Iron supplements are not required for Rugby Union football
Circadian rhythms in the human are characterized as endogenous or exogenous depending on the degree to which they are affected by factors extraneous to the individual. This chapter shows to affect performance both in gross motor performance measures and in co-ordination skills. It explains influences of travel fatigue and body clock disturbances. Athletes are mostly unaware of their effects until rhythms are desynchronized as occurs in jet-lag syndrome. These are the rhythms in body temperature, regarded as the fundamental variable, and the sleep-wake cycle, which humans order their rest-work schedules. These self-sustaining rhythms in exercise performance should be recognised by practitioners concerned with the preparation of footballers and their travel plans. A rhythm in isometric leg strength of the knee extensors incorporates amplitude of 7", similar to that observed in other muscle groups. Dynamic muscle performance as reflected in peak torque on an isokinetic dynamometer varies by about the same extent for back and for leg muscles.