Evaluating the relationship between quadriceps muscle quality captured using ultrasound with clinical severity in women with knee osteoarthritis

BackgroundInfiltration of muscle with non-lean tissue, such as fat, reduces muscle quality. Ultrasound captures muscle quality through measurement of echogenicity. Given the potential implications of quadriceps muscle quality on physical function, particularly in knee osteoarthritis, the purpose of this study was to investigate the relationship between echogenicity, muscle thickness and subcutaneous fat thickness with the clinical severity of osteoarthritis.MethodsThirty-one women with clinical knee osteoarthritis participated. Rectus femoris and vastus lateralis echogenicity, muscle thickness and subcutaneous fat thickness were measured from ultrasound images of the most symptomatic knee. Clinical severity of osteoarthritis was characterized with pain, self-reported function, six-minute walk test, and knee extensor strength. Correlation coefficients were calculated between muscle and fat architecture outcomes (muscle quality, muscle and fat thicknesses) and osteoarthritis clinical severity outcomes.FindingsData from 25 women were of sufficient quality for analysis. Echogenicity (muscle quality) related to the six-minute walk test for both rectus femoris (r = −0.52, p = 0.02) and vastus lateralis (r = −0.74, p = 0.004), with poorer muscle quality related to lower mobility. Subcutaneous fat thickness was related to the six-minute walk test (rectus femoris, r = −0.61, p = 0.0012; vastus lateralis, r = −0.73, p = 0.003) and strength (rectus femoris, r = −0.46, p = 0.02; vastus lateralis, r = −0.59, p = 0.03). Muscle thickness was not related to any severity outcomes.InterpretationMuscle quality, rather than thickness, is associated with mobility performance in women with knee osteoarthritis. Thus, interventions for osteoarthritis that specifically target muscle quality, rather than size, should be explored.     

Ankle strength impairments associated with knee osteoarthritis

BackgroundKnee Osteoarthritis seems to negatively impact ankle biomechanics. However, the effect of knee osteoarthritis on ankle muscle strength has not been clearly established. This study aimed to evaluate the ankle strength of the plantar flexors and dorsiflexors of patients with knee osteoarthritis in different degrees of severity.MethodsThirty-seven patients with knee osteoarthritis and 15 controls, subjected to clinical and radiographic analysis, were divided into three groups: control, mild, and moderate knee osteoarthritis. Participants answered a self-reported questionnaire and accomplished a muscle torque assessment of the ankle using the Biodex dynamometer in isometric, concentric and eccentric modes.FindingsThe mild osteoarthritis group (peak torque = 26.85(SD 3.58)) was significantly weaker than the control (peak torque = 41.75(SD 4.42)) in concentric plantar flexion (P < 0.05). The control and mild osteoarthritis groups were not significantly different from the moderate osteoarthritis group (peak torque = 36.12(SD 4.61)) in concentric plantar flexion. There were no significant differences for dorsiflexion among the groups; however the control and moderate osteoarthritis groups presented large and medium standardized mean differences. The mild osteoarthritis group was significantly lower than the control and moderate osteoarthritis groups in the concentric plantar flexion by concentric dorsiflexion torque ratio.InterpretationAnkle function exhibited impairments in patients with knee osteoarthritis, especially in the plantar flexion torque, in which the mild osteoarthritis group was weaker than the control. Interestingly, patients with moderate knee osteoarthritis showed results similar to the control group in plantar flexion torque. The results raise the possibility of a compensatory mechanism of the plantar flexors developed by patients in more advanced degrees to balance other muscle failures.     

