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.     

Effects of squats accompanied by hip joint adduction on the selective activity of the vastus medialis oblique

[Purpose] This study evaluated the effective selective activation method of the vastus medialis oblique for knee joint stabilization in patients with patellofemoral pain syndrome. [Subjects and Methods] Fifteen healthy college students (9 males, 6 females); mean age, height, and weight: 22.2 years, 167.8 cm, and 61.4 kg, respectively) participated. The knee angle was held at 60°. Muscle activities were measured once each during an ordinary squat and a squat accompanied by hip joint adduction. The muscle activities of the vastus medialis oblique and vastus lateralis were measured by electromyography for five seconds while maintaining 60° knee flexion. Electromyography signals were obtained at a sampling rate of 1,000 Hz and band pass filtering at 20–50 Hz. The obtained raw root mean square was divided by the maximal voluntary isometric contraction and expressed as a percentage. The selective activity of the vastus medialis oblique was assessed according to the muscle activity ratio of the vastus medialis oblique to the vastus lateralis. [Results] The activity ratio of the vastus medialis oblique was higher during a squat with hip joint adduction than without. [Conclusion] A squat accompanied by hip joint adduction is effective for the selective activation of the vastus medialis oblique.Key words: Patellofemoral pain syndrome, Vastus medialis oblique, Squat     

Improvements in kinematics,muscle activity and pain during functional tasks in females with patellofemoral pain following a single patterned electrical stimulation treatment

BackgroundIndividuals with patellofemoral pain present with altered hip muscle activation, faulty movement patterns, and pain during functional tasks. Examining new treatment options to address these impairments may better treat those with patellofemoral pain. The purpose of this study was to determine if patterned electrical stimulation to the lower extremity affects muscle activity, movement patterns, and pain following a single treatment.MethodsFifteen females with patellofemoral pain were randomized to receive a single 15-minute treatment of either a patterned electrical neuromuscular stimulation or a sham. Peak kinematics of the knee, hip, and trunk, electromyography and pain were examined pre and post-intervention during a single leg squat and lateral step-down task. Group means and pre/post reduced kinematic values were also plotted during the entire task with 90% confidence intervals to identify differences in movement strategies.FindingsNo baseline differences were found in peak kinematics between groups. No pre to post-intervention differences in peak knee, hip and trunk kinematics were found, however differences were seen when the quality of movement across the entire tasks was assessed. The electrical stimulation group had improved knee flexion and hip abduction during the lateral step-down. A significant improvement in gluteus medius activation following patterned electrical neuromuscular stimulation occurred during the step-down (P = 0.039). Significant pain improvements were also seen in both the single leg squat (P = 0.025) and lateral step-down (P = 0.006).InterpretationA single treatment of patterned electrical neuromuscular stimulation improved muscle activation, lower extremity kinematics during functional tasks, and pain.     

Neuromechanical gait adaptations in women with joint hypermobility — An exploratory study

BackgroundJoint hypermobility is known to be associated with joint and muscle pain, joint instability and osteoarthritis. Previous work suggested that those individuals present an altered neuromuscular behavior during activities such as level walking. Therefore, the aim of this study was to explore the differences in ground reaction forces, temporal parameters and muscle activation patterns during gait between normomobile and hypermobile women, including symptomatic and asymptomatic hypermobile individuals.MethodsA total of 195 women were included in this cross-sectional study, including 67 normomobile (mean 24.8 [SD 5.4] years) and 128 hypermobile (mean 25.8 [SD 5.4] years), of which 56 were further classified as symptomatic and 47 as asymptomatic. The remaining 25 subjects could not be further classified. Ground reaction forces and muscle activation from six leg muscles were measured while the subjects walked at a self-selected speed on an instrumented walkway. Temporal parameters were derived from ground reaction forces and a foot accelerometer. The normomobile and hypermobile groups were compared using independent samples t-tests, whereas the normomobile, symptomatic and asymptomatic hypermobile groups were compared using one-way ANOVAs with Tukey post-hoc tests (significance level = 0.05).FindingsSwing phase duration was higher among hypermobile (P = 0.005) and symptomatic hypermobile (P = 0.018) compared to normomobile women. The vastus medialis (P = 0.049) and lateralis (P = 0.030) and medial gastrocnemius (P = 0.011) muscles showed higher mean activation levels during stance in the hypermobile compared to the normomobile group.InterpretationHypermobile women might alter their gait pattern in order to stabilize their knee joint.     

