Effects of Reducing Resistance, Repetitions, and Frequency of Back-Strengthening Exercise in Healthy Young Women: A Pilot Study

Abstract

Hongo M, Itoi E, Sinaki M, Shimada Y, Miyakoshi N, Okada K. Effects of reducing resistance, repetitions, and frequency of back-strengthening exercise in healthy young women: a pilot study. Objective To determine the effects of reducing intensity or frequency of back-strengthening exercise on back extensor strength. Design Randomized controlled trial. Setting Exercises were performed in participants’ homes. Instruction and measurements were performed at the rehabilitation center in the hospital. Participants Fifty-eight healthy female volunteers (mean age, 20y). Interventions Participants were assigned to 1 of 5 exercise intervention groups: control; standard protocol (STD) that has been shown to increase back extensor strength; weight reduction (WRD); repetition reduction (RRD); and frequency reduction (FRD). Back exercises involved lifting a weighted backpack while in a prone position. The study period was 12 weeks. Main Outcome Measure Isometric back extensor strength. Results Back extensor strength increased significantly in all groups except the control group. The maximum increase was achieved by the STD group (39%), followed by the FRD (25%), WRD (22%), RRD (20%), and control (5%) groups. Percentage change in back extensor strength was significantly greater in the STD group than in all other groups except the FRD group. Conclusions Back extensor strength in the WRD, RRD, and FRD groups was significantly higher at 12 weeks compared with baseline. Reductions in intensity and frequency resulted in similar effects on increases in back extensor strength.