Humans begin to stand between 8 and 12 months of age. Spring action
Traditionally, such correction was explained by the spring action of the muscles, a local mechanism taking place without the intervention of the central nervous system (C.N.S.). Recent studies, however, show that this spring action by itself is insufficient to prevent a forward fall. Also, human sway is too complicated to be adequately explained by spring action. Nervous system
According to current theory, the nervous system continually and unconsciously monitors our direction and velocity. The vertical body axis alternates between tilting forward and backward. Before each tilt reaches the tipover point the nervous system counters with a signal to reverse direction. Sway also occurs in the hip and there is a slight winding and unwinding of the lower back.An analogy would be a ball that volleys back and forth between two players without touching the ground. The muscle exertion required to maintain an aligned standing posture is crucial but minimal. Electromyography has detected slight activity in the muscles of the calves, hips and lower back. Core muscles
The core muscles play a role in maintaining stability. The core muscles are deep muscle layers that lie close to the spine and provide structural support. The transverse abdominals wrap around the spine and function as a compression corset. The multifidi are intersegmental muscles. Dysfunction in the core muscles has been implicated in back pain. Expansion of pendulum model
Some investigators have replaced the ankle inverted pendulum analogy with a model of double linked pendulums involving both hip and ankle sway.
Society and culture
In 2020, generic versions were approved in the United States. Names
Salbutamol is the international nonproprietary name (INN) while albuterol is the United States Adopted Name (USAN). The drug is usually manufactured and distributed as the sulfate salt (salbutamol sulfate). It was first sold by Allen & Hanburys (UK) under the brand name Ventolin, and has been used for the treatment of asthma ever since. The drug is marketed under many names worldwide. Doping
As of 2011 there was no evidence that an increase in physical performance occurs after inhaling salbutamol, but there are various reports for benefit when delivered orally or intravenously. In spite of this, salbutamol required "a declaration of Use in accordance with the International Standard for Therapeutic Use Exemptions" under the 2010 WADA prohibited list. This requirement was relaxed when the 2011 list was published to permit the use of "salbutamol (maximum 1600 micrograms over 24 hours) and salmeterol when taken by inhalation in accordance with the manufacturers recommended therapeutic regimen. "Abuse of the drug may be confirmed by detection of its presence in plasma or urine, typically exceeding 1,000 ng/mL.