Research Report
Fuminari Kaneko, Kotaro Kawaguchi, Kiyoshi Onari, Serge H. Roy, Kazuhiro Tsukisaka
Objectives: The purpose of this study was to investigate the electromechanical properties of atrophied muscle in patients with anterior cruciate ligament (ACL) reconstruction and to examine the relationship of changes in these properties for a voluntarily elicited maximal isometric contraction and peripherally stimulated twitch contraction.
Background: It is not known if, following ACL reconstruction, a prolonged reaction time to a sudden stimulus is due to impaired proprioception in the knee joint, a prolonged processing interval in the central nervous system, or a greater elasticity in the series elastic component of the quadriceps femoris.
Methods:Seventeen patients were recruited 2 to 3 months following a unilateral ACL reconstruction. Both the involved leg (ACL-invo group) and the uninvolved leg (ACL uninvo group) were studied. Twenty-two athletes (training group) and 18 control subjects (control group) were also tested. These subjects performed voluntary maximal isometric contraction (MVC) of the quadriceps femoris. Maximal twitch response was also elicited by a supramaximal electrical stimulation to the femoral nerve, and surface electromyograms were recorded from the vastus lateralis in all 4 groups.
Results: Total reaction time for MVC in the ACL-invo group (250.47 ms) was prolonged compared to that of the control and training groups. Twitch response in the ACL-invo group (25.26 ms) was prolonged compared to that of the other 3 groups. Premotor time during both MVC and twitch response did not differ among the 4 groups. Electromechanical delay during MVC (53.62 ms) and the evoked electromechanical delay in twitch response (20.04 ms) were prolonged in the ACL-invo group as compared to the other 3 groups.
Conclusions: Prolonged electromechanical delay in twitch response may be due to peripheral physiological disruptions (eg, stiffness of the series elastic component, changes of peripheral muscle fiber-type composition, or a decrease in function of the excitation-contraction coupling process). A prolonged electromechanical delay in twitch response can also explain the prolonged electromechanical delay observed for MVC. These findings suggest that prolonged total reaction time in MVC, when secondary to a visual stimulus in atrophied human quadriceps femoris muscle after ACL reconstruction, may be principally due to prolongation of electromechanical delay produced by peripheral physiological alterations. However, the contribution of premotor time to prolonged total reaction time was not revealed. Our results do not completely eliminate the possibility that central nervous system processing time and other neural factors are involved in the prolongation of reaction time.
J Orthop Sports Phys Ther. 2002; 32(4):158–165.
Key Words: anterior cruciate ligament, electromechanical delay, electromyography, muscle atrophy, series elastic component
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Research Report
Christopher M. Powers, George J. Salem, Ruben Salinas, David A. Wallace
Study Design: Single-group, repeated-measures design.
Objective:To quantify patellofemoral joint reaction forces and stress while squatting with and without an external load.
Background: Although squatting exercises in the rehabilitation setting are often executed to a relatively shallow depth in order to avoid the higher joint forces associated with increased knee flexion, objective criteria for ranges of motion have not been established.
Methods and Measures: Fifteen healthy adults performed single-repetition squats to 90° of knee flexion without an external load and with an external load (35% of the subject’s body weight [BW]). Anthropometric data, three-dimensional kinematics, and ground reaction forces were used to calculate knee extensor moments (inverse dynamics approach), while a biomechanical model of the patellofemoral joint was used to quantify the patellofemoral joint reaction forces and patellofemoral joint stress. Data were analyzed during the eccentric (0–90°) and concentric (90–0°) phases of the squat maneuver.
Results: In both conditions, knee extensor moments, patellofemoral joint reaction forces, and patellofemoral joint stress increased significantly with greater knee flexion angles (P < 0.05). Peak patellofemoral joint force and stress was observed at 90° of knee flexion. Patellofemoral joint stress at 45°, 60°, 75°, and 90° of knee flexion during the eccentric phase, and at 75° and 90° during the concentric phase, was significantly greater in the loaded trials versus the unloaded trials.