Re-evaluating the functional implications of the Q-angle and its relationship to in-vivo patellofemoral kinematics

BackgroundThe Q-angle is widely used clinically to evaluate individuals with anterior knee pain. Recent studies have questioned the utility of this measure and have suggested that a large Q-angle may not be associated with lateral patellofemoral translation, as often assumed. The objective of this study was to determine: 1) how accurately the Q-angle represents the line-of-action of the quadriceps and 2) if adding active quadriceps contraction or a bent knee position to the measurement of the Q-angle improves its reliability, accuracy, and association with patellofemoral kinematics.MethodsThe study included individuals diagnosed with chronic idiopathic patellofemoral pain and control subjects (n = 43 and n = 30 knees). Three measures of the clinical Q-angle (straight- and bent-knee with relaxed quadriceps and straight-knee with maximum isometric quadriceps contraction) were obtained with a goniometer and compared to a fourth MR-based measure of Q-angle. Patellofemoral kinematics were derived from dynamic cine-phase contrast images, acquired while subjects extended/flexed their knee from approximately 0° and 45°.FindingsThe Q-angle did not represent the line-of-action of the quadriceps. The average difference between each clinical and the MR-based Q-angle ranged from 5° to 8°. These differences varied greatly across subjects (range: − 28.5° to 3.9^o). Adding an active quadriceps contraction or a bent knee position, did not improve the reliability of the Q-angle. An increased Q-angle correlated to medial patellar displacement and tilt (r = 0.38—0.54, P < 0.001) in the cohort with anterior knee pain.InterpretationClinicians are cautioned against using the Q-angle to infer patellofemoral kinematics.     

Local neuromuscular characteristics associated with patellofemoral pain: A systematic review and meta-analysis

BackgroundLocal neuromuscular deficits have been reported in people with patellofemoral pain. We synthesised the neuromuscular characteristics associated with patellofemoral pain to help identify interventional targets and potential mechanisms.MethodsFive databases were searched for local neuromuscular characteristics in case-control studies. Electromyography, flexibility, muscle performance and cross-sectional area data were derived from functional or isolated task investigations and synthesised accordingly. An evidence gap map was constructed.FindingsSixty-seven studies were included. In functional tasks, electromyographic investigations showed moderate evidence of small effect for vastus medialis onset-delays relative to vastus lateralis (0.44 [0.03, 0.85]) during stepping/stair negotiation tasks, and higher biceps femoris mean excitation amplitudes (0.55 [0.06, 1.04]) in single-leg triple-hop test. In isolated tasks, we found moderate evidence of medium effect for lower Hoffman-reflex amplitude of vastus medialis (−1.12 [−1.56, −0.67]). Muscle performance investigations showed; strong evidence with medium and small effects for lower extensors concentric (−0.61 [−0.81, −0.40]) and eccentric (−0.56 [−0.79, −0.33]) strength, and moderate evidence of medium effect of lower isometric (−0.64 [−0.87, −0.41]) strength, moderate evidence with small effect for rate of force development to 30% (−0.55[−0.89, −0.21]), 60% (−0.57[−0.90, −0.25]) and medium effect to 90% (−0.76[−1.43, −0.10]) of maximum voluntary contraction, and small effect for lower flexors concentric strength (−0.46 [−0.74, −0.19]) and extensors total work (−0.48 [−0.90, −0.07]). Flexibility investigations showed tighter hamstrings (−0.57 [−0.99, −0.14]).InterpretationDifferences within quadriceps and hamstrings motor-control, hamstrings tightness, and quadriceps and hamstrings weakness are associated with patellofemoral pain, and can be used to guide investigations of treatment effects.     

