Glossary

Abduction is an anatomical directional term meaning moving away from the body.

Adduction is an anatomical directional term meaning moving toward the body.

ATP is a molecule that is responsible for storing and releasing energy in the body. Due to this, biologists have coined ATP the "currency of life." ATP is generated in the mitochondria of cells; and it can be produced aerobically and anaerobically. The body stores only a small amount of ATP at any given time, so ATP must be continually regenerated on a cellular level.

The term aerobic refers to the type of energy metabolism carried out by your body in the presence of oxygen. Aerobic metabolism, or aerobic oxidation sustains exercise for longer durations of time. The aerobic system uses stored fats, carbohydrates (glycogen), and proteins as energy sources.

As the intensity level of exercise increases, the body must rely more upon anaerobic metabolism to meet its pressing energy needs.

Keep in mind that the different types of energy systems used by the body to fuel exercise are not mutually exclusive. They all operate during exercise but to differing degrees depending upon the intensity of the exercise.

Endurance training results in a higher aerobic capacity. Aerobic capacity is a term used synonymously with VO2max, or maximal oxygen consumption. These terms refer to the highest rate of oxygen transport and use by your body during maximal physical exertion.

VO2max is expressed through the Fick equation, which multiplies heart rate (HR) by stroke volume (SV) by arteriovenous oxygen difference (a-v O2 difference):

VO2max (mL / kg / min) = HR (beat / min) x SV (mL / beat) x (a-v O2 difference)

VO2max can be expressed in absolute terms as liters per minute (L/min), but is typically expressed relative to body weight so that comparisons among individuals can be made. Relative VO2max is therefore expressed as milliliters per kilogram per minute (mL/kg/min).

The higher your VO2max, or aerobic capacity, the faster you’re able to move over long distances. This is because a higher VO2max means a higher stroke volume—that is, for each heartbeat your heart will pump a greater amount of oxygenated blood to your muscles. Some of the top male endurance athletes in the world have recorded VO2max scores over 80 or even 90. For example, Greg LeMond's VO2max was 92.5. Steve Prefontaine's was 84.4. Mountain runners Matt Carpenter and Kilian Jornet have measured 92.0 and 89.5, respectively, and track runners Jim Ryun and Steve Scott measured 81.0 and 80.1, respectively. Some top female endurance athletes have recorded scores over 70. For example, 1984 Olympic marathon champion Joan Benoit Samuelson had a VO2max of 78.6;  marathoner Rosa Mota had one of 67.2. By comparison, anything above 55 for 20-29 year old men, above 52 for 30-39 year old men, above 50 for 40-49 year old men, above 49 for 50-59 year old men, or above 44 for men over 60 represent scores in the top 10 percentile of the male population, according to the norms provided by the American College of Sports Medicine. Likewise, anything above 49 for 20-29 year old women, above 45 for 30-39 year old women, above 42 for 40-49 year old women, above 37 for 50-59 year old women, or above 34 for women over 60 represent scores in the top 10 percentile of the female population.

Although an individual’s aerobic capacity is based to an extent on genetics, it is also highly malleable. Endurance training can substantially raise one’s VO2max. And per the reversibility principle, a lack of endurance training can lower one’s VO2max. And, as you can see from the norms mentioned above, it decreases with age. Moreover, being born with a high VO2max does not necessarily make a champion runner, cyclist, swimmer, triathlete or other type of endurance athlete. If that were the case, we might as well just all go to the lab to get our VO2max tested and turn in the results to race organizers. Obviously, there are many factors involved in being successful at endurance events, including mental skills, nutrition, and race tactics, just to name a few. Even when it comes to VO2max, two athletes that vary in their aerobic capacities may still possess equivalent effective aerobic capacities when taking into account economy of motion. In other words, Athlete A may achieve a 5K run time of 17 minutes with a VO2max of 62 and fair running economy while Athlete B may achieve that same 5K time with a VO2max of 58 and excellent running economy.

The bottom line is that laboratory recorded numbers are only a starting point. The key is knowing how to use those numbers to effectively train because endurance training will lead to better performance through many central and peripheral physiological adaptations, including an increased VO2max, increased stroke volume (i.e. amount of blood pumped with each heartbeat), increased capillary density in skeletal muscle, improved blood lipid profile, and increased lean body mass.

The following table shows VO2max norms for men and women (ACSM’s Guidelines for Exercise Testing and Prescription: Seventh Edition 2006, p. 79).

