Maximal Contraction Research Articles

A Review on the Pharmacokinetics and Toxicological Profile of Rabeprazole

Rabeprazole, a proton pump inhibitor, is used for individuals with ulcers. The prodrug is transformed into an active sulphenamide form by the acidic conditions present in the parietal cells. Rabeprazole inhibits the H+K+ ATPase of the gastric cells, leading to a decrease in the generation of stomach acid in both normal and stimulated situations. The present review was based on the pharmacokinetics and toxicological profile of Rabeprazole. Once absorbed into the body, approximately 96.3–97% of rabeprazole is bound to plasma proteins. In humans, the half-life of rabeprazole is approximately one hour. The peak concentration of rabeprazole in human plasma following a single oral dose does not appear until around 3.5 hours later. Rabeprazole is metabolised mostly by the liver. Once the liver has metabolised the medicine, 90% of it will be excreted via the kidneys. The elimination fraction is 10%. Rabeprazole is mostly metabolised by the cytochrome P450 enzymes CYP2C19 and CYP3A4. . It concluded that in the human pylorus, it decreased muscular tone, maximal contraction values, and contraction frequencies. When diclofenac sodium SR, glucosamine, diacerein, calcium, and vitamin D preparations were administered in addition to rabeprazole, the patients experienced GI bleeding, fatty liver grade 1, mild epigastric discomfort, black stools, and decreased haemoglobin content.

Achilles Tendon Stiffness: Influence of Measurement Methodology

ObjectiveMechanical stiffness derived from force-elongation curves is fundamentally different from shear wave (SW) elastography-based tissue properties. We compared these techniques, with a total of five methods of assessing Achilles tendon (AT) stiffness. MethodsSeventeen participants (12 male and 5 female) with unilateral AT rupture performed submaximal contractions at 30% and 10% maximal isometric contraction torque of the un-injured limb. SW velocity was acquired at rest. Force-elongation curves were assessed from the free AT and the medial gastrocnemius (MG) tendon. Mechanical stiffness was determined near the end of the linear region of the force-elongation curve and from the toe region. Bivariate correlations between mechanical stiffness and SW velocity, as well as pairwise t-tests between limbs, were computed. ResultsIn the injured limb, SW velocity correlated with MG tendon and free AT toe-region stiffness during 10% (r = 0.59, p = 0.020 and r = 0.60, p = 0.011, respectively) and 30% of submaximal contractions (r = 0.56, p = 0.018 and r = 0.67, p = 0.004, respectively). The un-injured limb showed no associations. In both limbs pooled together, SW velocity correlated with MG tendon toe-region stiffness in 30% of submaximal contractions (r = 0.43, p = 0.012). Free tendon mechanical stiffness was lower in the injured limb, with a mean difference of 148.5 Nmm⁻¹ (95% CI: 35.6–261.3, p = 0.013), while SW velocity was higher in the injured limb (1.67 m × s⁻¹, 95% CI; -2.4 to -0.9, p < 0.001). ConclusionSW elastography may reflect AT viscoelastic properties at the initial slope of the force-length curve with strains <1% but cannot offer insight into AT mechanics at higher loads. Extended toe regions in the injured limb could have caused the association between mechanical stiffness and SW-based stiffness.

Acute intermittent hypoxia increases maximal motor unit discharge rates in people with chronic incomplete spinal cord injury.

Acute intermittent hypoxia (AIH) is an emerging technique for enhancing neuroplasticity and motor function in respiratory and limb musculature. Thus far, AIH-induced improvements in strength have been reported for upper and lower limb muscles after chronic incomplete cervical spinal cord injury (iSCI), but the underlying mechanisms have been elusive. We used high-density surface EMG (HDsEMG) to determine if motor unit discharge behaviour is altered after 15×60s exposures to 9% inspired oxygen, interspersed with 21% inspired oxygen (AIH), compared to breathing only 21% air (SHAM). We recorded HDsEMG from the biceps and triceps brachii of seven individuals with iSCI during maximal elbow flexion and extension contractions, and motor unit spike trains were identified using convolutive blind source separation. After AIH, elbow flexion and extension torque increased by 54% and 59% from baseline (P=0.003), respectively, whereas there was no change after SHAM. Across muscles, motor unit discharge rates increased by ∼4 pulses per second (P=0.002) during maximal efforts, from before to after AIH. These results suggest that excitability and/or activation of spinal motoneurons is augmented after AIH, providing a mechanism to explain AIH-induced increases in voluntary strength. Pending validation, AIH may be helpful in conjunction with other therapies to enhance rehabilitation outcomes after incomplete spinal cord injury, due to these enhancements in motor unit function and strength. KEY POINTS: Acute intermittent hypoxia (AIH) causes increases in muscular strength and neuroplasticity in people living with chronic incomplete spinal cord injury (SCI), but how it affects motor unit discharge rates is unknown. Motor unit spike times were identified from high-density surface electromyograms during maximal voluntary contractions and tracked from before to after AIH. Motor unit discharge rates were increased following AIH. These findings suggest that AIH can facilitate motoneuron function in people with incomplete SCI.

