Exercise Science
97 flashcards by MentisLibrary
How the body actually adapts to training: energy systems, muscle fibers, VO2 max, lactate threshold, recovery, and periodization. The physiology behind every program, explained without the bro science.
- What are the three energy systems the body uses to resupply ATP?
- The phosphagen (ATP-PC) system, the glycolytic system, and the oxidative or aerobic system
- Which energy system powers an all-out effort lasting only a few seconds?
- The phosphagen system, using stored ATP and creatine phosphate
- What fuel does the glycolytic system break down?
- Glucose and stored muscle glycogen, broken down to pyruvate without requiring oxygen
- Which energy system supplies almost all the ATP for a long steady effort?
- The oxidative or aerobic system
- What is the role of creatine phosphate in a working muscle?
- It donates its phosphate group to ADP to regenerate ATP almost instantly
- Why can a muscle only sustain maximal effort for a few seconds on stored ATP alone?
- Resting muscle stores very little ATP, enough for only a second or two of maximal work
- What actually causes the burning sensation during very hard exercise?
- Accumulating hydrogen ions and other metabolites that lower muscle pH, not lactic acid itself
- Is lactate a waste product?
- No, it is a usable fuel that can be shuttled to other muscle fibers, the heart, and the liver
- What is the Cori cycle?
- The liver converting lactate back into glucose, which can then return to the muscle
- What characterizes Type I muscle fibers?
- Slow twitch, highly fatigue resistant, rich in mitochondria, capillaries, and myoglobin
- What characterizes Type IIx muscle fibers?
- The fastest and most powerful fibers, with the lowest fatigue resistance
- Where do Type IIa fibers sit between the other fiber types?
- They are fast twitch but also oxidative, combining decent power with decent fatigue resistance
- What does the sliding filament theory describe?
- Actin and myosin filaments slide past one another so the sarcomere shortens while filament lengths stay the same
- What is a sarcomere?
- The basic contractile unit of a muscle fiber, running from one Z line to the next
- What role does calcium play in muscle contraction?
- Released from the sarcoplasmic reticulum, it binds troponin and moves tropomyosin off the actin binding sites
- What is a motor unit?
- A single motor neuron together with every muscle fiber it innervates
- What does Henneman's size principle state?
- Motor units are recruited from smallest to largest as force demand increases
- What is rate coding?
- Increasing the firing frequency of already recruited motor units to produce more force
- Why do beginners often gain strength quickly without visible muscle growth?
- Early strength gains come mostly from neural adaptation rather than added muscle tissue
- What is muscle hypertrophy?
- An increase in the cross sectional area of existing muscle fibers
- What is considered the primary driver of hypertrophy?
- Mechanical tension placed on the muscle fibers
- What is metabolic stress in the hypertrophy literature?
- The buildup of metabolites such as lactate, hydrogen ions, and inorganic phosphate during sustained effort
- What is hyperplasia?
- An increase in the number of muscle fibers rather than their size
- What is the difference between myofibrillar and sarcoplasmic hypertrophy?
- Myofibrillar growth adds contractile proteins; sarcoplasmic growth adds non-contractile fluid and components
- What does VO2 max measure?
- The maximum rate at which the body can take in, transport, and use oxygen
- How is VO2 max measured directly in a lab?
- A graded exercise test to exhaustion while expired gases are analyzed by a metabolic cart
- What does the Fick equation say about VO2?
- VO2 equals cardiac output multiplied by the arteriovenous oxygen difference
- What is the lactate threshold?
- The exercise intensity at which blood lactate begins accumulating faster than the body clears it
- Why does lactate threshold predict endurance performance better than VO2 max among trained athletes?
- Trained athletes have similar VO2 max values, so the difference lies in what fraction of it they can sustain
- What is EPOC?
- Excess post-exercise oxygen consumption, the elevated oxygen use that persists after a session ends