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Effects of Fatigue on Lower Limb Mechanics during Landing Tasks: Implications for ACL Injury6822:30 PM – 2:45 PM

McLean, Scott G.; Calabrese, Gary; Passerallo, Allen; Fellin, Rebecca; Joy, Susan

Medicine & Science in Sports & Exercise: May 2006 - Volume 38 - Issue 5 - p S25
Presidential Closing Remarks 12:05 PM – 12:15 PM: Immediately Following President's Lectures ROOM: Ballroom 2/3 and Ballroom 1: B-17 Free Communication/Slide – Landing Mechanics: WEDNESDAY, MAY 31, 2006 1:00 PM – 3:00 PM: ROOM 401

The Cleveland Clinic Foundation, Cleveland, OH


Despite the ever-increasing number and complexity of training programs geared towards their prevention, non-contact anterior cruciate ligament (ACL) injuries persist in epidemic like proportions. It is thus plausible, that such programs continue to exclude key components of the underlying injury mechanism. Fatigue for example, compromises the neuromuscular response, and hence, may implicate directly within hazardous movement execution.

PURPOSE: The current study examined the effects of fatigue and sex on lower limb three-dimensional (3D) joint mechanics during landing tasks.

METHODS: Ten female (21.5 ± 2.0 yrs) and eight male (20.4 ± 2.3 yrs) NCAA athletes had 3D hip, knee and ankle kinematics and external kinetics quantified during the landing phase of five drop jump tasks, both before and after exposure to a standardized fatigue protocol. This protocol lasted precisely four minutes, and consisted of a continuous series of stepping and bounding tasks synonymous with game-play. Peak joint angles and moments were extracted from each trial, with mean subject values submitted to a two-way ANOVA to determine for the main effects of gender and fatigue. Fatigue level, denoted by maximum heart rate, was initially considered as a covariate within the model, but was found to be similar across subjects (power = 0.057).

RESULTS: Females demonstrated significant (p<0.01) increases in peak knee valgus and internal rotation, and ankle supination angles, and peak normalized (mass × height) knee varus, valgus and internal rotation moments compared to males. Fatigue also produced significant increases in peak knee valgus and internal rotation angles and moments, with these increases found statistically to be more pronounced in females (Figure 1).

Figure 1

Figure 1

Conclusions: The effects of fatigue on neuromuscular control during high-risk sports postures must be considered within current ACL injury prevention strategies. The ability to counter fatigue induced changes in out-of-plane knee mechanics appears particularly pertinent.

© 2006 American College of Sports Medicine