Disinhibitory Interventions and Voluntary Quadriceps Activation: A Systematic Review

Objective:

To determine the effects of various therapeutic interventions on increasing voluntary quadriceps muscle activation.

Background:

Decreased voluntary quadriceps activation is commonly associated with knee injury. Recently, research has focused on developing specific disinhibitory interventions to improve voluntary quadriceps activation; yet, it remains unknown which interventions are most effective in promoting this improvement.

Data Sources:

We searched Web of Science from January 1, 1965 through September 27, 2012, using the key words quadriceps activation and transcutaneous electrical nerve stimulation, transcranial magnetic stimulation, cryotherapy, focal joint cooling, joint mobilization, joint mobilisation, joint manipulation, manual therapy, and neuromuscular electrical stimulation.

Study Selection:

Studies evaluating the effect of disinhibitory interventions on volitional quadriceps activation were used in our review. Standardized effect sizes (Cohen d) and 95% confidence intervals (CIs) were calculated from voluntary quadriceps activation means and standard deviations measured at baseline and at all available postintervention time points from each study.

Data Synthesis:

Ten studies were grouped into 5 categories based on intervention type: manual therapy (4 studies), transcutaneous electrical nerve stimulation (2 studies), cryotherapy (2 studies), neuromuscular electrical stimulation (2 studies), and transcranial magnetic stimulation (1 study). Transcutaneous electrical nerve stimulation demonstrated the strongest immediate effects (d = 1.03; 95% CI = 0.06, 1.92) and long-term effects (d = 1.93; 95% CI = 0.91, 2.83). Cryotherapy (d = 0.76; 95% CI = −0.13, 1.59) and transcranial magnetic stimulation (d = 0.54; 95% CI = −0.33, 1.37) had moderate immediate effects in improving voluntary quadriceps activation, whereas manual therapy (d = 0.38; 95% CI = −0.35, 1.09) elicited only weak immediate effects. Neuromuscular electrical stimulation produced weak negative to strong positive effects (range of d values = −0.50 to 1.87) over a period of 3 weeks to 6 months.

Conclusions:

Transcutaneous electrical nerve stimulation demonstrated the strongest and most consistent effects in increasing voluntary quadriceps activation and may be the best disinhibitory intervention for improving the same.Key Words: arthrogenic muscle inhibition, disinhibitory modalities, kneeQuadriceps function is critical for optimal locomotion and energy attenuation in the lower extremity.^1,2 The ability to eccentrically contract the quadriceps is critical for optimal knee range of motion during the weight-acceptance phase of gait.¹ It is hypothesized that patients with quadriceps dysfunction lack the ability to eccentrically contract the quadriceps in an effort to obtain optimal knee range of motion, which is critical for attenuating energy and maintaining proper contact forces at the joint surfaces.³ Physical performance, as demonstrated with the get-up-and-go test, is also impaired in patients with knee injuries,⁴ indicating that concentric quadriceps dysfunction may limit patients'' ability to propel themselves during ambulation. After knee injury, patients often display stiffer knee-movement strategies or less knee flexion during the stance phase of gait, which is thought to alter joint contact forces and increase the risk of joint deterioration.³Quadriceps dysfunction predicts a compound variable of both physical performance and self-reported function⁵ in patients with knee osteoarthritis as well as mortality⁶ in patients with chronic obstructive pulmonary disorder. Osteoarthritis,⁷ total knee arthroplasty,⁸ anterior knee pain,⁹ and anterior cruciate ligament deficiency or reconstruction¹⁰ are examples of knee injuries that present with quadriceps dysfunction, suggesting that proper functioning of this muscle group is critical for patients to maintain an acceptable quality of life with a broad range of conditions.Impaired functioning of this crucial muscle group is thought to arise from central nervous system alterations presenting as decreased motor output of the knee extensors.¹¹ These neural alterations after knee injury often manifest as decreased voluntary quadriceps activation,¹⁰ which can be modulated by altered excitability of spinal reflexive^12,13 and cortical¹⁴ motor pathways. Immediately after knee joint injury, a decrease in voluntary quadriceps activation may be a protective mechanism to prevent further injury.^15–17 However, if these neural abnormalities are not targeted with specific interventions used to disinhibit an inhibited muscle, quadriceps dysfunction may persist and become a factor limiting successful knee-injury management.¹¹Conventional rehabilitation strategies typically focus on strength training to reestablish normal quadriceps function without specifically addressing decreased voluntary quadriceps activation.¹¹ Traditional therapeutic exercise has demonstrated minimal improvements in quadriceps strength and voluntary quadriceps activation¹⁸ and small effects in decreasing pain (standardized mean difference = 0.40) and improving disability (standardized mean difference = 0.37).¹⁹ Because restoring voluntary quadriceps activation predicts the ability to develop quadriceps muscle strength in clinical populations, interventions targeting these activation deficits seem imperative.²⁰ A new rehabilitative paradigm has been proposed that seeks to combine interventions to increase voluntary quadriceps activation with traditional therapeutic exercise to improve clinical outcomes.^11,15,17 Techniques specifically used to alter motor excitability after joint injury for the purpose of improving voluntary quadriceps activation and to enhance therapeutic exercise are termed disinhibitory interventions.¹⁵ Disinhibitory interventions are intended to alter neuromuscular function by targeting mechanoreceptors locally at the injured joint, targeting the peripheral nervous system at points either proximal or distal to the injured joint, or targeting the central nervous system directly.To date, a systematic evaluation of viable interventions that can effectively disinhibit the quadriceps, thus increasing voluntary quadriceps activation, has not been performed. Therefore, the purpose of our study was to investigate the effectiveness of documented disinhibitory interventions for increasing voluntary quadriceps activation. It is imperative to understand the preliminary effects of a variety of disinhibitory interventions as a foundation for further research that will guide future rehabilitative science and improve knee-injury management.     