Your aerobic threshold (AeT) corresponds to a "conversational" nose-breathing effort. You should be able to breathe through your nose and hold a back-and-forth conversation with someone running next to you when you’re at or below your AeT; breathing is moderate and not labored. 

In most athletes, the AeT corresponds to the top of Zone 2 if you're using the Friel heart rate zones or Zones 1-2 ("easy to moderate") if you're using the Stryd power zones as a guide. On a Borg 1-10 rating of perceived exertion (RPE) scale, this would be an RPE of 5-6 ("moderate").

Training at or below your aerobic threshold is foundational to building your aerobic endurance during base training, allowing you to better metabolize fat and spare glycogen (stored carbohydrate) as a long duration energy source. Work at or below your AeT during other phases of training still comprises the bulk of your training time.

Muscle or muscles that are primarily responsible for movement around a joint. Also called a "prime mover."

The term anaerobic refers to the type of energy metabolism carried out by your body without oxygen. Anaerobic metabolism, or anaerobic glycolysis is used to meet the body’s energy needs at higher levels of intensity. It uses carbohydrates (glycogen or glucose) to rapidly produce energy for the body.

The end product of anaerobic metabolism is lactate, which requires aerobic metabolism (and hence oxygen) to remove from the bloodstream. Any bout of exercise over a few minutes, therefore, cannot be sustained solely through anaerobic metabolism.

Keep in mind that the different types of energy systems used by the body to fuel exercise are not mutually exclusive. They all operate during exercise but to differing degrees depending upon the intensity of the exercise.

Anaerobic endurance refers to the ability to resist fatigue at very high intensity efforts when arm/leg turnover is rapid. Anaerobic endurance is classified as one of three advanced abilities—the other two being power and muscular endurance—according to the training system espoused by Joe Friel. It is a combination of the two basic abilities of speed skills plus endurance.

Muscle or muscles that act in opposition to the agonist muscle(s).

Oxygenated blood leaves the heart through arteries. As the blood circulates throughout the body, muscles extract some of that oxygen for use in energy production. The a-v O2 difference reflects the difference between the oxygen concentration in the arteries (leaving the heart) and the remaining oxygen concentration in the veins (returning to the heart).

At rest, the a-v O2 difference is typically around 5 milliliters of oxygen per deciliter (5 mL O2 / dL), representing a use coefficient of 25%. At exercise, the a-v O2 difference can increase up to around 15 mL O2 / dL with a use coefficient of 75%. In other words, more oxygen is extracted by working muscles as the intensity level increases.

Base training refers to the phase, or period of training that primarily works the aerobic system to build endurance and prepare the body for the demands of higher intensity training.

Your blood pressure consists of two numbers: systolic blood pressure (SBP) and diastolic blood pressure (DBP). The systolic blood pressure refers to the pressure exerted on the wall of your arteries when the heart contracts. The diastolic blood pressure refers to the arterial pressure during the relaxation phase of the heart’s ventricles.

Typical resting blood pressure is 120 / 80 (that is, 120 mm Hg for systolic pressure and 80 mm Hg for diastolic pressure). Consistent resting blood pressure readings at or above 140 / 90 generally constitute high blood pressure, or hypertension.

BMI is a value derived from the mass (weight) and height of a person. The BMI is defined as the body mass divided by the square of the body height, and is expressed in units of kilograms per meters squared.

The formula attempts to determine if an individual is underweight, average weight, or overweight, but is not an accurate tool to use for an athlete as it does not take body fat or muscle into consideration.

Cadence refers to the number of revolutions, or cycles per minute. For swimming, cadence refers to the number of swim strokes per minute. For cycling, cadence refers to the number of pedals strokes per minute. For running, cadence refers to the number of foot steps per minute.

Capillaries are the smallest blood vessels in the body. They increase in density based on how much blood supply is needed in a particular area. They are found in the tissues of the human body and transport blood from the arteries to the veins. Due to the thinness of the walls of capillaries, oxygen (O2), carbon dioxide (CO2), waste products and nutrients can pass through the walls.

Cardiac output refers to the volume of blood pumped by the heart each minute. Cardiac output (abbreviated Q with a dot over it, or Q-dot) is calculated by multiplying heart rate (HR) by stroke volume (SV).

Q = HR x SV

During a workout, cardiac drift refers to the natural increase or upward “drift” in heart rate while the overall intensity (e.g., respiration rate, effort level, caloric burn) stays the same.

Carbohydrates consist primarily of sugars and starches, making up one of the three principal types of macro-nutrients used as energy by the body (the other two are protein and fat). Carbohydrates are often classified as simple or complex. The classification depends on the chemical structure of the food, and how rapidly the sugar is digested and absorbed by the body.

