Fartlek: Speed play, or fartlek in Swedish (the concept originated in Sweden), is a speed work format in which you run faster for however long (or short) you want. Typically you would run 5 mins on (or fast) and 5 mins off (or slower) and repeat until the desired overall time is achieved.
Tempo run: Running at a faster pace than you're used to for an extended period of time (vs intervals, where you run fast for a short amount of time). Tempo running helps with speed and endurance. A pace that is in-between your short-interval training speed and your easy running pace.
Splits: The time it takes for you to run a predetermined distance (like a mile) within a race or workout. Knowing your split time helps you strategize when running a race or trying to increase your running pace. Negative splits, for example, means you run the latter half of a race or workout faster than the first half, which helps your overall time.
LSD: NOT the hallucinogen. LSD is an abbreviation for "Long, Slow Distance," which refers to the practice of running longer distances at an "easy" pace rather than shorter ones to exhaustion. The slower pace allows the runner to go longer and, therefore (supposedly), gain more fitness.
Cadence: Also known as stride turnover, a runner’s cadence is the number of steps taken per minute while running. The fastest and most efficient runners have a cadence of around 180 steps per minute, so find a fast-paced jam on the iPod and keep to the beat!
Aquajogging: Running against the water’s resistance in the deep end, where you can’t touch the bottom, provides many of the benefits of running on land.
Carb-loading: The practice of increasing the percentage of carbs in your diet during the days leading up to an endurance event such as a marathon, half-marathon, or even a long training run. (Note: Carb-loading is not simply eating more of everything.) Carb-loading stores glycogen in the muscles and liver so that it can be used during the race; it is most effective when done along with a tape
Dynamic Stretching: Controlled movements that increase flexibility, power, and range of motion. The best dynamic stretches for runners include lunges, squats, leg lifts, and butt-kicks.
Static Stretching: Holding major muscle groups in their most lengthened positions for at least 30 seconds, might bring it back to the middle school soccer days. While many still believe static stretches prior to running help prevent injuries, research now suggests stretching it out is more beneficial after breaking a sweat.
Hills: Workouts where a runner runs up a hill fast and jogs down then runs up again; helps develop leg power and aerobic capacity.
RICE: An acronym for rest, ice, compression and elevation; a procedure for treating certain injuries.
Runner's Knee: Knee pain usually caused by the knee cap not sliding properly during movement; may be related to muscular imbalances within the thigh muscles; can be treated with strengthening exercises for weak muscles (usually the inner thigh muscle).
Lactic Acid: Formed when the body cannot generate energy using oxygen, lactic acid is produced anaerobically (especially during hard workouts).
Cross Training: Exercising in other ways to help improve your running performance. Strength training, biking, or swimming, for example, help balance out your body by strengthening muscles you don't use as much when you run, which improves your running performance. Yoga also helps stretch muscles and hips to help with your form and performance.
Heat Index: A combined measurement of temperature and humidity that shows how hot it feels outside. When humidity is high, it cripples the body’s ability to sweat—the body’s self-cooling mechanism—so the body retains more heat and it’s riskier to be outside. High humidity also increases the risk for conditions like heat cramps, heat exhaustion, and heatstroke. The National Weather Service issues an alert when the heat index is expected to exceed 105 to 110 degrees Fahrenheit for at least two consecutive days.
Wind chill: How cold it really feels when you’re outside. As the wind grows stronger, it makes it feel much colder than the air temperature.
Ice baths: Typically taken after long runs, races, and hard workouts, ice baths involve immersing one’s legs in ice water for 15 to 20 minutes. The ice constricts blood vessels and decreases metabolic activity, which reduces swelling and tissue breakdown. Once you get out of the cold water, the underlying tissues warm up, causing a return of faster bloodflow, which helps flush waste products out of the cells.