Quadriceps Activation Following Knee Injuries: A Systematic Review

Context:

Arthrogenic muscle inhibition is an important underlying factor in persistent quadriceps muscle weakness after knee injury or surgery.

Objective:

To determine the magnitude and prevalence of volitional quadriceps activation deficits after knee injury.

Data Sources:

Web of Science database.

Study Selection:

Eligible studies involved human participants and measured quadriceps activation using either twitch interpolation or burst superimposition on patients with knee injuries or surgeries such as anterior cruciate ligament deficiency (ACLd), anterior cruciate ligament reconstruction (ACLr), and anterior knee pain (AKP).

Data Extraction:

Means, measures of variability, and prevalence of quadriceps activation (QA) failure (<95%) were recorded for experiments involving ACLd (10), ACLr (5), and AKP (3).

Data Synthesis:

A total of 21 data sets from 18 studies were initially identified. Data from 3 studies (1 paper reporting data for both ACLd and ACLr, 1 on AKP, and the postarthroscopy paper) were excluded from the primary analyses because only graphical data were reported. Of the remaining 17 data sets (from 15 studies), weighted mean QA in 352 ACLd patients was 87.3% on the involved side, 89.1% on the uninvolved side, and 91% in control participants. The QA failure prevalence ranged from 0% to 100%. Weighted mean QA in 99 total ACLr patients was 89.2% on the involved side, 84% on the uninvolved side, and 98.5% for the control group, with prevalence ranging from 0% to 71%. Thirty-eight patients with AKP averaged 78.6% on the involved side and 77.7% on the contralateral side. Bilateral QA failure was commonly reported in patients.

Conclusions:

Quadriceps activation failure is common in patients with ACLd, ACLr, and AKP and is often observed bilaterally.     

Cross-Education Strength and Activation After Eccentric Exercise

Context:

After injury, eccentric exercise of the injured limb is often contraindicated. Cross-education training, whereby the uninvolved limb is exercised, is an alternative that may improve quadriceps muscle strength and activation in the unexercised limb.

Objective:

To determine the effect of eccentric exercise on quadriceps strength and activation gains in the unexercised limb.

Patients or Other Participants:

Eighteen healthy individuals were randomly assigned to an eccentric training group or a control group.

Intervention(s):

Quadriceps strength and activation measures were collected at preintervention, midintervention, and postintervention. Eccentric training participants exercised their dominant limb with a dynamometer in eccentric mode at 60°/s, 3 times per week for 8 weeks.

