A Swedish word for speed play, fartlek training was developed in the 1930s as a form of conditioning for both anaerobic and aerobic energy systems. A form of continuous exercise, it involves mixing the intensity of an exercise session, with athletes alternating between running fast, running steady, and running slow. It can be combined into any training program as there is no set time or distance limit for sessions. While most athletes prefer to train for at least 30 minutes at a time, the benefits of fartlek are abundant, even when used for shorter amounts time. A traditional and established form of conditioning, it usually can be added to any athlete's schedule, whether training in general or aiming for a specific competitive event.
Increasing both aerobic and anaerobic capacities, in addition to increasing lactate threshold, training of this form is particularly beneficial due to its flexibility. Mostly used to condition runners, fartlek training programs can also be adapted for those in team sports such as rugby, football, and hockey. While continuous exercise can increase both high- and low-intensity movements, exercise can be altered to become appropriate to a specific sport. For example, instead of simply running in a straight line, those training in group field sports can alter their training to incorporate backward and side-to-side steps.
This form of training is primarily used by runners who want to cover long distances. By altering the body to cope with the distances run during half and full marathons, lung capacity can be greatly increased. In addition, short spurts of high-intensity training can gradually increase an athlete’s average speed, aid in covering distances quickly, and help an athlete achieve better time credentials.
In addition to many personal training programs, a wide range of traditional sessions already exist, including the Astrand Fartlek, the Saltin Fartlek, and the Hill Fartlek. The Astrand, used to train for the 800-meter (about 875 yards) dash, is a session at just under 30 minutes, made up of 10 minutes of steady exercise at each side of the program, with high and slow intensities for seven minutes in the middle. The Saltin, used for 1,500-meter (about 1,640 yards), 3-kilometer (about 1.86 miles), and 5-kilometer (about 3.12 miles) races, uses a similar structure but lasts for 45 minutes with longer periods of intensity in the middle. Hill Fartlek training is exactly that: running over a hilly course for 2 miles (3.2 km), individuals use high-intensity training to run up hills while jogging in between to facilitate recovery.