Effect of exercise-induced fatigue on postural control of the knee

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Abstract

Muscle fatigue is associated with reduced power output and work capacity of the skeletal muscle. Fatigue-induced impairments in muscle function are believed to be a potential cause of increased injury rates during the latter stages of athletic competition and often occur during unexpected perturbations. However the effect of fatigue on functionally relevant, full body destabilizing perturbations has not been investigated. This study examines the effect of muscle fatigue on the activation of the quadriceps and hamstrings to fast, full body perturbations evoked by a moveable platform. Surface electromyographic (EMG) signals were recorded from the knee extensor (vastus medialis, rectus femoris, and vastus lateralis) and flexor muscles (biceps femoris and semitendinosus) of the right leg in nine healthy men during full body perturbations performed at baseline and immediately following high intensity exercise performed on a bicycle ergometer. In each condition, participants stood on a moveable platform during which 16 randomized postural perturbations (eight repetitions of two perturbation types: 8 cm forward slides, 8 cm backward slides) with varying inter-perturbation time intervals were performed over a period of 2–3 min. Maximal voluntary knee extension force was measured before and after the high intensity exercise protocol to confirm the presence of fatigue. Immediately after exercise, the maximal force decreased by 63% and 66% for knee extensors and flexors, respectively (P < 0.0001). During the post-exercise postural perturbations, the EMG average rectified value (ARV) was significantly lower than the baseline condition for both the knee extensors (average across all muscles; baseline: 19.7 ± 25.4 μV, post exercise: 16.2 ± 19.4 μV) and flexors (baseline: 24.3 ± 20.9 μV, post exercise: 13.8 ± 11.0 μV) (both P < 0.05). Moreover the EMG onset was significantly delayed for both the knee extensors (baseline: 132.7 ± 32.9 ms, post exercise: 170.8 ± 22.9 ms) and flexors (baseline: 139.1 ± 38.8 ms, post exercise: 179.3 ± 50.9 ms) (both P < 0.05). A significant correlation (R2 = 0.53; P < 0.05) was identified between the percent reduction of knee extension MVC and the percent change in onset time of the knee extensors post exercise. This study shows that muscle fatigue induces a reduction and delay in the activation of both the quadriceps and hamstring muscles in response to rapid destabilizing perturbations potentially reducing the stability around the knee.

Introduction

Muscle fatigue is an inevitable part of high intensity exercise and is associated with reduced power output and work capacity of the skeletal muscle (Pilegaard et al., 1999). Failure to produce maximal force is the result of peripheral fatigue resulting from failure at the neuromuscular junction and beyond, and central fatigue resulting from a failure to activate the muscle voluntarily (failure to drive motor neurons) (Gandevia, 2001). Peripheral and/or central fatigue induced by metabolic and/or neurological changes impairs neuromuscular control (Enoka and Stuart, 1992).

Fatigue-induced impairments in neuromuscular control may adversely alter joint proprioception (Voight et al., 1996, Miura et al., 2004, Ribeiro et al., 2008) and are believed to be a potential cause for the increased injury rates during the latter stages of athletic competition particularly during sudden deceleration, landing and pivoting maneuvers (Boden et al., 2000). To date, studies assessing the impact of fatigue on postural control have focused primarily on the induction of localized muscle fatigue through isokinetic contractions of ankle or knee muscles, during quiet and perturbed standing (e.g. Miller and Bird, 1976, Gribble and Hertel, 2004a, Gribble and Hertel, 2004b, Gribble et al., 2004, Bellew and Fenter, 2006, Salavati et al., 2007, Lin et al., 2009, Springer and Pincivero, 2009).

This study examines the effect of fatigue on the response of the quadriceps and hamstrings to fast, functionally relevant, full body perturbations. These perturbations are produced by a computer-controlled platform that can be controlled in three-dimensional space to produce sliding perturbations that resemble perturbations that might be encountered during some sport activities. In this study it was hypothesized that the muscle activity elicited by rapid destabilizing perturbations would be reduced and delayed in the presence of fatigue potentially reducing stability around the knee. Understanding how the execution of a motor task changes under the influence of fatigue can limit the potential injurious role of fatigue during motor performance (Mair et al., 1996, Gorelick et al., 2003, Melnyk and Gollhofer, 2007, Greig and Walker-Johnson, 2007).

Section snippets

Subjects

Nine healthy recreationally active men (age, mean ± SD, 27 ± 3 yr, body mass 76.5 ± 10.4 kg, height 1.75 ± 0.06 m), with no history of lower limb disorders, participated in the study. All subjects were right leg dominant. The study was conducted in accordance with the Declaration of Helsinki and approved by the local ethics committee (N-20100045). Subjects provided informed written consent before participation in the study.

