testing of the quadriceps and hamstrings at a velocity of 60o

/second

assessed peak torque and position of peak torque. A 4-week supervised training programme of Nordic hamstring exercises was performed, which gradually increased the number of sessions per week and the number of repetitions per session. The results showed that the position of peak torque had significantly moved towards full knee extension (P=0.01) and there was a significant difference in hamstring position of peak torque between the dominant and non-dominant limbs. The subjects showed a 19.4% change in position of peak torque for the hamstrings towards a more extended knee after 4 weeks of training, which may allow protection against damage from eccentric exercise. The results of this study also suggest that training created a greater difference between dominant and non-dominant limbs. The limb with the higher initial angle for peak torque benefited more, indicating that, as the subject lowered themselves to the floor, the limb with the higher knee extension angle of peak torque may have needed to take over the control, causing overload and further increasing an imbalance. This may indicate a need for single leg training to ensure equality of both limbs. Despite the limited subject number within this study, a number of significant findings were observed. The exercise intervention used was easily replicated and overseen by the same supervisors, ensuring good interrater reliability. However, the validity of the study can be questioned: it was unclear whether any training was completed outside of these training sessions, there was no control group and the design did not ensure randomisation of subjects.

Study 4 Arnason and colleagues prospectively aimed to test the effect of eccentric muscle training and flexibility training on the incidence of hamstring muscle injury over 4 years (13). Seventeen

soccer teams from Iceland were recruited in 1999, 15 teams in 2000, 16 teams in 2001 and 10 teams in 2002. Fourteen Norwegian teams were recruited in 2000, 2001 and 2002. Baseline information regarding the number of hamstring strains and the time lost through injury was recorded in 1999 and 2000. A prevention programme of three exercise components was implemented 3 months before each season:

n Warm-up stretching (contract/relax hamstring exercise of 5–10 seconds per contraction and 20 seconds per relaxation on each leg, x3) n Flexibility training (stretching a partner’s hamstring) n Nordic hamstring progressive strength programme.

The teams were instructed to use the programme three times a week during the preseason and once or twice a week during the competitive season. The team’s medical team recorded hamstring strain location, how the injury was sustained and when the injury was sustained throughout the season. In 2001, seven of 14 Norwegian teams used the warm-up and flexibility interventions. The results did not show any significant difference (P=0.22) in the incidence of hamstring strains between the seven teams that used the interventions and the seven teams that did not; nor was there a significant difference compared with pre-intervention baseline levels (P=0.91). In 2002, five of 10 Icelandic teams and six of 14 Norwegian teams used the eccentric strength and warm-up stretching intervention. There was a significant difference in teams that used the eccentric strength training programme compared with those that did not, and with their own baseline (P<0.001). Overall the incidence of hamstring strains was 65% lower among teams that used the eccentric strength training programme compared with those that did not. Despite the

MUSCLE WEAKNESS, LACK OF FLEXIBILITY, POOR WARM-UP, MUSCLE FATIGUE AND POOR LUMBAR POSTURE AND CORE STABILITY

14

NUMEROUS RISK FACTORS FOR HAMSTRING STRAIN HAVE BEEN IDENTIFIED; INCLUDING

significance in results, the study may have introduced bias: there was a lack of randomisation (the teams chose whether or not to opt in to the interventions) and the study relied on other medical professionals’ opinions, ability to identify and document the data correctly, and ability to complete the regimes as originally shown, which means that all subjects may not have been treated equally. It was also documented that, despite some teams choosing not to participate in the strength intervention, some of the players still completed Nordic hamstring training as part of their own training. This may have reduced the number of hamstring injuries within this group, thus affecting the overall reliability of the results.

Study 5 Lack of overall flexibility of the hamstrings has been postulated as a risk factor for hamstring injury (14). Witvrouw and colleagues aimed to determine whether lack of flexibility in the lower limbs was a predisposing factor for muscle injury in the lower limb, and whether an athlete with decreased muscle flexibility could be identified as likely to suffer an injury (14). Before the 1999–2000 Belgian soccer season, 249 male professional soccer players had the flexibility of their hamstrings, quadriceps, adductors and gastrocnemius muscles measured goniometrically on both limbs, by the same two physiotherapists. During the season the footballers’ physiotherapists documented any injury of the lower limb, defined as “any tissue damage caused by soccer participation that kept a player out of practice or a game” (14). All players who had sustained a lower limb injury in the two years before the study were excluded. Results were collated from 146 players.

sportEX medicine 2009;39(Jan):12-16