Quadriceps Muscle Activity Research Articles

Effects of nano-Rhodiola rosea combined with treadmill exercise on anti-exercise fatigue in rats.

To explore the potential strategies and mechanisms for enhancing the bioavailability of Rhodiola rosea. 36 Sprague-Dawley rats (8-weeks-old) were randomly assigned to six groups (n = 6 per group). Groups I and II received nano-dose forms of R. rosea, groups III and IV received normal dose form of R. rosea, and groups V and VI served as distilled water control groups. Groups II, IV, and VI were combined with moderate -intensity treadmill exercise. Each group received a daily gavage with 0.5 mL of nano -R. rosea solution (0.01 mg/mL), normal R. rosea solution, and distilled water. All rats were subjected to exhaustive swimming after 4 weeks. Outcome measures include GSH-px activity, T-AOC activity, MDA content, hepatic glycogen content, and T-SOD activity. For plasma MDA content, group I was lower than group III (p < 0.01) and group V (p < 0.01), group II was lower than group III (p < 0.01), group VI was higher than group II (p < 0.05) and group IV (p < 0.05). For plasma T-AOC activity, group II was higher than group VI (p < 0.01). For plasma GSH-px activity, group I was lower than group IV (p < 0.05), groups II, III, and IV were higher than group V (p < 0.05), and group V was lower than that of group VI (p < 0.05). For T-SOD activity of quadriceps muscle, groups I and III were higher than that in group V (p < 0.05). R. rosea has a positive effect on anti-exercise fatigue in rats, with the nano-dosage form of R. rosea showing more significant efficacy than the normal form especially combined with aerobic exercise.

Quadriceps muscle activity during walking with a knee ankle foot orthosis is associated with improved gait ability in acute hemiplegic stroke patients with severe gait disturbance.

A knee-ankle-foot orthosis (KAFO) prevents knee buckling during walking and enables gait training for acute hemiplegic stroke patients with severe gait disturbances. Although the goal of gait training with a KAFO is to improve gait ability, that is, to acquire walking with an ankle-foot orthosis (AFO), it is not clear how gait training with a KAFO contributes to improving gait ability. Therefore, this study aimed to investigate the relationship between muscle activities during walking with a KAFO and the improvement of gait ability in hemiplegic stroke patients with severe gait disturbance. A prospective cohort study was conducted. Fifty acute hemiplegic stroke patients who could not walk with an AFO participated. Muscle activities of the paretic rectus femoris, biceps femoris, tibialis anterior, and soleus were assessed with surface electromyogram during walking with a KAFO. Electromyograms were assessed at the beginning of gait training and at the time the Ambulation Independence Measure score improved by 3 or higher, or discharge. Even in patients with complete hemiplegia, paretic rectus femoris, biceps femoris, and soleus showed periodic muscle activity during walking with a KAFO. Twenty-three patients improved to an Ambulation Independence Measure score of 3 or higher and were able to walk with an AFO (good recovery group). At the beginning of gait training, paretic rectus femoris muscle activity during the first double-limb support phase was significantly higher in the good recovery group than in the poor recovery group. The rectus femoris muscle activity significantly increased from before to after acute rehabilitation, which consisted mainly of gait training with a KAFO. For acute hemiplegic stroke patients with severe disturbance, the induction and enhancement of paretic quadriceps muscle activity during walking with a KAFO play an important role in acquiring walking with an AFO.

Age and gender differences in the perception and use of soft vs. rigid exoskeletons for manual material handling

We investigated age and gender differences in the perception and use of soft (Apex) vs. rigid (Paexo Back) passive back-support exoskeletons (BSE) for repetitive lifting and lowering. A gender-balanced sample of 20 young (18–30 years) and 16 old (45–60 years) individuals were recruited. In the first session, participants’ self-reported maximum acceptable load (MAL) was assessed using a psychophysical approach. Changes in muscle activity and kinematics due to BSE use in repetitive lifting/lowering tasks were also assessed. Overall, both BSEs increased MAL (by ∼7%), and reduced trunk extensor muscle activity across all groups (by ∼7–18%), compared to the control condition. Both BSEs promoted more squatting postures, increased quadriceps muscle activity (by ∼34%) and abdominal muscle activity during asymmetric tasks (by 5–20%). Some age and gender differences were significant, particularly for the trunk kinematics when using the Apex. Future work should include more diverse user groups in studying willingness to adopt BSEs and characterising their consequent effects on the body.

