Exercise Physiology, Training, and Nutrition
Physiology you must be able to reason with
The Fick equation (VO2 = cardiac output × arterial-venous oxygen difference) explains most cardiorespiratory adaptations: stroke volume rises with training, and so does peripheral oxygen extraction. Know the three energy systems, their substrates and durations, and the concept of lactate threshold, which marks the intensity above which lactate appearance exceeds clearance. Aerobic capacity responds to volume and intensity, while strength responds to progressive overload and specificity.
Training principles
Apply overload, specificity, reversibility, individuality, and periodization. Distinguish overreaching, which resolves with days of rest, from overtraining syndrome, which persists for weeks and includes mood and sleep disturbance. Recognize nonfunctional overreaching and relative energy deficiency in sport (RED-S), a low-energy availability state affecting bone, menstrual function, immunity, and performance.
Nutrition
Carbohydrate needs scale with load, roughly 3–5 g/kg/day for light training up to 8–12 g/kg/day for heavy endurance loading. Protein targets are about 1.2–2.0 g/kg/day. Hydration should be individualized using sweat rate: change in body mass plus fluid consumed, divided by exercise hours. Sodium replacement matters for salty sweaters and long events.
Traps
Lactate is a fuel and a marker, not the cause of the burning sensation or of acidosis; hydrogen ions from ATP hydrolysis drive that. Delayed-onset muscle soreness is not lactic acid. The "fat-burning zone" does not optimize weight loss. Creatine and caffeine have the strongest evidence among supplements; most others do not.
Worked example: an athlete weighs 70.0 kg before and 69.0 kg after a 2-hour ride, drinking 1.0 L. Sweat loss is 1.0 + 1.0 = 2.0 L over 2 hours, or about 1.0 L/h.