Fatigue's lack of effect on thigh-muscle activity in anterior cruciate ligament-reconstructed patients during a dynamic-landing task.
BACKGROUND
As individuals returning to activity after anterior cruciate ligament reconstruction (ACLr) likely experience fatigue, understanding how fatigue affects knee-muscle activation patterns during sport-like maneuvers is of clinical importance. Fatigue has been suggested to impair neuromuscular control strategies. As a result, fatigue may place ACLr patients at increased risk of developing posttraumatic osteoarthritis (OA).


OBJECTIVE
To determine the effects of fatigue on knee-muscle activity post-ACLr.


METHODS
Case control.


METHODS
University laboratory.


METHODS
12 individuals 7-10 mo post-ACLr (7 male, 5 female; age 22.1 ± 4.7 y; 1.8 ± 0.1 m; mass 77.7 ± 11.9 kg) and 13 controls (4 male, 9 female; age 22.9 ± 4.3 y; 1.7 ± 0.1 m; mass 66.9 ± 9.8 kg).


METHODS
Fatigue was induced via repetitive sets of double-leg squats (n = 8), which were interspersed with sets of single-leg landings (n = 3), until squats were no longer possible.


METHODS
2 × 2 repeated-measures ANOVA was used to detect the main effects of group (ACLr, control) and fatigue state (prefatigue, postfatigue) on quadriceps:hamstring cocontraction index (Q:H CCI).


RESULTS
All subjects demonstrated higher Q:H CCI at prefatigue compared with postfatigue (F(1,23) = 66.949, P ≤ .001). Q:H CCI did not differ between groups (F(1,23) = 0.599, P = .447).


CONCLUSIONS
The results indicate that regardless of fatigue state, ACLr individuals are capable of restoring muscle-activation patterns similar to those in healthy subjects. As a result, excessive muscle cocontraction, which has been hypothesized as a potential mechanism of posttraumatic OA, may not contribute to joint degeneration after ACLr.
School of Kinesiology, University of Michigan, Ann Arbor, MI, USA.
Lindsey K
LK
Lepley
Abbey C
AC
Thomas
Scott G
SG
McLean
Riann M
RM
Palmieri-Smith
D000293:Adolescent; D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction / Q000009:adverse effects*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction; D018763:Muscle Fatigue / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000209:etiology; D052097:Quadriceps Muscle / Q000503:physiopathology*; D013848:Thigh / Q000502:physiology; D055815:Young Adult