Hemodynamic and neuromuscular basis of reduced exercise capacity in patients with end-stage renal disease.

The present study aimed to characterize the exercise-induced neuromuscular fatigue and its possible links with cerebral and muscular oxygen supply and utilization to provide mechanistic insights into the reduced exercise capacity characterizing patients with end-stage renal disease (ESRD). Thirteen patients with ESRD and thirteen healthy males (CTR group) performed a constant-force sustained isometric contraction at 50% of their maximal voluntary isometric contraction (MVC) until exhaustion. Quadriceps muscle activation during exercise was estimated from vastus lateralis, vastus medialis, and rectus femoris EMG. Central and peripheral fatigue were quantified via changes in pre- to postexercise quadriceps voluntary activation (ΔVA) and quadriceps twitch force (ΔQtw,pot) evoked by supramaximal electrical stimulation, respectively. To assess cerebral and muscular oxygenation, throughout exercise, near-infrared spectroscopy allowed investigation of changes in oxyhemoglobin (∆O2Hb), deoxyhemoglobin (∆HHb), and total hemoglobin (∆THb) in the prefrontal cortex and in the vastus lateralis muscle. ESRD patients demonstrated lower exercise time to exhaustion than that of CTR (88.8 ± 15.3s and 119.9 ± 14.6s, respectively, P < 0.01). Following the exercise, MVC, Qtw,pot, and VA reduction were similar between the groups (P > 0.05). There was no significant difference in muscle oxygenation (∆O2Hb) between the two groups (P > 0.05). Cerebral and muscular blood volume (∆THb) and oxygen extraction (∆HHb) were significantly blunted in the ESRD group (P < 0.05). A significant positive correlation was observed between time to exhaustion and cerebral blood volume (∆THb) in both groups (r2 = 0.64, P < 0.01). These findings support cerebral hypoperfusion as a factor contributing to the reduction in exercise capacity characterizing ESRD patients.

Quadriceps vascular occlusion does not alter muscle action or balance: A cross-sectional study.

Partial vascular occlusion (PVO) can increase muscle strength and hypertrophy without joint overload. However, PVO could increase the possibility of imbalances and injuries during physical activity. To identify changes in strength, muscle activation, and postural control during the use of PVO in young women. A total of 14 healthy women aged between 18 and 30 years were evaluated. Dynamometry was used to analyse the strength of the quadriceps muscle, and surface electromyography to evaluate quadriceps muscle activity. A force platform was utilised to assess postural control, static single-legged support, single-legged squat, and climbing and descending stairs. Participants were randomly assigned to the evaluations either with or without PVO. The results were compared and correlated. The performance of static, dynamic, or stair exercises, with or without PVO, did not indicate differences in muscle strength and recruitment (p > 0.05). The use of PVO improved the velocity of anteroposterior (AP) oscillation of static postural control (p = 0.001). We found a moderate negative correlation between muscle strength and postural control during the ascending stairs task with the use of PVO (r = -0.54; r = -0.59), while in the group without PVO, the correlation was moderate to high (r = -0.55; r = -0.76). The use of PVO did not impair muscle strength and recruitment of the quadriceps or postural control in healthy women. Partial vascular occlusion can be used during dynamic exercises without impairing the balance and muscle strength of the quadriceps during its execution.

Evaluation of lumbar and hip movement characterization and muscle activities during gait in patients with knee osteoarthritis

Patients with knee osteoarthritis (KOA) might have gait deviations, but few previous studies have discussed gait compensatory movements of the proximal and distal parts of muscle groups related to KOA. The study aimed to measure lumbar and hip movements during gait test and collect muscle activities of the lower extremities. Thirty-four participants with KOA and 28 healthy participants aged over 50 years were recruited for this study. Lumbar and hip motions during walking test were measured using inertial measurement units. Four muscle groups of the lower extremity (erector spinae, gluteus maximus, quadriceps muscle, and gastrocnemius) activities in gait were collected using surface EMGs. KOA patients used an 2.12∘anterior inclined lumbar spine (p = 0.007) and 22.94∘ flexed hip (p = 0.001) in gait compared to healthy participants. The KOA patients had a small hip movement range 30.19∘(p = 0.001) and a higher asymmetric stance time ratio 0.39 (p = 0.006). Patients with KOA showed decreased erector spinae and gluteus maximus muscle activation and increased activation of the quadriceps and gastrocnemius muscles during gait. In conclusion, patients with KOA used a hyperlordotic lumbar and hip flexed strategy, which overactivates distal extensor muscles through the whole gait and might cause overstress on the lower extremity joints.