The cooldown, or warmdown period involves a transition from the exercise session back to a resting level. It involves low-level activity to clear lactate from the blood while allowing the heart rate, blood pressure, and respiration rate to lower.

Core muscles stabilize and support the pelvis and spine. Core muscles include the rectus abdominis, external obliques, internal obliques, transverse abdominis, erector spinae, hip flexors (psoas) and gluteal muscles.

DOMS refers to muscle soreness that reaches its peak 24-48 hours after exercise has ended. DOMS primarily results from movements that involve eccentric muscle contractions, such as running downhill where your quads do a lot of eccentric movements.

Training duration refers to the amount of time of a training session. The frequency of training sessions plus the duration of those training sessions comprise training volume.

Electrolytes are minerals that break into small electrically charged particles called ions. They are present wherever there’s water in your body. They help regulate the body’s fluids to maintain a healthy blood pH balance and create the electrical impulses essential to all aspects of physical activity – from basic cell function to complex neuromuscular interactions needed for athletic performance. The kidneys work to keep the electrolyte concentrations in the blood constant despite changes in the body. Sodium is one of the many important electrolytes.

Endurance refers to the ability to resist fatigue and delay its onset during prolonged activity. Endurance is classified as one of three basic abilities—the other two being force and speed skills—according to the training systems espoused by Tudor Bompa and Joe Friel, among others.

To sustain movement over time, we utilize energy. In our bodies, the basic currency of energy comes in the form of a high-energy compound called adenosine triphosphate (ATP). Our muscles store ATP in limited amounts which can be quickly tapped for energy. The amounts are so limited that any type of activity over a few seconds in duration requires the creation of additional ATP.

One way the body can immediately manufacture additional ATP is by utilizing creatine phosphate (CP) to produce a few more seconds of energy. Like ATP, only a limited amount of CP is stored in the muscles so it’s only useful for short bursts of activity. Fortunately, the body is equipped with additional (although slower) manufacturing processes to supply that needed ATP.

For more pressing energy needs, the next pathway involves a process that breaks down carbohydrate stored in the muscles (glycogen) or carried in the bloodstream (glucose). As with the immediate pathways that use stored ATP and stored CP, this process occurs without the presence of oxygen. It is termed anaerobic glycolysis. The prefix an- derives from the Greek “without” while aero- refers to “oxygen” and bic- “pertaining to life.” So the term anaerobic means 'life without oxygen.' Since there is no oxygen present, the metabolic reaction creates an end-product called lactate in addition to the ATP it produces. As this energy pathway continues to produce small amounts of ATP, lactate continues to accumulate in the cells. When your bloodstream begins to accumulate more lactate than it can clear; then a decline in performance occurs within a few minutes.

To continue supplying energy, the body needs a more efficient energy pathway. If oxygen is present, then that oxygen can be mixed into the metabolic reaction to form much larger quantities of ATP. In addition, this process—aerobic oxidation (aerobic meaning 'life with oxygen')—can metabolize not only carbohydrate, but also fat and protein. The drawback, however, is that it takes much longer to produce the ATP than do the anaerobic pathways. As a result, your body must slow down a bit to accommodate the energy production process.

So the major energy pathways the body uses to produce energy can be characterized as either anaerobic (without oxygen) or aerobic (in the presence of oxygen).

It is important to emphasize that these are not mutually exclusive pathways. Anytime you head out the door for a run, you utilize all of the available energy pathways. But you use those pathways to differing degrees depending upon the intensity at which you’re exercising.

The faster you run (and hence the higher the energy demands placed on the body), the more you rely upon anaerobic pathways to supply quick energy. The slower you run, the more you are able to rely upon the aerobic pathway to supply your energy needs.

Endurance athletes want to go as fast as possible over long distances. The better you can tap into the aerobic energy pathway while maintaining higher intensity speeds, the more successful you will be.

Excess post-exercise oxygen consumption (EPOC) refers to the increased intake of oxygen after you finish exercise. In other words, once you finish running hard, you continue breathing hard a while longer. The purpose of EPOC is to eliminate the "oxygen debt" that accrues during exercise, bringing your body back to a resting state. EPOC is greater with higher intensity exercise that targets the anaerobic system. But EPOC is why higher intensities that primarily target the anaerobic system also train the aerobic energy system; this is because the oxidative (aerobic) energy system works hard to bring you back to a baseline level after finishing those hard intervals.

