Background There are conflicting results concerning associations between match congestion and injury rates in professional football.

Objective To analyze associations between short term match congestion and injury rates in professional football and to study the influence of long term match congestion on such associations.

Design Prospective cohort study.

Setting Male professional football.

Participants 122 743 individual match exposures for 2 625 players.

Assessment of Risk Factors Short term match congestion was defined as the number of days recovery between two match exposures. Long term match congestion was defined as the total match exposure in 30 days preceding a match. Injury rates during individual player match exposures were compared depending on short term match congestion (≤3, 4, 5, 6, and 7 to 10 recovery days). To analyse the influence of players' long term match congestion all match observations were grouped into tertiles (long term match congestion ≤5.0, 5.0 to 7.5 and ≥7.5 hours respectively) and analysed separately.

Main Outcome Measurements Muscle injury rates.

Results There was no difference in muscle injury rates in matches preceded by four (OR 1.03, 95% CI 0.90 to 1.19) or five (OR 1.03, 95% CI 0.85 to 1.25) days recovery compared with the reference group three or less. However, muscle injury rates were lower in matches preceded by six (OR 0.80, 95% CI 0.65 to 0.97) or seven to ten days of recovery (OR 0.81, 95% CI 0.70 to 0.93) compared with three or less. The same patterns persisted in all long term match congestion tertiles.

Conclusions While no protective effect was seen after four or five days recovery compared to three or less days muscle injury rates were lower after six or more days recovery between matches.