2. Physiological Determinants of
1. Endurance Performance in Soccer Cardiorespiratory Endurance
Efforts to improve soccer performance often fo- Cardiorespiratory endurance has long been
cus on technique and tactics at the expense of fitness recognised as one of the fundamental components of
and applied physiology. During a 90-minute game, physical fitness.[18,19] Since accumulation of lactic
elite level players run 8–12km[1-3] at an average acid is associated with skeletal muscle fatigue, anaintensity
close to the lactate threshold (LT).[4-6] The erobic metabolism cannot contribute at a quantitahighest
work rate, oxygen uptake (V˙ O2) or heart rate tively significant level to the energy expended.[4]
(HR) in dynamic work using large muscle groups, Pate and Kriska[20] have described a model that
where production and elimination of lactate are bal- incorporates the three major factors accounting for
anced, is defined as LT.[7] The high-intensity bouts inter-individual variance in aerobic endurance perthat
are dependent on anaerobic or alactic energy formance, namely V˙ O2max, LT and work economy
sources are restored using aerobic energy. This (C). Numerous published studies support this
makes it necessary for the player to spend a substan- model.[21-25] Thus, the model should serve as a useful
tial time at an intensity lower than LT. In a study of framework for comprehensive examination of the
elite junior soccer players,[8] the LT was 82–85% of effects of aerobic training on endurance performmaximal
oxygen uptake (V˙ O2max) and 87–90% of ance.
maximal heart rate (HRmax). Another LT protocol V˙ O2max is probably the single most important
derived from fixed blood lactate values (3 or 4 factor determining success in an aerobic endurance
mmol/L) gave corresponding values for elite adult sport.[18,26] However, within the same person, peak
male players.[4,9] The distance covered during a oxygen transport is specific to a given type of acgame
is thus related to both the aerobic power of the tivity. Therefore, in order to obtain relevant values,
player and the player’s capacity to sustain a high emphasis is placed on testing in sport-specific activfractional
utilisation of aerobic power. Studies of ities.[27]
Danish league players[1] confirm earlier observa- Shephard[28] has presented an integrated model
tions that 5–9% greater distance is covered in the based on electrical analogues of the oxygen path-