ELECTROMYOGRAPHIC AND KINEMATIC ANALYSIS OF GRADED TREADMILL WALKING AND THE IMPLICATIONS FOR KNEE REHABILITATION

Muscle activity, joint angles, and heart rate during uphill walking we re compared for application in knee rehabilitation. The objectives oi this study were to quantify muscle activation levels at different trea dmill grades and to determine the grade(s) at which knee range oi moti on would not further compromise the joint. Average and peak electromyo graphic activity of the quadriceps (vastus medialis oblique and vastus lateralis) and hamstrings [biceps femoris and medial hamstrings (semi membranosus/semitendinosus)] was recorded during walking at 0, 12, and 24% grade. Six subjects (age = 28.5 +/- 3.7 years, stature = 1.19 +/- .05 m, and mass = 74.1 +/- 7.9 kg) walked at sell-selected speeds at each grade while ankle, knee, and hip angles, heart rate, and electrom yographic activity (surface electrodes) were recorded. Maximum volunta ry contractions provided a relative reference for the electromyographi c activity during walking. Average and peak electromyographic activity increased significantly across grades for the vastus medialis oblique (125 and 154%), vastus lateralis (109 and 139%), and biceps femoris ( 53 and 46%), but remained similar for the medial hamstrings. Maximum k nee flexion at heel strike increased significantly with grade. Despite decreased sell-selected speeds with increasing grade, there were sign ificant increases in heart rate across grades. The results of this stu dy provide a basic understanding of the quadriceps and hamstrings acti vity levels, lower extremity joint range of motion, and cardiovascular requirements of graded treadmill walking in normal subjects. The resu lts also suggest that a grade just greater than 12% may be most benefi cial for knee rehabilitation to minimize patellofemoral discomfort or potential strain on the anterior cruciate ligament. The benefits achie ved through this functional activity encourage its implementation in r ehabilitation and provide a basis for comparison with injured patients .