An Electromyographic and Goniometric Analysis of the Lower Extremity During Stair Climbing With and Without the Use of EZ-STEPS^TM In An Elderly Population

Staci L. Fethkenher, MPT and Thomas M. Mohr, PhD, PT
Dept. of Physical Therapy, University of North Dakota, Grand Forks, ND

INTRODUCTION:  
Stairs pose an architectural barrier to many elderly individuals. The inability to negotiate stairs may result in extended hospital stays or premature admission into an institution. There is a need for stair modifications that improve stair accessibility for the elderly population.

PURPOSE: 
EZ-Steps™ is a device that fits into an existing stairwell which decreases the height of each step by half. It is hypothesized, that by decreasing the step height, less muscle activity and knee joint range of motion (ROM) would be required for stair negotiation, making stair climbing less burdensome. The purpose of this study was to determine if there is a difference in lower extremity muscle activity and knee joint ROM between stair climbing with and without the use of EZ-Steps™ in an elderly population.

METHODS:  
Eight, healthy, elderly (aged 65-89 years) male and female subjects volunteered to participate in the study. Surface electromyography (sEMG) was used to assess muscle activity in four lower extremity muscles during stair climbing standard steps and steps installed with EZ-Steps™. The four muscles assessed were:

• gluteus maximus (GM)
• biceps femoris (BF)
• rectus femoris (RF)
• medial head of the gastrocnemius (GS)

An electrogoniometer was used to measure knee joint ROM. The EMG and electrogoniometric data were telemetried to a Noraxon Telemyo8 receiver and digitized by a NET 486DX computer. The data was then stored in the computer using the Myosoft data collection software that accompanies the system. Analysis of the data was performed using the Norquest software package that is included with the system.

To normalize the data, the EMG data for each of the four muscles was expressed as a percentage of that muscle's maximal voluntary contraction (MVC). Descriptive statistics were used to compare muscle activity between negotiation of standard and EZ-Steps™, and knee joint ROM between the two stair types.

RESULTS:  
The results indicated that less lower extremity muscle activity occurred during both stair ascension (Fig. 1) and descension (Fig. 2) with the EZ-Steps^TM installed. There was also less knee joint ROM during both ascension and descension with the EZ-Steps™ installed (Fig. 3).

Figure 1.  EMG activity during stair ascension.

Figure 2.  EMG activity during stair descension.

Figure 3.  Knee joint ROM during stair climbing.

The biomechanics of stair climbing is altered by changes in stair dimensions. The decrease in knee joint ROM that occurred with the EZ-Steps^TM may have resulted because less knee flexion is required to clear the foot during the swing phase of stair climbing. During descension of the EZ-Steps^TM, the distance the body must be lowered is less than that of standard steps, requiring less knee flexion. Because of the decreased knee flexion, less muscle activity is required to control the body's descent. Also, the center of mass is displaced a lesser distance during both stair ascension and descension, which may account for less work (work = force x distance), and subsequently less muscle activity to negotiate steps with a decreased height.

CLINICAL IMPLICATIONS: 
EZ-Steps^TM may be a beneficial stair modification for elderly individuals with limitations in strength or ROM who experience difficulty with stair climbing activities.