Intramuscular pressure and surface EMG in voluntary ankle dorsal flexion: Influence of elastic compressive stockings

Effect of gait protocols and postoperative shoes on off-loading of forefoot in preoperative patients for forefoot disorders

OBJECTIVES

The purpose of this study was to clarify the effect of gait protocols and postoperative shoes on forefoot load in preoperative patients for forefoot disorders and compare footwear comfort between different types of postoperative shoes.

METHODS

Fourteen subjects scheduled to undergo forefoot surgeries were recruited. The maximum force under the forefoot region was measured during 10 m straight walking in two gait patterns with six different shoe types. Visual analogue scale (VAS) scores for footwear comfort, subjective lower thigh pain, and electrical activities of lower thigh muscles were also evaluated.

RESULTS

The body weight-normalized maximum force under the forefoot region significantly decreased in step-to gait compared to normal gait regardless of the shoe types used. Under the same gait condition, no significant difference was observed in the forefoot off-loading effect between the different shoe types used. Significantly worse VAS scores, significantly higher tibialis anterior muscle activities, and complaints of lower thigh pain were demonstrated in the gait with the reverse camber shoe.

CONCLUSIONS

Gait protocol of step-to gait had more forefoot off-loading effect than postoperative shoes. The forefoot off-loading effect did not differ among the postoperative shoes, suggesting that postoperative shoes can be selected with an emphasis on footwear comfort.

Acute effects of graduated and progressive compression stockings on leg vein cross-sectional area and viscoelasticity in patients with chronic venous disease

OBJECTIVE

To determine the effects of graduated and progressive elastic compression stockings (ECS) on postural diameter changes and viscoelasticity of leg veins in healthy controls and in limbs with chronic venous disease (CVD).

METHODS

In 57 patients whose legs presented with C_1S, C₃, or C₅ CEAP classes of CVD and treated primarily with compression, and 54 healthy controls matched for age and body mass index, we recorded interface pressures at 9 reference leg levels. Cross-sectional areas of the small saphenous vein (SSV) and a deep calf vein (DCV) were measured with B-mode ultrasound with subjects supine and standing, recording the force (PF) applied on the ultrasound probe to collapse each vein with progressive ECS, and with and without graduated 15‒20 mmHg and 20‒36 mmHg elastic stockings. We chose these veins because they were free of detectable lesion and could be investigated at the same level (mid-height of the calf), while their compression by the ultrasound probe was not hampered by bone structures.

RESULTS

Interface pressures decreased from ankle to knee with graduated 15‒20 and 20‒36 mmHg, but increased with progressive ECS, and were 8.4‒13.8 mmHg lower for C_1s than for control or C₃ and C₅ limbs. Without ECS, SSV median [lower‒upper quartile] cross-sectional area was 4.9[3.6‒7.1] and 7.1[3.0‒9.9]mm² in C₃ and C₅ limbs vs. 2.9[1.8‒5.2] and 3.8[2.1‒5.4]mm² in controls (p<.01), respectively while supine and standing. It remained greater in C₃ and C₅ than in C_1S and control limbs wearing any ESC. Wearing compression, especially with progressive ECS, decreased SSV and DCV cross-sectional area only with subjects supine, thus lowering postural changes which remained highly diverse between individuals. The SSV cross-sectional area vs. PF function traced a hysteresis loop of which the area, related to viscosity, was greater in C₃ and C₅ limbs than controls, even with graduated 15‒20 or 20‒36 mmHg ECS. Progressive ECS lowered vein viscosity in the supine position whereas 20‒36 mm Hg and progressive ECS increased distensibility in the standing position.

CONCLUSION

Elastic compression stockings reduce cross-sectional area of superficial and deep calf veins with patients supine but not upright. C_1s limbs show distinctive features, especially regarding interface pressures. Graduated 20‒36 mm Hg and progressive stockings lower viscosity and increase distensibility of the small saphenous vein.