Main Outcome Measure(s):

Quadriceps strength was quantified at 30° and 60°/s in concentric and eccentric modes. Quadriceps activation was assessed using the burst superimposition technique and quantified via the central activation ratio. A 2 × 3 repeated-measures analysis of variance was used to detect the effects of group and testing session on quadriceps strength and activation. Where appropriate, post hoc Bonferroni multiple-comparisons procedures were used.

Results:

We found greater eccentric strength in the unexercised limbs of eccentric training participants between preintervention and midintervention and between preintervention and postintervention (preintervention to midintervention: 30°/s P = .05; preintervention to postintervention: 30°/s P = .02, 60°/s P = .02). No differences were noted in concentric strength (P > .05). An overall trend toward greater quadriceps activation in the unexercised knee was detected between preintervention and postintervention (P = .063), with the eccentric training group demonstrating a strong effect (Cohen d = 0.83). Control strength did not change (P > .05).

Conclusions:

Exercising with eccentric actions resulted in mode-specific and velocity-specific gains in quadriceps strength in the unexercised limb. A trend toward greater quadriceps activation in the unexercised knee was noted, suggesting that strength gains may have occurred because of enhanced neural activity. This type of therapy may be a useful addition to rehabilitation programs designed to improve quadriceps strength.Key Words: cross-education training, knee, quadriceps muscle, rehabilitation

Key Points

• Five weeks of eccentric cross-exercise led to consistently stronger eccentric contractions in the unexercised limb.
• A trend toward greater quadriceps muscle activation was detected in the unexercised limb.
• To improve the recovery of quadriceps strength and activation after knee injury, clinicians may be able to use eccentric cross-education as an alternative rehabilitation approach for strengthening the involved limb.

The quadriceps muscle group plays a pivotal role in dynamic stabilization of the knee joint. Consequently, after injury, the restoration of quadriceps function is often central to any knee rehabilitation protocol. However, despite the best efforts of clinicians and researchers to improve rehabilitative techniques, quadriceps weakness often persists long after rehabilitation concludes.^1–3 Given the importance of the quadriceps muscle to knee-joint health, it is critical that rehabilitation approaches that are capable of maximizing postoperative quadriceps function be identified.It has been well established that the potential to improve muscle strength by overloading the tissue is greater with eccentric strengthening than with concentric strengthening.^4,5 Yet the application of early eccentric resistance to the injured or surgical limb is often contraindicated because of the potential for injury to the graft, articular cartilage, or surrounding soft tissue structures.⁶ Although some evidence has recently shown that early eccentric exercise can be used safely post–anterior cruciate ligament (ACL) reconstruction,⁷ the long-term safety and effectiveness of this intervention are unknown. As a result, there is still a clear need to identify a rehabilitative protocol that can be used to safely overload the quadriceps muscle early to induce strength.Cross-education training of the uninvolved limb is an alternative to early eccentric exercise of the involved limb that could potentially improve quadriceps function post–knee injury. Cross-education describes the ability of exercise of 1 limb to cause an increase in strength of the contralateral unexercised limb.⁸ Protocols using cross-education have been shown to successfully improve quadriceps strength in the limbs of healthy, uninjured participants.^9–11 Although the exact mechanism of cross-education has yet to be identified, the strength gains that are produced in the unexercised limb are thought to occur as a result of alterations in neural activity.^12,13 Because deficits in quadriceps strength after injury are hypothesized to occur, in part from alterations in quadriceps activation,¹⁴ identifying if cross-education training can improve quadriceps activation could help researchers to develop targeted interventions for populations with volitional muscle-activation failure.To date, limited evidence shows that gains in quadriceps strength in the unexercised limb of healthy individuals can be improved through an eccentric exercise protocol,^10,11 and we are unaware of any data that document the effectiveness of a single-legged eccentric exercise protocol on volitional quadriceps muscle activation in the unexercised leg. Recent authors¹⁵ have shown that eccentric exercise in the ACL-reconstructed limb at 9 months after surgery improves quadriceps muscle activity, warranting further questioning as to whether or not eccentric training results in neuromuscular gains of the unexercised limb after cross-education training. Also, if greater quadriceps strength and muscle activation can be achieved with an eccentric training protocol in the unexercised limb of healthy individuals, future investigators may be able to use this training protocol with populations in whom eccentric exercise in the injured limb may be contraindicated (eg, meniscal injury or repair, acute quadriceps injury, ACL injury, total knee arthroplasty). Therefore, the primary purpose of our study was to determine the cross-education benefits of a single-legged eccentric exercise program on quadriceps muscle strength and activation of the unexercised limb in a healthy population. A secondary objective was to determine the dose of eccentric exercise necessary to elicit quadriceps strength and activation gains in the unexercised knee.     