Association Between Knee Joint Muscle Activation and Knee Joint Moment Patterns During Walking in Moderate Medial Compartment Knee Osteoarthritis: Implications for Secondary Prevention

ObjectiveTo determine associations between knee moment features linked to osteoarthritis (OA) progression, gait muscle activation patterns, and strength.DesignCross-sectional secondary analysis.SettingGait laboratory.ParticipantsConvenience sample of 54 patients with moderate, medial knee OA (N=54).InterventionsNone.Main Outcome MeasuresKnee moments and quadriceps and hamstrings activation were examined during walking. Knee extensor and flexor strength were measured. Waveform patterns were extracted using principal component analysis. Each measured waveform was scored against principal components (PCs) that captured overall magnitude (PC1) and early to midstance difference (PC2) features, with higher PC2 scores interpreted as greater moment differential and more prolonged muscle activity. Correlations were calculated between moment PC scores and muscle PC and strength scores. Regression analyses determined moment PC score variance explained by muscle PC scores and strength.ResultsAll correlations for knee adduction moment difference feature (KAMPC2) and prolonged muscle activity (PC2) were significant (r=−0.40 to −0.54). Knee flexion moment difference feature (KFMPC2) was significantly correlated with all quadriceps and medial hamstrings PC2 scores (r=−0.47 to −0.61) and medial hamstrings magnitude feature (PC1) (r=−0.52). KAMPC2 was significantly correlated with knee flexor strength (r=0.43), and KFMPC2 was significantly correlated with knee extensor (r=0.60) and flexor (r=0.55) strength. Regression models including muscle PC2 scores and knee flexor strength explained 46% of KAMPC2 variance, whereas muscle PC2 scores and knee extensor strength explained 59% of KFMPC2 variance.ConclusionsMuscle activation patterns and strength explained significant variance in moment difference features, highest for the knee flexion moment. This supports that exercises such as neuromuscular training, focused on appropriate muscle activation patterns, and strengthening have the potential to alter dynamic loading gait patterns associated with knee OA clinical progression.     

Effect of gender on strength gains after isometric exercise coupled with electromyographic biofeedback in knee osteoarthritis: A preliminary study

ObjectiveThe objective of this trial was to evaluate the effect of gender on strength gains after five week training programme that consisted of isometric exercise coupled with electromyographic biofeedback to the quadriceps muscle.Materials and methodsForty-three (20 men and 23 women) patients with knee osteoarthritis (OA), were placed into two groups based on their gender. Both groups performed isometric exercise coupled with electromyographic biofeedback for five days a week for five weeks.ResultsBoth groups reported gains in muscle strength after five week training. However, the difference was found to be statistically insignificant between the two groups (P = 0.224).ConclusionThe results suggest that gender did not affect gains in muscle strength by isometric exercise coupled with electromyographic biofeedback in patients with knee OA.     

Impact loading following quadriceps strength training in individuals with medial knee osteoarthritis and varus alignment

BackgroundGreater impact loading at initial contact is postulated to play a role in the progression of osteoarthritis. Quadriceps weakness is common in individuals with knee osteoarthritis and may contribute to high impact loading. The purpose of this study was to examine the effects of quadriceps strengthening on impact loading parameters.MethodsData from 97 individuals with knee osteoarthritis who participated in a randomized clinical trial examining effects of a 12-week quadriceps strengthening program was used to conduct this secondary exploratory analysis. Participants completed a three-dimensional gait assessment within 10% of 1.0 m/s from which maximum rate of loading (Body Weight/second), average rate of loading (Body Weight/second), and peak vertical ground reaction force during early stance (Body Weight) were determined. Peak isometric quadriceps strength (Nm/kg) was also assessed.FindingsThere was a significant increase in quadriceps strength in the training group (mean change (95%CI): 0.35(0.25, 0.045) Nm/kg, P = 0.01) with no change in the control group (mean change (95%CI): 0.03(− 0.39, 0.45) Nm/kg, P > 0.05). There were no changes in impact loading variables. With data from both groups combined, changes in quadriceps strength explained 3% of variance in the change in maximum rate of loading. Change in quadriceps strength was not predictive of the change in peak vertical ground reaction force or average rate of loading.InterpretationsWhile change in strength was predictive of change in maximal loading rate, this explained only a small proportion of the variance. Future research examining the role parameters such as neuromuscular control play in impact loading are warranted.     