The role of vitamin D supplementation on levator ani muscle remodeling post-delivery

HIGHLIGHTS 1. In pregnant women, vitamin D insufficiency may plays a role in the development of post-delivery illness.2. Vitamin D supplementation is significant in remodeling of post-delivery levator ani muscle. ABSTRACT Objectives: Vitamin D is considered a crucial vitamin for the restoration of levator ani muscle strength. Therefore, this study aimed to evaluate the association between vitamin D and levator ani muscle remodeling in the post-delivery period.Materials and Methods: The literature search was conducted across three electronic databases, namely PubMed, Google Scholar, and Springerlink. Our investigation yielded a total of 2613 studies, out of which 8 studies were found to meet the inclusion criteria and were subsequently included in our study. Among these, 4 studies specifically examined the impact of vitamin D micronutrient status on the levator ani/pelvic muscles during the post-delivery period.Results: The mean maximum contraction strength of the levator ani muscles following the administration of vitamin D supplements was 26.77 ± 7.15 cmH2O. The analysis conducted utilizing a paired t-test yielded a p-value of less than 0.05, indicating statistical significance. Additionally, a coefficient correlation of 0.831 was observed, with a p-value also less than 0.05. The findings of this study indicate a noteworthy correlation between levels of vitamin D and the magnitude of levator ani muscle contractions, as evidenced by a statistically significant p-value of less than 0.05.Conclusion: The administration of vitamin D supplements has been found to play a significant role in the remodeling of the levator ani muscle during the post-delivery period. This is evidenced by the observed increase in strength of the levator ani muscles following vitamin D supplementation.

Normal values of scapular muscle activity ratio during arm elevation and the relationship to muscle strength and sex difference.

The normal value of the scapular muscle activity ratio during arm elevation is not clear. To obtain normal values of the scapular muscle activity ratio during arm elevation in healthy individuals. This cross-sectional study enrolled 47 healthy people. The participants performed shoulder flexion and lowered task with 90-degree movements every 2 seconds. Muscle activities of scapular muscles were measured. For normalization, the maximum isometric contraction of the shoulder flexion was measured at 90∘ (reference contraction). The integrated electromyographic value (IEMG) obtained during the task was normalized by IEMG during the reference contraction and the relative IEMG value was calculated. Then, the scapular muscle activity ratio was computed. The relationship between muscle strength and other factors was also investigated. The median values for upper trapezius/serratus anterior and upper trapezius/lower trapezius were often approximately 1, and that for upper trapezius/middle trapezius was often between 1 and 2. The shoulder flexion isometric strength and scapular muscle activity ratio showed significant negative correlations in multiple phases. Normal values for upper trapezius/serratus anterior and upper trapezius/lower trapezius during arm elevation and lowering were generally 1. Low muscle strength may contribute to an abnormal scapular muscle activity balance.

Influence of compression garments on perceived exertion during maximal isometric exercises

Compression garments have gained popularity in the sports world as a means to enhance athletic performance and accelerate recovery. This study investigates the effectiveness of upper-body compression garments and their impact on the rate of perceived exertion (RPE) during maximal isometric contractions. Eight adult males, students of a Master's degree program in Sports Sciences, participated in the study, conducting tests in controlled conditions at the University of Salerno. The subjects performed maximal isometric contractions in three separate sessions, wearing compression garments (CG), traditional sportswear (noCG), and a tight-fitting garment without compression effect, to minimize the placebo effect (Placebo), respectively. Perceived exertion was assessed using the modified CR-10 scale. Statistical analysis revealed a significant reduction in RPE when athletes wore compression garments compared to other conditions, suggesting a benefit in the use of such clothing. The findings indicate that compression garments can attenuate the perception of exertion during intense physical activities, with potential implications for performance, comfort, and recovery. This study contributes to the existing literature by expanding the understanding of the effects of compression clothing and highlighting the importance of further research to optimize the use of these garments in enhancing athletic performance.