Strength and passive stiffness of the quadriceps are associated with patellar alignment in older adults with knee pain

BackgroundMaintaining normal patellar alignment is important for knee health. Altered activation of individual quadriceps muscles have been found related to patellar alignment. However, the relationships between strength and passive stiffness of the quadriceps and patellar alignment remains unexplored. MethodsParticipants aged between 60 and 80 years with activity-induced knee pain were recruited. Knee pain was quantified using an 11-point numeric rating scale. Quadriceps strength was assessed using a Cybex dynamometer and passive stiffness of rectus femoris, vastus lateralis, and vastus medialis were measured by shear-wave ultrasound elastography. Patellar alignments were assessed using MR imaging. Linear regression was used to examine relationships between quadriceps properties and patellar alignments with and without controlling for potential covariates. FindingsNinety-two eligible participants were assessed (71.7% females, age: 65.6 ± 3.8 years; pain scale: 4.6 ± 2.0), most of whom had knee pain during stair climbing (85.9%). We found that 17% of patellar lateral tilt angle could be explained by lower quadriceps strength (adjusted R2 = 0.117; P < 0.001), especially in females (R2 = 0.281; P < 0.001; adjusted R2 = 0.211; P < 0.001). In addition, a higher stiffness ratio of vastus lateralis/medialis accounted for 12% of patellar lateral displacement (adjusted R2 = 0.112; P = 0.008). InterpretationQuadriceps strength and relative stiffness of lateral to medial heads are associated with patellar alignment in older adults with knee pain. It suggests that quadriceps weakness and relatively stiffer lateral quadriceps may be risk factors related to patellar malalignments in the elderly.

Kadınlarda Dinamik Denge Üzerinde Kuadriseps Kas Aktivasyonu ile Q Açısı Arasındaki İlişki

Introduction: Lower extremity biomechanics affects the relationship between Q angle, quadriceps muscle activation and the balance.&#x0D; Objectiveː The aim was to examine the relationship between Q angle and quadriceps muscle activation on dynamic balance position in women. &#x0D; Materials and Methodsː Forty women were included in the study. The muscle activation of the quadriceps during dynamic balance in a single leg stance was recorded. A tape measure was used to measure Q angle, surface electromyography was used to assess muscle activation, the Flamingo Balance Test was used to assess static balance, the TechnoBody PK 200WL computerized balance device was used to assess dynamic balance, and the Short Form Musculoskeletal Assessment was used to assess functionality.&#x0D; Resultsː There was a statistically significant positive correlation between the Q angle standing and supine position and vastus medialis muscle activation respectively, (r=0.35, p=0,02; r=0.40, p=0.01). There was a statistically significant positive correlation between the perimeter length and Q angle in standing/supine position respectively, (r=0.33, p=0.04; r=0.32, p=0.04). Area gap percentage and Q angle standing (r=0.89, p=0.02), supine position Q angle values (r=0.63, p=0.03) were positively correlated.&#x0D; Conclusionː If vastus medialis is more strengthened, Q angle would be more normalized, so quadriceps muscle strengthening exercises are helpful for the normalization of the Q angle. Also, when the Q angle is normalized, a single leg balance would be revealed.

Role of ankle dorsiflexion in sports performance and injury risk: A narrative review

The objective of this literature review is to understand the role of ankle dorsiflexion range of motion in sports performance and the risk of injuries. The ankle harmonizes the interaction between the body and the supporting surface through adjusting to the supporting surface and handling forces to contribute effectually to different functional activities. Ankle dorsiflexion is an essential construct in many sport-specific skills. Ankle dorsiflexion is associated with activation of brain areas involved in movement preparation, sensory integration, motor planning/execution, balance, and visuomotor coordination. Ankle dorsiflexion was associated with enhanced activation of deep core and quadriceps muscles. Decreased ankle dorsiflexion is linked to compensations and altered kinetics and kinematics that can potentially affect sports performance and increase the chances of sustaining injuries. It is vindicated to consider more focus on ankle dorsiflexion range of motion in research studies, sports-related pre-season screening, clinical examination, injury rehabilitation, and return-to-sports judgment.

