study by Harridge and colleagues concluded that very old adults (age 85–97 years) had significant impairments in central activation (mean: 81%; range: 69–93%). Another study by Stevens and colleagues combined previously collected data on the impact of aging on knee extensor central activation and found that central activation in older adults was much less than that of young adults (87% vs 98% activation). Causes Biological Possible biological contributors to dynapenia include the nervous system’s deteriorating control of voluntary skeletal muscle activation and a decreased number of functioning motor units. The nervous system's lowered ability to stimulate a full muscle contraction subsequently leads to loss of muscle strength and power. A study by Harridge et al. also showed that all dynapenic subjects had incomplete voluntary activation during a maximum contraction (69-93%), suggesting that loss of voluntary muscle activation plays an important role in the loss of muscle strength. Studies involving the dissection of cadavers have uncovered a 43% decrease in the cell body size of neurons found in the premotor cortex compared to those of younger adults. New studies have recently verified this finding in living subjects using high resolution magnetic resonance imaging (MRI). Recent evidence suggests that aging is also related to the loss of myelinated nerve fiber length and the mass of white matter, with individuals losing approximately 45% of total nerve fiber length as they age. These changes that develop through the aging process affect the connectivity of the cortex within itself as well as its connectivity to the rest of the central nervous system. Another potential contributor to dynapenia is a disruption of the process that converts electrical signal given for muscular activation into an actual contraction. Particularly, impairments in the release of calcium (Ca2+) from the sarcoplasmic reticulum have been suggested to explain why decreased muscle quality is so prevalent in older adults. A systematic review on the literature regarding the relationship between type II muscle fiber loss and aging found that the total number of fibers in the vastus lateralis decreases tremendously with age. This decline is first observed around 25 years of age and proceeds at an even greater rate throughout the lifespan. The age-related Type II fiber loss highlights the negative effect of aging on muscle power. Nutritional It has also been suggested that nutritional factors may contribute to the onset of dynapenia. It has been proposed that low levels of Vitamin E,