Neuromuscular activity during stair descent in ACL reconstructed patients : A pilot study

Background:
The anterior cruciate ligament (ACL) rupture is a severe knee injury. Altered kinematics
and kinetics in ACL reconstructed (ACL-R) patients compared to healthy participants
(ACL-I) are known and attributed to an altered sensorimotor control. However, studies on neuromuscular control often lack homogeneous patient cohorts. The objective was to examine
neuromuscular activity during stair descent in patients one year after ACL reconstruction.

Method:
Neuromuscular activity of vastus medialis (VM) and lateralis (VL), biceps femoris (BF)
and semitendinosus (ST) was recorded by electromyography in 10 ACL-R (age: 26 ± 10
years; height: 175 ± 6 cm; mass: 75 ± 14 kg) and 10 healthy matched controls (age:
31 ± 7 years; height: 175 ± 7 cm; mass: 68 ± 10 kg). A 10-minute walking treadmill
warm-up was used for submaximal normalization. Afterwards participants descended 10 times
a six-step stairway at a self-selected speed. The movement was separated into pre-activation
(PRE), weight acceptance (WA) and push-off phase (PO). Normalized root mean squares for
each muscle, limb and movement phase were calculated. Kruskal-Wallis ANOVA compared
ACL-R injured and contralateral leg and the ACL-I leg (α = 0.05).

Results:
Significant increased normalised activity in ST during WA in ACL-R injured leg compared
to ACL-I and during PO in VL in the ACL-R contralateral leg compared to ACL-I. Decreased
activity was shown in VM in ACL-R injured compared to contralateral leg (p b 0.05).

Conclusion:
Altered neuromuscular activations are present one year after ACL reconstruction
compared to the contralateral and healthy matched control limb. Current standard rehabilitation
programs may not be able to fully restore sensorimotor control and demand further
investigations.