A comparison of maximal knee flexor and extensor strength for assessing bilateral imbalance in Swedish elite hockey players.

Sammanfattning: Aim The aim of this study was to determine knee extensor (Q) and flexor (H) muscle strength characteristics in a group of professional Swedish hockey players, including maximal isokinetic torque and any asymmetries seen in these.    Method This study was designed to measure strength and power performance during unilateral movement involving the lower extremities in open chain.  The contribution of each leg were discerned for subsequent comparison of left to right quadriceps (Q) and hamstrings (H), mean and peak value of hamstrings to quadriceps (H/Q ratio) and dominant to non-dominant legs for the purpose of examining imbalances between the legs.  The dominant leg (D) was defined as the strongest leg (either right or left) from the collected torque data for each player and then calculated as one value for the whole group. Subjects had a defined warm-up session and any static stretching that subjects feel necessary to assist them in performing the tests was also permitted. Maximal concentric (con) and eccentric (ecc) quadriceps and hamstring muscle strength was obtained by measuring maximal force moments (torque) during isokinetic knee extension and flexion movements both in 90°·s-1and 300°·s-1. An Isomed2000 (D&R Ferstl GmbH, Germany) was used for the measurements.   Results In a comparison of D to ND, significant differences were obtained in peak torque for Q (p=0,0005) and H at con 90°·s-1(p=0,027) and H at ecc 90°·s-1(p=0,014). When comparing mean torque between D and ND significant differences were obtained for Q for con 90°·s-1(p=0,026) and H at ecc 90°·s-1(p=0,007). When looking at H/Q ratio between right and left sides a significant difference was seen for peak torque at con 90°·s-1and moderate relationship was seen at mean values at con 90°·s-1and ecc 90°·s-1.    Conclusions The result shows that the elite hockey players in the tested group seem to have one significant stronger leg and a week hamstrings compared to quadriceps. This means that they tend to be asymmetrical which might affect performance but may also increase the incidence of injury.   This has to be evaluated with further research.