sacral curve—Curve which is formed from the sacrum and coccyx in the area of the lower back and buttocks.

saddle joint—Joint in which the concave surfaces of two bones articulate with one another; movement is possible in two planes; a bi-axial joint; resembles a saddle; capable of flexion, extension, abduction, adduction and circumduction; Example: the thumb is a saddle joint.

sagittal plane—Anatomical term referring to the imaginary longitudinal line that divides the body or any of its parts into right and left sections; the mid-sagittal line divides both halves equally; Motions within the sagittal plane include flexion and extension.

SAID principle—Acronym for the exercise training principle "specific adaptations to imposed demands"; training must be relative to the sport or activity for physiological change to take place and is specific to the action, energy systems, and muscle fibers.

salmonella—Salmonella is a Gram-negative bacterium, occurring in many animals, especially poultry and swine. In the environment, salmonella can be found in water, soil, insects, factory and kitchen surfaces, animal fecal matter, and raw meats, poultry (including eggs) and seafood. Acute symptoms of the illness caused by the Salmonella species include nausea, vomiting, diarrhea, abdominal cramps, headache and fever.

sarcomere—Repeating base unit that composes a muscle fiber.

saturated fats—Fatty acids that have the maximum number of hydrogen atoms they can accommodate; found primarily in animal sources and a few plant fats; may lead to high cholesterol and heart disease; these fats are solid at room temperature.

scoliosis—Lateral curvature of the spine; usually evident in the upper or lower back.

secondary assessment—Assessment performed on an injured person after immediate life or limb-threatening injuries and illnesses have been identified; this more thorough evaluation is performed to identify more subtle, yet still important, injuries such as broken bones, sprains, strains, cuts, and other injuries.

sedentary—Not active.

seizure—A disorder originating from the brain in which there is a disturbance of movement, behavior, sensation, or consciousness.

set—A grouping of repetitions performed without rest; Example: an exerciser may perform 8 repetitions in a set of leg extensions.

set-point theory—A weight-control theory that states that each person has an established normal body weight, deviation from this set point will lead to changes in body metabolism to return to established ‘normal weight’ of that individual’s body.

shin splints—An overuse syndrome including pain in the anterior lower leg; recommended treatment: R.I.C.E., wrap the shin, and support the plantar arch if necessary; see R.I.C.E.

side stitch (ache)—A pain in the side usually caused by insufficient oxygen to the diaphragm, improper breathing, or intestinal gas.

sliding filament theory—An accepted theory explaining the interaction between actin and myosin proteins and ATP to cause muscle contraction.

slow-twitch (type I fiber)—Muscle fiber characterized by its slow speed of contraction and a high capacity for aerobic glycolysis; also referred to as "red muscle fibers."

smooth muscle—Involuntary muscle tissue found in the walls of almost every organ of the body.

somatotype—Body type; see endomorph, ectomorph, and mesomorph.

spasm—See muscle cramp.

specificity of training—Principle of exercise training which refers to the fact that training the muscles in a specific way for a specific sport does not condition the body for different sports or exercises; Example: a marathon runner trains for distance running, but may not be able to do intense weight lifting. Only the systems we overload become stronger. see also SAID principle.

sphygmomanometer—An instrument used for measuring blood pressure in the arteries, usually at the brachial artery.

spina bifida—Spina bifida is a birth defect in which the infant is born with the spinal cord exposed. These children can grow to adulthood although they often suffer from paralysis and other disabilities. Also, see "neural tube defects (NTDs)."

spondylolisthesis—Forward displacement of one vertebra over another; usually occurs at the 4th or 5th lumbar vertebrae.

spondylolysis—The breaking down (dissolving into another) of a vertebra; usually beginning with a stress fracture.

sport performance—The ability to achieve a high level of physical function within a given sport.

spot reducing—A myth suggesting that a high number of exercise repetitions in a particular area can significantly reduce the fat content in that area.

sprain—Stretching or tearing of ligaments of a joint, following a sudden twisting, wrenching or external force.

stabilizer muscle—Muscle that stabilizes (or fixes) one joint so a desired movement can be performed in another joint.

staleness—Term referring to the experience of reaching a plateau in one’s training program.

