Science of Sport: Hamstring strains

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The role of stretching in enhancing flexibility and reducing injury risk remains contentious, with some studies finding no relation between flexibility training and injury and others pointing to a positively harmful effect. Now, however, a carefully conducted survey of flexibility training protocols in English professional football clubs has suggested that stretching helps to prevent hamstring strains – the commonest and most problematic muscle strains associated with competitive sport.

Questionnaire-based data on flexibility training methods and hamstring strain rates were collected from 30 football clubs in the four divisions during the 1998/99 season and analysed for evidence of any relationship between the two.

Key findings were as follows:

• Hamstring strains represented 11% of all injuries and one third of all muscle strains;
• About 14% of hamstring strains were reinjuries;
• Hamstring strain rates were highest in the Premiership and lowest in Division 2;
• The vast majority of hamstring strains were minor or moderate, with two thirds occurring in the late stages of training sessions or matches;
• Forwards were injured most often;
• Use of the standard stretching protocol (a warm-up session followed by either a static or PNF stretching technique, holding the static stretch for 15-30 seconds) was the only factor significantly related to hamstring strain rates, suggesting a protective effect.

‘Our findings clearly suggest,’ conclude the researchers, ‘that the current stretching practices of professional footballers are not detrimental, and an improvement in the quality and consistency of use of more appropriate stretching may possibly further reduce [hamstring strain rates].

‘Stretching is probably involved in a complex, interactive and multifactorial relation with hamstring strain. However, stretching may be beneficial only if the technique employed and the stretch holding times are adequate; the number of repetitions of a stretch may not be important.

‘The flexibility training protocols currently used by the professional football clubs need to be reviewed to ensure consistency in the use of static stretching/PNF with a stretch holding time of 15-30 seconds.’

Br J Sports Med 2004;38:388-394

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