Influence of pulse waveform and frequency on evoked torque, stimulation efficiency, and discomfort in healthy subjects

The aim of the study was to determine the influence of neuromuscular electrical stimulation pulse waveform and frequency on evoked torque, stimulation efficiency, and discomfort at two neuromuscular electrical stimulation levels. Design: This is a repeated measures study. The quadriceps muscle of 24 healthy men was stimulated at submaximal (neuromuscular electrical stimulationsub) and maximal (neuromuscular electrical stimulationmax) levels using two pulse waveforms (symmetrical, asymmetrical) and three pulse frequencies (60, 80, 100 Hz). Repeated measures analysis of variance and effect sizes were used to verify the effect of pulse waveform and pulse frequency on stimulation efficiency (evoked torque/ current intensity) and discomfort and to assess the magnitude of the differences, respectively. Results: Stimulation efficiency was higher for symmetrical (neuromuscular electrical stimulationsub = 0.88 ± 0.21 Nm/mA; neuromuscular electrical stimulationmax = 1.27 ± 0.46 Nm/mA) compared with asymmetrical (neuromuscular electrical stimulationsub = 0.77 ± 0.21 Nm/mA; neuromuscular electrical stimulationmax = 1.02 ± 0.34 Nm/mA; P ≤ 0.001; effect size = 0.56–0.66) but did not significantly differ between frequencies (P = 0.17). At both neuromuscular electrical stimulation levels, there were no statistically significant differences in discomfort between pulse waveforms or frequencies. Conclusions: The higher stimulation efficiency of symmetrical pulses suggests that this waveform would be preferred to asymmetrical pulses in clinical practice. Stimulation frequencies between 60 and 100 Hz can be used interchangeably because of similar efficiency and discomfort

Functional taping effects on pain and electrical activation in patients with low back pain

Background: Low back pain (LBP) is a high prevalence health problem and it has several treatments available, among them it is the functional taping. Objective: To evaluate the influence of functional taping on the electrical activation of the erector spinae muscle, the degree of pain and the functionality in subjects with LBP. Methods: Twenty female with LBP participated in the study, and were divided in two groups: with and without the use of the functional taping. The electrical activity of the erector spinae muscle was obtained bilaterally by electromyography (EMG). The root mean square (RMS) value of the EMG was calculated for three maximum voluntary contractions (MVC) obtained before and 48 hours after the application of the taping. The RMS value of each MVC was normalized by the mean RMS value of the first test for each group. The visual analog pain scale was used to measure the pain, and the Roland Morris questionnaire to evaluate the functionality. Comparisons between groups (α=5%) were performed using the Mann Whitney test, and intra-group using the Wilcoxon test. Results: There was no decrease in muscular electrical activation, a significant decrease in pain, and an improvement in functionality. Conclusion: The use of functional taping in the lumbar spine promoted positive effects related to pain and functionality

Force produced after stretch in sarcomeres and half-sarcomeres isolated from skeletal muscles

The goal of this study was to evaluate if isolated sarcomeres and half-sarcomeres produce a long-lasting increase in force after a stretch is imposed during activation. Single and half-sarcomeres were isolated from myofibrils using micro-needles, which were also used for force measurements. After full force development, both preparations were stretched by different magnitudes. The sarcomere length (SL) or half-sarcomere length variations (HSL) were extracted by measuring the initial and final distances from the Z-line to the adjacent Z-line or to a region externally adjacent to the M-line of the sarcomere, respectively. Half-sarcomeres generated approximately the same amount of isometric force (29.0 ± SD 15.5 nN·μm(−2)) as single sarcomeres (32.1 ± SD 15.3 nN·μm(−2)) when activated. In both cases, the steady-state forces after stretch were higher than the forces during isometric contractions at similar conditions. The results suggest that stretch-induced force enhancement is partly caused by proteins within the half-sarcomere

Maturity status effects on torque and muscle architecture of young soccer players

