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Effects of movement speed and joint position on knee flexor torque in healthy and post-surgical subjects.
Eur J Appl Physiol Occup Physiol. 1999 Jul; 80(2):100-6.EJ

Abstract

Coactivation of knee flexors during knee extension assists in joint stability by exerting an opposing torque to the anterior tibial displacement induced by the quadriceps. This opposing torque is believed to be generated by eccentric muscle actions that stiffen the knee, thereby attenuating strain to joint ligaments, particularly the anterior cruciate ligament (ACL). However, as the lengths of knee muscles vary with changes in joint position, the magnitude of flexor/extensor muscle force coupling may likewise vary, possibly affecting the capacity for active knee stabilization. The purpose of this study was to assess the effect of changes in movement speed and joint position on eccentric/concentric muscle action relationships in the knees of uninjured (UNI) and post-ACL-surgery (INJ) subjects (n = 14). All subjects were tested for maximum eccentric and concentric torque of the contralateral knee flexors and extensor muscles at four isokinetic speeds (15 degrees-60 degrees x s(-1)) and four joint position intervals (20 degrees-60 degrees of knee flexion). Eccentric flexor torque was normalized to the percentage of concentric flexor torque generated at each joint position interval for each speed tested (flexor E-C ratio). In order to estimate the capacity of the knee flexors to resist active knee extension, the eccentric-flexor/concentric-extensor ratios were also computed for each joint position interval and speed (flexor/extensor E-C ratio). The results revealed that eccentric torque surpassed concentric torque by 3%-144% across movement speeds and joint position intervals. The magnitude of the flexor E-C ratio and flexor/extensor E-C increased significantly with speed in both groups of subjects (P < 0.05) and tended to rise with muscle length as the knee was extended; peak values were generated at the most extended joint position (20 degrees-30 degrees). Although torque development patterns were symmetrical between the contralateral limbs in both groups, between-group comparisons revealed significantly higher flexor/extensor E-C ratios for the INJ group compared to the UNI group (P < 0.05), particularly at the fastest speed tested (60 degrees x s(-1)). The results indicate that joint position and movement speed influence the eccentric/concentric relationships of knee flexors and extensors. The INJ subjects appeared to accommodate to surgery by developing the eccentric function of their ACL and normal knee flexors, particularly at higher speeds and at more extended knee joint positions. This may assist in the dynamic stabilization of the knee at positions where ACL grafts have been reported to be most vulnerable to strain.

Authors+Show Affiliations

Department of Exercise and Movement Science, University of Oregon, Eugene 97403, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Clinical Trial
Comparative Study
Journal Article

Language

eng

PubMed ID

10408319

Citation

Osternig, L R., et al. "Effects of Movement Speed and Joint Position On Knee Flexor Torque in Healthy and Post-surgical Subjects." European Journal of Applied Physiology and Occupational Physiology, vol. 80, no. 2, 1999, pp. 100-6.
Osternig LR, James CR, Bercades D. Effects of movement speed and joint position on knee flexor torque in healthy and post-surgical subjects. Eur J Appl Physiol Occup Physiol. 1999;80(2):100-6.
Osternig, L. R., James, C. R., & Bercades, D. (1999). Effects of movement speed and joint position on knee flexor torque in healthy and post-surgical subjects. European Journal of Applied Physiology and Occupational Physiology, 80(2), 100-6.
Osternig LR, James CR, Bercades D. Effects of Movement Speed and Joint Position On Knee Flexor Torque in Healthy and Post-surgical Subjects. Eur J Appl Physiol Occup Physiol. 1999;80(2):100-6. PubMed PMID: 10408319.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effects of movement speed and joint position on knee flexor torque in healthy and post-surgical subjects. AU - Osternig,L R, AU - James,C R, AU - Bercades,D, PY - 1999/7/17/pubmed PY - 1999/7/17/medline PY - 1999/7/17/entrez SP - 100 EP - 6 JF - European journal of applied physiology and occupational physiology JO - Eur J Appl Physiol Occup Physiol VL - 80 IS - 2 N2 - Coactivation of knee flexors during knee extension assists in joint stability by exerting an opposing torque to the anterior tibial displacement induced by the quadriceps. This opposing torque is believed to be generated by eccentric muscle actions that stiffen the knee, thereby attenuating strain to joint ligaments, particularly the anterior cruciate ligament (ACL). However, as the lengths of knee muscles vary with changes in joint position, the magnitude of flexor/extensor muscle force coupling may likewise vary, possibly affecting the capacity for active knee stabilization. The purpose of this study was to assess the effect of changes in movement speed and joint position on eccentric/concentric muscle action relationships in the knees of uninjured (UNI) and post-ACL-surgery (INJ) subjects (n = 14). All subjects were tested for maximum eccentric and concentric torque of the contralateral knee flexors and extensor muscles at four isokinetic speeds (15 degrees-60 degrees x s(-1)) and four joint position intervals (20 degrees-60 degrees of knee flexion). Eccentric flexor torque was normalized to the percentage of concentric flexor torque generated at each joint position interval for each speed tested (flexor E-C ratio). In order to estimate the capacity of the knee flexors to resist active knee extension, the eccentric-flexor/concentric-extensor ratios were also computed for each joint position interval and speed (flexor/extensor E-C ratio). The results revealed that eccentric torque surpassed concentric torque by 3%-144% across movement speeds and joint position intervals. The magnitude of the flexor E-C ratio and flexor/extensor E-C increased significantly with speed in both groups of subjects (P < 0.05) and tended to rise with muscle length as the knee was extended; peak values were generated at the most extended joint position (20 degrees-30 degrees). Although torque development patterns were symmetrical between the contralateral limbs in both groups, between-group comparisons revealed significantly higher flexor/extensor E-C ratios for the INJ group compared to the UNI group (P < 0.05), particularly at the fastest speed tested (60 degrees x s(-1)). The results indicate that joint position and movement speed influence the eccentric/concentric relationships of knee flexors and extensors. The INJ subjects appeared to accommodate to surgery by developing the eccentric function of their ACL and normal knee flexors, particularly at higher speeds and at more extended knee joint positions. This may assist in the dynamic stabilization of the knee at positions where ACL grafts have been reported to be most vulnerable to strain. SN - 0301-5548 UR - https://www.unboundmedicine.com/medline/citation/10408319/Effects_of_movement_speed_and_joint_position_on_knee_flexor_torque_in_healthy_and_post_surgical_subjects_ DB - PRIME DP - Unbound Medicine ER -