Explosive Quadriceps Strength Symmetry and Landing Mechanics Limb Symmetry After Anterior Cruciate Ligament Reconstruction in Females

ContextEmerging evidence suggests that a lower quadriceps rate of torque development (RTD) after anterior cruciate ligament (ACL) reconstruction (ACLR) may be associated with altered landing mechanics. However, the influence of quadriceps RTD magnitude and limb symmetry on landing mechanics limb symmetry remains unknown.ObjectiveTo assess the influence of quadriceps RTD magnitude and limb symmetry on limb symmetry in sagittal-plane landing mechanics during functional landing tasks in females with or without ACLR.DesignCross-sectional study.SettingLaboratory.Patients or Other ParticipantsA total of 19 females with ACLR (age = 19.21 ± 1.81 years, height = 164.12 ± 6.97 cm, mass = 63.79 ± 7.59 kg, time after surgery = 20.05 ± 9.50 months) and 19 females serving as controls (age = 21.11 ± 3.28 years, height = 167.26 ± 7.26 cm, mass = 67.28 ± 9.25 kg).Main Outcome Measure(s)Landing mechanics were assessed during a double-legged (DL) jump-landing task, a single-legged jump-landing task, and a side-cutting task. Quadriceps RTD was collected during isometric muscle contractions. Separate stepwise multiple linear regression models were used to determine the variance in limb symmetry in the sagittal-plane knee moment at initial contact, peak vertical ground reaction force, and loading rate that could be explained by quadriceps RTD magnitude or limb symmetry, group (ACLR or control), and their interaction.ResultsIn the ACLR group, greater limb symmetry in quadriceps RTD was associated with greater symmetry in sagittal-plane knee moment at initial contact during the DL task (P = .004). Peak vertical ground reaction force and loading rate could not be predicted by quadriceps RTD magnitude or limb symmetry, group, or their interaction during any task.ConclusionsDeveloping greater symmetry but not magnitude in quadriceps RTD likely enabled more symmetric sagittal-plane knee landing mechanics during the DL task in the ACLR group and thus may reduce the risk of a second ACL injury. Such a protective effect was not found during the single-legged or side-cutting tasks, which may indicate that these tasks do not allow for the compensatory landing mechanism of shifting load to the uninvolved limb that was possible during the DL task.     

Gait Biomechanics in Individuals Meeting Sufficient Quadriceps Strength Cutoffs After Anterior Cruciate Ligament Reconstruction

ContextQuadriceps weakness is associated with disability and aberrant gait biomechanics after anterior cruciate ligament reconstruction (ACLR). Strength-sufficiency cutoff scores, which normalize quadriceps strength to the mass of an individual, can predict who will report better function after ACLR. However, whether gait biomechanics differ between individuals who meet a strength-sufficiency cutoff (strong) and those who do not (weak) remains unknown.ObjectiveTo determine whether vertical ground reaction force, knee-flexion angle, and internal knee-extension moment differ throughout the stance phase of walking between individuals with strong and those with weak quadriceps after ACLR.DesignCase-control study.SettingLaboratory.Patients or Other ParticipantsIndividuals who underwent unilateral ACLR >12 months before testing were dichotomized into strong (n = 31) and weak (n = 116) groups.Main Outcome MeasuresMaximal isometric quadriceps strength was measured at 90° of knee flexion using an isokinetic dynamometer and normalized to body mass. Individuals who demonstrated maximal isometric quadriceps strength ≥3.0 N·m·kg⁻¹ were considered strong. Three-dimensional gait biomechanics were collected at a self-selected walking speed. Biomechanical data were time normalized to 100% of stance phase. Vertical ground reaction force was normalized to body weight (BW), and knee-extension moment was normalized to BW × height. Pairwise comparison functions were calculated for each outcome to identify between-groups differences for each percentile of stance.ResultsVertical ground reaction force was greater in the weak group for the first 22% of stance (peak mean difference [MD] = 6.2% BW) and less in the weak group between 36% and 43% of stance (MD = 1.4% BW). Knee-flexion angle was greater (ie, more flexion) in the strong group between 6% and 52% of stance (MD = 2.3°) and smaller (ie, less flexion) between 68% and 79% of stance (MD = 1.0°). Knee-extension moment was greater in the strong group between 7% and 62% of stance (MD = 0.007 BW × height).ConclusionsIndividuals with ACLR who generated knee-extension torque ≥3.0 N·m·kg⁻¹ exhibited different biomechanical gait profiles than those who could not. More strength may allow for better energy attenuation after ACLR.     