Conclusion: The data indicate that during squatting, patellofemoral joint stress increases as the knee flexion angle increases, and that the addition of external resistance further increases patellofemoral joint stress. These findings suggest that in order to limit patellofemoral joint stress during squatting activities, clinicians should consider limiting terminal joint flexion angles and resistance loads.
J Orthop Sports Phys Ther. 2002; 32(4):141–148.
Key Words: biomechanics, knee, patellofemoral joint reaction force, patellofemoral joint stress
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Research Report
Craig R. Denegar, Jose Fonseca, Jay Hertel
Study Design: Retrospective study.
Objective:Assess range of motion, posterior talar glide, and residual joint laxity following ankle sprain in a population of athletes who have returned to unrestricted activity.
Background: Lateral ankle sprains occur frequently in athletic populations and the reinjury rate may be as high as 80%. In an effort to better understand risk factors for reinjury, the sequelae to injury in a sample of college athletes were assessed.
Methods and Measures: Twelve athletes with a history of lateral ankle sprain within the last 6 months and who had returned to sport participation were tested. Only athletes who reported never injuring the contralateral ankle were included. The injured and uninjured ankles of subjects were compared for measures of joint laxity, ankle dorsiflexion range of motion, and posterior talar glide. Friedman’s test of rank order was used to analyze the laxity measures and a MANOVA was used to assess the dorsiflexion and posterior talar glide measures.
Results: Laxity was significantly greater at the talocrural and subtalar joints of the injured ankles. There were no significant differences in any of the ankle dorsiflexion measurements between injured and uninjured ankles, but posterior talar glide was significantly reduced in injured ankles as compared to uninjured ankles.
Conclusion: In our sample of subjects, residual ligamentous laxity was commonly found following lateral ankle sprain. Dorsiflexion range of motion was restored in the population studied despite evidence of restricted posterior glide of the talocrural joint. Although restoration of physiological range of motion was achieved, residual joint dysfunction persisted. Further research is warranted to elucidate the role of altered arthrokinematics after lateral ankle sprain.
J Orthop Sports Phys Ther. 2002; 32(4):166-173.
Key Words: arthrokinematic motion, inversion ankle sprain, ligamentous laxity
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Research Report
James M. Byers, Jeffrey L. Krafft, Brian Lackey, Kathy M. Melton, Michael T. Gross
Study Design: Single-group, pre-, and postintervention repeated-measures design.
Objective:To determine the impact of custom semirigid foot orthotics on pain and disability for individuals with plantar fasciitis.
Background: Few studies have examined the efficacy of foot orthotics for plantar fasciitis, and no single study has yet examined the effects of semirigid foot orthotics on an established quality-of-life instrument.
Methods and Measures: Eight men and 7 women (mean ages 44.7 ± 9.0 years) who reported having plantar fasciitis symptoms for an average of 21.3 ± 23.7 months participated in the study. Subjects were timed for a 100-m walk at a self-selected speed, then they rated the pain they experienced during the walk using a 10-cm visual analog scale. Subjects also completed the pain and disability subsections of the Foot Function Index questionnaire. All measures were acquired before the fabrication of custom semirigid foot orthotics and 12 to 17 days following onset of foot orthotic use.
Results: Postorthotic 100-m walk times were not significantly different (t = 0.39, P = 0.70) than preorthotic values. Postorthotic pain ratings (mean = 0.7 ± 0.7) for the 100-m walk were significantly less than (Wilcoxon t =1,P < 0.005) preorthotic pain ratings (mean = 3.0 ± 1.7). Postorthotic Foot Function Index pain subsection ratings (Wilcoxon t = 0, P < 0.005) were significantly less than preorthotic ratings, demonstrating a 66% reduction in pain ratings. Postorthotic Foot Function Index disability subsection ratings (Wilcoxon t =0,P < 0.005) were significantly less than preorthotic ratings, demonstrating a 75% reduction in disability ratings.
Conclusion: Custom semirigid foot orthotics may significantly reduce pain experienced during walking and may reduce more global measures of pain and disability for patients with chronic plantar fasciitis.
J Orthop Sports Phys Ther. 2002; 32(4):149–157.
Key Words: heel pain, orthotics, plantar fasciitis
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