Fatigue-Induced ACL Injury Risk Stems from a Degradation in Central Control

McLean, Scott; Samorezov, Julia E.

doi:10.1249/mss.0b013e31819ca07b

Cited by 150 publications

(201 citation statements)

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“…Specifically, trunk movement patterns were altered, as evidenced as a result of fatigue, during a repetitive lifting task (Sparto et al, 1997). McLean & Samorezov (2009) also demonstrated that central fatigue is a key player in ACL injury risk upon fatigue-induced landing. Unilateral fatigue led to a fatigue crossover to the contralateral limb when performing single-leg landings, which altered landing strategies (McLean & Samorezov, 2009).…”

Section: Introductionmentioning

confidence: 90%

“…McLean & Samorezov (2009) also demonstrated that central fatigue is a key player in ACL injury risk upon fatigue-induced landing. Unilateral fatigue led to a fatigue crossover to the contralateral limb when performing single-leg landings, which altered landing strategies (McLean & Samorezov, 2009). If asymmetries increase with fatigue, they may then partially explain this increase in injury risk.…”

Section: Introductionmentioning

confidence: 90%

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Effects of Fatigue on Bilateral Ground Reaction Force Asymmetries during the Squat Exercise

Hodges

Patrick

Reiser

2011

Journal of Strength and Conditioning Research

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OF THESIS EFFECTS OF FATIGUE ON BILATERAL GROUND REACTION FORCE ASYMMETRIES DURING THE SQUAT EXERCISEPhysical performance and risk for injury have been related to functional asymmetries of the lower extremity. The squat exercise is an important, functional movement serving as the major multi-joint, closed-chain lower extremity exercise in many strength and conditioning programs, as well as a large component in rehabilitation.Examinations of asymmetries during the squat exercise have revealed bilateral differences in the net joint torques, indicating unequal actions between the lower extremities. To date, no study has examined how fatigue affects these asymmetries. PURPOSE:The goal of this investigation was to examine functional bilateral asymmetries of the lower extremities during the squat exercise, exploring how they may change during the course of an individual set, as well as across multiple sets with fatigue.Based on a review of literature related to the effects of fatigue on functional asymmetries, it was hypothesized that asymmetries would increase with fatigue. METHODS:Seventeen recreationally trained men (n=9) and women (n=8) (mean ± SD age: 22.3 ± 2.5 yrs; height 170 ± 9.3 cm; mass 73.4 ± 13.8 kg) performed five sets of eight repetitions with 90% of their predetermined eight-repetition maximum (8RM 113 ± 35 % of their body mass). Anthropometric measurements and vertical ground reaction force (GRFv) data were collected. GRFv asymmetries were calculated by subtracting the % load on the iv right foot from that of the left foot. Initially highly symmetric subjects (± 1.7%) were removed from the analyses. The first two (R1&2) and last two (R7&8) repetitions of each set were examined. Eight subjects were reassessed for repeatability measures. RESULTS:R7&8 took longer to complete than R1&2 within a single set (p<0.001), however this finding was not observed across sets (p=0.867). The average asymmetry level across all sets for the absolute average was 4.3 ± 2.5% and 3.6 ± 2.3% for R1&2 and R7&8, respectively. There was no difference in whole group analysis (n=17) for any of the GRFv asymmetry analyses. Initially symmetric subjects were removed for the following analyses. For absolute peak instantaneous forces, the average asymmetry level across all sets was 3.8 ± 2.3% and 3.2 ± 2.3% for R1&2 and R7&8, respectively. Within a set, based on absolute asymmetry, levels of asymmetry dropped from beginning to end of a set (p=0.044). Exploring general shifts towards the left or right leg revealed a significant difference in peak instantaneous asymmetry with subjects becoming more symmetric with fatigue during the course of a single set (p=0.042). Of those who placed more weight on their right side at the beginning of a set, based on average asymmetry, a significant movement towards symmetry was seen for repetitions within a single set (p=0.036). Anthropometrics (segment lengths and circumferences) were generally not highly correlated to the asymmetries. Anthropometric measures were highly repeatable (Cronbac...

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Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 90%

Effects of Fatigue on Bilateral Ground Reaction Force Asymmetries during the Squat Exercise

Hodges

Patrick

Reiser

2011

Journal of Strength and Conditioning Research

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“…Peripheral fatigue refers to a decrease in the ability of a muscle to produce force because of changes that occur at or distal to the neuromuscular junction, whereas central fatigue refers to an exercise-induced reduction in voluntary activation of a muscle because of changes that occur in a motor unit proximal to the neuromuscular junction. A recent study 54 provides evidence that central fatigue alone may be sufficient to produce measureable changes in lower extremity mechanics during single-leg landings. The reduction in gluteus medius activation latency we observed may also be the result of central fatigue effects, such as delayed anticipatory activation from the motor cortex or decreased a motor neuron conduction velocity from reduced excitability of the motor neuron membrane after repetitive activations.…”

Section: Electromyographymentioning

confidence: 99%

“…As noted earlier, decreased gluteus medius activation latency may be a consequence of some change in central control associated with participation in the isolated fatigue protocol. Some 54 have argued that targeted training of central control mechanisms may more effectively minimize the likelihood of altered lower extremity mechanics linked with ACL injury risk than interventions focused on strengthening alone. Indeed, adding visual feedback to a general lower extremity strengthening program has recently been found to elicit greater changes in frontal-plane hip kinematics during jumping than a strengthening program alone.…”

