ISOMETRIC TORSO ROTATION STRENGTH - EFFECT OF TRAINING FREQUENCY ON ITS DEVELOPMENT

Objective: To examine training frequency's effect on torso rotation mu scle strength. Design: The study followed a pretest-posttest randomize d-group design. Setting: University laboratory. Patients: Subjects, 33 men (age 30 +/- 11 yr) and 25 women (age 28 +/- 10 yr) with no histor y of low back pain, volunteered to participate in the study and were t ested for isometric (IM) torso rotation strength before (T1) and after (T2) 12 weeks of training. Measurements of maximal voluntary LM torso rotation torque (N . m) were made through a 108 degrees range of moti on (54 degrees, 36 degrees, 18 degrees, 0 degrees, -18 degrees, -36 de grees, -54 degrees). Subjects were stratified by peak torque at T1, an d randomized to a nonexercising control group (C, n = 10), or groups t hat trained once a week (1 x/wk, n = 16), twice a week (2 x/wk, n = 17 ), or three times a week (3 x/wk, n = 15); and all groups were similar in strength. Interventions: Training consisted of 8 to 12 repetitions of full range dynamic variable resistance exercise to volitional fati gue, for both left and right rotation. Main Outcome: To determine the best training frequency for the development of torso rotation strength . Results: Relative improvements (average increase in strength gained at each angle) for the training groups were 4.9%, 16.3%, and 11.9% for the 1, 2, and 3 x/wk groups, respectively. The 1 x/wk group did not i ncrease in IM torso rotation strength compared to the control group at any angle. Both the 2 and 3 x/wk groups increased their IM torso rota tion strength compared to the control group at all but one angle. Ther e were no significant differences in IM torso rotation strength betwee n the groups that trained 2 or 3 x/wk. During the training period, the 2 and 3 x/wk groups increased their dynamic training load significant ly more than the 1 x/wk group. Conclusions: Posttraining dynamic stren gth was not different between training frequencies of 2 and 3 x/wk. Th erefore, training the rotary torso muscles 2 x/wk is recommended. (C) 1997 by the American Congress of Rehabilitation Medicine and the Ameri can Academy of Physical Medicine and Rehnbilitation