Lean muscle volume of the thigh has a stronger relationship with muscle power than muscle strength in women with knee osteoarthritis

BackgroundThigh lean muscle and intramuscular fat have been implicated in the impairment of physical function observed in people with knee osteoarthritis. We investigated the relationships of quadriceps and hamstrings intramuscular fat fraction and lean muscle volume with muscle power and strength, controlling for neuromuscular activation, and physical performance in women with knee OA.MethodsWomen (n = 20) 55 years or older with symptomatic, radiographic knee osteoarthritis underwent a 3.0T magnetic resonance imaging scan of the thigh of their most symptomatic knee. Axial fat-separated images were analyzed using software to quantify intramuscular fat and lean muscle volumes of the quadriceps and hamstrings. To quantify strength and power of the knee extensors and flexors, participants performed maximum voluntary isometric contraction and isotonic knee extensions and flexions, respectively. Electromyography of the quadriceps and hamstrings was measured. Participants also completed five physical performance tests.FindingsQuadriceps and hamstrings lean muscle volumes were related to isotonic knee extensor (B = 0.624; p = 0.017) and flexor (B = 1.518; p = 0.032) power, but not knee extensor (B = 0.001; p = 0.615) or flexor (B = 0.001; p = 0.564) isometric strength. Intramuscular fat fractions were not related to isotonic knee extensor or flexor power, nor isometric strength. No relationships were found between intramuscular fat or lean muscle volume and physical performance.InterpretationMuscle power may be more sensitive than strength to lean muscle mass in women with knee osteoarthritis. Thigh lean muscle mass, but neither intramuscular nor intermuscular fat, is related to knee extensor and flexor power in women with knee osteoarthritis.     

Comparison of muscle activation levels and knee valgus between individuals with medial patellofemoral ligament reconstruction and healthy individuals during fatiguing step down task

BackgroundMedial patellofemoral ligament reconstruction becomes first-choice surgical procedure for patients with a history of lateral patellar dislocations but there is limited knowledge about neuromuscular activation patterns of individuals with a history of patellar dislocation who underwent medial patellofemoral ligament reconstruction.ObjectiveThe aim of this study was to compare muscle activation levels and knee valgus during step down performance test between individuals with a history of medial patellofemoral ligament reconstruction and healthy individuals.MethodsFifteen individuals with medial patellofemoral ligament reconstruction and 15 healthy individuals were included. Vastus medialis obliquus, vastus lateralis and gluteus medius muscle activation levels and knee valgus were measured during 60-s- step down performance test. Two-way repeated-measures of analysis of covariance was used for statistical analysis.FindingsCompared to the healthy individuals, individuals with medial patellofemoral ligament reconstruction showed lower vastus medialis obliquus (p = .04) and gluteus medius (p = .005) activation levels, and higher knee valgus (p = .002) in last period of the step down performance test.InterpretationSince the significant results were only observed in the fatiguing section of the test, endurance tests may provide more information about neuromuscular control of the individuals with history of medial patellofemoral ligament reconstruction. Future studies should investigate whether endurance exercises that target to improve vastus medialis obliquus and gluteus medius activity result in better clinical outcomes than conventional programs for individuals with medial patellofemoral ligament reconstruction.     

Temporal activity of vastus medialis obliquus and vastus lateralis in symptomatic knee osteoarthritis

OBJECTIVE: Knee osteoarthritis has a major impact on quadriceps function, yet its effect on the specific temporal recruitment of vastus medialis obliquus and vastus lateralis is unknown. The aim of this study was to determine the electromyographic onset of vastus medialis obliquus activity relative to that of vastus lateralis in individuals with symptomatic knee osteoarthritis and in an asymptomatic control group during the functional task of stair climbing. DESIGN: Cross-sectional, comprising 41 participants with symptomatic knee osteoarthritis and 33 controls matched for age, sex, and body mass. RESULTS: No significant differences were detected in the timing of onset of vastus medialis obliquus relative to that of vastus lateralis between the osteoarthritis and control groups. Radiographic osteoarthritis severity, presence of patellofemoral joint disease, and pain intensity did not seem to influence the temporal relationship of the vastii in the osteoarthritis group. CONCLUSION: The presence of symptomatic, radiographic knee osteoarthritis is not associated with deficits in the temporal recruitment of vastus medialis obliquus and vastus lateralis during stair climbing. This implies that selective retraining of the individual components of the quadriceps is not indicated in rehabilitation programs for patients with this disease.     

