The effect of different height of stair on electrical activites of muscules

Abstract

Introduction: Stairs are a frequently encountered obstacle in daily life. Due to their abundance, the ability to ascend and descend stairs without difficulty or pain is important to quality of life. The Consumer Product Safety Commission has reported an estimated two million injuries and 1... deaths each year associated with stair falls and in Australia stair and step fall injuries increased by over 7. percent during the decade 1333/4 to 2..2/3. In the U.S., for falls involving stairways where the location of the stairway is reported, °59 occur in residential settings. Many studies have shown that stairs are among the main common factors involved in low (below two meters) fall accidents.For ascent and descent, it would appear that larger riser heights (e.g. height of each step) cause under stepping at the point of incident, and this was the major design factor associated with stair accidents. The purpose of this study was, therefore, to investigate the EMG activity of the leg muscles involved in ascending and descending stairs with different heights. Methods : Eighteen females with a mean age of 23 ± 5..2 year, height of 161.33 ± 4.3 cm, and body weight of 53.66 ± 5.57 kg, and with no history of neuromuscular disorder and injury to the lower extremities participated in this study. Three heights of stairs were specially designed and built for the purpose of this study. The custombuilt steel and wood staircase of 4 steps with the dimensions of 1° cm, 15.5 cm, 1. cm (riser), 3. cm (tread), and 3. deg (the total slope of the stairs) were used. No hand railings were available. Subjects were asked to ascend and descend a staircase of four steps. They tested 3 sets of stairways with different riser dimensions, with the order of presentation of the stair conditions randomized across the participants. Muscle activity was measured using ME6... Biomonitor EMG System.EMG recordings were made using a pair of surface electrodes(silver-silver chloride, 55 mm) placed over the Tbialis anterior(TA),Soleus(SOL), Rectus femoris(RF) and Gluteusmaximus(G.MAX) muscles of the dominant leg. The data were analyzed using SPSS version 15.5 Significantly different conditions between stairs were included in subsequent analyses as covariance structure (linear mixed model).90 Results: The muscle activity levels of the SOL muscle were significantly higher than those of the TA, RF and G.MAX muscles for both ascending and descending conditions (p = .....). The results of the study also showed significant differences in the muscle activity levels of the RF,G.MAX and SOL muscles between ascending and descending conditions .(F(1,2..)=13.36,P<....1) F(1,133)=154.57, P<....1) (F(1,21.)=1°.4.6, P<....1). However, the results showed no significant difference in the muscle activity levels of the TA between ascending and descending conditions (F(1,134)=2.22, p = ..3°.). The results showed significant effect of stair height on the muscle activity levels of RF (F(2,172)=11.°2,P<....1) but no significant effect of stair height on the muscle activity levels of SOL(F (2,122) =...73,p = ..33.) or TA (F(2,156) =2.271,p = ..1.7) or G.max )F(2,154)=..57,P=..6 ( muscles. Conclusions: The main findings of the study were that the EMG activity of the SOL muscle was significantly higher than the TA , RF and G.MAX muscles activity and that the muscle activity level of the SOL , RF and G.MAX muscles was significantly higher when ascending compared to descending condition, although the stair height had no significant effect of the EMG activity of the TA, SOL and G.MAX muscles, but the stair height had significant effect of the EMG activity of the RF muscle. These findings provide an insight that how the muscles of the leg are influenced by stair height during ascending and descending stairs