Fast twitch muscle fibers are often referred to as “Type II” fibers. They are classified into two types: IIA and IIB. The primary characteristic of fast twitch muscle fibers is that they contract with a high degree of force but lack the ability to fire repeatedly without fatigue. Fast twitch fibers are non-oxidative, meaning they do not require oxygen to contract.

Fat is a major energy source for the body during long endurance outings. The primary location for fat storage is adipose tissue (i.e., body fat) within the body. The majority of the adipose tissue that is used for energy is called subcutaneous fat (below the skin). Adipose tissue is comprised of adipocytes, or fat cells. Adipocytes are where triglycerides are stored and synthesized. Fat, along with carbohydrates and protein are known as macro-nutrients.

Flexibility refers to the range of motion around joints.

Force refers to the ability to overcome resistance. Force is classified as one of three basic abilities—the other two being endurance and speed skills—according to the training systems espoused by Tudor Bompa and Joe Friel, among others.

Training frequency refers to the number of training sessions done per week. The frequency of training sessions plus the duration of those training sessions comprise training volume.

Functional strength refers to strength that directly benefits sport-specific movements and activities.

Hans Selye, a Hungarian biologist who worked around the middle of the twentieth century, outlined a model that underlies the training process. When you train, you introduce a stimulus, or “stress” to your body. This is followed by a “response” from the body which leads to a physiological “adaptation.” Selye called this stress-response-adaptation process the general adaptation syndrome (GAS).

The work you do during a training session breaks down the body, followed by a recovery phase during which the body rebuilds stronger than before. This is another way of describing the general adaptation syndrome. As a result of the process, you gain fitness, or the ability to perform faster and longer than before.

Many athletes take the ideas of the GAS and reason, “If training makes me stronger and faster, more training should make me even stronger and even faster.” This is true as long as you are adequately recovering in between those training sessions. You can run into trouble, however, if you are comparing your training load with other athletes and simply trying to match the volume and intensity of their training programs. Crucially, it is not the absolute training load that matters, but the training load that your body can handle.

Glucose is a carbohydrate (sugar) that circulates in your bloodstream, acting as an energy source for the body’s cells.

Glycogen is a form of carbohydrate that is stored in the muscles and liver, and can be converted to glucose for energy.

Glycogen depletion refers to low levels of glycogen in the body, often resulting in the loss of energy and extreme fatigue. Glycogen is primarily stored in the liver and the muscles, and gets used during exercise. The body can store around 2,000 calories of glycogen.

Heart rate refers to the number of times your heart beats per minute.

Heart rate training zones are ranges used for exercise prescription. They can be percentages based on, among other things, VO2max, VO2 Reserve, HRmax, HR Reserve, LTHR, among others.

The heart rate training zones primarily used in Alp Fitness training plans is Joe Friel's seven-zone system. Each zone corresponds to a range of percentages of lactate threshold heart rate (LTHR).

Zone 1 – Recovery / Easy effort
Zone 2 – Aerobic / Extensive endurance
Zone 3 – Tempo / Intensive endurance
Zone 4 – Sub-threshold
Zone 5a – Super-threshold
Zone 5b – Aerobic capacity
Zone 5c – Anaerobic capacity / Power

The lactate threshold corresponds to the bottom of Zone 5a; thus zones 1-4 are below the lactate threshold and zones 5a-c are above the lactate threshold.

Keep in mind that heart rate training zones are sport specific. You will have different training zones for running, cycling, swimming, skiing, etc.

Hyperthermia, or overheating, occurs when an individual's body temperature is elevated beyond normal. The person's body produces or absorbs more heat than it dissipates.

Hyponatremia refers to a low sodium concentration in the blood, a type of electrolyte imbalance that often results from overhydration (drinking too much water).

Hypothermia occurs when the core body temperature drops below what is required for normal body functioning. This happens when the body loses heat faster than it can produce heat.

Training intensity refers to the effort put forth during a training session, as measured through effort, exertion, speed, power, etc. Training intensity is one of two key axes around which your training revolves—the other is volume.

In general terms, interval training refers to the use of higher intensity work intervals interspersed with recovery intervals, or rest intervals. The length of the work and recovery intervals can vary depending upon what training effect you are trying to achieve.

Running coach Jack Daniels used the term intervals in a more specific way to refer only to VO2max or race pace intervals of 3-5 minutes in duration. He uses the term reps (repetitions) to refer to work periods of less than 2 minutes in duration at highest intensity.

