Rapid hamstrings/quadriceps strength in ACL-reconstructed elite Alpine ski racers.
OBJECTIVE
Because of the importance of hamstrings (HAM) and quadriceps (QUAD) strength for anterior cruciate ligament (ACL) injury prevention and the high incidence of ACL injury in ski racing, HAM and QUAD maximal and explosive strength were assessed in ski racers with and without ACL reconstruction (ACL-R).


METHODS
Uninjured (n = 13 males, n = 8 females) and ACL-R (n = 3 males, n = 5 females, 25.0 ± 11.3 months after operation) elite ski racers performed maximal voluntary isometric HAM and QUAD contractions to obtain maximal torque (MVC) and rate of torque development (RTD) at 0-50, 0-100, 0-150, and 0-200 ms. MVC and RTD (per kilogram body mass) were calculated for the uninjured group to compare between sexes and to compare the control group with the ACL-R limb and unaffected limb of the ACL-R skiers. HAM/QUAD MVC and RTD strength ratios (H/Q ratios) were also compared.


RESULTS
The ACL-R limb demonstrated significant HAM and QUAD deficits compared with the contralateral limb for MVC and late-phase RTD (P < 0.05). Uninjured male skiers also displayed a limb difference for HAM MVC and RTD at 150 ms (P < 0.05). QUAD MVC and RTD deficits were observed in the affected limb of ACL-R skiers, which led to an inflated H/Q ratio (50 ms) compared with that in uninjured controls (P < 0.05). Compared with male skiers, females displayed greater relative HAM RTD (50 ms) and an elevated H/Q RTD ratio (50 ms), suggesting enhanced ACL protection (P < 0.05).


CONCLUSIONS
Because of the strength demands of ski racing, our results suggest the importance of including HAM and QUAD strength assessments in the physical evaluation of uninjured skiers. Furthermore, HAM and QUAD strength should be assessed over a long-term period after surgery to identify chronic strength deficits in ACL-R ski racers.
1Human Performance Laboratory, University of Calgary, Calgary, Alberta, CANADA; and 2Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster, University of Southern Denmark, Odense, DENMARK.
Matthew J
MJ
Jordan
Per
P
Aagaard
Walter
W
Herzog
D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007537:Isometric Contraction; D007718:Knee Injuries / Q000517:prevention & control; D008297:Male; D053580:Muscle Strength; D018908:Muscle Weakness / Q000175:diagnosis; D052097:Quadriceps Muscle / Q000503:physiopathology*; D012737:Sex Factors; D012865:Skiing / Q000293:injuries* / Q000502:physiology; D013848:Thigh; D019415:Torque; D055815:Young Adult