Increased Contact Time and Strength Deficits in Runners With Exercise-Related Lower Leg Pain

ContextExercise-related lower leg pain (ERLLP) is common in runners.ObjectiveTo compare biomechanical (kinematic, kinetic, and spatiotemporal) measures obtained from wearable sensors as well as lower extremity alignment, range of motion, and strength during running between runners with and those without ERLLP.DesignCase-control study.SettingField and laboratory.Patients or Other ParticipantsOf 32 young adults who had been running regularly (>10 mi [16 km] per week) for ≥3 months, 16 had ERLLP for ≥2 weeks and 16 were healthy control participants.Main Outcome Measure(s)Both field and laboratory measures were collected at the initial visit. The laboratory measures consisted of alignment (arch height index, foot posture index, navicular drop, tibial torsion, Q-angle, and hip anteversion), range of motion (great toe, ankle, knee, and hip), and strength. Participants then completed a 1.67-mi (2.69-km) run along a predetermined route to calibrate the RunScribe devices. The RunScribe wearable sensors collected kinematic (pronation excursion and maximum pronation velocity), kinetic (impact g and braking g), and spatiotemporal (stride length, step length, contact time, stride pace, and flight ratio) measures. Participants then wore the sensors during at least 3 training runs in the next week.ResultsThe ERLLP group had a slower stride pace than the healthy group, which was accounted for as a covariate in subsequent analyses. The ERLLP group had a longer contact time during the stance phase of running (mean difference [MD] = 18.00 ± 8.27 milliseconds) and decreased stride length (MD = −0.11 ± 0.05 m) than the control group. For the clinical measures, the ERLLP group demonstrated increased range of motion for great-toe flexion (MD = 13.9 ± 4.6°) and ankle eversion (MD = 6.3 ± 2.7°) and decreased strength for ankle inversion (MD = −0.49 ± 0.23 N/kg), ankle eversion (MD = −0.57 ± 0.27 N/kg), and hip flexion (MD = −0.99 ± 0.39 N/kg).ConclusionsThe ERLLP group exhibited a longer contact time and decreased stride length during running as well as strength deficits at the ankle and hip. Gait retraining and lower extremity strengthening may be warranted as clinical interventions in runners with ERLLP.     

Quadriceps H-reflex modulation during pedaling

The main aims of this study were 1) to investigate possible phase-, speed-, and task-dependent changes in the quadriceps H-reflex during pedaling, and to achieve this, 2) to develop an optimized H-reflex recording and processing procedure for recording of quadriceps H-reflexes during movement. It was hypothesized that the behavior of the quadriceps H-reflex concerning phase, speed, and task dependency corresponds to the behavior of the soleus H-reflex during rhythmical leg movements. The applied H-reflex procedure appeared to be reliable for obtaining the quadriceps H-reflex modulation during leg movement. The vastus lateralis (VL) and rectus femoris (RF) H-reflexes showed a phase-dependent modulation during pedaling at a frequency of 80 rpm with almost parallel changes in the reflex amplitude and motor recruitment level. However, when the speed of movement was reduced from 80 to 40 revolutions per minute (rpm) and crank load simultaneously increased (i.e., a halving of the movement speed with a constant motor recruitment level), the quadriceps H-reflex modulation pattern changed significantly in relation to the pattern of motor recruitment, i.e., at 40 rpm, the reflex excitability remained high during a gradual derecruitment during power generation in downstroke. Comparison of the "operationally defined H-reflex gain function" obtained during 1) pedaling at 80 rpm and 2) isometric quadriceps contractions in sitting position showed no significant task-dependent changes in the quadriceps H-reflex. Consequently, the hypothesis was only partly corroborated, and the findings indicate differences in the neural control of the soleus and the quadriceps muscle during rhythmical movements.     