Lactate is a by-product of your body’s energy production and the lactate threshold (LT) is the point at which blood lactate begins to accumulate in the bloodstream. This occurs when the rate of lactate production increases faster than the rate of removal (clearance).

Workloads above the lactate threshold can only be sustained for up to several minutes before the body must slow down. Workloads right at the lactate threshold can generally be maintained for about an hour or even two. Workloads below the lactate threshold can be maintained much longer.

An important effect of endurance training is to ‘raise your lactate threshold.’ Whereas before training you could run, say, seven minutes per mile while at LT, after training the same pace would represent an intensity level below your LT. This means that you would be able to go faster at a lower level of effort.

Your lactate threshold heart rate (LTHR) is the heart rate that corresponds to your lactate threshold (LT). It is specific to the activity, so you will have a different LTHR for running, cycling, swimming, skiing, etc. An athlete’s LTHR for cycling is typically 5-10 beats lower than that athlete’s LTHR for running, so it is possible to estimate one from the other if sport-specific tests are not available for both.

Mitochondria is an organelle that acts as the 'power plant' of cells by converting the potential energy from food molecules into ATP.

Endurance sports are all about movement. And to move our bodies through space and time we use muscles. Muscles operate when a signal is sent from the central nervous system (CNS) to individual cells (also called muscle fibers) in your skeletal muscles. As a sufficient number of muscle fibers are recruited for the task, they then contract to produce movement toward your goal.

Skeletal muscle fibers come in different flavors. When you see the difference between the leg meat and breast meat of a chicken, you know that this is literally true—dark meat tastes different than light meat. These different color patterns are a result of the chicken legs consisting of a higher percentage of slow-twitch muscle fibers while chicken breasts contain a higher percentage of fast-twitch muscle fibers.

Slow-twitch muscle fibers—also called Type I—contract more slowly, just as the name implies. They are built to bring in oxygen and maximize the production of energy through the aerobic pathway. To those ends, they contain a greater number of capillaries and proteins called myoglobin to carry oxygen into the cells, along with a greater number of mitochondria which act as cellular factories for aerobic energy production. The iron-rich pigments associated with myoglobin are responsible for the color of dark meat.

Fast-twitch muscle fibers—also called Type IIb (or IIx)—contract more quickly and with more force than any other fiber type. They contribute substantially to shorter bursts of speed and do so through anaerobic energy production pathways. When a chicken is startled and flaps its wings to get away from a perceived threat, it recruits those fast-twitch fibers in the chest to move quickly. In contrast, the slow-twitch muscle fibers in the chicken’s legs are recruited for the long duration task of walking around the farmyard all day long.

There’s also a third muscle fiber type. These are called intermediate fast-twitch, or Type IIa muscle fibers. These muscle fibers possess some of the aerobic characteristics of the slow-twitch fibers as well as some of the increased contractile capability of the fast-twitch fibers.

When you decide to move your body, the first fibers to be recruited are the slow-twitch fibers. If the force demands are great enough, then the intermediate fast-twitch fibers are recruited and finally the fast-twitch fibers are called up for duty. The more force and speed you need for a given activity, the higher up the recruitment list you go.

Crucially, another factor that leads to recruiting higher up the list is fatigue. When your slow-twitch fibers become fatigued, the intermediate and fast-twitch fibers are recruited to share some of the burden. This is why even endurance athletes need to train all the fiber types. Even fast-twitch fibers are brought in to help out in endurance events as fatigue sets in. The athlete who has trained those fibers through faster paced speed work will be in a better position than the athlete who only trained by doing long aerobic workouts at lower end speeds.

Although it’s true that genetics have a great deal to do with what type of fibers predominate in your skeletal muscles, endurance training can increase the aerobic capabilities of even fast-twitch fibers. A world-class sprinter may never become a world-class marathoner, but that sprinter can nevertheless improve his or her marathon time substantially through endurance training.

Muscular endurance refers to the ability of muscles to maintain a relatively high force load for a prolonged period of time. Muscular endurance is classified as one of three advanced abilities—the other two being power and anaerobic endurance—according to the training system espoused by Joe Friel. It is a combination of the two basic abilities of force plus endurance.

Myofascial release refers to the reduction of tightness and restrictiveness of the muscles and fascia. Fascia is the web of connective tissue that surrounds all muscles, bones, nerves and blood vessels; it has a large affect on posture and muscle balance. Restricted fascia creates pain and muscle dysfunction, which can be addressed with types of bodywork that provide myofascial release.

Outcome goals are what we typically think of as “goals.” When you race, you may have a target time you’re aiming for or you may want to achieve a certain place. We have the least control over these goals.

