Anaerobic power and capacity Karim CHAMARI a,1 Anis CHAOUACHI a and Sebastien RACINAIS b a Research Unit ‘’Evaluation, Sport, Health’’, National Center of Medicine and Science in Sport, Tunis, TUNISIA b ASPETAR – Qatar Orthopaedic and Sports Medicine Hospital, Doha, QATAR E-mail address: karimchamari@gmx.net Introduction The ability to develop power is important in many sports in which the body or a tool should accelerate at the fastest possible speed, in the shortest possible time. The capacity to sustain this power is also a major determinant of sports performance. If the assessment of power can be used to track performance improvements or decrements, the duration and characteristics of the testing procedure will influence the qualities investigated by the test (i.e. muscle force, power, and anaerobic capacity). This chapter presents the standard ways to investigate mechanical power output as an index of muscle power and anaerobic function. The effects of training and fatigue will be presented as well as the reliability of anaerobic evaluations. 1. Which precision for which measure? 1.1. Power output versus anaerobic power Coaches commonly use the terminologies of anaerobic power and anaerobic capacity. However, all of the tests presented in this chapter are measuring an output (e.g. power output) but not a metabolism (e.g. anaerobic power). Consequently, in most of the case, the terminology anaerobic function could be replaced by muscle function. The following paragraphs present how to obtain indexes of anaerobic function. 1.2. How to record anaerobic metabolism? Capacity of energy metabolism may be defined as the sum of all work that can be gained from energy stored in chemical form. Analogously, power may be defined as the sum of the maximal metabolic rates of the different energy transfer systems. All substrate needed for anaerobic processes are located inside the muscle cell. These substances can only be measured directly by laboratory methods - for example, muscle biopsy or 31 P-MR spectroscopy (see Chapter 4 of Section 1 for the latter method). The 1 Corresponding Author.