OBJECTIVE

To investigate the effect of a structured warm-up program in reducing the occurrence of knee and ankle injuries in teenage handball players.

DESIGN

Block randomized controlled trial with a sample size designed to achieve 90% power with [alpha] = 5% to detect a relative risk (RR) reduction of 50%. Clubs within the randomization blocks were matched by region, playing level, and number and sex of players.

SETTING

Norwegian Handball Federation clubs in the 16-year and 17-year divisions during the 2002 to 2003 season.

PARTICIPANTS

Clubs in the division were invited to participate in the study before the season (n = 123 clubs recruited; 85% of the 145 invited clubs). After 3 clubs were excluded or dropped out, 1837 eligible players (uninjured at baseline) aged 15 to 17 years (86% young women) were included in the analysis.

INTERVENTION

Coaches of the intervention group clubs (958 players) were instructed in exercises to improve awareness and control of knees and ankles during standing, running, cutting, jumping, and landing. The program comprised exercises with the ball, including the use of the wobble board and balance mat, for warm-up, technique, balance, and strength. Players were to spend 4 to 5 minutes on each group of exercises for a total of 15 to 20 minutes at the first 15 training sessions and thereafter once per week. Coaches recorded attendance and details of the sessions on standard forms. Coaches of the control group clubs (879 players) were asked to continue with their usual training methods and to record types and volume of exercises used.

MAIN OUTCOME MEASURES

The primary outcome measure was an acute injury to the knee or ankle during a match or training session that required the player to have medical attention or miss part of the next session. Secondary outcomes were any injury to the lower limbs, injuries overall, and injuries to the upper limb. Injuries were recorded by physiotherapists blinded to group assignment who were in contact with the coaches at least every month. The physiotherapists interviewed injured players in person or by telephone as soon as possible (range, 1 day to 4 months).

MAIN RESULTS

During the season 262 players (14%) were injured at least once (241 acute and 57 overuse injuries). In intention-to-treat analysis, the intervention group had lower risks than the control group of acute knee or ankle injuries (RR, 0.53; 95% CI, 0.35-0.81), lower limb injuries (RR, 0.51; CI, 0.36-0.73), any injury (RR, 0.49; CI, 0.36-0.68), and upper limb injuries (RR, 0.37; CI, 0.20-0.69). Rate ratios for moderate and major injuries (absence from play for 8 to > or =21 days) were lower for the intervention group for all injuries (P < 0.001) and for acute knee or ankle injuries (P < or = 0.03). Fewer players in the intervention group had > or =2 injuries. Risk of injury did not differ for young men and women. Crossovers to the other intervention occurred in 13% of the intervention clubs (noncompliance with the training program) and 22% of the control clubs (use of similar preventive exercises to the intervention group).

CONCLUSIONS

The rate of acute knee and ankle injuries and all injuries to young handball players was reduced by half by a structured program designed to improve knee and ankle control during play.