Increased Neuromuscular Activity, Force Output, and Resistance Exercise Volume When Using 5-Minute Compared with 2-Minute Rest Intervals Between the Sets.

McMahon, G, Best, N, Coulter, T, and Erskine, RM. Increased neuromuscular activation, force output and resistance exercise volume when using 5-minute compared with 2-minute rest intervals between the sets. J Strength Cond Res 38(9): 1527-1534, 2024-Longer rest intervals between resistance exercise (RE) sets may promote greater muscle hypertrophy and strength gains over time by facilitating the completion of greater training volume and intensity. However, little is known about the acute neuromuscular responses to RE sets incorporating longer vs. shorter rest intervals. Using a within-subject, crossover design, 8 healthy, young subjects completed 2 separate acute bouts of 4 sets of 8 × 3-s maximal isometric contractions using either a 2-minute (REST-2) or 5-minute (REST-5) rest interval between sets. Peak torque (PT) and electromyography (EMG) were measured pre and 5 minutes postexercise. Peak torque and mean torque (MT), EMG, mean, and median frequencies were measured during each set, whereas blood lactate (BLa), heart rate (HR), and rating of perceived exertion (RPE) were measured following each set. Peak torque and MT were lower ( p < 0.05) in sets 3 and 4, and sets 2-4 in REST-2 compared with REST-5, respectively. Electromyography and BL were lower and higher, respectively, in REST-2 vs. REST-5. There was no main effect of condition on HR or RPE. Pre-to-post exercise reductions in PT (-17 ± 9% vs. -4 ± 7%) and EMG (-29 ± 14% vs. -10 ± 7%) were greater ( p < 0.001) in REST-2 vs. REST-5. Total exercise volume was less in REST-2 vs. REST-5 (9,748 ± 2296 N·m -1 vs. 11,212 ± 2513 N·m -1 , p < 0.001). These results suggest that incorporating 5-minute between-set rest intervals into a resistance exercise session facilitates improved neuromuscular function, increased exercise volume, and less metabolic stress compared with 2-minute rest intervals. Thus, 5-minute rest intervals may be more efficacious for promoting muscle hypertrophy and strength gains in a chronic resistance training program.

A new anal manometry technique for assessing the functional state of the rectal sphincter apparatus

Objective. To develop a new modern precession strain gauge sphincterometer for assessing the functional state of the sphincteric apparatus of the rectum in the normal state with an increase in the accuracy of the results of recording the absolute pressure values generated in it. Materials and methods. The results of anal manometry (sphincterometry) of 90 patients (45 men and 45 women) aged 18 to 72 years without anorectal pathology and manifestations of anal incontinence were analysed to establish normal indicators of the state of the sphincteric apparatus of the rectum using a newly developed modern precession strain gauge sphincterometer. Results. The conducted sphincterometric study allowed to establish the following indicators of the functional state of the sphincteric apparatus of the rectum in the norm for men: sphincter tone (26.7 ± 2.2) mm Hg, maximum contraction (35.6 ± 5.1) mm Hg, gradient of voluntary contraction (9 ± 4.9) mm Hg, cough test (36.5 ± 4.9) mm Hg, test with straining (38.2 ± 3.5) mm Hg; for women: sphincter tone (23.3 ± 2.5) mm Hg, maximum contraction (31.3 ± 4.3) mm Hg, voluntary contraction gradient (8.0 ± 3.6) mmHg, cough test (31.6 ± 3.0) mmHg, and expiratory test (32.4 ± 3.0) mmHg. Conclusions. The proposed method of anal manometry allows for a detailed study and objective assessment of the functional state of the sphincteric apparatus of the rectum in men and women in the normal state according to such indicators as sphincter tone and maximum contraction, gradient of voluntary contraction, as well as cough and straining tests.

