Older adults exhibit a reduced ability to fully activate their biceps brachii muscle

Background. Voluntary muscle strength declines significantly in older adult s. One contributing factor to the strength loss is muscle atrophy developed in old age. Whether the ability to maximally activate the muscle decreases with age, however, is unknown. This study was intended to determine if the central nervous system command to maximally activate the biceps brachii mu scle deteriorates with age. Methods. Electrical stimulation pulses were applied to the skin overlying t he biceps brachii muscle during maximal voluntary elbow-flexion contraction s. The magnitude of force evoked on the maximal voluntary force was measure d to determine the activation level (AL) of the muscle. Results. The AL was 94% for the elderly group and 97% for the young group ( 100% AL indicates complete activation). The AL for both the elderly and you ng groups was significantly (p < .05) lower than 100%. The AL of the elderl y group was significantly (p < .05) lower than that of the young group. Conclusions. The loss of voluntary strength in older adults is a mixed resu lt of muscle atrophy and a reduced ability to fully activate muscle.