Endurance refers to the limit of time over which work of given intensity may be performed. The main factor which limits and at the same time affects performance is fatigue. Thus, a person is considered to have endurance when he/she does not easily fatigue, or when a person has the ability to continue work in a state of fatigue. An athlete is capable of doing that if he/she is adapted to the specifics of the work performed. Endurance depends on many factors such as: speed, muscle force, technical abilities of performing a movement efficiently, the ability to economically use physiological potentials, and psychological status when perforrming work.
Considering the needs of training there are two kinds of endurance:
1. GENERAL ENDURANCE is considered by Ozolin (1971) to be the capacity of performing a type of activity which involves many muscle groups and systems (CNS, neuro muscular and cardio respiratory system) for prolonged period of time. A good level of general endurance, regardless of the sport's specialization, facilitates success in various types of training activities. However, athletes involved in sports where endurance, especially aerobic endurance, is dominant, do have a high lever of general endurance suggesting that there is a strong relationship between general and specific endurance. On the other hand, athletes taking part in sports of short duration or of high technical sophistication do not hold a good level of general endurance. General endurance is vigorously needed by each athlete. It assists the athletes to successfully perform a high volume of work, to overcome fatigue in competitions of long duration, and to recover faster following training or competitions.
2. SPECIFIC ENDURANCE, which often is referred to as endurance of playing, sprinting, and the like, is dependent on the particularities of each sport, or the many repetitions of the motor acts of each sport. Although specific endurance is imprinted in the characteristics of certain sports, it may be affected by the excitement of competitions, the performance of difficult athletic tasks, or the type of training performed. Also, as Teodorescu (1975) put it, a very demanding tactical game often affects an athlete's specific endurance, thus the athletes may be subject to various technical and tactical faults during the second part of the contest Consequently, the stronger the specific endurance which is developed from a solid base of general endurance, the easier the athletes may overcome various training and competition stressors. The types of endurance presented above refer' and are paramount to a successful performance in each sport. However, as for as cyclic sports are concerned, the following classification suggested (Pfeifer,1982)
- ENDURANCE LONG DURATION is required for sports that endure for more than eight minutes. Energy is supplied almost exclusively by the aerobic system, and the cardiovascular and respiratory systems are highly involved. During an endurance race falling in this category, the heart rate is very high (over 180 bpm), the heart's minute volume (the volume of blood pumped by the heart in one minute) is between 30-40 litres, and the lungs ventilate 120-140 litres of air per minute (Pfeifer, 1982). Obviously for long duration races (i.e., marathon) these values are lower. The O2 supply is a determinant factor for a good performance. Therefore, the vital capacity and the minute volume of the heart represent limiting factors for high athletic results. They also reflect the athlete's adaptation to the stress of such activities. Work of medium intensity seems to favour the body's adaptation and capillary vascularization so vital for the supply of O2 to the muscle cells (Mader and Hollmann, 1977).
- ENDURANCE OF MEDIUM DURATION is specific for sports/events where work is performed over a duration of 2-6 minutes. The intensity is higher than in sports requiring endurance of long duration. The O2 supply cannot totally meet the body's needs: therefore, the athlete develops an O2 debt. The energy produced by the anaerobic system is proportional to the speed magnitude. Pfeifer (1982) claims that for the 3000 m run the anaerobic system supplies approximately 20%, and for 1500 m up to 50% of the total energy required by the athlete. As in the above case, the O2 absorption has a determinant role in performance.
- ENDURANCE SHORT DURATION are sports which travel a distance which is covered in a duration between 45 seconds-2 minutes. For sports which are classified in this category, the anaerobic processes partake intensely in supplying the energy required to perform the athletic task. Strength and speed play an important role in producing high results. The O2 debt is quite high, and according to Pfeifer (1982) the anaerobic system provides 80% of the required energy for a 400 m and 60-70% for the 800 m run. The basis for the development of the anaerobic capacity is the aerobic capacity. Consequently, a high aerobic capacity has to be developed even for sports/ events which compose this category.
- MUSCULAR ENDURANCE which was referred to in strength training is facilitated by a high strength development blended with an adequate endurance. Sports like rowing, swimming, and canoeing, are the main beneficiaries of this combined ability.
- ENDURANCE OF SPEED represents the resistance of the athlete's to fatigue under conditions of maximum intensity. Most of the work is done in apnea requiring from the athlete both maximum speed and strength (also refer to speed training).