Impact of a 5-min massage session on the gastrocnemius contractile and passive mechanical properties in young adults - A randomized controlled trial

The analysis of the impact of a 5-min massage session on the gastrocnemius contractile and passive mechanical properties in young adults - a randomized controlled trial. BackgroundThe effect of massage therapy on the muscle properties is unclear. New technologies make investigation more in-depth and reliable. ObjectivesThis study examined the effects of a 5-min massage session on the muscle stiffness and tone reduction in healthy young adults. Materials and methodsParticipants aged between 19 and 24 were randomly assigned to an intervention group (IG) (n = 40) or a control group (CG) (n = 40). The IG participated in a 5-min massage session of the lateral and medial gastrocnemius muscle (LGCM and MGCM respectively). The muscle contractile properties were assessed by tensiomyography (TMG). It measured maximal displacement (Dm), delay time (Td) and contraction time (Tc). Oscillation frequency (F) and stiffness (S) were used to assess muscle passive mechanical properties. These measurements were collected by MytonPro. ResultsThere were no differences between the groups in the pre-test measurements. The results of mixed-model ANOVA showed significant (p < 0.05) time × group interactions, with greater alteration in the IG compared to the CG in the LGCM for Dm (%diff = 22.5, ƞp2 = 0.41), Td (%diff = 3.63, ƞp2 = 0.02), Tc (%diff = 13.38, ƞp2 = 0.1), F (%diff = 5.55, ƞp2 = 0.07) and in the MGCM for Dm (%diff = −14.34, ƞp2 = 0.06), F (%diff = −7.53, ƞp2 = 0.12). No difference (p > 0.05) was noticed in other variables. ConclusionsA 5-min massage session impacts the contractile and passive mechanical properties of the LGCM and MGCM. The size and direction of changes may depend on the muscle type, its geometry as well as other factors.

Normalization of rapid force to peak force in an isometric hamstring assessment using force plates

PurposeThe aim of this investigation was to determine the reliability of normalizing rapid force (RF) production to peak force assessed during an isometric knee flexor assessment, and to present a novel method of classifying athletes' potential training needs within the 90–90 isometric hamstring assessment. ProceduresTwenty elite female soccer players (age: 20.7 ± 4.7 years; height: 168.2 ± 5.5 cm; body mass: 62.8 ± 7.0 kg), with no recent (>6 months) history of hamstring strain injury, volunteered to participate in the study. Following a standardized warm-up, each participant performed three maximal isometric hamstring contractions, with their heel resting on a force plate, elevated on a box, to ensure that their hips and knees were at 90° Data was analyzed to determine peak for (PF), RF was established as force expressed at 100 ms (F100) and force expressed at 200 ms (F200), with force at each time-point subsequently normalized to a percentage of PF. FindingsF100 and F200 normalized to PF demonstrated good absolute reliability (%CV = 6.12–7.62) and moderate relative reliability (ICC = 0.689–0.703). Concurrently observing PF and normalized F100 and F200 could provide clear training and monitoring goals. ConclusionsNormalizing measures of RF production, including F100 and F200, to PF can be performed reliability. Therefore, could be tracked overtime to identify changes as an effect of training or for fatigue monitoring purposes. However, further research is required to determine how knee flexor force-time characteristics change in relation to focused training and how these characteristics change in response to fatiguing activities.

Origami-Inspired Bionic Soft Robot Stomach with Self-Powered Sensing.

The stomach is a vital organ in the human digestive system, and its digestive condition is critical to human health. The physical movement of the stomach during digestion is controlled by the circular and oblique muscles. Existing stomach simulators are unable to realistically reproduce the physical movement of the stomach. Due to the complexity of gastric motility, it is challenging to simulate and sense gastric motility. This study proposes for the first time a bionic soft robotic stomach (BSRS) with an integrated drive and sensing structure inspired by origami and self-powered sensing technology. This soft stomach (SS) can realistically simulate and sense the movements of various parts of the human stomach in real-time. The contraction force and contraction rate of the BSRS are investigated with different viscosity contents, and the experimental values are similar to the physiological range (maximum contraction force is 3.2 N, and maximum contraction rate is 0.8). This paper provides an experimental basis for the study of gastric digestive medicine and food science by simulating the peristaltic motion of the BSRS according to the human stomach and by combining the triboelectric nanogenerator (TENG) sensing technology to monitor the motion of the BSRS in real-time.