This study investigated the effects of maturity status on knee extensor torque and vastus lateralis architecture of young soccer players. Thirty-four males aged 13–18 years were divided into two groups: pubescent (PUB, n = 15) and postpubescent (POSP, n = 19). Torque by angle interaction was established for absolute [F(2.649, 84.771) = 9.066, p < 0.05] and relative to body mass [F(2.704, 86.533) = 4.050, p < 0.05] isometric torque with the POSP group showing greater values. Muscle volume torque-angle relationship was similar between groups. Absolute, relative to body mass, and relative to muscle volume concentric and eccentric torque-velocity relationship showed a nonsignificant interaction but a significant group effect in favour the POSP group for absolute and concentric torque relative to body mass. Torque-angle and torque-velocity relationship normalized by body mass allometric exponents showed a non-significant interactions and group effects. Muscle thickness (3.6 ± 0.6 vs. 3.8 ± 0.6 cm), fascicle length (8.3 ± 1.4 vs. 8.9 ± 1.6 cm) and pennation angle (15.0 ± 2.3 vs. 14.3 ± 3.2 degrees) was similar between PUB and POSP groups, respectively. Maturity status did not show a significant effect on muscle architecture and on isometric and dynamic torques when allometrically normalized

Triceps surae muscle architecture adaptations to eccentric training

Eccentric exercises have been used in physical training, injury prevention, and rehabilitation programs. The systematic use of eccentric training promotes specific morphological adaptations on skeletal muscles. However, synergistic muscles, such as the triceps surae components, might display different structural adaptations due to differences in architecture, function, and load sharing. Therefore, the purpose of this study was to determine the effects of an eccentric training program on the triceps surae (GM, gastrocnemius medialis; GL, gastrocnemius lateralis; and SO, soleus) muscle architecture. Methods: Twenty healthy male subjects (26 ± 4 years) underwent a 4-week control period followed by a 12-week eccentric training program. Muscle architecture [fascicle length (FL), pennation angle (PA), and muscle thickness (MT)] of GM, GL, and SO was evaluated every 4 weeks by ultrasonography. Results: Fascicle lengths (GM: 13.2%; GL: 8.8%; SO: 21%) and MT (GM: 14.9%; GL: 15.3%; SO: 19.1%) increased from pre- to post-training, whereas PAs remained similar. GM and SO FL and MT increased up to the 8th training week, whereas GL FL increased up to the 4th week. SO displayed the highest, and GL the smallest gains in FL post-training. Conclusion: All three synergistic plantar flexor muscles increased FL and MT with eccentric training. MT increased similarly among the synergistic muscles, while the muscle with the shortest FL at baseline (SO) showed the greatest increase in FL

Triceps surae muscle-tendon properties as determinants of the metabolic cost in trained long-distance runners

Purpose: This study aimed to determine whether triceps surae’s muscle architecture and Achilles tendon parameters are related to running metabolic cost (C) in trained long-distance runners. Methods: Seventeen trained male recreational long-distance runners (mean age = 34 years) participated in this study. C was measured during submaximal steady-state running (5 min) at 12 and 16 km h–1 on a treadmill. Ultrasound was used to determine the gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and soleus (SO) muscle architecture, including fascicle length (FL) and pennation angle (PA), and the Achilles tendon cross-sectional area (CSA), resting length and elongation as a function of plantar flexion torque during maximal voluntary plantar flexion. Achilles tendon mechanical (force, elongation, and stiffness) and material (stress, strain, and Young’s modulus) properties were determined. Stepwise multiple linear regressions were used to determine the relationship between independent variables (tendon resting length, CSA, force, elongation, stiffness, stress, strain, Young’s modulus, and FL and PA of triceps surae muscles) and C (J kg–1m–1) at 12 and 16 km h–1. Results: SO PA and Achilles tendon CSA were negatively associated with C (r2 = 0.69; p < 0.001) at 12 km h–1, whereas SO PA was negatively and Achilles tendon stress was positively associated with C (r2 = 0.63; p = 0.001) at 16 km h–1, respectively. Our results presented a small power, and the multiple linear regression’s cause-effect relation was limited due to the low sample size. Conclusion: For a given muscle length, greater SO PA, probably related to short muscle fibers and to a large physiological cross-sectional area, may be beneficial to C. Larger Achilles tendon CSA may determine a better force distribution per tendon area, thereby reducing tendon stress and C at submaximal speeds (12 and 16 km h–1). Furthermore, Achilles tendon morphological and mechanical properties (CSA, stress, and Young’s modulus) and triceps surae muscle architecture (GM PA, GM FL, SO PA, and SO FL) presented large correlations with C

