EFFECTS OF AN 8-WEEK STRETCHING PROGRAM ON THE PASSIVE RESISTIVE TORQUE AND STATIC STRESS-RELAXATION PROPERTIES OF THE CALF MUSCLE-TENDON UNIT OF OLDER WOMEN.

Abstract

Purpose/Hypothesis: Calf muscle-tendon unit (MTU) stretching programs are used to increase dorsiflexion range of motion at the ankle. Their effects on the passive resistive torque (PRT) and static stress relaxation (SSR) properties of aged calf MTUs, however, have not been studied. The purpose of this initial study was to describe and examine the effects of an 8-week stretching program on the PRT and SSR properties of the calf MTU of older women. Number of Subjects: Thirteen women aged 65-82 years with limited active dorsiflexion RoM ≤8° participated with informed consent. Materials/Methods: After a pre-testing stretching exercise and relaxation training, a Kin-Com® dynamometer stretched the right calf MTU by moving the ankle from relaxed plantarflexion to maximal tolerated dorsiflexion (DF) and held a static (constant) stretch at the maximal DF angle for 60 seconds (s). The decline in torque during the 60s stretch was recorded while negligible surface EMG activity was monitored for the soleus, gastrocnemius and tibialis anterior muscles. The women were then randomly assigned to a group that stretched both ankles to maximal DF 10 times for 15s each, 3-times a week for 8-weeks (n=6, SG) or to a control group (n=7, CG) that did not stretch. The tests were repeated after the stretching program and descriptive statistics and ANOVA analyses were used to examine the program's influence on the maximal DF angle, the maximal tolerated PRT, and the SSR measured as the absolute torque decline and the percent torque decline (maximal PRT=100%) during the 60s static stretch. Results: The maximal passive DF angle increased for the SG from 12.3plus or minus 3.1° to 18.5plus or minus 4.37° (P=0.003), but not for the CG (test=13.6 ± 4.4°, retest=13.7 ± 5.9°). The maximal PRT increased for the SG from 16.1 ± 2.3 Nm to 26.6 ± 10.6 Nm (P=0.033), but not for the CG (test=17.5 ± s 5.3 Nm, retest=17.6 ± 4.5 Nm). The absolute torque decline increased for the SG from 2.9plus or minus 0.7 Nm to 4.1 ± 1.4 Nm, and the total percent torque decline decreased from 18.3 ± 7.3% to 15.5 ± 2.6%, but the changes were not significant. The CG showed similar test-retest values for the absolute torque decline (2.6 ± 0.7 to 2.5 ± 0.8) and the total percent torque decline (15.0 ± 2.9% to 14.0 ± 1.9%). Conclusions: The stretching program increased the maximal tolerated DF stretch angle and PRT. Although the lack of significant changes in the SSR properties was probably influenced by the small sample size, the stretching program appeared to increase the ability to sustain a greater PRT load during the 60s maximal DF stretch. The responses suggest physical adaptations in the calf MTU that increased their ability to sustain and maintain a tolerated static stretch load. Clinical Relevance: Calf MTU stretching programs for older women can increase the maximal DF angle, and also bring about the ability to withstand a maximal tolerated static stretch. The passive static adaptations may have implications for enhancing functional static and dynamic balance and ambulatory activities.