Immediate effects of electrical stimulation, diathermy, and physical exercise on lower limb arterial blood flow in diabetic women with peripheral arterial disease: a randomized crossover trial

OBJECTIVE

The purpose of this study was to assess the effects of high-voltage electrical stimulation (HVES), continuous short wave diathermy, and physical exercise on arterial blood flow in the lower limbs of diabetic women with peripheral arterial disease.

METHODS

A crossover study was carried out involving 15 diabetic women (mean age of 77.87 ± 6.20 years) with a diagnosis of peripheral arterial disease. One session of each therapeutic resource was held, with a 7-day washout period between protocols. Blood flow velocity was evaluated before each session and 0, 20, 40 and 60 minutes after the administration of each protocol. Two-way repeated-measures analysis of variance with Bonferroni post hoc test was used for the intragroup and intergroup comparisons.

RESULTS

In the intragroup analysis, a significant reduction (P < .05) was found in blood flow velocity in the femoral and popliteal arteries over time with HVES and physical exercise and in the posterior tibial artery with the physical exercise protocol. However, no significant differences were found in the intergroup analysis (P > .05).

CONCLUSION

Proximal blood circulation in the lower limb of diabetic women with peripheral arterial disease was increased by a single session of HVES and physical exercise, whereas distal circulation was only increased with physical exercise.

On the effect of thermal agents in the response of the brachial biceps at different contraction levels

The objective of this study was to assess electromyographic features of the brachial biceps muscle after the application of cryotherapy and short-wave diathermy. Sixty healthy volunteers participated in the study and were equally divided into three groups: cryotherapy - application of ice packs for 30 min; short-wave diathermy for 20 min; and control. The thermal agents were applied to the anterior and posterior regions of the non-dominant arm. The electromyographic (EMG) signal from the brachial biceps was recorded before and after the application of thermal agents during flexion of the elbow joint at 25%, 50%, 75% of a maximum voluntary isometric contraction defined at least two days before the actual experiments (MVICbl). The volunteers also were asked to execute a free MVIC before and after the application of the thermal agents (MVIC free). A linear regression model with mixed effects (random and fixed) was used. Intra-group analysis showed a reduction in root mean square (RMS) at MVIC free, with no change in the median frequency of the EMG signal at any contraction level for the short-wave diathermy group. An increase on RMS values and a decrease on median frequencies were found after the application of cryotherapy for all contraction levels. The results imply that cryotherapy plays an important role on changing neuromuscular responses at various levels of muscle contraction. Therapists should be aware of that and carefully consider its use prior to activities in which neuromuscular precision is required.

Muscle-related differences in mechanomyography–force relationships are model-dependent

INTRODUCTION

In this study we examined the mechanomyographic amplitude (MMG(RMS))–force relationships with log-transform and polynomial regression models for the vastus lateralis (VL), rectus femoris (RF), and first dorsal interosseous (FDI) muscles.

METHODS

Twelve healthy (age 23 ± 3 years) men performed isometric ramp contractions of the leg extensors and index finger from 10% to 80% of their maximal voluntary contraction (MVC) with MMG sensors positioned on the VL, RF, and FDI. Log-transform and polynomial regression models were fitted to the relationships.

RESULTS

There were differences for the a terms (intercepts) and b terms (slopes) from the log-transform model between the FDI, VL, and RF; however, there were no consistent differences identified with the polynomial regression models.

CONCLUSIONS

The log-transform model quantified differences in the patterns of responses between the FDI and the leg extensors, but polynomial regression could not distinguish such differences.

Relationships between skinfold thickness and electromyographic and mechanomyographic amplitude recorded during voluntary and non-voluntary muscle actions

INTRODUCTION

The purpose of this study was to examine possible correlations between skinfold thicknesses and the a terms from the log-transformed electromyographic (EMGRMS) and mechanomyographic amplitude (MMGRMS)-force relationships, EMG M-Waves, and MMG gross lateral movements (GLM).

METHODS

Forty healthy subjects performed a 6-s isometric ramp contraction from 5% to 85% of their maximal voluntary contraction with EMG and MMG sensors placed on the vastus lateralis (VL) and rectus femoris (RF). A single electrical stimulus was applied to the femoral nerve to record the EMG M-waves and MMG GLMs. Skinfold thickness was assessed at the site of each electrode. Pearson's product correlation coefficients were calculated comparing skinfold thicknesses with the a terms from the log-transformed EMGRMS-and MMGRMS-force relationships, EMG M-waves, and MMG GLMs.

RESULTS

There were no significant cor1relations (p>0.05) between the a terms and skinfold thicknesses for the RF and VL from the EMGRMS and MMGRMS-force relationships. However, there were significant correlations (p<0.05) between skinfold thicknesses and the EMG M-waves and MMG GLMs for the RF (r=-0.521, -0.376) and VL (r=-0.479, -0.484).

DISCUSSION

Relationships were only present between skinfold thickness and the amplitudes of the EMG and MMG signals during the non-voluntary muscle actions.

Effects of temperature and fatigue on the electromechanical delay components

INTRODUCTION

Neuromuscular activation can be influenced by both muscle temperature (Tm) and fatigue.

METHODS

To assess the effects of Tm and fatigue on the electromechanical delay (EMD), 15 participants performed voluntary isometric contractions of different intensities under neutral (TmN), low (TmL), and high (TmH) Tm, before and after a fatiguing exercise. During contraction, electromyogram (EMG), mechanomyogram (MMG), and force (F) were recorded from the biceps brachii muscle. The EMD and the latencies between EMG and MMG (Δt EMG-MMG, which includes the electrochemical processes of EMD) and between MMG and F (Δt MMG-F, which includes the mechanical processes of EMD) were calculated.