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.     

Determination of patellofemoral pain sub-groups and development of a method for predicting treatment outcome using running gait kinematics

BackgroundNot all patients with patellofemoral pain exhibit successful outcomes following exercise therapy. Thus, the ability to identify patellofemoral pain subgroups related to treatment response is important for the development of optimal therapeutic strategies to improve rehabilitation outcomes. The purpose of this study was to use baseline running gait kinematic and clinical outcome variables to classify patellofemoral pain patients on treatment response retrospectively.MethodsForty-one individuals with patellofemoral pain that underwent a 6-week exercise intervention program were sub-grouped as treatment Responders (n = 28) and Non-responders (n = 13) based on self-reported measures of pain and function. Baseline three-dimensional running kinematics, and self-reported measures underwent a linear discriminant analysis of the principal components of the variables to retrospectively classify participants based on treatment response. The significance of the discriminant function was verified with a Wilk's lambda test (α = 0.05).FindingsThe model selected 2 gait principal components and had a 78.1% classification accuracy. Overall, Non-responders exhibited greater ankle dorsiflexion, knee abduction and hip flexion during the swing phase and greater ankle inversion during the stance phase, compared to Responders.InterpretationThis is the first study to investigate an objective method to use baseline kinematic and self-report outcome variables to classify on patellofemoral pain treatment outcome. This study represents a significant first step towards a method to help clinicians make evidence-informed decisions regarding optimal treatment strategies for patients with patellofemoral pain.     

A Study on the Differences of Quadriceps Femoris Activities by Knee Alignment during Isometric Contraction

[Purpose] This study attempted to identify how genu varum or valgum affects the electromyographic activities of the vastus medialis, vastus lateralis, and rectus femoris during knee isometric contraction. [Subjects] Fifty-two healthy young adults were enrolled in this study. They were enrolled and classified into three groups by knee alignment conditions: the genu varum, genu valgum, and control groups. [Methods] The electromyographic activity ratio of the vastus medialis to the vastus lateralis and rectus femoris were calculated using the percentage of maximum voluntary contraction. The participants contracted their quadriceps during isometric contraction at 30 and 60° of knee flexion. [Results] The genu varum group had more activity in the vastus medialis than in the vastus lateralis and rectus femoris, whereas the genu valgum group had more activity in the vastus lateralis and rectus femoris than in the vastus medialis. There was a significant difference in the muscle activity ratio between the vastus medialis and vastus lateralis by angle of knee flexion degree only in the genu valgum. There were no significant differences in any of the three groups in terms of the muscle activity ratio of the vastus medialis to the rectus femoris by angle of knee flexion. [Conclusion] The quadriceps femoris was used for different strategies according to knee alignment during isometric contraction at 30 and 60°. This study suggests that rehabilitation training programs used to strengthen the quadriceps should consider the knee alignment conditions of the target subjects.Key words: Electromyography, Quadriceps muscle, Isometric contraction     

The effects of squatting with visual feedback on the muscle activation of the vastus medialis oblique and the vastus lateralis in young adults with an increased quadriceps angle

[Purpose] The purpose of this study was to identify the effects of performing squat exercises with visual feedback on the activation of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles in young adults with an increased quadriceps angle (Q-angle). [Subjects] This study used a motion analysis program (Dartfish, Switzerland) to select 20 young adults with an increased Q-angle, who were then divided into a squat group that received visual feedback (VSG, n=10) and a squat group that received no visual feedback (SG, n=10). [Methods] The intensity of exercises was increased every two weeks over a six-week exercise period in both groups. A visual marker was attached to the patella of the subjects in the VSG, and they then performed squat exercises with a maximum of 90° of knee flexion within a route marked on a mirror. The SG performed squat exercises with a maximum 90° of knee flexion without attaching a visual feedback device. [Results] Analysis of the muscle activation due to 90° squat exercises indicated that both groups had statistically significant increases in activation of the VL. The VSG exhibited statistically significant increases in activation of the VMO. [Conclusion] This study confirmed that squat exercises with visual feedback are effective in activation of the VMO and VL muscles. The findings are meaningful in terms of preventing the occurrence of patellofemoral pain.Key words: Q-angle, Visual feedback squat exercise, VMO     

