (n = 8, p = .001), and .685 in the 85-year-old women (n = 23, p < . 001). The regression lines for leg extension power and walking speed w ere coincident, indicating that the power requirements to attain a giv en walking speed were similar for both sexes. The minimum power thresh old for those with a maximal walking speed of 1.30-1.49 m.s(-1) was on the order of 4 W.kg(-1); a maximal walking speed of 1.50-1.99 m.s(-1) required 7 W.kg(-1); and for a speed over 2.00 m.s(-1) the power thre shold was 9.5 W.kg(-1). Conclusions. Their lower average leg extension power may be one of the factors explaining the greater prevalence of mobility problems among women than men.