Shoulder Injuries in the Throwing Athlete

Shoulder injuries in the throwing athlete are becoming more frequent. Sports specialization at a younger age, playing multiple seasons, increased awareness of injury and injury prevention, advances in diagnosis, and surgical treatment all play a part in the increase in diagnosis of these injuries. Understanding the biomechanics of throwing and pathologies that are encountered in the throwing athlete can aid the clinician in successful diagnosis and nonoperative/operative treatment of the throwing athlete. This article discusses the relevant anatomy, biomechanics, and pathoanatomy of the throwing shoulder. Additionally, understanding the kinetic chain can assist in the nonoperative rehabilitation of the injured shoulder. Surgical reconstruction is indicated when nonoperative efforts have been exhausted and is directed based on the extent of the pathology to the capsuloligamentous structures, labrum, and rotator cuff

A phenomenological model that predicts forces generated when electrical stimulation is superimposed on submaximal volitional contractions

Superimposition of electrical stimulation during voluntary contractions is used to produce functional movements in individuals with central nervous system impairment, to evaluate the ability to activate a muscle, to characterize the nature of fatigue, and to improve muscle strength during postsurgical rehabilitation. Currently, the manner in which voluntary contractions and electrically elicited forces summate is not well understood. The objective of the present study is to develop a model that predicts the forces obtained when electrical stimulation is superimposed on a volitional contraction. Quadriceps femoris muscles of 12 able-bodied subjects were tested. Our results showed that the total force produced when electrical stimulation was superimposed during a volitional contraction could be modeled by the equation T = V + S[(MaxForce − V)/MaxForce]N, where T is the total force produced, V is the force in response to volitional contraction alone, S is the force response to the electrical stimulation alone, MaxForce is the maximum force-generating ability of the muscle, and N is a parameter that we posit depends on the differences in the motor unit recruitment order and firing rates between volitional and electrically elicited contractions. In addition, our results showed that the model predicted accurately (intraclass correlation coefficient ≥0.97) the total force in response to a wide range of stimulation intensities and frequencies superimposed on a wide range of volitional contraction levels. Thus the model will be helpful to clinicians and scientists to predict the amount of stimulation needed to produce the targeted force levels in individuals with partial paralysis