The effect of programmed resistance training on the muscle myofibrillar proteome

Resistance training increases muscle size but little is known about the dynamic processes that underpin the gains in muscle mass. We investigated rat muscle during 30 days of unilateral programmed resistance training (PRT) using the stable isotope (deuterium oxide; D2O) in vivo and proteomics. Three-month-old, male Wistar rats (body weight 348 ± 20 g) were assigned to four groups (n = 4, in each), including a control group and experimental groups that received D2O for 10, 20 or 30 days. Under ethically approved procedures, deuterium was administered, and a stimulating device was surgically implanted to activate the left peroneal nerve and cause maximal contraction of the dorsiflexors (inc. tibialis anterior; TA) and partial contraction of the plantar flexors. PRT consisted of 1 bout per day of 5 sets of 10 repetitions (1 repetition consisted of 2 s stimulation at 100 Hz with 2 s rest between repetitions and 2.5 min between sets). One hour after the final training bout (i.e. day 10, 20, or 30) animals were killed and the left (stimulated) and right (contralateral control) TA were extracted and weighed. Muscles were fractionated into myofibrillar and sarcoplasmic components. Protein content was calculated via Bradford assay and proteomic analysis of myofibrillar proteins was conducted via liquid chromatography-tandem mass spectrometry of peptide digests. Statistical analysis was conducted using R (v4.3.2.) and functional annotation was performed using the STRING database. Two-way mixed ANOVA was used to investigate differences between condition (stimulated vs contralateral control) and time (0, 10, 20, or 30 days). The protein content of stimulated TA increased (P &lt; 0.05) from 0.579 ± 0.05 mg at day zero to 1.096 ± 0.15 mg after 30 days of PRT, whereas the protein content of control TA (0.618 ± 0.04 mg) was consistent across the 30-day experimental period. Proteomic analysis encompassed 244 proteins and the abundance of 45 proteins exhibited a significant (P &lt; 0.05) interaction between condition and time. Stimulated muscle was enriched in mitochondrial enzymes. For example, the beta-subunit of ATPase synthase (ATPB) increased from 14.6 ± 4.5 to 74 ± 15.6 μg in stimulated TA and was 17 ± 5 in control TA. PRT also increased the abundance of neonatal myosin heavy chain (MYH8), four-and-a-half LIM domains protein 1 (FHL1) and muscular LMNA interacting protein (MLIP). These findings suggest the energy requirements of daily PRT are met by mitochondrial metabolism and PRT may be associated with activation of the muscle developmental programme.

Levator ani muscle avulsion and subsequent vaginal delivery: 8-year longitudinal follow-up.

To assess the evolution of levator ani muscle (LAM) avulsion from 1 year to 8 years after first delivery in women with and those without subsequent vaginal delivery. In addition, to assess whether women with full or partial avulsion 8 years after first delivery have larger LAM hiatal area and more symptoms of pelvic organ prolapse compared to women with normal LAM insertion. In this single-center longitudinal study, 195 women who were primiparous at the start of the study were included and underwent transperineal ultrasound examination 1 year and 8 years after first delivery. Muscle insertion was assessed by tomographic ultrasound imaging in the axial plane. Full LAM avulsion was defined as abnormal muscle insertion in all three central slices. Partial LAM avulsion was defined as abnormal muscle insertion in one or two central slices. Eight years after the first delivery, LAM hiatal area was assessed at rest, during maximum pelvic floor muscle contraction and on maximum Valsalva maneuver. To assess symptoms of pelvic organ prolapse, the vaginal symptoms module of the International Consultation on Incontinence Questionnaire was used. At 1-year follow-up, 25 (12.8%) women showed signs of LAM avulsion, of whom 20 fulfilled the sonographic criteria of full avulsion and five of partial avulsion. Eight years after the first delivery, 35 (17.9%) women were diagnosed with avulsion, of whom 25 were diagnosed with full avulsion and 10 with partial avulsion. No woman with partial or full avulsion at 1 year had improved avulsion status at the 8-year follow-up. Of the 150 women who had subsequent vaginal delivery, 21 (14.0%) women were diagnosed with partial or full LAM avulsion 1 year after first delivery, and 31 (20.7%) women were diagnosed with partial or full avulsion 8 years after first delivery. Of the 45 women without subsequent vaginal delivery, one woman with partial avulsion 1 year after first delivery was diagnosed with full avulsion at the 8-year follow-up. All women with full avulsion at 1-year follow-up were diagnosed with full avulsion at the 8-year follow-up regardless of whether they had subsequent vaginal delivery. At 8-year follow-up, women with full avulsion had statistically significantly larger LAM hiatal area compared to women with normal muscle insertion. Mean ± SD vaginal symptom scores ranged between 5.5 ± 5.7 and 6.0 ± 4.0 and vaginal symptom quality of life scores ranged between 0.9 ± 1.4 and 1.5 ± 2.2 and did not differ significantly between women with normal muscle insertion and women with partial or full avulsion at 8-year follow-up. More LAM avulsions were present 8 years compared with 1 year after first delivery in women with subsequent vaginal delivery. Except for one primipara, all women without subsequent vaginal delivery had unchanged LAM avulsion status between 1 year and 8 years after their first delivery. Larger LAM hiatal area was found in women with full avulsion compared to those with normal muscle insertion at 8-year follow-up. Vaginal symptoms scores were low and did not differ between women with normal muscle insertion and those with partial or full avulsion at 8-year follow-up. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Eccentric Muscle Strengthening Using Maximal Contractions Is Deleterious in Knee Osteoarthritis: A Randomized Clinical Trial.