The impact of knee pain on body balance and electromyographic activity of the quadriceps muscle in fencers during the lunge movement

Introduction. The lack of research on fencing in Indonesia and the absence of analysis on muscle activation in the lower leg muscles, especially the quadriceps muscles, during fencing movements, such as lunges, is a significant gap in the existing literature. This knowledge gap is especially pronounced for athletes with knee pain and quadriceps angle differences. Knee pain causes athletes to experience a decrease in performance, one of which is caused by a decrease in balance. Purpose: This study aims to determine the difference in balance in athletes with knee pain and without knee pain and to determine the activation of the rectus femoris muscle, vastus medialis muscle, and vastus lateralis muscle in the lunge movement in athletes participating in fencing with sable and floret numbers. in the Fencing Sports Activity Unit at Tunas Pembangunan University (UTP) Surakarta. Methods. A descriptive and analytical observational research design was employed for this cross-sectional study, using purposive sampling to recruit seven fencing athletes of UTP. Stork balance test was used to check the balance score and surface electromyography records were used to collect data, and the data analysis was conducted using the nonparametric Mann-Whitney U test. Results. The results of this study prove that the body balance scores of athletes who have complaints of knee pain are significantly worse (p &lt; 0.05) compared to fencers who do not have complaints of knee pain. Knee pain also significantly reduced the activation of the rectus femoris, vastus medialis, and vastus lateralis muscles (p &lt; 0.05). Conclusion. Based on the results and discussion above, knee pain significantly decreases body balance and quadriceps muscle activity.

Effects of a Tart Cherry Supplement on Recovery from Exhaustive Exercise.

The aim of this study was to investigate the effects of a tart cherry supplement on recovery from exercise-induced muscle damage. Seventeen recreationally active women (mean age ± SD = 22.2 ± 3.3 years, height = 162.0 ± 6.0 cm, body mass = 65.1 ± 11.1 kg, BMI = 24.7 ± 3.5 kg·m2) supplemented with 1000 mg of concentrated tart cherry or a placebo for eight consecutive days. An overload protocol of 8 sets of 10 repetitions of maximal effort concentric and eccentric muscle actions of the leg extensors at a velocity of 60°·s-1 was performed on the fourth day of supplementation. Testing sessions consisted of a muscle function test (MFT) to examine pre- and post-testing peak torque, peak power, total work, time-to-peak torque, mean power, muscle activation of the quadriceps, and muscle soreness at baseline and post-testing at 0 h, 24 h, 48 h, and 72 h. A second trial of testing was repeated two weeks later using the opposite supplement to the one assigned for the first trial. No significant interaction for time × condition × velocity (p = 0.916) and no significant main effect for condition (p = 0.557) were demonstrated for peak torque. However, there were main effects for time and velocity for concentric quadriceps peak torque (p < 0.001). For muscle soreness, there was no two-way interaction for time x condition (p > 0.05) and no main effect for condition (p > 0.05), but there was a main effect for time (p < 0.001). In conclusion, a tart cherry supplement did not attenuate losses in isokinetic muscle peak torque, peak power, total work, time-to-peak torque, muscle soreness, or quadriceps muscle activation.

Effect of Aerobic Training on the Relationship Between Loading Rate and Quadriceps Muscle Activities in Men With Diabetic Neuropathy: A Clinical Trial

Background and Aims The increase in loading rate is associated with lower limb injuries such as tibial stress fracture. Quadriceps muscle activities absorb ground reaction force (GRF) shocks by eccentric activation. This study aims to evaluate the effect of aerobic training on the relationship between loading rate and quadriceps muscle activities in men with diabetic neuropathy (DN). Methods In this double-blinded, randomized, controlled clinical trial, participants were 40 men with DN who were selected by a convenience sampling method and randomly divided into two groups of training (n=20, age: 54.9±7.3, body mass index: 28.4±5.4) and control (n=20; age: 54.1±7.3, body mass index: 28.5±5.1). The GRF data was recorded using a force plate system during walking. The electrical activity of selected lower limb muscles was recorded using electromyography method. The training group performed aerobic training for 12 weeks (three sessions per week). Results The results showed an increase in the negative relationship between vertical loading rate and vastus lateralis activities after training (P=0.028). The activities of vastus medialis and rectus femoris muscles showed no significant relationship with loading rate after training (P&gt;0.05). Conclusion Aerobic training can improve the relationship between vastus lateralis muscle activity and vertical loading rate in men with DN.

