have found that early strength gains throughout training are associated with increased amplitude in SEMG activity. These findings along with various other theories explain increases in strength without increases in muscle mass. Other theories for increases in strength relating to neural adaptation include: agonist-antagonist muscle decreased co-activation, motor unit synchronization, and motor unit increased firing rates. Neural adaptations contribute to changes in V-waves and Hoffmann's reflex. H-reflex can be used to assess the excitability of spinal α-motoneurons, whereas V-wave measures the magnitude of motor output from α-motoneurons. Studies showed that after a 14-week resistance training regime, subjects expressed V-wave amplitude increases of ~50% and H-reflex amplitude increases of ~20%. This showed that neural adaptation accounts for changes to functional properties of the spinal cord circuitry in humans without affecting organization of the motor cortex. Habituation vs. adaptation The terms neural adaptation and habituation are often confused for one another. Habituation is a behavioral phenomenon while neural adaptation is a physiological phenomenon, although the two are not entirely separate. During habituation, one has some conscious control over whether one notices something to which one is becoming habituated. However, when it comes to neural adaptation, one has no conscious control over it. For example, if one has adapted to something (like an odor or perfume), one can not consciously force themselves to smell that thing. Neural adaptation is tied very closely to stimulus intensity; as the intensity of a light increases, one's senses will adapt more strongly to it. In comparison, habituation can vary depending on the stimulus. With a weak stimulus habituation can occur almost immediately but with a strong stimulus the animal may not habituate at all e.g. a cool breeze versus a fire alarm. Habituation also has a set of characteristics that must be met to be termed a habituation process. Rhythmic behaviors Short-term adaptations Short term neural adaptations occur in the body during rhythmic activities. One of the most common activities when these neural adaptations are constantly happening is walking. As a person walks, the body constantly gathers information about the environment and the surroundings of the feet, and slightly adjusts the muscles in use according to the terrain. For example, walking uphill requires different muscles than walking on flat pavement. When the brain recognizes that the body is walking uphill, it makes neural adaptations that send more activity to muscles required for uphill walking. The rate of