Title: Neuromechanics
Content:  Electromyography (EMG) is a tool used to measure the electrical outputs produced by skeletal muscles upon activation. Motor nerves innervate skeletal muscles and cause contraction upon command from the central nervous system. This contraction is measured by EMG and is typically measured on the scale of millivolts (mV). Another form of EMG data that is analyzed is integrated EMG (iEMG) data. iEMG measures the area under the EMG signal which corresponds to the overall muscle effort rather than the effort at a specific instant.
Title: Electrophysiological techniques for clinical diagnosis
Content:  Electromyography is the measurement and analysis of the electrical activity in skeletal muscles. This technique is useful for diagnosing the health of the muscle tissue and the nerves that control them. EMG measures action potentials, called Motor Unit Action Potentials (MUAPs), created during muscle contraction. A few common uses are determining whether a muscle is active or inactive during movement (onset of activity), assessing the velocity of nerve conduction, and the amount of force generated during movement. Of these uses, determining the onset of muscle activity has been shown to be the most accurate.
Title: Electrogram
Content:  An electromyogram (EMG) is an electrical recording of the activity of a muscle or muscle group. An EMG study can be combined with a nerve conduction study to diagnose neuromuscular diseases such as peripheral neuropathy and amyotrophic lateral sclerosis.
Title: Electromyography
Content:  Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyograph detects the electric potential generated by muscle cells when these cells are electrically or neurologically activated. The signals can be analyzed to detect abnormalities, activation level, or recruitment order, or to analyze the biomechanics of human or animal movement. Needle EMG is an electrodiagnostic medicine technique commonly used by neurologists. Surface EMG is a non-medical procedure used to assess muscle activation by several professionals, including physiotherapists, kinesiologists and biomedical engineers. In Computer Science, EMG is also used as middleware in gesture recognition towards allowing the input of physical action to a computer as a form of human-computer interaction.
Title: Skeletal muscle
Content:  the motor axons from nerve impulses sent to the muscle. EMG is used in research for determining if the skeletal muscle of interest is being activated, the amount of force generated, and an indicator of muscle fatigue. The two types of EMG are intra-muscular EMG and the most common, surface EMG. The EMG signals are much greater when a skeletal muscle is contracting verses relaxing. However, for smaller and deeper skeletal muscles the EMG signals are reduced and therefore are viewed as a less valued technique for measuring the activation. In research using EMG, a maximal voluntary contraction (MVC) is commonly performed on the skeletal muscle of interest, to have reference data for the rest of the EMG recordings during the main experimental testing for that same skeletal muscle.
Title: Body reactivity
Content:  The detection, amplification, and recording of changes in skin voltage produced by underlying skeletal muscle contraction is called electromyography. Motor recruitment and skeletal muscle fatigue can be examined by combining EMG and dynamometry, which measures power. Facial EMG can measure startle response in humans.
Title: Electromyography
Content:  One basic function of EMG is to see how well a muscle can be activated. The most common way that can be determined is by performing a maximal voluntary contraction (MVC) of the muscle that is being tested. Muscle force, which is measured mechanically, typically correlates highly with measures of EMG activation of muscle. Most commonly this is assessed with surface electrodes, but it should be recognized that these typically record only from muscle fibers in close proximity to the surface. Several analytical methods for determining muscle activation are commonly used depending on the application. The use of mean EMG activation or the peak contraction value is a debated topic. Most studies commonly use 
Title: Electromyography
Content:  several seconds or more after the movement ceases. After assessing resting and insertional activity, the electromyographer assess the activity of muscle during voluntary contraction. The shape, size, and frequency of the resulting electrical signals are judged. Then the electrode is retracted a few millimetres, and again the activity is analyzed. This is repeated, sometimes until data on 10–20 motor units have been collected in order to draw conclusions about motor unit function. Each electrode track gives only a very local picture of the activity of the whole muscle. Because skeletal muscles differ in the inner structure, the electrode has to be placed at various locations to obtain an accurate study. 
Title: Muscle coactivation
Content:  Muscle coactivation is measured using a technique called electromyography(EMG). This is performed by using surface EMG that responds to electrical activity of the muscle through the skin. Electrical activity is only present in the muscle when the muscle voluntarily contracts. When the muscle is contracted, the EMG is able to display the force of the contraction or how the nerves can respond to stimulation. An EMG of coactivation would display the agonist and antagonist muscle contracting simultaneously. Although it is believed many muscles are involved in the mechanism of coactivation, methods to measure coactivation are finite to specific instances or two muscle systems. Because of this, little is understood about the role of coactivation in a multiple muscle system.
Title: Skeletal muscle
Content:  Myopathies have been modeled with cell culture systems of muscle from healthy or diseased tissue biopsies. Another source of skeletal muscle and progenitors is provided by the directed differentiation of pluripotent stem cells. Research on skeletal muscle properties uses many techniques. Electrical muscle stimulation is used to determine force and contraction speed at different frequencies related to fiber-type composition and mix within an individual muscle group. In vitro muscle testing is used for more complete characterization of muscle properties. The electrical activity associated with muscle contraction is measured via electromyography (EMG). Skeletal muscle has two physiological responses: relaxation and contraction. The mechanisms for which these responses occur generate electrical activity measured by EMG. Specifically, EMG can measure the action potential of a skeletal muscle, which occurs from the hyperpolarization 

Question: what features of muscle contraction can be determined from an emg (electromyogram)?
Answer: electric potential generated.