The overload principle states that any new training gain requires an appropriate training stimulus that is greater than the amount of training stress to which the body is currently adapted. Just as the name of the principle implies, you must “overload” the system to bring about a response and adaptation. Keep in mind that the training stimulus must still be appropriate, however. It needs to be an appropriate stress to ratchet up your fitness level incrementally, rather than a stress that completely overwhelms the system and leads to overtraining or injury.

Fitness professionals use the acronym FIT as a mnemonic for the key elements that comprise a training load: frequency, intensity, and time. Frequency refers to the number of training sessions done per week. Intensity refers to the effort level put forth during a training session. Time, or what is also commonly termed duration, refers to how long a training session lasts.

When taken together, these three elements—frequency, duration, and intensity—comprise your overall training load. Frequency and duration combine to give you training volume. Training volume contrasts with training intensity. In this way, your training load consists of volume plus intensity, or the sum total of training stress you throw at your body in its various forms.

Training Load = Volume + Intensity

Since training volume refers to the total amount of training you do, to quantify training volume you need to take into account the frequency of your training (i.e., how many times per week you train) plus the duration of each of those sessions. Many competitive athletes are accustomed to thinking in mileage or yardage instead of hours trained. In that case, training volume is quantified as distance rather than duration.

Training intensity refers to the exertion level put forth during your training sessions. Whereas volume refers to the quantity of your training, intensity deals with the qualitative nature of your training.

In sum, the overload principle states that you need to provide an appropriate training stress to achieve a fitness gain. Not enough stress and the body will fail to achieve a fitness gain. Too much stress and the body will fail to positively adapt, resulting in overtraining or injury. In other words, you need to deliver a training stimulus appropriate to your current fitness level to move you forward toward your performance goals.

Overreaching involves the accumulation of an amount of stress that causes a temporary decrease in performance without showing the signs of overtraining. If overreaching continues long enough without adequate recovery, overtraining can result.

Overtraining refers to the accumulation of too much stress (training or other types of stress) that leads to extreme fatigue (physical and mental). Overtraining occurs when overreaching is carried too far without adequate recovery. With overtraining, the athlete has dug him/herself a hole that may take several weeks to get out of. Extreme cases can be season ending. Overtraining is obviously to be avoided and the administration of an appropriate training plan can help the athlete use the overload principle for performance gains without overtraining.

If you are lethargic, have heavy legs or difficulty elevating your heart rate during training at increased intensity levels; then these are signs you are overtraining. If these signs continue for more than a day; then take a few days off completely followed by a few days of short, easy workouts before returning to your regular program.

The peak training period is done prior to the athlete’s key race or races of the season. It occurs after base training has laid a strong aerobic foundation, and it involves a reduction in training volume along with an increase in training intensity to allow the athlete to achieve a high level of fitness for optimal performance.

Performance goals are the principles that guide how you show up as an athlete during training and racing regardless of the obstacles you may encounter. Think of these as “performance standards” that you’ve set for yourself in terms of attitude, level of effort, etc. We have control over these if we train to implement them, so spend most of your time developing these types of goals.

Periodization refers to the structuring of training into phases or blocks that target different training effects.

First used by the Soviets and soon refined by Romanian sport scientist Tudor Bompa, periodization involves breaking the year up into distinct training phases that build upon one another to peak an athlete for the most important competitions at the end of the season. Periodization is therefore different from doing the same type of training week-in and week-out. It is also different than randomly switching routines every month or so just for the sake of variation. What periodization contributes to training is a systematic approach to progress the athlete through successive stages over the course of the training year. Long-term progression is the goal so that the athlete arrives at the major competitions of the year in peak form.

Following the principle of specificity, periodized programs progress from general to specific, starting with general preparation and base training phases, moving through build phases, and culminating with peak training and race phases. The closer to the key race, the more specific the training becomes to target the demands of the race. After the season ends, the athlete shifts gears back to a general active recovery or transition phase before starting again with base training for the next year.

The training year as a whole is referred to as a macrocycle. It usually involves one or a few target races or events, either stacked together at the end of the year or spread apart by at least two months. The macrocycle is then divided into smaller phases of about two to six weeks in length called mesocycles. Each mesocycle has a particular training focus. The mesocycles in turn consist of smaller blocks of training that typically align with weeks. These are referred to as microcycles. It is quite possible to use microcycles of, say, 10 days instead of the seven-day week. Such an approach could have advantages for some athletes, but for many it is easier to schedule a microcycle around the typical calendar week.

