Age-related differences in the symmetry of electromyographic activity and muscle force in lower limbs

Increased reaction time and asymmetrical force generation in muscles may elevate the risk of falling among seniors. Therefore, it seems useful to analyze the symmetry of strength and amplitude parameters that evaluate neuromuscular control. The aim of the study was to evaluate force parameters for the quadriceps and biceps femoris muscles in young and older women performing maximal voluntary contraction.

Fifty women (1 group in their twenties and the other in their sixties) participated in the study. The study used surface electromyography methodology and measured peak torque under static conditions. Electromyographic signals and peak torque were recorded separately in knee extensors and flexors of the right and left lower limbs after a visual signal. The following parameters were selected for analysis: 1) maximum the electromyographic amplitude signal; 2) peak torque; 3) rate of torque development; 4) relative force; and 5) "flexor-extensor" ratio.

The analysis demonstrated a decrease in the values of all parameters in the elderly group and symmetry in EMG amplitude in both the younger and older women. Asymmetry was found in the group of elderly women for peak torque and the relative force for knee flexors and "flexor-extensor" ratio.

The decline in values of force parameters in knee flexors and their asymmetry (not extensors) revealed in the elderly group might prove an important factor in the assessment of risk factors for falling among the elderly.