The desynchronisation of an athlete's physiological and psychological cycles has adverse effects on his/her performance. The primary cause of dysrhythmia in an athlete is jet-lag, which is a rapid displacement across the earth's time zones and is often experienced while competing in international events and in continental leagues. General symptoms which arise from dysynchronization include malaise, appetite loss, tiredness during the day and disturbed sleep. The specific symptoms resulting from jet-lag are characterised as phase shifts in physiological and psychological cycles. These phase shifts occur in body temperature, ability to mobilise energy substrates, excretion of water and metabolites, arousal levels, sleep/wake cycles and reaction time. The severity of these adverse effects and therefore the time required for resynchronization depends on the ability to preset the bodily rhythms prior to flying, the number of time zones crossed, the direction of flight, the type of individual (introvert/extrovert), age, social interaction and activity, diet plan and prescribed use of chronobiotic drugs.