Muscle imbalance and reduced ankle joint motion in people with hammer toe deformity

BackgroundMultiple factors may contribute to hammer toe deformity at the metatarsophalangeal joint. The purposes of this study were to (1) compare the ratio of toe extensor/flexor muscle strength in toes 2–4 among groups with and without hammer toe deformity, (2) to determine correlations between the ratio of toe extensor/flexor muscle strength in toes 2–4, and metatarsophalangeal joint deformity (3) to determine if other clinical measures differ between groups and if these measures are correlated with metatarsophalangeal joint angle.MethodsTwenty-seven feet with visible hammer toe deformity and 31 age matched feet without hammer toe deformity were tested. Toe muscle strength was measured using a dynamometer and the ratio of toe extensor muscle strength to flexor muscle strength was calculated. Metatarsophalangeal joint angle was measured from a computerized tomography image. Ankle and subtalar joint range of motion, and tibial torsion were measured using goniometry.FindingsExtensor/flexor toe muscle strength ratio was 2.3–3.0 times higher in the hammer toe group compared to the non-hammer toe group, in toes 2–4. The ratios of extensor/flexor toe muscle strength for toes 2–4 and metatarsophalangeal joint angle were highly correlated (r = 0.69 ? 0.80). Ankle dorsiflexion and metatarsophalangeal joint angle were negatively correlated for toes 2–4 (r = ?0.38 to ?0.56) as were eversion and metatarsophalangeal joint angle.InterpretationThese results provide insight into potential risk factors for the development of hammer toe deformity. Additional research is needed to determine the causal relationship between hammer toe deformity and the ratio of toe extensor/flexor muscle strength in toes 2–4.     

Effects of a low-intensity dynamic-resistance training protocol using an isokinetic dynamometer on muscular strength and aerobic capacity after coronary artery bypass grafting

ObjectiveStudy the effect of muscle strength training on muscle strength, maximal oxygen uptake (VO₂max), hemodynamic and anthropometric parameters as well as quality of life after coronary artery bypass grafting (CABG).MethodsAfter CABG surgery, 32 patients were randomized into two groups. The first group was to perform aerobic-type training with a cycle ergometer (AT = 16). The second group was to perform low-intensity muscle strength training of the quadriceps and hamstrings using an isokinetic dynamometer (i.e. 20 to 30% of peak torque) (ST = 16). Before and after the strength training program we conducted a stress test, evaluation of isokinetic force production, 6-minute walking test, body impedance analysis (BIA) and SF-36 quality of life test.ResultsCompared to the AT group, the ST group showed better results with improved quadriceps strength (48.2% vs. 8.2%), VO₂max (P < .001) and diastolic blood pressure at rest (P = 0.01). Quality of life improved in both groups.ConclusionThe dynamic-resistance muscle strength training protocol using isokinetic dynamometer can safely (i.e. without clinical symptoms or changes to the ECG and arterial blood pressure) improve muscle strength and VO₂max without any major risks in patients post-CABG. These findings should encourage additional studies to validate the relevance of these strength training modalities in rehabilitation centers.     

The immediate effects of foot orthoses on hip and knee kinematics and muscle activity during a functional step-up task in individuals with patellofemoral pain

BackgroundEvidence shows that anti-pronating foot orthoses improve patellofemoral pain, but there is a paucity of evidence concerning mechanisms. We investigated the immediate effects of prefabricated foot orthoses on (i) hip and knee kinematics; (ii) electromyography variables of vastus medialis oblique, vastus lateralis and gluteus medius during a functional step-up task, and (iii) associated clinical measures.MethodsHip muscle activity and kinematics were measured during a step-up task with and without an anti-pronating foot orthoses, in people (n = 20, 9 M, 11 F) with patellofemoral pain. Additionally, we measured knee function, foot posture index, isometric hip abductor and knee extensor strength and weight-bearing ankle dorsiflexion.FindingsReduced hip adduction (0.82°, P = 0.01), knee internal rotation (0.46°, P = 0.03), and decreased gluteus medius peak amplitude (0.9 mV, P = 0.043) were observed after ground contact in the ‘with orthoses’ condition. With the addition of orthoses, a more pronated foot posture correlated with earlier vastus medialis oblique onset (r = − 0.51, P = 0.02) whilst higher Kujala scores correlated with earlier gluteus medius onset (r = 0.52, P = 0.02).InterpretationAlthough small in magnitude, reductions in hip adduction, knee internal rotation and gluteus medius amplitude observed immediately following orthoses application during a task that commonly aggravates symptoms, offer a potential mechanism for their effectiveness in patellofemoral pain management. Given the potential for cumulative effects of weight bearing repetitions completed with a foot orthoses, for example during repeated stair ascent, the differences are likely to be clinically meaningful.     