Use of a Mobile Intermittent Pneumatic Compression Device (Vekroosan) in Mobile Patients With Chronic Venous Disease

Background

Compression therapy is an essential part of chronic venous disorder (CVD) treatment in reducing associated complications. This observational study aimed to note the use, effects and tolerance of a mobile intermittent pneumatic calf compression (IPC) device, Vekroosan^® (DVT Solution P/L).

Methods

In 56 patients, Doppler ultrasonography was used to measure venous blood peak flow velocity (PFV) at external iliac, common femoral, distal superficial femoral and popliteal vein levels both before and after application of Vekroosan calf compressor for comparison.

Results

Vekroosan was able to show significant clinical benefit in 45 patients (80%). There was a significant increase in femoral PFV pressure in post-compression measurement when compared to the pre-compression measurement (43.1 vs. 32.4 cm/s, P < 0.001), even when patients mobilize. On average, the PFV pressure increased by 10.7 cm/s when compared to baseline. A significant decrease was seen in calf swelling after calf compression (31.3 vs. 21.9 cm, P < 0.01), also with mobilization. Eighty-seven percent of patients tolerated the device well.

Conclusions

Our study shows that use of mobile IPC devices, such as Vekroosan, is safe and effective in the treatment of CVD, can be used while mobilizing and can achieve results comparable to non-mobile devices.

Can Graduated Compressive Stockings Reduce Muscle Activity During Running?

PURPOSE

Graduated compressive stockings (GCS) have been suggested to influence performance by reducing muscle oscillations and improving muscle function and efficiency. However, no study to date has analyzed the influence of GCS on muscle activity during running. The objective of the study was to analyze the influence of GCS on the perception of comfort and muscle activation of the main muscles of the lower leg during running.

METHOD

Thirty-six participants ran on a treadmill with (GCS) or without (control) GCS. The running tests consisted of a 10-min warm-up followed by a 20-min intense run at 75% of the athlete's maximal aerobic speed. Surface electromyography of the tibialis anterior, peroneus longus, gastrocnemius lateralis (GL), and gastrocnemius medialis (GM) were recorded every 5 min during the run and analyzed using a non-linearly scaled wavelet analysis. Perception of comfort of the GCS was measured before and after the run.

RESULTS

The GCS were reported as comfortable garments and reduced GL activity at Minute 0 (p < .05, [Formula: see text]= .245) and Minute 5 (p < .05, [Formula: see text]= .326) and GM activity at Minute 0 (p < .05, [Formula: see text]= .233) compared with running without garments, but their effect was temporary and disappeared after 5 min of running.

CONCLUSION

Even though GCS reduced gastrocnemius muscle activity during the initial minutes of running, it is hypothesized that the GCS could have lost their initial levels of compression after some minutes of exercise, thereby reducing their influence on muscle activation. However, this hypothesis needs to be further investigated.

A 1D pulse wave propagation model of the hemodynamics of calf muscle pump function

The calf muscle pump is a mechanism which increases venous return and thereby compensates for the fluid shift towards the lower body during standing. During a muscle contraction, the embedded deep veins collapse and venous return increases. In the subsequent relaxation phase, muscle perfusion increases due to increased perfusion pressure, as the proximal venous valves temporarily reduce the distal venous pressure (shielding). The superficial and deep veins are connected via perforators, which contain valves allowing flow in the superficial-to-deep direction. The aim of this study is to investigate and quantify the physiological mechanisms of the calf muscle pump, including the effect of venous valves, hydrostatic pressure, and the superficial venous system. Using a one-dimensional pulse wave propagation model, a muscle contraction is simulated by increasing the extravascular pressure in the deep venous segments. The hemodynamics are studied in three different configurations: a single artery-vein configuration with and without valves and a more detailed configuration including a superficial vein. Proximal venous valves increase effective venous return by 53% by preventing reflux. Furthermore, the proximal valves shielding function increases perfusion following contraction. Finally, the superficial system aids in maintaining the perfusion during the contraction phase and reduces the refilling time by 37%.