In general, training programs can vary in how they put together the pieces to create a periodization schedule. In addition, any periodization schedule is highly individual in that it needs to take into account the athlete’s goals, background, and current fitness level.

Power refers to the ability to apply maximum force quickly. Force is classified as one of three advanced abilities—the other two being muscular endurance and anaerobic endurance—according to the training system espoused by Joe Friel. It is a combination of the two basic abilities of force plus speed skills.

Process goals are the daily, weekly, monthly processes needed to achieve the outcome goals. Think of these as the intermediary steps we take to move toward the desired outcomes. We have the most control over these goals.

A PNF stretch consists of a passive stretch followed by an isometric muscle contraction. During PNF stretching, a muscle is repeatedly contracted and relaxed, which triggers the golgi tendon reflex numerous times.

Protein is a molecule composed of one or more chains of amino acids. Protein is necessary for the structure, function, and regulation of the body’s cells, tissues, and organs. Protein, along with carbohydrates and fat are known as macro-nutrients.

The most common RPE scales are the Borg 6-20 and Category-Ratio Scales.

A recovery interval refers to the time between work intervals in interval training. It may involve resting (i.e. a rest interval) or moving at a slower pace to allow some recovery before the next work interval.

Just as too great of a training stimulus can be detrimental to one’s progression, so can be too little of a training stimulus. This follows directly from the overload principle and represents the flip side of overtraining. If you trained for and ran a marathon a few years ago and have not run since, you should not expect any carryover from that training for a marathon you decide to run on a whim next weekend. Plainly stated, the principle of reversibility states that inactivity leads to performance decline. Performance gains are reversed when the athlete ceases to train at a given level.

Obviously, reversibility does not mean that you can never take a break from training. The substantial losses of fitness associated with the principle of reversibility do not occur overnight. Substantial reversals in fitness gains take one to three weeks of inactivity to accumulate. But there is no need to be completely inactive for that period of time as long as you are healthy and have time to train.

Even during times when you are simply unable to train at your normal levels because other areas of your life prevent you from getting in the training you planned (work deadlines, holiday travels, unexpected illnesses, etc.), fitness can be maintained by following a reduced training schedule. The key is to not stop exercising completely.

One general rule when entering into maintenance mode is to counterbalance decreased training volume with increased intensity. Aim for a short, intense workout instead of the longer workout you had planned. Also, remember that training volume is the sum of both frequency and duration. If you don’t have a big block of time for that long run you originally planned, try to schedule shorter runs on back to back days or split the target duration over morning and evening runs that day. Strategies like these will allow you to maintain fitness for up to several weeks on a reduced training schedule. Just remember, something is better than nothing. The key to navigating those times of reduced training is to remain active and avoid complete inactivity.

Slow twitch muscle fibers are often referred to as “Type 1” muscle fibers. They can contract repeatedly for long periods of time, but with relatively low force. Short twitch fibers rely on oxygen for energy and thus are red due to the many blood vessels. Think of the leg of a chicken with its dark meat vs. the breast of a chicken with its white meat.

The principle of specificity states that training adaptations are specific to the system worked. For example, to improve running performance, one must run rather than swim. It also means that within a given sport, the type of training needs to be geared for the type of racing to be done or performance gains desired.

It is true that endurance training results in a certain amount of central adaptations—that is, general adaptations to the central respiratory and cardiovascular systems. However, these improvements will only go so far in improving your sport specific performance. You also need the peripheral adaptations that occur in muscle groups used for a particular activity. To return to our example of the athlete that swims in preparation for a marathon, that athlete would lack the peripheral adaptations that would occur in the legs with run-specific training.

For multisport athletes, the principle of specificity means that you must train in each of the disciplines used during your races. It also means that you need to gear the type of training you do for the particular distance you will be racing. A program designed for short-course triathlons looks different than a program designed for long-course triathlons, for example, just as a running program designed for a 5K looks different than one for an ultra-marathon. Finally, given that everyone is an individual and responds in their own ways to different types of training, it is important that you tailor training specifically to your individual needs and situation.

Speed skills refer to the ability to move efficiently and effectively. Speed skill is classified as one of three basic abilities—the other two being endurance and force—according to the training systems espoused by Tudor Bompa and Joe Friel, among others.

Stroke volume refers to the amount of blood your heart—specifically, your left ventricle—ejects when it contracts.

Tapering refers to a decrease in training volume prior to a key race to rest and sharpen the athlete for competition.