RESULTS

TmL increased only Δt EMG-MMG, both before and after fatigue. Fatigue lengthened EMD, Δt EMG-MMG, and Δt MMG-F under all Tm to a similar extent.

CONCLUSIONS

While fatigue increased all EMD components, muscle cooling affected only the electrochemical but not the mechanical processes of EMD.

Electromyographic, but not mechanomyographic amplitude-force relationships, distinguished differences in voluntary activation capabilities between individuals

The purpose of the present study was to examine the influence of activation capabilities on the electromyography (EMGRMS) and mechanomyography amplitude (MMGRMS)-force relationships of the vastus lateralis (VL) and rectus femoris (RF). Thirteen men (mean±SD; age=22±3 year) performed nine submaximal contractions (10-90% maximal voluntary contraction [MVC]) with the interpolated twitch technique performed during a separate contraction at 90% MVC to calculate percent voluntary activation (%VA). Nine participants with >90% VA were categorized into the high-activated group with the remaining categorized into the moderate-activated group. Slopes (b terms) were calculated from the log-transformed EMGRMS and MMGRMS-force relationships. The b terms (collapsed across the VL and RF) for the EMGRMS-force relationships were greater for the high- (1.29±0.31) than the moderate-activated (1.10±0.20) group. In contrast, there were no differences in the b terms for the MMGRMS-force relationships between the high- and moderate-activated groups. For the EMGRMS and MMGRMS-force relationships, the b terms were greater for the RF (1.38±0.30, 0.81±0.20) than the VL (1.08±0.19, 0.60±0.13) collapsed across groups. The b terms from the EMGRMS-force relationships, but not the MMGRMS-force relationships, reflected differences in %VA.

Combined effects of fatigue and temperature manipulation on skeletal muscle electrical and mechanical characteristics during isometric contraction

Peripheral fatigue and muscle cooling induce similar effects on sarcolemmal propagation properties. The aim of the study was to assess the combined effects of muscle temperature (Tm) manipulation and fatigue on skeletal muscle electrical and mechanical characteristics during isometric contraction. After maximum voluntary contraction (MVC) assessment, 16 participants performed brief and sustained isometric tasks of different intensities in low (Tm(L)), high (Tm(H)) and neutral (Tm(N)) temperature conditions, before and after a fatiguing exercise (6s on/4s off at 50% MVC, to the point of fatigue). During contraction, the surface electromyogram (EMG) and force were recorded from the biceps brachii muscle. The root mean square (RMS) and conduction velocity (CV) were calculated off-line. After the fatiguing exercise: (i) MVC decreased similarly in all Tm conditions (P<0.05), while EMG RMS did not change; and (ii) CV decreased to a further extent in Tm(L) compared to Tm(N) and Tm(H) in all brief and sustained contractions (P<0.05). The larger CV drop in Tm(L) after fatigue suggests that Tm(L) and fatigue have a combined and additional effect on sarcolemmal propagation properties. Despite these changes, force generating capacity was not affected by Tm manipulation. A compensatory mechanism has been proposed to explain this phenomenon.

Influence of heat on fatigue and electromyographic activity of the biceps brachii muscle

Electromyography enables registering muscle activity during contraction and can identify muscle fatigue. In the present study, 30 volunteers between 18 and 30 years of age were submitted to an exertion 1 min of maximal voluntary isometric contraction. The electromyographic signal of the biceps brachii muscle and the strength of the flexor muscles of the elbow were determined before and after the administration of microwave diathermy in order to analyze the influence of heat over the strength of the elbow flexor muscles and fatigue of the biceps brachii. The results demonstrate that the strength of the elbow flexor muscles diminished significantly following the application of heat (p<0.05). Heat also led to a significant reduction in the electrical activity of the muscle studied. The present study demonstrates that microwave diathermy on the biceps brachii muscle reduces the flexion strength of the elbow as well as signs of muscle fatigue in the biceps.

A noninvasive, log-transform method for fiber type discrimination using mechanomyography

This study examined the log-transformed mechanomyographic (MMG(RMS)) and electromyographic (EMG(RMS)) amplitude vs. force relationships for aerobically-trained (AT), resistance-trained (RT), and sedentary (SED) individuals. Subjects performed isometric ramp contractions from 5% to 90% maximal voluntary contraction. Muscle biopsies were collected and thigh skinfolds, MMG and EMG were recorded from the vastus lateralis muscle. Linear regression models were fit to the log-transformed EMG(RMS) and MMG(RMS) vs. force relationships. The slope (b coefficient) and the antilog of the y-intercept (a coefficient) were calculated. The AT group had the highest percentage of type I fiber area, the RT group had the highest percentage of type IIa fiber area, and the SED group had the highest percentage of type IIx fiber area. The a coefficients were higher for the AT group than the RT and SED groups in both the MMG(RMS) and EMG(RMS) vs. force relationships, whereas the b coefficients were lower for the AT group than the RT and SED groups only in the MMG(RMS) vs. force relationship. The group differences among the a coefficients may have reflected subcutaneous fat acting as a filter thereby reducing EMG(RMS) and MMG(RMS). The lower b coefficients for the AT group in the MMG(RMS) patterns may have reflected fiber area-related differences in motor unit activation strategies.