Background Triathlon injury research is in its early stages- with no consensus on injury definition and recording methods having been reached, and few prospective data yet available. Levy et al., (1986) suggested that less injury may occur within this sport than in its component disciplines. Massimino et al., (1988) proposed the opposite.

Objective To determine whether swim, cycle and or run training exert a cumulative stress effect on triathlon overuse injury (OU) risk.

Design Seven month prospective longitudinal training diary based survey, from the endurance base period up to World Championships.

Setting British Olympic distance specialists.

Participants Top 50 finishers at their non-drafting National Championships in the year of, or year prior to, the study.

Assessment of risk factors Both absolute (ie, duration) and derived training variables were assessed. Derived variables included both training that was weighted for each of five intensity levels it comprised, and combined training for more than one discipline. Log values (% difference from the previous week) and (difference from the previous week) for training variables for 1, 2, 3, and 4 weeks prior to injury were used.

Main outcome measurements ‘New OU’ was used as the dependant variable in a binary logistic regression analysis, involving combinations of 1–4 training related variables. Anatomical location, discipline(s) that OU was attributed to (on first and subsequent occurrence(s), and performance decrement (PD) were also assessed.

Results Return rates were 43, 38, 33, 26, 21, 14 and 11 for each consecutive month. 60% of athletes reported OU with concomitant PD at least once. New OU was associated with an increase in the log of combined weighted cycle and run training in levels 3, 4 and 5 two weeks prior to onset (p<0.05).

Conclusion The extent to which cycle and run training have a cumulative effect on triathlon injury risk deserves further investigation.