Hemophilic Arthropathy of the Knee and Its Association with Reduced Muscle Strength and Activation and the Pressure Pain Threshold: A Case-Control Study.

(1) Background: Hemophilia is characterized by recurrent hemarthrosis leading to degenerative arthropathy. The aim was to evaluate the differences in muscle strength and activity and the pressure pain threshold between patients with knee arthropathy and their healthy peers; (2) Methods: A case-control study in which 23 adult patients with knee arthropathy and 24 healthy peers matched in terms of characteristics were recruited. The study variables were quadriceps muscle strength, muscle activation and the pressure pain threshold; (3) Results: There were significant differences between the two groups in quadriceps strength on the dominant (CI95%: 64.69, 129.2) and non-dominant (CI95%: 29.95, 93.55) sides and in the pressure pain threshold on the dominant (CI95%: 3.30, 43.54) and non-dominant (CI95%: 3.09, 45.25) sides. There were differences in neuromuscular fatigue on the non-dominant side in the vastus medialis (CI95%: 8.72, 21.51), vastus lateralis (CI95%: 4.84, 21.66) and rectus femoris (CI95%: 6.48, 24.95) muscles; (4) Conclusions: Muscle strength and the pressure pain threshold are lower in patients with hemophilia. Quadriceps muscle activation in patients with hemophilic knee arthropathy does not in any way differ from activation in healthy subjects. However, muscle fatigue is greater in patients with knee arthropathy. Strength training in patients with hemophilia should focus on the activation of the vastus medialis and lateralis muscles.

Tricompartment offloader knee brace reduces sagittal plane knee moments, quadriceps muscle activity, and pain during chair rise and lower in individuals with knee osteoarthritis

The Levitation tricompartment offloader (TCO) knee brace provides an assistive knee extension moment with the goal of unloading all three compartments of the knee and reducing pain for individuals with multicompartment knee osteoarthritis (OA). This study aimed to determine the effect of the TCO brace on sagittal plane knee moments, quadriceps muscle activity, and pain in individuals with multicompartment knee OA. Lower limb kinematics, kinetics, and electromyography data were collected during a chair rise and lower to determine differences between bracing conditions. TCO brace use significantly decreased the peak net knee external flexion moment in high power mode, providing extension assistance during chair rise [p<0.001; mean difference (MD) (98.75% CI) -0.8 (-1.0, -0.6)%BWxH] and bodyweight support during chair lower [p<0.001; -1.1 (-1.6, -0.7)%BWxH]. Quadriceps activation intensity was significantly reduced with brace use by up to 67% for the vastus medialis [Z = -2.55, p = 0.008] and up to 39% for the vastus lateralis [Z = -2.67, p = 0.004]. Participants reported significantly reduced knee pain with the TCO brace worn in high power mode compared to the no brace condition [p = 0.014; MD (97.5% CI) -18.8 (-32.22, -2.34) mm]. These results support the intended mechanism of joint unloading via extension assistance with the TCO brace. The observed biomechanical changes were accompanied by immediate reductions in user reported pain levels, and support the use of the TCO for conservative management to reduce knee pain in patients with multicompartment knee OA.

Tricompartment offloader knee brace reduces contact forces in adults with multicompartment knee osteoarthritis.

The levitation tricompartment offloader (TCO) brace is designed to unload all three knee compartments by reducing compressive forces caused by muscle contraction. This study aimed to determine the effect of the TCO on knee contact forces and quadriceps muscle activity in individuals with knee osteoarthritis. Lower limb kinematics, kinetics, and electromyography data were collected during a chair rise-and-lower task. A three-dimensionalinverse dynamics model of the lower leg and foot was used with a sagittal plane knee model to compute knee joint forces. TCO brace use significantly decreased forces in the tibiofemoral [p = 0.001; mean difference,MD (97.5% confidence interval,CI) -0.62 (-0.91, -0.33) body weight (BW)] and patellofemoral [p = 0.001; MD (97.5% CI) -0.88 (-1.36, -0.39) BW] compartments in high-power mode. Significant reductions in quadriceps tendon force [p = 0.002; MD (97.5% CI) -0.53 (-0.83, -0.23) BW] and electromyography intensity of the vastus medialis [p = 0.018, MD (97.5% CI) -30.7 (-59.1, -2.3)] and vastus lateralis [p = 0.012, MD (97.5% CI) -26.2 (-48.5, -3.9)] were also observed. The TCO significantly reduced tibiofemoral and patellofemoral contact forces throughout chair lower, and when knee flexion was greater than 50° during chair rise in high power. These results demonstrate that the TCO reduces contact forces in the tibiofemoral and patellofemoral joint compartments and confirms that the TCO unloads the joint by reducing compressive forces caused by the quadriceps. Clinical significance: The magnitude of knee joint unloading provided by the TCO is similar to that achieved by clinically recommended levels of bodyweight loss and is therefore expected to result in clinical benefits for knee osteoarthritis patients.