Reliability of knee extensor neuromuscular structure and function and functional tests’ performance

Introduction The aim of this study was to evaluate the intra and inter-rater and inter-analyzer reliability of neuromuscular variables and functional tests. Methods Cross-sectional crossover design. Two independent raters and analyzers evaluated twenty-two healthy subjects. Knee-extensor strength was assessed from three maximal voluntary isometric contractions. Muscle activation was obtained from the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) muscles. VL and RF muscles’ architecture [fascicle length (FL), pennation angle (PA), muscle thickness (MT)] was obtained at rest by ultrasound. The time from five sit-to-stand (STS) trials, and the distance from the 6-min walk test (6MWT) were obtained. Intraclass correlation coefficient was determined and classified as strong (r = 0.75–1.00), moderate (r = 0.40–0.74), and weak (r < 0.40). Strong intra-rater reliability values were observed for strength (r = 0.97), muscle activation [VL (r = 0.91); RF (r = 0.92); VM (r = 0.80)], VL [FL (r = 0.90); PA (r = 0.94); MT (r = 0.99)] and RF [MT (r = 0.85)] muscle architecture, STS (r = 0.95), and 6MWT (r = 0.98). Inter-rater reliability also presented strong values for strength (r = 0.97), muscle activation [VL (r = 0.94); RF (r = 0.79); VM (r = 0.78)], muscle architecture VL [PA (r = 0.81) and MT (r = 0.88)] and RF [MT (r = 0.80)], STS (r = 0.93), and 6MWT (r = 0.98). A moderate correlation VL muscle architecture [FL (r = 0.69)]. Inter-analyzer muscle architecture reliability presented strong VL [FL (r = 0.77); PA (r = 0.76); MT (r = 0.91)] and RF [MT (r = 0.99)]. Conclusion The high intra and inter-rater and inter-analyzer reliability values for most variables is evidence that they can be used for clinical evaluation. Muscle architecture might need a longer training period by different raters and analyzers to increase reliability

Proximal, local, and distal muscle morphology in women with patellofemoral pain

Objective: The objective of this study was to compare proximal, local, and distal muscle morphology in women with and without patellofemoral pain (PFP). Materials and Methods: Proximal, local, and distal muscle thicknesses (MTs) were obtained with B-mode sonography in healthy (control group [CG], n = 20) and PFP (PFP group, n = 20) women. In addition, muscle mass was measured by the sum of the synergistic MTs. Data were analyzed by independent t-test, Mann-Whitney U test, and effect size. Results: PFP women had smaller gluteus medius (P = .02, d = 0.7), vastus medialis (P < .01, d = 1.0), and flexor digitorum brevis (P < .01, d = 1.0) MT and greater gastrocnemius medialis (P = .04, d = 0.6) MT than CG. Quadriceps muscle mass (P = .01, d = 0.8) and foot muscle mass (P = .008, d = 0.9) were smaller, while plantar flexor muscle mass was greater in the PFP group than in CG (P = .01, d = 0.8). Conclusion: PFP women have proximal, local, and distal MT alterations in comparison with CG, which may explain possible changes in muscle strength and functionality

Are Patients with Polycystic Ovarian Syndrome Ideal Candidates for Oocyte Donation?

Background. The use of donated oocytes for in vitro fertilization treatment in patients with ovarian failure is universally recognized. But would patients with polycystic ovarian syndrome (PCOS) be a good choice for egg donation programs? Objective. Comparing the pregnancy rates of egg receptors from donor patients diagnosed with PCOS to receptors from donors without PCOS. Design. Retrospective cohort study. Methods. A total of 234 patients who had undergone egg reception program were separated into two groups: Group I, receptors from PCOS donors ( = 36); Group II, receptors from donors without PCOS ( = 198). Medical records were reviewed and the fertilization, implantation, and pregnancy rates were calculated. Results. PCOS patients had an average of 3.23 more oocytes retrieved, but there were no differences in the number of mature oocytes that were used for donation between the groups. We also observed that the number of transferred embryos was also not significantly different, as well as the fertilization and implantation rates. The clinical pregnancy rates were not significantly different: 28% and 26% in Group I and Group II, respectively. Conclusions. Women with PCOS should not be excluded from egg donation programs