Carbohydrate --  a nutrient essential to runners (and everybody else for that matter) stored in the body as “Glycogen” and found in fruit, vegetables, pasta and bread; when not converted into energy, carbohydrates are
Essential nutrient of body found in pastas, breads, fruits, vegetables; should comprise the majority of calories in a runner's diet; stored in the body as glycogen in the muscles and liver; overconsumption is converted to fat

Chromium Picolinate – a nutritional supplement claiming to aid in insulin processing and chiefly advertised as a weight loss supplement. The Food and Drug administration does not evaluate the claims of nutritional supplements, and independent studies have returned unpromising results

Cool-down – a light run following a tougher workout, aids in recovery

CoolMax -- a DuPont manufactured, quick-drying, moisture-absorbing polyester fiber 

Creatine Supplements – an athletic nutritional supplement claiming to fill the body’s creatine phosphate storage to capacity, aiding in the development of skeletal muscles. The Food and Drug administration does not evaluate the claims of nutritional supplements, and though creatine-based products are one of the most popular supplements for weight lifters, any benefits to runners are not proven, and in fact, some studies have shown creatine supplements to inhibit fat loss

Cross-Training – branching out into other forms of exercise – cycling, swimming, etc. – in order to improve running abilities and develop muscles differently; can help to improve injuries or break up the monotony of an all—running workout schedule

Cruise Intervals – a workout intended to delay the point “Lactic Acid” enters the muscles, by running repetitions of medium distances at the “Anaerobic Threshold” speed and allowing only short rest intervals 

Cushioning – shock absorbent padding meant to reduce the damage running can do to your feet, the arrangement and thickness of the cushioning can be specially designed for various runner types – “Pronator,” “Under Pronator,” etc. 
Dehydration – a lack of fluid in the body, can result from perspiration outweighing liquid intake

Delayed Onset Muscle Soreness (DOMS) – the muscle pain occurring in the days following a workout of higher than normal intensity; beginning runners become very well acquainted with DOMS

Did Not Finish (DNF) – the status of a runner who leaves a race before completing it

Electrolytes – sodium and potassium salts which replenish lost bodily fluids; the amount of electrolytes found in sports drinks are generally only necessary to prevent “Dehydration” after an intense  several hour workout such as a “Triathlon”