Exacerbated central fatigue and reduced exercise capacity in early-stage breast cancer patients treated with chemotherapy

PurposeThe present study aimed to characterize the etiology of exercise-induced neuromuscular fatigue and its consequences on the force-duration relationship to provide mechanistic insights into the reduced exercise capacity characterizing early-stage breast cancer patients.MethodsFifteen early-stage breast cancer patients and fifteen healthy women performed 60 maximal voluntary isometric quadriceps contractions (MVCs, 3 s of contraction, 2 s of relaxation). The critical force was determined as the mean force of the last six contractions, while W’ was calculated as the force impulse generated above the critical force. Quadriceps muscle activation during exercise was estimated from vastus lateralis, vastus medialis and rectus femoris EMG. Central and peripheral fatigue were quantified via changes in pre- to postexercise quadriceps voluntary activation (ΔVA) and quadriceps twitch force (ΔQTw) evoked by supramaximal electrical stimulation, respectively.ResultsEarly-stage breast cancer patients demonstrated lower MVC than controls preexercise (− 15%, P = 0.022), and this reduction persisted throughout the 60-MVC exercise (− 21%, P = 0.002). The absolute critical force was lower in patients than in controls (144 ± 29N vs. 201 ± 47N, respectively, P < 0.001), while W’ was similar (P = 0.546), resulting in lower total work done (− 23%, P = 0.001). This was associated with lower muscle activation in the vastus lateralis (P < 0.001), vastus medialis (P = 0.003) and rectus femoris (P = 0.003) in patients. Immediately following exercise, ΔVA showed a greater reduction in patients compared to controls (− 21.6 ± 13.3% vs. − 12.6 ± 7.7%, P = 0.040), while ΔQTw was similar (− 60.2 ± 13.2% vs. − 52.8 ± 19.4%, P = 0.196).ConclusionThese findings support central fatigue as a primary cause of the reduction in exercise capacity characterizing early-stage breast cancer patients treated with chemotherapy.Clinical trials registration No. NCT04639609—November 20, 2020.

Perceived Discomfort and Voluntary Activation of Quadriceps Muscle Assessed with Interpolated Paired or Triple Electrical Stimuli.

Voluntary drive of the exercising muscle is usually assessed with the interpolated twitch technique (ITT), using paired supramaximal electrical stimuli. The aim of this study was to directly compare voluntary activation (VA) of the quadriceps muscle (QM) measured with the ITT, using paired and triple electrical stimuli during maximal voluntary isometric contraction (MVIC). In addition, perceived discomfort was compared with the use of paired and triple electrical stimuli during ITT. Ten healthy participants (23.6 ± 1.6 years) were included. They performed four MVIC, with paired or triple stimuli, in random order. MVIC torque, superimposed evoked torque, evoked torque at rest, VA, and visual analogue scale for pain (VAS-pain), were analysed. The amplitude of the triplet-evoked torque was higher than doublet-evoked torque, i.e., the signal-to-noise ratio increased. However, the differences between the estimation of VA with paired and triple stimuli were not significant (p = 0.136). Triple stimuli yielded higher VAS-pain scores than paired stimuli (p = 0.016). The limits of agreement for the VA using the Bland-Altman method were 7.66/0.629. It seems that the use of additional electrical stimuli is not a recommended solution for the evaluation of VA, because the advantages (i.e., better signal-to-noise ratio) do not outweigh the disadvantages (i.e., an increase in pain).

Inhibition of knee joint sensory afferents alters covariation across strides between quadriceps muscles during locomotion.