Topology of EEG Coherence Changes May Reflect Differential Neural Network Activation in Cold and Pain Perception

Pain perception in the brain can be analyzed by neuroimaging (PET, fMRI) and electrophysiological parameter mapping (EEG, ERP/MEG, MEF). These studies have generally been focused on the localization of cerebral activation. Whether pain can be conceptualized as localized function or best be understood by distributed function is important to the theory of human pain processing in the brain. Here, we report that cold and pain perception in the brain is characterized by webs of EEG coherence changes which may reflect coupling or de-coupling of different cortical areas during cold and pain processing. EEG was recorded during cold and pain perception (right hand immersion in 15°C cool-water vs. 0.3°C ice-water for 3 min.) with eyes opened. Subjects rated the cold perception at 2.3 (cool to cold, but no pain) and the pain perception at 6.7 (moderate-strong pain) in a 1-10 scale. The obtained EEG spectral parameters were compared with the corresponding parameters of the resting baseline using paired Wilcoxon tests in the sense of statistical filters to depict those differences which differ clearly from changes by chance. The results were presented in probability maps. The EEG results indicated highly differential coherence networks between cold and pain perception. The cold perception was characterized as decreased coherence in the theta band mainly between frontal electrodes and increased interhemispheric coherence in the alpha range mainly between central and frontal positions. During pain perception almost no coherence changes in the theta band were observed, but great coherence increase in the delta band between central, parietal and frontal electrodes. The network of coherence changes in the alpha band showed strong involvement of electrode C3 concerning coherence increases with frontal positions. In the beta-1 band coherence increase within the left hemisphere was much more pronounced during pain than during cold. The differential characteristics of EEG coherence changes based on neural networks and their spatial organization in the neocortex indicate the distributed brain processing between cold and pain perception in man. This study may contribute to our understanding of the large scale neural networks in cognition based on neurophysiological binding hypothesis and network connections of neural ensembles.     

太极拳转体动作中下肢关节活动顺序性和肌肉力表现及肌肉激活特征

目的 分析太极拳转体与弓步动作中下肢关节活动顺序性、肌肉力表现和肌肉激活程度的差异,揭示太极拳转体动作的特征。 方法 募集 20 名练习时长超过 3 年的健康太极拳练习者,采用三维运动捕捉系统、测力台和表面肌电同步采集转体与弓步两种动作运动学、动力学和肌肉激活信息,并通过 OpenSim 仿真软件获取下肢肌力。结果 与弓步相比,转体动作髋、踝关节外旋幅度显著增大;膝关节外展和外旋力矩显著增大,股二头肌、半腱肌和内外侧腓肠肌峰值肌力显著增强,股二头肌、内外侧腓肠肌峰值肌力时刻显著提前,而股内外侧肌和胫骨前肌峰值肌力显著减小,胫骨前肌肌力最早达到峰值;股二头肌、股内外侧肌和内侧腓肠肌的平均激活水平和激活时间显著增加。 结论 太极拳转体动作由踝、髋关节依次转动组成,肌肉力表现的独特性在于重心两次转移致使支撑腿内外侧肌力曲线呈双峰型,因为全足着地延迟方式引发了腓肠肌与股四头肌激活顺序和肌肉平均激活水平改变。研究结果提示全足着地延迟方式具有调节肌肉激活顺序的作用,合理利用有助于提升临床康复效果。     

Quadriceps muscle function characteristics in severely obese and nonobese adolescents

The purpose of this cross-sectional study was to compare quadriceps muscle strength and fatigue between severely obese (body mass index 34 kg/m²) and nonobese adolescents. Maximal isokinetic torque and angle of peak torque as well as isometric torque at short (40° of knee flexion) and long (80° of knee flexion) muscle length were measured using an isokinetic dynamometer. Muscle fatigue was quantified as the percent torque loss during an isokinetic voluntary protocol and an electrical stimulation isometric protocol. Obese adolescents produced greater absolute isokinetic (+16%; P < 0.05) and isometric torque at short (+25%; P < 0.01) but not at long muscle length (P > 0.05) compared to their lean counterparts. The angle of peak torque was significantly lower in obese than in nonobese subjects (−11%; P < 0.05), i.e., obese produced their maximal strength at shorter muscle length. Isokinetic and isometric torque normalized to the fat-free mass were not significantly different between the two groups. No significant difference in voluntary and stimulated torque loss was observed between groups. Muscle strength per unit of fat-free mass and muscle fatigue were similar in the obese and nonobese adolescents tested in this study, therefore suggesting that obesity has little or no effect on quadriceps muscle function characteristics. On the other hand, it remains to be confirmed whether the observed quadriceps muscle length specificity contributes to the reduced functional capacity of obese adolescents during complex motor tasks involving deep knee flexion (squatting, kneeling).     