The role of knee joint moments and knee impairments on self-reported knee pain during gait in patients with knee osteoarthritis

BackgroundThe association between high mechanical knee joint loading during gait with onset and progression of knee osteoarthritis has been extensively studied. However, less attention has been given to risk factors related to increased pain during gait. The purpose of this study was to evaluate knee joint moments and clinical characteristics that may be associated with gait-related knee pain in patients with knee osteoarthritis.MethodsSixty-seven participants with knee osteoarthritis were stratified into three groups of no pain (n = 18), mild pain (n = 27), or moderate/severe pain (n = 22) based on their self-reported symptoms during gait. All participants underwent three-dimensional gait analysis. Quadriceps strength, knee extension range of motion, radiographic knee alignment and self-reported measures of global pain and function were also quantified.FindingsThe moderate/severe pain group demonstrated worse global pain (P < 0.01) and physical function scores (P < 0.01) compared to the no pain and the mild pain groups. The moderate/severe pain group also walked with greater knee flexion moments during the midstance phase of gait compared to the no pain group (P = 0.02). Additionally, the moderate/severe pain group demonstrated greater varus knee malalignment (P = 0.009), which was associated with higher weight acceptance peak knee adduction moments (P = 0.003) and worse global pain (P = 0.003) and physical function scores (P = 0.006).InterpretationGreater knee flexion moment is present during the midstance phase of gait in patients with knee osteoarthritis and moderate/severe pain during gait. Additionally, greater varus malalignment may be a sign of increased global knee joint dysfunction that can influence many activities of daily living beyond gait.     

The influence of isokinetic peak torque and muscular power on the functional performance of active and inactive community-dwelling elderly: a cross-sectional study

ObjectiveTo verify the importance of the isokinetic muscular torque and power of knee extensors and flexors on the functional performance of active and inactive elderly women.MethodsA cross-sectional observational study was conducted with 116 community-dwelling women (≥60 years old) without severe cognitive and/or motor dysfunction. Isokinetic muscle function was measured by peak torque and muscle power at 60°/s (5 repetitions) and 180°/s (15 repetitions), respectively. Mobility was evaluated by means of the Timed Up and Go test (TUG) and the Habitual Gait Speed (HGS) test. Balance was evaluated via the alternate step and semitandem tests. Lower limb strength was assessed using the Sit-to-stand test. Univariate and multivariate logistic regression analysis was used to determine association between independent and dependent variables (α = 0.05).ResultActive elderly women had better muscle function and functional performance than inactive elderly women for almost all variables. Peak torque and muscular power of knee extensor muscles explained the dynamic balance, mobility, and lower limb strength among inactive elderly women (OR: 0.89–0.95; p < 0.05). Muscular power of knee flexors influenced tasks that required mobility and lower limb strength among active elderly (OR: 0.82–0.87; p < 0.05).ConclusionsThe muscular power of knee flexors was shown to be more important for the functional performance of active elderly women. The muscular power of knee extensors had a stronger influence on the performance of the inactive elderly women.     

Is synergistic organisation of muscle coordination altered in people with lateral epicondylalgia? A case–control study

