Quadriceps and hamstrings coactivation during common therapeutic exercises.
BACKGROUND
Anterior tibial shear force and knee valgus moment increase anterior cruciate ligament (ACL) loading. Muscle coactivation of the quadriceps and hamstrings influences anterior tibial shear force and knee valgus moment, thus potentially influencing ACL loading and injury risk. Therefore, identifying exercises that facilitate balanced activation of the quadriceps and hamstrings might be beneficial in ACL injury rehabilitation and prevention.


OBJECTIVE
To quantify and compare quadriceps with hamstrings coactivation electromyographic (EMG) ratios during commonly used closed kinetic chain exercises.


METHODS
Cross-sectional study.


METHODS
Research laboratory.


METHODS
Twenty-seven healthy, physically active volunteers (12 men, 15 women; age = 22.1 ± 3.1 years, height = 171.4 ± 10 cm, mass = 72.4 ± 16.7 kg).


METHODS
Participants completed 9 separate closed chain therapeutic exercises in a randomized order.


METHODS
Surface electromyography quantified the activity level of the vastus medialis (VM), vastus lateralis (VL), medial hamstrings (MH), and biceps femoris (BF) muscles. The quadriceps-to-hamstrings (Q:H) coactivation ratio was computed as the sum of average quadriceps (VM, VL) EMG amplitude divided by the sum of average hamstrings (MH, BF) EMG amplitude for each trial. We used repeated-measures analyses of variance to compare Q:H ratios and individual muscle contributions across exercises (α = .05), then used post hoc Tukey analyses.


RESULTS
We observed a main effect for exercise (F(3,79) = 22.6, P< .001). The post hoc Tukey analyses revealed smaller Q:H ratios during the single-limb dead lift (2.87 ± 1.77) than the single-limb squat (5.52 ± 2.89) exercise. The largest Q:H ratios were observed during the transverse-lunge (7.78 ± 5.51, P< .001), lateral-lunge (9.30 ± 5.53, P< .001), and forward-lunge (9.70 ± 5.90, P< .001) exercises.


CONCLUSIONS
The most balanced (smallest) coactivation ratios were observed during the single-limb dead-lift, lateral-hop, transverse-hop, and lateral band-walk exercises. These exercises potentially could facilitate balanced activation in ACL rehabilitation and injury-prevention programs. They also could be used in postinjury rehabilitation programs in a safe and progressive manner.
Sports Medicine Research Laboratory, Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. rbegalle@email.unc.edu
Rebecca L
RL
Begalle
Lindsay J
LJ
Distefano
Troy
T
Blackburn
Darin A
DA
Padua
D016118:Anterior Cruciate Ligament / Q000502:physiology*; D000070598:Anterior Cruciate Ligament Injuries; D003430:Cross-Sectional Studies; D004576:Electromyography; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000517:prevention & control / Q000534:rehabilitation; D007719:Knee Joint / Q000502:physiology; D008297:Male; D052097:Quadriceps Muscle / Q000502:physiology*; D013180:Sprains and Strains / Q000517:prevention & control* / Q000628:therapy*; D013848:Thigh; D055815:Young Adult