Influence of wearing an unstable shoe on thigh and leg muscle activity and venous response in upright standing

PURPOSE

To quantify the effect of unstable shoe wearing on muscle activity and haemodynamic response during standing.

METHODS

Thirty volunteers were divided into 2 groups: the experimental group wore an unstable shoe for 8 weeks, while the control group used a conventional shoe for the same period. Muscle activity of the medial gastrocnemius, tibialis anterior, rectus femoris and biceps femoris and venous circulation were assessed in quiet standing with the unstable shoe and barefoot.

RESULTS

In the first measurement there was an increase in medial gastrocnemius activity in all volunteers while wearing the unstable shoe. On the other hand, after wearing the unstable shoe for eight weeks these differences were not verified. Venous return increased in subjects wearing the unstable shoe before and after training.

CONCLUSIONS

The unstable shoe produced changes in electromyographic characteristics which were advantageous for venous circulation even after training accommodation by the neuromuscular system.

Work partitioning of transversally loaded muscle: experimentation and simulation

Skeletal muscles are surrounded by other muscles, connective tissue and bones, which may transfer transversal forces to the muscle belly. Simple Hill-type muscle models do not consider transversal forces. Thus, the aim of this study was to examine and model the influence of transversal muscle loading on contraction dynamics, e.g. on the rate of force development and on the maximum isometric muscle force (Fim). Isometric experiments with and without transversal muscle loading were conducted on rat muscles. The muscles were loaded (1.3 N cm⁻²) by a custom-made plunger which was able to move in transversal direction. Then the muscle was fully stimulated, the isometric force was measured at the distal tendon and the movement of the plunger was captured with a high-speed camera. The interaction between the muscle and the transversal load was modelled based on energy balance between the (1) work done by the contractile component (CC) and (2) the work done to lift the load, to stretch the series elastic structures and to deform the muscle. Compared with the unloaded contraction, the force rate was reduced by about 25% and Fim was reduced by 5% both in the experiment and in the simulation. The reduction in Fim resulted from using part of the work done by the CC to lift the load and deform the muscle. The response of the muscle to transversal loading opens a window into the interdependence of contractile and deformation work, which can be used to specify and validate 3D muscle models.

Effects of local elastic compression on muscle strength, electromyographic, and mechanomyographic responses in the lower extremity

The purpose of this study was to investigate the effect of elastic compression on muscle strength, electromyographic (EMG), and mechanomyographic (MMG) responses of quadriceps femoris during isometric and isokinetic contractions. Twelve participants performed 5s isometric maximal voluntary contractions (MVC) and 25 consecutive and maximal isokinetic knee extensions at 60 and 300°/s with no (control, CC), medium (MC), and high (HC) compression applied to the muscle. The EMG and MMG signals were collected simultaneously with muscle isometric and isokinetic strength data. The results showed that the elevated compression did not improve peak torque, peak power, average power, total work, and regression of torque in the isometric and isokinetic contractions. However, the root mean squared value of EMG in both HC and MC significantly decreased compared with CC at 60 and 300°/s (p<0.01). Furthermore, the EMG mean power frequency in HC was significantly higher than that in CC at 60°/s (p<0.05) whereas no significant compression effect was found in the MMG mean power frequency. These findings provide preliminary evidence suggesting that the increase in local compression pressure may effectively increase muscle efficiency and this might be beneficial in reducing muscle fatigue during concentric isokinetic muscle contractions.

Identification of the material parameters of soft tissues in the compressed leg

Elastic compression is recommended in prophylaxis and the treatment of venous disorder of the human leg. However, the mechanisms of compression are not completely understood and the response of internal tissues to the external pressure is partially unknown. To address this later issue, a 3D FE model of a human leg is developed. The geometry is derived from 3D CT scans. The FE model is made up of soft tissues and rigid bones. An inverse method is applied to identify the properties of soft tissues which are modelled as hyperelastic, near-incompressible, homogeneous and isotropic materials. The principle is to calibrate the constitutive properties using CT scans carried out with and without the presence of a compression sock. The deformed geometry computed by the calibrated FE model is in agreement with the geometry deduced from the CT scans. The model also provides the internal pressure distribution, which may lead to medical exploitation in the future.