Isokinetic Hamstrings:Quadriceps Ratios in Intercollegiate Athletes

OBJECTIVE: To compare the differences in the concentric hamstrings:quadriceps (H:Q) ratio among athletes in different sports at 3 velocities. DESIGN AND SETTING: We measured the H:Q ratio of both knees using the Biodex Pro Isokinetic Device. SUBJECTS: Eighty-one male and female collegiate athletes. MEASUREMENTS: We performed analyses for sport, velocity, and side of body for each sex. To compare the means of the concentric H:Q ratios for mean peak torque and mean total work, a 2 x 3 x 4 mixed-factorial analysis of variance was computed for women and a 2 x 2 x 3 mixed-factorial analysis of variance was computed for men. RESULTS: We observed no significant interactions for men and women for the concentric H:Q ratio for mean peak torque. There was a significant mean difference among velocity conditions and a significant difference for men with respect to velocity. No significant differences were found for side of body or sport. CONCLUSIONS: The H:Q ratio increased as velocity increased. No differences existed for the H:Q ratio for sport or side of body.     

Quadriceps augmentation of undersized hamstrings during ACL reconstruction

Background

Double hamstring autograft for anterior cruciate ligament (ACL) reconstruction is a well-established graft option; however, a major concern with this method arises when the prepared graft is too small. Resorting to allograft can be a solution to this problem, but some surgeons prefer to use autograft in particular situations and some patients may refuse allograft. We investigate the merits of using autogenous quadriceps tendons to augment the insufficient hamstrings and compare the autograft composite graft to a standard hamstrings graft of equal size.

Effusion cytology in burkitt's lymphoma

The American form of Burkitt's lymphoma is a high-grade malignancy which usually involves the abdomen in children and young adults. There is only a limited literature which describes the cytologic features of Burkitt's lymphoma in serous effusions. We present three children with Burkitt's lymphoma initially diagnosed by effusion cytology. the first patient, an 11-yr-old boy, presented with bilateral pleural effusions, ascites, and abdominal masses and had diagnostic pleural fluid cytology without tissue confirmation (ultrastructural examination was performed on the effusion specimen). He died 7 months after the initial diagnosis. the second patient, a 9-yr-old boy, presented with ascites and abdominal masses and had diagnostic peritoneal fluid cytology with a subsequent confirmatory chest wall biopsy. the third patient, a 16-yr-old girl, presented with a 2-month history of irregular menses, a large pelvic mass, lymphadenopathy, and liver masses. Although an ovarian malignancy was clinically suspected, cytologic examination of her peritoneal fluid revealed Burkitt's lymphoma. Surgical exploration revealed involvement of her right ovary, cecum, and terminal ileum. the second and third patients are currently alive with no apparent disease following chemotherapy. in all three patients, effusion cytology revealed Burkitt's lymphoma, characterized by a uniform population of noncohesive lymphoid cells with noncleaved nuclei, prominent multiple nucleoli, and scanty-to-moderate basophilic cytoplasm. Cytoplasmic and/or nuclear vacuoles were also seen, more prominent in Diff-Quik—stained, air-dried smears. These cases demonstrate the importance of recognizing the cytologic features of Burkitt's lymphoma, as serous fluid may be the initial diagnostic specimen.     

Effusion cytology of epithelioid rhabdomyosarcoma

We report a case of epithelioid rhabdomyosarcoma in a pleural effusion. In contrast to most rhabdomyosarcomas in effusions, the cells presented as cohesive clusters of atypical cells with abundant eosinophilic cytoplasm which mimicked an adenocarcinoma. Immunohistochemistry was positive for epithelial membrane antigen and muscle markers and negative for keratins.     