BackgroundLateral epicondylalgia is a common musculoskeletal disorder and is associated with deficits in the motor system including painful grip. This study compared coordination of forearm muscles (muscle synergies) during repeated gripping between individuals with and without lateral epicondylalgia.MethodsTwelve participants with lateral epicondylalgia and 14 controls performed 15 cyclical repetitions of sub-maximal (20% maximum grip force of asymptomatic arm), pain free dynamic gripping in four arm positions: shoulder neutral with elbow flexed to 90° and shoulder flexed to 90° with elbow extended both with forearm pronated and neutral. Muscle activity was recorded from extensor carpi radialis brevis/longus, extensor digitorum, flexor digitorum superficialis/profundus, and flexor carpi radialis, with intramuscular electrodes. Muscle synergies were extracted using non-negative matrix factorisation.FindingsAnalysis of each position and participant, demonstrated that two muscle synergies accounted for > 97% of the variance for both groups. Between-group differences were identified after electromyography patterns of the control group were used to reconstruct the patterns of the lateral epicondylalgia group. A greater variance accounted for was identified for the controls than lateral epicondylalgia (p = 0.009). This difference might be explained by an additional burst of flexor digitorum superficialis electromyography during grip release in many lateral epicondylalgia participants.InterpretationThese data provide evidence of some differences in synergistic organisation of activation of forearm muscles between individuals with and without lateral epicondylalgia. Due to study design it is not possible to elucidate whether changes in the coordination of muscle activity during gripping are associated with the cause or effect of lateral epicondylalgia.     

Stretching versus strength training in lengthened position in subjects with tight hamstring muscles: A randomized controlled trial

Stretching is used to modify muscle length. However, its effects seem to be temporary. There is evidence in animal models that strengthening in a lengthened position may induce long lasting changes in muscle length. The objective of this study was to compare changes in hamstrings flexibility, peak torque angle and stretch tolerance after two training programs: stretching and strengthening in a lengthened position. Forty-five subjects with tight hamstrings were randomly assigned into three groups: control, stretching and strength training in lengthened position. The interventions were performed three times a week for eight weeks. The subjects were assessed before and after the end of the programs. Data provided by an isokinetic dynamometer were used to assess hamstrings flexibility, peak torque angle, and stretch tolerance. The data analysis demonstrated that strengthening in lengthened position changed peak torque angle in the direction of knee extension (p = 0.001). No change in flexibility was observed (p = 0.449). Both experimental groups showed an increase in stretch tolerance (p = 0.001). The results demonstrated that strengthening in a lengthened position produced a shift of the torque–angle curve, which suggests an increase in muscle length. Conversely, stretching did not produce modification of torque–angle curve and flexibility; its effects appear restricted to increases in stretch tolerance.     

Is forward head posture relevant to cervical muscles performance and neck pain? A case–control study

BackgroundForward head posture (FHP) and muscular dysfunction are likely contributing factors to chronic neck pain (CNP) but there are inconsistent findings on the relevance of these factors to clinical CNP characteristics.ObjectiveTo compare FHP, cervical muscles size and endurance between CNP and asymptomatic participants and to investigate their association with pain and disability and relative involvement of deep/superficial and flexor/extensor muscles.MethodsThirty-two patients with CNP and 35 asymptomatic participants were included in this case–control study. FHP in standing, extensor and flexor muscles endurance and dimensions were assessed using digital photography, clinical tests and ultrasonographic imaging, respectively. The visual analog scale and neck disability index were also used to evaluate CNP patients’ clinical characteristics.ResultsDeep flexor (mean difference = 0.06, 95% CI = 0.02–0.11) and extensor muscles size (mean difference = 0.07, 95% CI = 0.01–0.12) were found to be significantly smaller in CNP patients. CNP patients also demonstrated lower levels of flexor (mean difference = 14.68, 95% CI = 3.65–25.72) and global extensor endurance capacity. FHP was neither different between the groups nor correlated with any of the dependent variables. Neither FHP nor endurance was correlated with pain/disability. Extensor endurance in both groups and flexor endurance in the asymptomatic group showed significant correlations with muscles size.ConclusionsFHP was found neither different between groups nor correlated with muscle performance or CNP clinical characteristics. While cervical endurance was found lower in CNP patients, it did not show any association with pain/disability. The muscular size–endurance relationship seems to become more complex in the presence of NP. While deep muscles seem to be differentially affected in the presence of CNP, the alterations do not seem to be uniform in the flexor and extensor groups.     