Mixed experimental and numerical approach for characterizing the biomechanical response of the human leg under elastic compression

Elastic compression is the process of applying an elastic garment around the leg, supposedly for enhancing the venous flow. However, the response of internal tissues to the external pressure is still partially unknown. In order to improve the scientific knowledge about this topic, a slice of a human leg wearing an elastic garment is modeled by the finite-element method. The elastic properties of the tissues inside the leg are identified thanks to a dedicated approach based on image processing. After calibrating the model with magnetic resonance imaging scans of a volunteer, the pressure transmitted through the internal tissues of the leg is computed. Discrepancies of more than 35% are found from one location to another, showing that the same compression garment cannot be applied for treating deficiencies of the deep venous system or deficiencies of the large superficial veins. Moreover, it is shown that the internal morphology of the human leg plays an important role. Accordingly, the approach presented in this paper may provide useful information for adapting compression garments to the specificity of each patient.

A novel intermittent mechanical compression device for stasis prevention in the lower limbs during limited mobility situations

INTRODUCTION

Intermittent pneumatic mechanical compression is commonly applied to obviate venous stasis in patients with increased risk of thromboembolism. Aviafit is a small battery-operated intermittent compression device using a patented mechanical, non-pneumatic technology. Our objective was to examine its ability to prevent venous stasis.

MATERIALS AND METHODS

Doppler ultrasonography was used to determine venous hemodynamics of 22 healthy volunteers in both legs, before applying the Aviafit to one randomly selected leg, upon device activation and after 30 min. Each measurement provided values for peak flow velocity (PFV) and total volume flow (TVF).

RESULTS

The PFV values were significantly higher in the treated leg upon activation of the Aviafit and at 30 min, compared to the baseline value and to the PFV of the untreated leg at the corresponding time points (p<0.001 for each). The TVF increased in the treated leg from baseline of 48 ml/min to 56 ml/min at T0, and then gradually decreased, similar to the untreated leg. At T30, 64% of the treated legs had a higher TVF than their untreated counterparts.

CONCLUSIONS

The lightweight, battery-operated and user-friendly Aviafit can provide the same hemodynamic benefits as larger conventional intermittent pneumatic compression devices. Its potential advantages for prophylaxis of thromboembolism and increased compliance in rehabilitation and homecare, and for use during long periods of immobility such as during flights, are evident.

Human muscle fatigue and elastic compressive stockings

The present study was performed to test if elastic compressive stockings (ECSs) increase muscle fatigability during sustained muscle contraction or if it improves the recovery after fatigue. Surface electromyograms (EMGs) were recorded on 4 leg and thigh muscles, and static ankle dorsal flexion force levels were measured in the right limb of 15 healthy subjects. The subjects maintained a 50% maximum ankle dorsal flexion force (MVF) for as long as possible without and, after a 30 min rest, with a European class I ECS. Finally, after another 30 mn rest, the pressure exerted by the ECS on the skin was measured at standard points on the limb, using a Salzmann apparatus. During the first 10 min of both rest periods, the subjects performed brief static maximum ankle dorsal flexions every 30 s. ECS exerted a 14.3 mm Hg mean pressure at tibial level C. Linear relationships, whose slopes were not influenced by ECS, existed between the maintenance time and both the mean power frequency and the logarithm of the total power of the tibialis anterior and gastrocnemius lateralis EMGs. The endurance times, the force recovery times after fatigue and the linear relationships between the logarithm of the time elapsing after exhaustion and the MVF reached during the recovery period were also independent of ECS. The results show that class I ECSs are not responsible for greater muscle fatigability; but they do not improve force recovery during rest following static fatiguing voluntary contractions.