The influence of orthotic devices and vastus medialis strength and timing on patellofemoral loads during running

OBJECTIVE: To use a musculoskeletal model and simulation of running to examine: (1) the influence of two commonly prescribed treatments for patellofemoral pain (vastus medialis oblique strengthening and orthoses) and (2) the functional significance of timing differences between vastus medialis oblique and vastus lateralis on lateral patellofemoral joint loads. DESIGN: A three-dimensional musculoskeletal model of the lower extremity was used to simulate running at 4 m/s. BACKGROUND: Repetitive and excessive joint loading is often associated with overuse injuries that require clinical treatments to reduce pain and restore function. Affecting one in four runners, patellofemoral pain is one of the most common injuries in running. Although conservative treatments have been reported to successfully treat patellofemoral pain, the effectiveness is often based on subjective or empirical data, which have generated disagreement on the most effective treatment. METHODS: Nine subject specific running simulations were generated and experiments were performed by applying the treatments and timing differences to the nominal simulations. RESULTS: Both treatments significantly reduced the average patellofemoral joint load and the vastus medialis strengthening also significantly reduced the peak patellofemoral joint load. In addition, when the vastus medialis oblique timing was delayed and advanced relative to the vastus lateralis timing, a significant increase and decrease in the joint load was observed, respectively, during the loading response.Conclusions. Increasing vastus medialis oblique strength yielded more consistent results across subjects than the orthosis in reducing patellofemoral joint loads during running. The effect of orthoses was highly variable and sensitive to the individual subject's running mechanics. Vastus medialis oblique activation timing is an important determinant of lateral patellofemoral joint loading during the impact phase. RELEVANCE: These findings indicate that a reduction in patellofemoral pain may be achieved through techniques that selectively increase the vastus medialis oblique strength. Therefore, future studies should be directed towards identifying such techniques. Additionally, the functional significance of timing differences between the vastus medialis oblique and vastus lateralis is an important consideration in patellofemoral pain treatment and orthoses may be beneficial for some patients depending on their running mechanics.     

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.     

Squat test performance and execution in children with and without cerebral palsy

BackgroundKnowledge on lower extremity strength is imperative to informed decision making for children with cerebral palsy (CP) with mobility problems. However, a functional and clinically feasible test is not available. We aimed to determine whether the squat test is suitable for this purpose by investigating test performance and execution in children with cerebral palsy and typically developing (TD) peers.MethodsSquat test performance, defined by the number of two-legged squats until fatigue (max 20), was assessed in twenty children with bilateral CP (6–19 years; gross motor function classification system I–III) and sixteen TD children (7–16 years). Muscle fatigue was assessed from changes in electromyography (EMG). Joint range-of-motion and net torque were calculated for each single squat, to investigate differences between groups and between the 2nd and last squat.FindingsFifteen children with CP performed < 20 squats (median = 13, IQR = 7–19), while all TD children performed the maximum of 20 squats. Median EMG frequency decreased and amplitude increased in mm. quadriceps of both groups. Ankle and knee range-of-motion were reduced in children with CP during a single squat by 10 to 15°. No differences between 2nd and last squat were observed, except for knee range-of-motion which increased in TD children and decreased in children with CP.InterpretationSquat test performance was reduced in children with CP, especially in those with more severe CP. Muscle fatigue was present in both children with CP and TD peers, confirming that endurance of the lower extremity was tested. Minor execution differences between groups suggest that standardized execution is important to avoid compensation strategies. It is concluded that the squat test is feasible to test lower extremity strength in children with CP in a clinically meaningful way. Further clinimetric evaluation is needed before clinical implementation.     