Section: Electromyographymentioning

confidence: 99%

Hip-Abductor Fatigue and Single-Leg Landing Mechanics in Women Athletes

Patrek

Kernozek

Willson

et al. 2011

Journal of Athletic Training

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Context: Reduced hip-abductor strength and muscle activation may be associated with altered lower extremity mechanics, which are thought to increase the risk for anterior cruciate ligament injury. However, experimental evidence supporting this relationship is limited. Objective: To examine the changes in single-leg landing mechanics and gluteus medius recruitment that occur after a hip-abductor fatigue protocol. Design: Descriptive laboratory study. Patients or Other Participants: Twenty physically active women (age = 21.0 ± 1.3 years). Intervention(s): Participants were tested before (prefatigue) and after (postfatigue) a hip-abductor fatigue protocol consisting of repetitive side-lying hip abduction. Main Outcome Measure(s): Outcome measures included sagittal-plane and frontal-plane hip and knee kinematics at initial contact and at 60 milliseconds after initial contact during 5 single-leg landings from a height of 40 cm. Peak hip and knee sagittal-plane and frontal-plane joint moments during this time interval were also analyzed. Measures of gluteus medius activation, including latency, peak amplitude, and integrated signal, were recorded. Results: A small (<1°) increase in hip-abduction angle at initial contact and a small (<1°) decrease in knee-abduction (valgus) angle at 60 milliseconds after contact were observed in the postfatigue landing condition. No other kinematic changes were noted for the knee or hip at initial contact or at 60 milliseconds after initial contact. Peak external knee-adduction moment decreased 27% and peak hip adduction moment decreased 24% during the postfatigue landing condition. Gluteus medius activation was delayed after the protocol, but no difference in peak or integrated signal was seen during the landing trials. Conclusions: Changes observed during single-leg landings after hip-abductor fatigue were not generally considered unfavorable to the integrity of the anterior cruciate ligament. Further work may be justified to study the role of hip-abductor activation in protecting the knee during landing.

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“…Sagittal-plane knee mechanics were altered with fatigue; specifically, a decrease in knee flexion was seen at peak vertical ground reaction force, peak posterior ground reaction force, and peak knee flexion. Researchers who did not completely use a SLO-FP or FAST-FP but induced lower extremity fatigue found similar results for these kinematic variablesy, 12,20 An interesting result to note is the lack of difference between fatigue protocols (SLO-FP and FAST-FP). Most prefatigue to postfatigue changes were observed regardless of the fatigue protocol used, with minimal differences noted between the 2 protocols.…”

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confidence: 92%

Two Different Fatigue Protocols and Lower Extremity Motion Patterns During a Stop-Jump Task

Quammen

Cortés

Lunen

et al. 2012

Journal of Athletic Training

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Context: Altered neuromuscular control strategies during fatigue probably contribute to the increased incidence of noncontact anterior cruciate ligament injuries in female athletes.Objective: To determine biomechanical differences between 2 fatigue protocols (slow linear oxidative fatigue protocol [SLO-FP] and functional agility short-term fatigue protocol [FAST-FP]) when performing a running-stop-jump task. Design: Controlled laboratory study. Setting: Laboratory. Patients or Other Participants:A convenience sample of 15 female soccer players (age = 19.2 ± 0.8 years, height = 1.67 ± 0.05 m, mass = 61.7 ± 8.1 kg) without injury participated. Intervention(s):Five successful trials of a running-stopjump task were obtained prefatigue and postfatigue during the 2 protocols. For the SLO-FP, a peak oxygen consumption (V02peak) test was conducted before the fatigue protocol. Five minutes after the conclusion of the V02peak test, participants started the fatigue protocol by performing a 30-minute interval run. The FAST-FP consisted of 4 sets of a functional circuit. Repeated 2 (fatigue protocol) x 2 (time) analyses of variance were conducted to assess differences between the 2 protocols and time (prefatigue, postfatigue Conclusions: bur results demonstrated a more erect landing posture due to a decrease in hip and knee flexion angles in the postfatigue condition. The changes were similar between protocols; however, the FAST-FP was a clinically applicable 5-minute protocol, whereas the SLO-FP lasted approximately 45 minutes.Key Words: anterior cruciate ligament, hip, knee, biomechanics Key Points• Both the slow linear oxidative fatigue protocol (SLO-FP) and the functional agility short-term fatigue protocol (FAST-FP) demonstrated that the lower extremity is at a higher risk for sustaining injury when fatigue and unanticipated movement are combined.• Similar lower extremity biomechanical modifications occurred after 5 minutes of fatigue during the FAST-FP and after 45 minutes of fatigue during the SLO-FP.• Fatigue-induced decreases in hip and knee flexion resulted in a more extended landing posture, which can increase anterior tibial translation and thus increase strain on the anterior cruciate ligament.

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Fatigue-Induced ACL Injury Risk Stems from a Degradation in Central Control

Cited by 150 publications

References 41 publications

Effects of Fatigue on Bilateral Ground Reaction Force Asymmetries during the Squat Exercise

Effects of Fatigue on Bilateral Ground Reaction Force Asymmetries during the Squat Exercise

Hip-Abductor Fatigue and Single-Leg Landing Mechanics in Women Athletes

Two Different Fatigue Protocols and Lower Extremity Motion Patterns During a Stop-Jump Task

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