The Effect of Stump Level on Activity and Fatigability of Knee Extensor Muscles

Muscle fatigue is tiredness, in other words, loss of productive capacity of power in response to the activity. The development of fatigue during prolonged exercise may be evaluated by repeated assessments of maximal voluntary force. This study aimed to determine the effect of muscle fatigue on trans-tibial stump level in knee extensor muscles (vastus lateralis, vastus medialis, and rectus femoris) at 30 and 45 degree knee flexions by using surface electromyography.
Forty male amputees with trans-tibial amputation, aged between 18-50 years were assigned randomly in three groups; performed three isometric contractions with extended knee at 80% of the maximal voluntary contraction. Median Frequency (MDF) and Root Mean Square (RMS) values were obtained by surface electromyography from the knee extensor muscles at 30 and 45 degree knee flexions. Force values in stump and sound sides during knee flexion at 30 and 45 degree were also compared.
Median frequency on sound side showed more fatigue and MDF-RMS between stump levels was short, medium, and long for knee extensor muscles at 30 and 45 degree, before and after the fatigue. No significant effect between stump and sound side was found. Vastus lateralis muscle showed more power than vastus medialis and rectus femoris muscles before fatigue. But after fatigue, rectus femoris muscle showed more power than vastus medialis and vastus lateralis.
Results have confirmed that trans-tibial amputees with good functional ability showed more fatigability on the sound side while stump side showed more power. Vastus lateralis muscle had maximum power on both sides. Vastus medialis and rectus femoris of long stump levels and vastus lateralis muscle of short levels were more powerful.