Training Humans 101......
Brain leads, muscle follows. 
Design training programs around the brain and nervous system, not muscle. 
"...failure of the Central Nervous System in providing an optimal neural drive to the contracting skeletal muscles may contribute to the development of fatigue during prolonged exercise. Oxidation of glucose from the bloodstream is under normal circumstances the only energy source for the Central Nervous System, and a continuous systemic supply is essential, as glucose storage in neuronal tissue is limited."

"..the idea that carbohydrate availability for the brain is important in maintaining an adequate neural drive to the muscles is supported by the finding that glucose infusion directly in the carotid artery can delay fatigue.."

"...hypoglycemia (low glucose levels) impairs the ability to sustain a high neural drive to the muscles.."

"...exercise is associated with an activation of large regions of the brain including the motor cortex areas as well as regions involved in cardio-respiratory regulation, and endothelial glucose transport may become rate limiting for the cerebral metabolic rate of glucose when the arterial glucose concentration falls below a critical point.."

"A continuous supply of blood glucose to the brain is essential..."

"..central fatigue during strenuous exercise could relate to depletion of brain glycogen stores."

"...exercise-induced hypoglycemia in endurance trained subjects lowers the average force production....and the reduced force development is associated with a diminished activation drive from the Central Nervous System."

CNS Fatigue And Prolonged Exercise: Effect Of Glucose Supplementation
Medicine & Science In Sports & Exercise....Volume 35 #4..April 2003..page589 - 594

"Adaptive changes can occur in the nervous system in response to training."

"..increased efferent neuronal outflow with training, including increases in maximal firing frequency.."

"..increases in maximal contraction force and power as well as maximal rate of force development will a result of changes in the nervous system."

"Importantly, the rate of force development plays an important role in the ability to perform rapid and forceful movements, both in highly trained athletes as well as elderly individuals..."

"..the rate of force development is enhanced with an increase in efferent neural drive.."

"An increased central descending motor drive results in an increased motor neuron recruitment and firing rate, which increases outflow of efferent motor impulses in the axons."

Training-Induced Changes In Neural Function
Exercise & Sport Sciences Reviews....Volume 31 #2..April 61 - 67

"..the training induced gains in contractile Rate Of Force Development and impulse, were attributed to an enhanced neural drive.."

Increased Rate Of Force Development and Neural Drive Of Human Skeletal Muscle Following Resistance Training
Journal Of Applied Physiology....Volume 1318 - 1326