Sport-related injuries to articular structures often alter the sensory information conveyed by joint structures to the nervous system. However, the role of joint sensory afferents in motor control is still unclear. Here, we evaluate the role of knee joint sensory afferents in the control of quadriceps muscles, hypothesizing that such sensory information modulates control strategies that limit patellofemoreal joint loading. We compared locomotor kinematics and muscle activity before and after inhibition of knee sensory afferents by injection of lidocaine into the knee capsule of rats. We evaluated whether this inhibition reduced the strength of correlation between the activity of vastus medialis (VM) and vastus lateralis (VL) both across strides and within each stride, coordination patterns that limit net mediolateral patellofemoral forces. We also evaluated whether this inhibition altered correlations among the other quadriceps muscle activity, the time-profiles of individual EMG envelopes, or movement kinematics. Neither the EMG envelopes nor limb kinematics was affected by the inhibition of knee sensory afferents. This perturbation also did not affect the correlations between VM and VL, suggesting that the regulation of patellofemoral joint loading is mediated by different mechanisms. However, inhibition of knee sensory afferents caused a significant reduction in the correlation between vastus intermedius (VI) and both VM and VL across, but not within, strides. Knee joint sensory afferents may therefore modulate the coordination between the vasti muscles but only at coarse time scales. Injuries compromising joint afferents might result in altered muscle coordination, potentially leading to persistent internal joint stresses and strains.NEW & NOTEWORTHY Sensory afferents originating from knee joint receptors provide the nervous system with information about the internal state of the joint. In this study, we show that these sensory signals are used to modulate the covariations among the activity of a subset of vasti muscles across strides of locomotion. Sport-related injuries that damage joint receptors may therefore compromise these mechanisms of muscle coordination, potentially leading to persistent internal joint stresses and strains.

Trunk Position Influence H:Q RATIO of Lead Lower Extremity During Bulgarian Split Squat Exercise

This study aimed to investigate the variation in the H:Q ratio by comparing two trunk angles during the Bulgarian Split Squat (BSS) exercise. It has been shown that the ratio of quadriceps muscle activity to hamstring muscle activity is important, affecting knee joint function and injury risk. Twenty-one healthy male participants were recruited in this study. The participants were guided to repeat the BSS three times at normal posture and 30° trunk anterior tilt. The surface electromyography (EMG) activity was measured for 5 sec on the rectus femoris and hamstring muscles during a phase of BSS when the participant's knee touched the mat to be lifted again. The EMG activity was normalized via the maximal voluntary isometric contraction (MVIC) estimated using the manual muscle test. To examine the variation in the H:Q ratio, the paired sample t-test was used and the significance level was set to .05. The result showed that the H:Q ratio was higher at 30° trunk anterior tilt. The findings of this study indicate that the 30° trunk anterior tilt during the BSS could increase the H:Q ratio and positively control the stress on the anterior cruciate ligament (ACL), compared to the normal posture. It is suggested that experts should always evaluate the relative muscle strength of the femoral quadriceps and hamstrings in addition to H:Q RATIO for injury prevention purposes.

A broad and variable lumbosacral myotome map uncovered by foraminal nerve root stimulation.

The human myotome is fundamental to the diagnosis and treatment of neurological disorders. However, this map was largely constructed decades ago, and its breadth, variability, and reliability remain poorly described, limiting its practical use. The authors used a novel method to reconstruct the myotome map in patients (n = 42) undergoing placement of dorsal root ganglion electrodes for the treatment of chronic pain. They electrically stimulated nerve roots (n = 79) in the intervertebral foramina at T12-S1 and measured triggered electromyography responses. L4 and L5 stimulation resulted in quadriceps muscle (62% and 33% of stimulations, respectively) and tibialis anterior (TA) muscle (25% and 67%, respectively) activation, while S1 stimulation resulted in gastrocnemius muscle activation (46%). However, L5 and S1 both resulted in abductor hallucis (AH) muscle activation (17% and 31%), L5 stimulation resulted in gastrocnemius muscle stimulation (42%), and S1 stimulation in TA muscle activation (38%). The authors also mapped the breadth of the myotome in individual patients, finding coactivation of adductor and quadriceps, quadriceps and TA, and TA and gastrocnemius muscles under L3, L4, and both L5 and S1 stimulation, respectively. While the AH muscle was commonly activated by S1 stimulation, this rarely occurred together with TA or gastrocnemius muscle activation. Other less common coactivations were also observed throughout T12-S1 stimulation. The muscular innervation of the lumbosacral nerve roots varies significantly from the classic myotome map and between patients. Furthermore, in individual patients, each nerve root may innervate a broader range of muscles than is commonly assumed. This finding is important to prevent misdiagnosis of radicular pathologies.