STRENGTH TRAINING IMPROVES THE STEADINESS OF SLOW ECCENTRIC CONTRACTIONS IN OLDER ADULTS.

Abstract

1103 When older adults participate in a heavy-load, strength-training program, they experience an increase in muscle strength and in the steadiness of submaximal contractions. The purpose of this study was to determine the effect of light- (10% 1RM) and heavy-load (80% 1RM) strength training on the ability of older adults to perform steady slow movements. Twelve older adults (62-90 yrs; 5 control, 4 light, 3 heavy) participated in a four-week training program designed to strengthen the first dorsal interosseous muscle. Before and after training, subjects performed slow (6 s for 10 °) abduction (concentric) and adduction (eccentric) movements with the index finger against an adduction load of 20% MVC. Index finger position was recorded with a low-friction, linear-displacement transducer. A least squares regression was used to determine average movement velocity. The smoothness of the movement(fluctuations about the average velocity for the middle 4 s) was determined by subtracting the regression (trend) from the data. There was no effect of training on the MVC force for either group. Both training groups had significant gains in 1RM load (% change: low = 29 ±12%; high = 47±14%). There were no changes in the steadiness of the concentric contractions for any group. However, both training groups experienced significant improvements in the steadiness of the eccentric contractions (% change: control = 1.8 ±.0.1%; low = 42.4 ±.0.1%; high = 57.5±.0.1%). It appears that the improvement in steadiness experienced by older adults who perform strength training is similar whether they train with light or heavy loads.