Association of Quadriceps and Hamstrings Cocontraction Patterns With Knee Joint Loading

Context:

Sex differences in neuromuscular control of the lower extremity have been identified as a potential cause for the greater incidence of anterior cruciate ligament (ACL) injuries in female athletes compared with male athletes. Women tend to land in greater knee valgus with higher abduction loads than men. Because knee abduction loads increase ACL strain, the inability to minimize these loads may lead to ACL failure.

Objective:

To investigate the activation patterns of the quadriceps and hamstrings muscles with respect to the peak knee abduction moment.

Design:

Cross-sectional study.

Setting:

Neuromuscular research laboratory.

Patients or Other Participants:

Twenty-one recreationally active adults (11 women, 10 men).

Main Outcome Measure(s):

Volunteers performed 3 trials of a 100-cm forward hop. During the hop task, we recorded surface electromyographic data from the medial and lateral hamstrings and quadriceps and recorded lower extremity kinematics and kinetics. Lateral and medial quadriceps-to-hamstrings (Q∶H) cocontraction indices, the ratio of medial-to-lateral Q∶H cocontraction, normalized root mean square electromyographic data for medial and lateral quadriceps and hamstrings, and peak knee abduction moment were calculated and used in data analyses.

Results:

Overall cocontraction was lower in women than in men, whereas activation was lower in the medial than in the lateral musculature in both sexes (P < .05). The medial Q∶H cocontraction index (R²  =  0.792) accounted for a significant portion of the variance in the peak knee abduction moment in women (P  =  .001). Women demonstrated less activation in the vastus medialis than in the vastus lateralis (P  =  .49) and less activation in the medial hamstrings than in the lateral hamstrings (P  =  .01).

Conclusions:

Medial-to-lateral Q∶H cocontraction appears to be unbalanced in women, which may limit their ability to resist abduction loads. Because higher abduction loads increase strain on the ACL, restoring medial-to-lateral Q∶H cocontraction balance in women may help reduce ACL injury risk.     

膝关节以不同速度作等动运动时股四头肌的生物力学分析

本文用ＣＹＢＥＸ等动测试系统测试和分析了膝关节在不同的角度下作等动伸膝时股四头肌的力矩，功，功率。本文结果表明膝关节以不同的速度作等动伸屈运动时，在０至６０度／秒范围内股四头肌收缩力矩有上升趋势，既而下降。股四头肌收缩功率随速度的增大而增大，但在２４０至３００度／秒范围内有下降趋势。由此可知膝关节运动在超出一定的正常生理范围时不利于正常的生物力学功能的发挥。并用数学模型模拟了股四头肌伸膝时力矩随速     

胸腹腔积液中肿瘤标志物联检对鉴别良、恶性的价值

目的：探讨胸腹腔积液中肿瘤标志物联检对鉴别良、恶性的价值,并与细胞学检查进行对照。方法：对92例恶性胸腔积液及78例恶性腹腔积液标本均作了6项肿瘤标志物的检测与细胞学检查,其中CA50用放免法,其余CA125,CA15-3,CYFRA21-1,βHCG,HCG均采用电化学发光法。结果：6项肿瘤标志物检测中,以CA125阳性率为最高,其他依次为CA50〉CA15-3〉CYFRA21-1〉β-HCG〉HCG。其中HCG及βHCG虽然阳性率较低,但几乎没有假阳性,故仍具有采用价值。以二项标志物联检,则首选CA125＋CYFRA21-1或CA125＋CA50,最为敏感。如有高度怀疑不决时,下列标准对提示恶性可供参考。①四项CA中二项阳性者;②一项CA＋βHCG或HCG阳性者;③βHCG及HCG均阳性者。肿瘤标志物检测对细胞学检查可疑者可为互补。结论：胸腹腔积液中肿瘤标志物联检对确立恶性诊断殊有帮助。     

胸腹水粘度测定的实验研究

目的 :探讨胸水与腹水粘度测定的可行性及临床意义。方法 :使用锥板式粘度仪 ,对胸腹水进行三种切变率 ( 2 0s- 1 、40s- 1 、80s- 1 )下的粘度进行测定。结果 :胸腹水的成分符合粘度测定的要求 ,即具有非牛顿流体的特性。结论 :胸腹水粘度测定对胸腹水性质的判定及对临床观察治疗有积极意义。