Challenging presumptions: Is reciprocal inhibition truly reciprocal? A study of reciprocal inhibition between knee extensors and flexors in humans

Reciprocal inhibition (RI) between different muscles has been used as an explanation for the effect of some treatments. Consequently, there may be a presumption that RI is bi-directional and equal between every agonist antagonist muscle pair. That is, the strength of RI from agonist to antagonist is equal to that from antagonist to agonist. With this in mind we investigated RI between quadriceps and hamstrings using 2 techniques to explore if a) it is evoked between this agonist antagonist pair and b) if it is equal and opposite in strength. Firstly, electromygraphic (EMG) activity of one muscle was recorded whilst stimulating group Ia afferents from the other. The second approach involved conditioning a reflex evoked in one muscle by stimulating Ia afferents from the other. Using the first approach, short-latency inhibition thought to be RI, was observed more frequently (p < 0.000) and was larger (p < 0.05) from femoral nerve stimulation to hamstrings than the inhibition evoked in quadriceps by sciatic nerve stimulation. The second approach revealed a similar pattern. RI between quadriceps and hamstrings is not actually reciprocal i.e. not equal in both directions. Our presumptions about the frequency and strength of other pathways between different agonist antagonist pairs need to be assessed.     

Relationship between the duration of taekwondo training and lower limb muscle strength in adolescents

Previous studies have suggested that different durations of taekwondo (TKD) training may result in different lower limb muscle strengths. The objective of this study was to explore the relationship between the duration of TKD training (i.e., number of hours spent training per week) and lower limb muscle strength (at both fast and slow testing speeds) in adolescents. Isokinetic concentric knee and ankle muscle strengths were measured in 20 TKD practitioners (mean age: 15.8 years) at two different speeds (60°/second and 240°/second). Pearson’s correlation coefficient (two-tailed) showed that the number of TKD training hours per week was positively correlated with the peak torque of the knee extensors (r = 0.639, p = 0.002) and knee flexors (r = 0.472, p = 0.036) at 240°/second. This study did not show any significant correlation between TKD training duration and the peak torque of the knee flexors and extensors at slower speeds (60°/second) or the ankle plantar flexors at any speed. Our results support the notion that the more time one spends in TKD training the greater the muscle strength one could gain and that any subsequent improvements in knee muscle strength is velocity specific. Further study is needed to confirm the optimal amount of training and training parameters required to develop knee muscle strength in TKD athletes.     

The role of muscle strength & activation patterns in patellofemoral pain

BackgroundTo investigate the extent to which quadriceps muscle activation and strength are responsible for patellofemoral pain.MethodsA pain on–off switch system synchronized with a force transducer and surface electromyography was utilized on 32 volunteer patellofemoral pain patients during maximal isometric and squat exercises.FindingsThere were 26 patients out of the 32 tested who complained of pain during the squat or isometric test, of these 20 subjects presented a significant advantage for the vastus lateralis compared to the vastus medialis obliquis activation and 12 patients had decreased quadriceps strength of the symptomatic compared to the non symptomatic leg. All patients who demonstrated weak vastus medialis obliquis activation during the isometric exercise possessed the same symptoms during the squat. On the other hand, 9 patients who showed diminished vastus medialis obliquis activation during the squat displayed equal activation between the vastus medialis obliquis and the vastus lateralis during the isometric task. With regard to the timing for the onset of muscle activation, there were only 4 patients who had a difference (P = 0.03) between the symptomatic (0.042 s) and non-symptomatic legs (0.011 s).InterpretationCauses for patellofemoral pain vary and are not necessarily a result of quadriceps strength deficit or vastus medialis obliquis activation weakness. Patellofemoral pain patients who possess lower vastus medialis obliquis activation compared to the vastus lateralis do not necessarily have quadriceps weakness while patients presenting with quadriceps strength deficits do not always have an imbalance between vastus medialis obliquis and vastus lateralis activation.     

Reduced inspiratory muscle strength increases pneumonia in patients with acute myocardial infarction

