Methods of training

Continuous training: exercising at a steady, moderate intensity for at least 20 minutes without rest, such as a 30-minute run. It improves cardiovascular endurance.
Fartlek training ("speed play"): continuous exercise with changes of speed and terrain, such as jogging, then sprinting uphill. It suits games players.
Interval training: periods of work followed by rest. Short, intense intervals improve anaerobic fitness; longer ones improve aerobic fitness. High-intensity interval training (HIIT) uses very hard bursts.
Circuit training: a series of exercises at stations, done one after another. It can be adapted to work on many components of fitness.
Weight (resistance) training: lifting weights, measured in sets and repetitions. Low reps with heavy weights build strength; high reps with light weights build muscular endurance.
Plyometrics: jumping and bounding exercises, such as box jumps, that use eccentric then concentric contractions to build power.
Static stretching: holding a stretch for about 30 seconds to improve flexibility.

Choosing a method

Match the method to the sport and component: continuous training for a marathon runner, plyometrics for a high jumper, Fartlek for a hockey player.
Consider the advantages: circuits can be done in groups and adapted; continuous training needs little equipment.
Consider the disadvantages: continuous training can be boring and doesn't train anaerobic fitness; weight training needs equipment and a good technique.

At high altitude there is less oxygen, so the body makes more red blood cells.
When the performer returns to sea level, more oxygen can be carried to the muscles, helping endurance.
The benefits are lost quickly when training at altitude stops, and it can cause altitude sickness.