Quadriceps rate of torque development and disability in individuals with anterior cruciate ligament reconstruction

BackgroundThe purpose of this study was to determine associations between self-reported function (International Knee Documentation Committee Index), isometric quadriceps strength and rate of torque development in individuals with a unilateral anterior cruciate ligament reconstruction.MethodsForty-one individuals [31% male, BMI mean 25 (SD 4) kg/m², months post anterior cruciate ligament reconstruction mean 49 (SD 40)] completed the self-reported function and isometric quadriceps function testing. Rate of torque development was assessed at 0–100 ms (early), 100–200 ms (late) ms, and peak following the onset of contraction. Associations were examined between rate of torque development, strength, and self-reported function. Linear regression was used to determine the unique amount of variance explained by the combination of rate of torque development and strength.FindingsHigher rate of torque development 100–200 ms is weakly associated with higher self-reported function in individuals with a unilateral anterior cruciate ligament reconstruction (r = 0.274, p = 0.091); however, rate of torque development 100–200 ms does not predict a significant amount of variance in self-reported function after accounting for strength (ΔR² = 0.003, P = 0.721).InterpretationQuadriceps strength has a greater influence on self-reported function compared to rate of torque development in individuals with an anterior cruciate ligament reconstruction with time from surgery.     

Effects of a home-based rehabilitation program in obese type 2 diabetics

ObjectiveTo assess, in obese type 2 diabetics (T2D), the impact of a home-based effort training program and the barriers to physical activity (PA) practice.MethodTwenty-three obese T2D patients (52.7 ± 8.2 years, BMI = 38.5 ± 7.6 kg/m²) were randomized to either a control group (CG), or an intervention group (IG) performing home-based cyclergometer training during 3 months, 30 min/day, with a monthly-supervised session. The initial and final measurements included: maximal graded effort test on cyclergometer, 6-minute walk test (6MWT) and 200-meter fast walk test (200mFWT), quadriceps maximal isometric strength, blood tests and quality of life assessment (SF- 36). A long-term assessment of the amount of physical activity (PA) and the barriers to PA practice was conducted using a questionnaire by phone call.ResultsPatients in the CG significantly improved the maximal power developed at the peak of the cyclergometer effort test (P < 0.05) as well as the quadriceps strength (P < 0.01). There were no significant changes in the other physical and biological parameters, neither in quality of life. At a mean distance of 17 ± 6.4 months, the PA score remained low in the two groups. The main barriers to PA practice identified in both groups were the perception of a low exercise capacity and a poor tolerance to effort, lack of motivation, and the existence of pain associated to PA.ConclusionThis home-based intervention had a positive impact on biometrics and physical ability in the short term in obese T2D patients, but limited effects in the long term. The questionnaires completed at a distance suggest considering educational strategies to increase the motivation and compliance of these patients.     

Quadriceps activation following aerobic exercise in persons with low back pain and healthy controls

BackgroundA relationship between the muscles that stabilize the lumbar spine and the lower extremity exists that may result in neuromuscular and biomechanical changes during prolonged aerobic exercise in those with low back pain.MethodsTwenty recreationally active adults with healthy lower extremity joints, 7 with recurring episodes of low back pain performed a standard 15-minute aerobic exercise protocol on a treadmill. Quadriceps torque during a maximal isometric voluntary contraction, quadriceps central activation ratio and superimposed burst torque as measured with the superimposed burst technique, and vastus lateralis median frequency were recorded before and after treadmill exercise. A burst of electrical stimuli was superimposed during maximal knee extension causing a transient increase in torque. Quadriceps central activation was calculated as the ratio between maximal volitional and superimposed burst torques. We recorded vastus lateralis surface Electromyography (EMG) during knee extension contractions and calculated the median frequency.FindingsWe observed a 12.4% reduction in the quadriceps central activation ratio after aerobic exercise in participants with recurrent low back pain; healthy controls only experienced a 1.7% reduction. There was no change in quadriceps median frequency following aerobic exercise.InterpretationDeteriorated quadriceps function following aerobic exercise was observed in patients with recurrent episodes of low back pain who had healthy knee joints. This reduction is mediated by a central process that may arise from poor strength and endurance in the muscles surrounding the spine, which is common in persons with recurrent low back pain.     

Vastus Lateralis Motor Unit Firing Rate Is Higher in Women With Patellofemoral Pain

Objective

To compare neural drive, determined from motor unit firing rate, in the vastus medialis and lateralis in women with and without patellofemoral pain.