High intensity running results in an impaired neuromuscular response in ACL reconstructed individuals

Abstract

Anterior cruciate ligament (ACL) reconstruction reestablishes electromyographic activity during moderate activities such as walking but is unclear if this is also the case in sports activities such as high intensity running that results in accumulation of metabolic fatigue. Nine bone-patella tendon-bone ACL reconstructed athletes were evaluated 19.2 (5.7) months post-operatively using a telemetric electromyographic system. The neuromuscular response of vastus lateralis and biceps femoris muscles was tested bilaterally on separate occasions during 10 min running at moderate intensity (20% below the lactate threshold) and 10 min running at high intensity (40% above the lactate threshold). During moderate intensity running, electromyographic activity did not change for either leg. During high intensity running, electromyographic activity did not change for the vastus lateralis of the ACL reconstructed leg [267.8 (142.8)-263.8 (128.9) microV, P > 0.05] while it increased significantly [294.2 (120.6)-317.1 (140.5) microV, P = 0.03] for the vastus lateralis of the intact leg. High intensity exercise that is associated with accumulation of metabolic fatigue, results in an impaired neuromuscular response for the vastus lateralis muscle of the ACL reconstructed leg.

Can muscle coordination be precisely studied by surface electromyography?

“…Numerous authors have focused on alterations in EMG activity level of some lower limb muscles during sub-maximal fatiguing pedaling exercises (Petrofsky, 1979;Housh et al, 2000) (Hautier et al, 2000;Billaut et al, 2005) or sub-maximal fatiguing running exercises (Kellis and Liassou, 2009;Patras et al, 2009). Most of these studies interpreted an increase in the EMG/intensity ratio as a sign of neuromuscular fatigue, i.e., (i) an additional recruitment of motor units (MU) to compensate for the decrease in the force of contraction that occurs in fatigued muscle fibers (Edwards and Lippold, 1956); (ii) an increased firing frequency and/or synchronization of motor unit recruitment (Gandevia, 2001); and/or (iii) the slowing of muscle fiber action potential conduction velocity (Linstrom et al, 1970).…”

Quadriceps Muscle Function After Exercise in Men and Women With a History of Anterior Cruciate Ligament Reconstruction

“…In healthy individuals, lower extremity muscles weaken after acute bouts of high-intensity and high-volume exercise. [15][16][17] Previous investigators have used fatiguing-exercise protocols to better understand the effects of simulated athletic participation in healthy individuals 15,16,[18][19][20][21][22] and, to a lesser extent, individuals after ACLR. [23][24][25] In healthy people, decreased knee-extension strength and altered gait biomechanics have been noted after isokinetic fatigue of the hamstrings and quadriceps.…”

Biomechanical Adaptations After Fatiguing Exercise in Healthy and ACL Reconstructed Individuals

“…104 Furthermore, individuals with ACLR demonstrate altered quadriceps and hamstring activation after high-intensity exercise. 152,153 No changes in muscle activation have been noted after moderate-intensity exercise. 152 This supports evaluating individuals with ACLR when fatigued for patients attempting to return to high-intensity exercise, however there is no current model of laboratory-based fatiguing exercise that simulates movements experienced by an athlete during a game or match.…”

“…152,153 No changes in muscle activation have been noted after moderate-intensity exercise. 152 This supports evaluating individuals with ACLR when fatigued for patients attempting to return to high-intensity exercise, however there is no current model of laboratory-based fatiguing exercise that simulates movements experienced by an athlete during a game or match. Exercise protocols widely vary between research studies, ranging from localized muscle fatigue induced through isokinetic exercise to sport-specific exercise predominantly comprised of walking.…”

“…Vastus lateralis activation increases in healthy limbs during high-intensity running, defined as 40% above lactate threshold, while vastus lateralis activation remained unchanged in the ACLR limb. 152,153 This impaired response to high intensity exercise may be in an effort to minimize force attenuation at the knee joint, displacing forces proximally to the hip and trunk. 104 The up regulation of hip involvement during running gait dissipates when fatigued, as patients with ACLR decrease hip flexion angle and external hip flexion moment while increasing external knee flexion moment.…”