Procedure

Three maximal voluntary contractions (MVC) of knee flexion and extension were

Maximal voluntary contraction

The maximal voluntary contraction torque decreased immediately after exercise by 63% (P < 0.0001) for the quadriceps (pre: 635.5 ± 141.5 N m; post: 430.0 ± 107.4 N m) and 66% (P < 0.0001) for the hamstring muscles (pre: 149.2 ± 36.3 N m; post: 224.0 ± 40.7 N m).

Postural perturbations

Across both perturbation types there was a significant effect for muscle (F = 4.5, P < 0.05) with the greatest reduction of ARV observed for the BF compared to the other four muscles (SNK: P < 0.05). The larger reduction in hamstring muscle activity post exercise

Discussion

This study investigated the effects of fatigue on postural control of the knee during unexpected rapid postural perturbations in healthy young men. Reduced and delayed onset of activity for both the quadriceps and hamstring muscles were observed during the destabilizing perturbations in the presence of fatigue, suggesting a reduced ability of the muscles to stabilize the knee joint during such a perturbation.

Maximum knee extension and flexion force was significantly reduced post exercise

Conclusion

Muscle fatigue induces reduced and delayed activation of both the quadriceps and hamstring muscles in response to rapid destabilizing perturbations. Muscle fatigue may increase the risk for musculoskeletal injury during rapid perturbations (as occurs in most sport activities) and therefore, exercise programs for patients and athletes should be carefully monitored for signs of fatigue to avoid deficits that might compromise dynamic joint stability.

Hamidollah Hassanlouei, born in Makoo, Iran in 1977, graduated in exercise physiology from Shahid beheshty University, Tehran, Iran in 2003. Since 2009 he has been enrolled as a Ph.D. candidate in motor control, supported by the Center for Sensory-Motor Interaction (SMI), Aalborg University, Denmark. He is currently involved in projects in the field of training and motor control, and has published several papers in peer review journals in this field.

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  • Cited by (0)

    Hamidollah Hassanlouei, born in Makoo, Iran in 1977, graduated in exercise physiology from Shahid beheshty University, Tehran, Iran in 2003. Since 2009 he has been enrolled as a Ph.D. candidate in motor control, supported by the Center for Sensory-Motor Interaction (SMI), Aalborg University, Denmark. He is currently involved in projects in the field of training and motor control, and has published several papers in peer review journals in this field.

    Lars Arendt-Nielsen, born in 1958, received the Master of Science degree in biomedical sciences from Aalborg University, Denmark, in 1983, and the Ph.D. degree in 1992. In 1994 he received his Dr. Sci. degree in Medicine from the Medical Faculty, Aarhus University, Denmark. From 1983 to 1984 he was a Research fellow, Dept. of Clinical Neurophysiology, The National Hospital for Nervous Diseases, London and in 1998 guest professor at Institute for Physiological Sciences, Okasaki, Japan. Since 1988 he has been with the Department of Health Sciences and Technology, Aalborg University and was appointed professor in 1993. In 1993 he was co-founder of Center for Sensory-Motor Interaction, at Aalborg University for which he is now the director. He is also director for R&D at C4Pain, Aalborg, Denmark.

    Uwe Kersting is Associate Professor at the Center of Sensory-Motor Interaction within the Department of Health Science and Technology, Aalborg University, Aalborg, Denmark, since 2007. He is Research Director of the Gait Laboratory at Hammel Neurocenter, Hammel, Denmark and Adjunct Professor at Mid Sweden University, Östersund, Sweden. He earned his Ph.D. at the German Sport University, Cologne, Germany. His main work interest lies in acute and chronic injuries in sport. He aims at understanding injury mechanisms in a biological and mechanical context. He has published numerous papers on lower extremity and back loading in various sports as well as on tissue adaptation during walking and running.

    Deborah Falla received her Ph.D. in Physiotherapy from The University of Queensland, Australia in 2003. In 2005 she was awarded Fellowships from the International Association for the Study of Pain and the National Health and Medical Research Council of Australia to undertake postdoctoral research at the Center for Sensory-Motor Interaction, Aalborg University, Denmark. From 2008 to 2011 she was an Associate Professor at the Faculty of Medicine, Department of Health Science and Technology, Aalborg University, Denmark. Since 2011 she is a Professor in Physiotherapy at the Center for Anesthesiology, Emergency and Intensive Care Medicine and the Department of Neurorehabilitation Engineering, University Hospital Göttingen, Germany. Her research involves the integration of neurophysiological and clinical research to evaluate neuromuscular control of the spine in people with chronic pain. Her research interests also include motor skill learning and training for musculoskeletal pain disorders. In this field she has published over 70 papers in peer-reviewed Journals, more than 100 conference papers/abstracts and received the Delsys Prize for Electromyography Innovation. She has given over 60 invited lectures and has provided professional continuing education courses on the management of neck pain in over 20 countries. She is co-author of the book entitled “Whiplash, Headache and Neck Pain: Research Based Directions for Physical Therapies” published by Elsevier and is Associate Editor of the journal Manual Therapy. Since 2010 she is a Council member of the International Society of Electrophysiology and Kinesiology (ISEK).

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