BackgroundInspiratory muscle strength is associated with pneumonia in patients after surgery or those with subacute stroke. However, inspiratory muscle strength in patients with acute myocardial infarction (AMI) has not been studied.ObjectiveTo evaluate the predictive value of inspiratory muscle strength for pneumonia in patients with AMI.MethodsPatients with AMI were consecutively enrolled from March 2019 to September 2019. Measurements of maximal inspiratory pressure (MIP) were used to estimate inspiratory muscle strength and mostly were taken within 24 hr after culprit-vessel revascularization. Patients were divided into 3 groups by MIP tertile (T1: < 56.1 cm H₂O, n = 88; T2: 56.1–84.9 cm H₂O, n = 88; T3: > 84.9 cm H₂O, n = 89). The primary endpoint was in-hospital pneumonia.ResultsAmong 265 enrolled patients, pneumonia developed in 26 (10%). The rates of pneumonia were decreased from MIP T1 to T3 (T1: 17%, T2: 10%, T3: 2%, P = 0.004). In-hospital all-cause mortality and major adverse cardiovascular events (MACEs) did not differ between groups. Multivariate logistic regression confirmed increased MIP associated with reduced risk of pneumonia (odds ratio 0.78, 95% confidence interval 0.65–0.94, P = 0.008). Receiver operating characteristic curve analysis indicated that MIP had good performance for predicting in-hospital pneumonia, with an area under the curve of 0.72 (95% confidence interval 0.64–0.81, P < 0.001).ConclusionsThe risk of pneumonia but not in-hospital mortality and MACEs was increased in AMI patients with inspiratory muscle weakness. Future study focused on training inspiratory muscle may be helpful.     

Patients with osteoarthritic knees have shorter orientation and tangent indicatrices during gait

BackgroundThis study introduces two novel outcomes that could be used to identify people with knee osteoarthritis from healthy controls. These outcomes examine the lengths of paths on a sphere derived from knee angle and knee position during gait.MethodsParticipants with moderate knee osteoarthritis (n = 47) and no knee pathology (n = 51) walked overground. The time-varying orientation matrices and position vectors of the knee (leg relative to the thigh) were measured, then arclength (constant speed) parameterized. The orientation matrix column aligned with the long axis of the leg, and the tangent, normal and binormal vectors (Frenet Frame) along the position vectors were calculated. These unit length vectors all scribe paths (indicatrices) on a unit sphere. The path lengths of these indicatrices, for all or part of a gait cycle, were the novel outcomes. A stepwise discriminant analysis defined a linear function that included those outcomes that best allocated a participant to the osteoarthritis or control group.FindingsGroup differences were best detected with the indicatrix lengths associated with the orientation of the leg’s long axis over a gait cycle (P < 0.001) and the tangent vector over the stance phase (P = 0.014). Both outcomes were smaller in the knee osteoarthritis compared to control group. Walking speed was poorly correlated with all indicatrix lengths (ρ < |0.484|) and a discriminate analysis correctly classified 83.7% of the participants.InterpretationSmaller indicatrix measures distinguished those with knee osteoarthritis from healthy controls. These outcomes introduce a promising new kinematic approach when examining gait data.     

Lumbar extensor muscle force control is associated with disability in people with chronic low back pain

BackgroundThe ability to control lumbar extensor force output is necessary for daily activities. However, it is unknown whether this ability is impaired in chronic low back pain patients. Similarly, it is unknown whether lumbar extensor force control is related to the disability levels of chronic low back pain patients.MethodsThirty-three chronic low back pain and 20 healthy people performed lumbar extension force-matching task where they increased and decreased their force output to match a variable target force within 20%–50% maximal voluntary isometric contraction. Force control was quantified as the root-mean-square-error between participants' force output and target force across the entire, during the increasing and decreasing portions of the force curve. Within- and between-group differences in force-matching error and the relationship between back pain group's force-matching results and their Oswestry Disability Index scores were assessed using ANCOVA and linear regression respectively.FindingsBack pain group demonstrated more overall force-matching error (mean difference = 1.60 [0.78, 2.43], P < 0.01) and more force-matching error while increasing force output (mean difference = 2.19 [1.01, 3.37], P < 0.01) than control group. The back pain group demonstrated more force-matching error while increasing than decreasing force output (mean difference = 1.74, P < 0.001, 95%CI [0.87, 2.61]). A unit increase in force-matching error while decreasing force output is associated with a 47% increase in Oswestry score in back pain group (R² = 0.19, P = 0.006).InterpretationLumbar extensor muscle force control is compromised in chronic low back pain patients. Force-matching error predicts disability, confirming the validity of our force control protocol for chronic low back pain patients.