Training zones refer to intensity levels used during exercise. Training zones can be based on heart rate, power, velocity, ratings of perceived exertion or some other measurement of work capacity.

Ventilatory threshold refers to the point at which breathing becomes labored during exercise of increasing intensity. It corresponds closely with lactate threshold (LT).

Until the VT is reached, the workload and respiration rate increase linearly. After the ventilatory threshold is reached, the ventilation rate increases faster than the workload.

VO2max (also known as maximal oxygen consumption, or aerobic capacity) refers to the highest rate of oxygen transport and use by your body during maximal physical exertion.

VO2max is expressed through the Fick equation, which multiplies heart rate (HR) by stroke volume (SV) by arteriovenous oxygen difference (a-v O2 difference):

VO2max (mL / kg / min) = HR (beat / min) x SV (mL / beat) x (a-v O2 difference)

VO2max can be expressed in absolute terms as liters per minute (L/min), but is typically expressed relative to body weight so that comparisons among individuals can be made. Relative VO2max is therefore expressed as milliliters per kilogram per minute (mL/kg/min).

The higher your VO2max, or aerobic capacity, the faster you’re able to move over long distances. This is because a higher VO2max means a higher stroke volume—that is, for each heartbeat your heart will pump a greater amount of oxygenated blood to your muscles. Some of the top male endurance athletes in the world have recorded VO2max scores over 80 or even 90. For example, Greg LeMond's VO2max was 92.5. Steve Prefontaine's was 84.4. Mountain runners Matt Carpenter and Kilian Jornet have measured 92.0 and 89.5, respectively, and track runners Jim Ryun and Steve Scott measured 81.0 and 80.1, respectively. Some top female endurance athletes have recorded scores over 70. For example, 1984 Olympic marathon champion Joan Benoit Samuelson had a VO2max of 78.6;  marathoner Rosa Mota had one of 67.2. By comparison, anything above 55 for 20-29 year old men, above 52 for 30-39 year old men, above 50 for 40-49 year old men, above 49 for 50-59 year old men, or above 44 for men over 60 represent scores in the top 10 percentile of the male population, according to the norms provided by the American College of Sports Medicine. Likewise, anything above 49 for 20-29 year old women, above 45 for 30-39 year old women, above 42 for 40-49 year old women, above 37 for 50-59 year old women, or above 34 for women over 60 represent scores in the top 10 percentile of the female population.

Although an individual’s aerobic capacity is based to an extent on genetics, it is also highly malleable. Endurance training can substantially raise one’s VO2max. And per the reversibility principle, a lack of endurance training can lower one’s VO2max. And, as you can see from the norms mentioned above, it decreases with age. Moreover, being born with a high VO2max does not necessarily make a champion runner, cyclist, swimmer, triathlete or other type of endurance athlete. If that were the case, we might as well just all go to the lab to get our VO2max tested and turn in the results to race organizers. Obviously, there are many factors involved in being successful at endurance events, including mental skills, nutrition, and race tactics, just to name a few. Even when it comes to VO2max, two athletes that vary in their aerobic capacities may still possess equivalent effective aerobic capacities when taking into account economy of motion. In other words, Athlete A may achieve a 5K run time of 17 minutes with a VO2max of 62 and fair running economy while Athlete B may achieve that same 5K time with a VO2max of 58 and excellent running economy.

The bottom line is that laboratory recorded numbers are only a starting point. The key is knowing how to use those numbers to effectively train because endurance training will lead to better performance through many central and peripheral physiological adaptations, including an increased VO2max, increased stroke volume (i.e. amount of blood pumped with each heartbeat), increased capillary density in skeletal muscle, improved blood lipid profile, and increased lean body mass.

The following table shows VO2max norms for men and women (ACSM’s Guidelines for Exercise Testing and Prescription: Seventh Edition 2006, p. 79).

These are muscle contractions that are controlled by the central nervous system (CNS) and the origin of the contraction is a conscious thought by the brain. An example of this is a hamstring curl.

Training volume refers to the amount of training done per week. The frequency of training sessions plus the duration of those training sessions comprise training volume. Training volume is one of two key axes around which your training revolves—the other is intensity.

The warmdown, or cooldown period involves a transition from the exercise session back to a resting level. It involves low-level activity to clear lactate from the blood while allowing the heart rate, blood pressure, and respiration rate to lower.

The warmup period involves a gradual transition from rest to higher intensity exercise. It involves gradually warming up the body temperature through low-level activity.

A work interval, or workbout refers to the time spent in the target training zone in interval training. Work intervals are interspersed with recovery intervals.