static—Position held without noticeable movement; Static stretching involves a slow, deliberate stretch until you feel a tightness in the muscle, but before you feel pain. Hold the stretch for 15-60 seconds.

statistical power—A mathematical quantity that indicates the probability a study has of obtaining a statistically significant effect. A high power of 80 percent, or 0.8, indicates that the study - if conducted repeatedly - would produce a statistically significant effect 80 percent of the time. On the other hand, a power of only 0.1 means there would be a 90 percent chance that the research missed the effect - if one exists at all.

statistical significance—The probability of obtaining an effect or association in a study sample as or more extreme that the one observed if there was actually no effect in the population. Based on the hypothesis that if there truly is no effect, the results of a study are unlikely to have occurred. A P value of less than five percent (P<0.05) means the result would occur less than five percent of the time if there were no effect, and is generally considered evidence of a true treatment effect or a true relationship.

steroids – Naturally-occurring and synthetic chemicals that include some hormones, bile acids, and other substances; see anabolic androgenic steroids and ‘roids.

strain—An injury of muscles or tendons or adjacent tissue such as the fascia as a result of over stretching or overexertion; see muscle tear.

strength—The ability to apply a force for a given distance; the ability to move a given amount of weight for a given distance; Strength = Force x Distance.

stress fracture—Fine, hairline fracture of the bone usually from repetitive stress; it may not show in an X-ray for several weeks; characterized by sharp persistent pain; Stress fractures are commonly caused by overuse, hard surfaces, or improper footwear.

stretch reflex—The body’s automatic defensive action that stops the stretch action and protects against severe injury or abuse during stretching; see proprioceptive neuromuscular facilitation, Golgi tendon organ (GTO), and muscle spindle.

stroke volume—Amount of blood pumped per beat by the left ventricle; increases with regular aerobic exercise.

stroke—A sudden and often severe attack due to blockage of an artery into the brain; see cerebrovascular accident.

subluxation—A partial dislocation of a joint that usually reduces itself.

submaximal aerobic exercise test—A cardiorespiratory fitness test designed so that the intensity does not exceed 85 percent of heart-rate reserve or maximal oxygen uptake; this provides an estimation of maximal oxygen uptake without the risks associated with maximal exercise testing.

sucralose— Sucralose is the only low-calorie sweetener that is made from sugar. It is approximately 600-times sweeter and does not contain calories. Sucralose is highly stable under a wide variety of processing conditions. Thus, it can be used virtually anywhere sugar can, including cooking and baking, without losing any of its sugar-like sweetness. Currently, sucralose is approved in over 25 countries around the world for use in food and beverages.

sucrose—Sucrose, a type of sugar, is a disaccharide composed of glucose and fructose. Also, see "carbohydrates."

sugar—Although the consumer is confronted by a wide variety of sugars -- sucrose, raw sugar, turbinado sugar, brown sugar, honey, corn syrup -- there is no significant difference in the nutritional content or energy each provides, and therefore no advantage of one nutritionally over another. There also is no evidence that the body can distinguish between naturally occurring or added sugars in food products.

superficial—External; located close to or on the body surface

superior—Anatomical term meaning located closer to the head; opposite of inferior.

superset—Alternating between two exercises until the prescribed number of sets is completed; the two exercises generally involve a protagonist and antagonist (e.g., the pectoralis major and latissimus dorsi), but common usage of the term can mean any two exercises alternated with one another.

supination—Upward rotation of a limb, usually the hand or forearm, in an opened position.

supine—Horizontal position of the body, lying with the face upwards.

sympathetic nervous system—A division of the autonomic nervous system that activates the body to cope with some stressor (i.e., fight or flight response).

syncope—Fainting; a transient state of unconsciousness resulting from a lack of oxygen to the brain.

synergistic—Working together in a coordinated fashion; a synergistic muscle assists another muscle in its function.

synovial fluid—Transparent, viscous lubricating fluid found in the joints, bursae, and tendon sheaths; a proper warm-up stimulates its secretion.

systole—The contraction phase of the cardiac cycle during which blood leaves the ventricles.

systolic blood pressure—The pressure exerted by the blood on the blood vessel walls during ventricular contractions.