258 Glossary of Terms Individuality: Genetics plays a major role in how fast and to what degree one will respond to a particular training program. Individual zones of optimal functioning (IZOF): This theory takes into account that people have different levels of anxiety and arousal that are unique in making them perform at their best. Some people perform their best with low anxiety, some with a medium amount and others with a high amount. The amount of anxiety/arousal that an individual requires to perform their best is based on individual characteristics. Insomnia: Habitual sleeplessness or the inability to sleep. Insoluble fiber: A type of fiber that does not dissolve in water. Insoluble fiber in found in wheat bran, vegetables, and whole grains. Intensity: Amount of effort or work that must be invested into a specific training session. Intermittent fasting: Specific dietary strategy that requires an intentional abstention from food, drink, or both, for a period of time for the primary purpose of losing weight. Interval training: A form of endurance training that involves high-intensity intervals (typically 3-5 minutes in duration) close to VO2max. Inverted-U theory: This theory suggests there is a medium amount of arousal and anxiety that causes an individual to perform better. Too little arousal and anxiety or too much arousal and anxiety will result in decreased performance. Isokinetic contraction: Muscular contraction that occurs at a constant speed. A piece of equipment called an Isokinetic Dynamometer is used to measure the (constant) speed of isokinetic muscle contraction. Isometric contraction: A type of strength training in which the joint angle and muscle length do not change during contraction (as compared to isotonic contractions). Isotonic contraction: Muscular contraction against resistance in which the length of the muscle changes. Isotonic movements are either concentric or eccentric. Jet lag: The extreme tiredness and other physical effects felt by a person after a long flight across several time zones. Joint: Point of articulation between two or more bones. Kaizen principle (aka micro-dosing): A training principle, based on the Japanese word Kaizen, that strives for small and continuous improvements over time. Ketoacidosis: A life-threatening condition resulting from dangerously high levels of ketones in the blood. Ketones: Organic compound containing a carbonyl group bonded to two hydrocarbon groups formed when fats (instead of carbohydrates) are broken down for energy.
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