Endurance training

Endurance training is the act of exercising to increase endurance. The term endurance training generally refers to training the aerobic system as opposed to anaerobic. The need for endurance in sports is often predicated as the need of cardiovascular and simple muscular endurance, but the issue of endurance is far more complex. Endurance can be divided into two categories including: general endurance and specific endurance. It can be shown that endurance in sport is closely tied to the execution of skill and technique. A well conditioned athlete can be defined as, the athlete who executes his or her technique consistently and effectively with the least effort.

Endurance in sports
Endurance training is essential for a variety of endurance sports. A notable example is distance running events (800 meters upwards to marathon and ultra-marathon) with the required degree of endurance training increasing with race distance. Two other popular examples are cycling (particularly road cycling) and competitive swimming. These three endurance are combined in triathlon. Other endurance sports for which extensive amounts of endurance training is required include rowing and cross country skiing. Athletes can also undergo endurance training when their sport may not necessarily be an endurance sport in the whole sense but may still demand some endurance. For instance aerobic endurance is necessary (to varying extents) in racket sports, football, rugby, martial arts and basketball. Endurance exercise tends to be popular with non-athletes for the purpose of increasing general fitness or burning more calories to increase weight loss potential.

Physiological effects
Long-term endurance training induces many physiological adaptations both centrally and peripherally mediated. Central cardiovascular adaptations include decreased heart rate, increased stroke volume of the heart, increased blood plasma, without any major changes in red blood cell count, which reduces blood viscosity and increased cardiac output as well as total mitochondrial volume in the muscle fibers used in the training (i.e. the thigh muscles in runners will have more mitochondria than the thigh muscles of swimmers). Mitochondria increase in both number and size and there are similar increases in myoglobin and oxidative enzymes. Adaptations of the peripheral include capillarization, that is an increase in the surface area that both the venous and arterial capillaries supply. This also allows for increased heat dissipation during strenuous exercise. The muscles heighten their glycogen and fat storing capabilities in endurance athletes in order to increase the length in time in which they can perform work. Endurance training primarily work the slow twitch (type 1) fibers and develop such fibers in their efficiency and resistance to fatigue. Catabolism also improves increasing the athletes capacity to use fat and glycogen stores as an energy source. These metabolic processes are known as glycogenolysis, glycolysis and lipolysis. There is higher efficiency in oxygen transport and distribution. In recent years it has been recognized that oxidative enzymes such as succinate dehydrogenase (SDH) that enable mitochondria to break down nutrients to form ATP increase by 2.5 times in well trained endurance athletes  In addition to SDH, myoglobin increases by 75-80% in well trained endurance athletes.

Methods and training plans
Common methods for training include periodization, intervals, hard easy, long slow distance, and in recent years high-intensity interval training. The periodization method is very common and was accredited to Tudor Bompa and consists of blocks of time, generally 4–12 weeks each. The blocks are called preparation, base, build and race. The goal of a structured training program with periodization is to bring the athlete into peak fitness at the time of a big race or event. Preparation as the name suggests lays the groundwork for heavier work to follow. For a runner contemplating a competitive marathon the preparation phase might consist of easier runs of 1–4 miles 3-4 times per week and including 2–3 days of core strengthening. In the base phase the athlete now works on building cardiovascular endurance by having several long runs staying in heart rate zone 1-2 every week and each week adding slightly more mileage (using 10% rule for safely increasing the mileage). Core strengthening is continued in the base period. Once the base phase is complete and the athlete has sufficient endurance, the build period is needed to give the athlete the ability to hold a faster pace for the race duration. The build phase is where duration of runs is traded for intensity or heart rate zones 3-5. An easy method to obtain intensity is interval training and interval training starts to happen in the build phase. Through interval training during the build phase the athlete can achieve higher lactate threshold and in some athletes VO2 max is increased. Because interval training is demanding on the body, a professional coach should be consulted. In the very least the athlete should do a warm up and active stretching before the interval session and static stretch or yoga after hard interval sessions. It is also advisable to have days of rest or easy workouts the day after interval sessions. Finally the race phase of the periodization approach is where the duration of the workouts decreases but intense workouts remain so as to keep the high lactate threshold that was gained in the build phase. In Ironman training, the race phase is where a long "taper" occurs of up to 4 weeks for highly trained Ironman racers. A final phase is designated transition and is a period of time, where the body is allowed to recover from the hard race effort and some maintenance endurance training is performed so the high fitness level attained in the previous periods will not be lost.

Devices to assess endurance fitness
The heart rate monitor is one of the relatively easy methods to assess fitness in endurance athletes. By comparing heart rate over time fitness gains can be observed when the heart rate decreases for running or cycling at a given speed. In cycling the effect of wind on the cyclists speed is difficult to subtract out and so many cyclists now use power meters built into their bicycles. The power meter allows the athlete to actually measure power output over a set duration or course and allows direct comparison of fitness progression. In the 2008 Olympics Michael Phelps was aided by repeated lactate threshold measurement. This allowed his coaches to fine tune his training program so that he could recover between swim events that were sometimes several minutes apart. Much similar to blood glucose for diabetes, lower priced lactate measurement devices are now available but in general the lactate measurement approach is still the domain of the professional coach and elite athlete.