Objectives: To show the superiority of eccentric versus concentric strengthening in terms of improving quadriceps strength in knee osteoarthritis (OA), a randomized controlled study was conducted to perform 12 sessions of either eccentric or concentric isokinetic muscle strengthening over 6 weeks. Methods: We recruited males and females, aged between 40 and 70 years, with predominantly unilateral femorotibial OA. Exclusion criteria were having a prosthesis, inflammatory arthritis or flare-up of OA, symptomatic patellofemoral OA, cardiovascular or pulmonary disease that could be a contraindication to the study treatment, and any pathology that could cause muscle weakness. The primary endpoint was the between-group difference in change in maximum concentric isokinetic knee extension peak torque (PT) at 60°/s on the OA side at 6 weeks. Secondary endpoints were between-group difference in change in concentric hamstring PT at 60°/s; eccentric quadriceps and hamstring PT at 30°/s; 10 m and 200 m walking speeds; pain and functional status (WOMAC score) at 6 weeks and 6 months. Results: The sample consisted of 11 females and 27 males, with a mean age of 57.7 ± 7.52 years and a body mass index (BMI) of 25.95 ± 3.93 kg/m2. Quadriceps strength increased more at 6 weeks in the concentric than the eccentric group with no statistical difference. There was a rate of 25% major adverse events in the eccentric group. Conclusions: Eccentric training resulted in a smaller improvement in quadriceps strength than concentric training and was associated with a high risk of muscle injury, particularly to the hamstring muscles.

Reliability of ankle dorsiflexor muscle strength, rate of force development, and tibialis anterior electromyography after stroke.

Measures of hemiparetic ankle dorsiflexor muscle strength and rate of force development (RFD) are often used to determine the efficacy of rehabilitation interventions after stroke. However, evidence supporting the reliability of these measures is limited. This brief report provides a secondary analysis investigating the between-session reliability of isometric ankle dorsiflexor muscle strength, rate of force development (RFD), and tibialis anterior electromyography (TA EMG), in people with chronic stroke. Participants (n=15) completed three maximal isometric contractions of the ankle dorsiflexor muscles as fast as possible using a rigid dynamometer. Tests were repeated seven days later. Outcomes included ankle dorsiflexor isometric maximal voluntary contraction (MVC), RFD in the first 200ms (RFD200ms), time to reach 90% MVC, and peak TA EMG. Data were analysed for 13 participants using intra-class correlation coefficients (ICC) and standard error of the measure percentage (SEM%). Reliability was higher when analysing the mean of three trials rather than the best of three trials. There was excellent reliability for isometric dorsiflexor MVC (ICC 0.97 [95% CI 0.92, 0.99], SEM% 7%). However, for other outcomes, while the ICC indicated good reliability, the lower bound of the 95% confidence interval of the ICC fell in the moderate range for TA EMG (ICC 0.86 [95% CI 0.60, 0.96], SEM% 25%) and time to reach 90% MVC (ICC 0.8 [95% CI 0.53, 0.93], SEM% 23%) and in the poor range for dorsiflexor RFD200ms (ICC 0.79 [95% CI 0.48, 0.92], SEM% 24%). The findings raise concerns about the reliability of measures of rapid force production in the dorsiflexor muscles after stroke. Given the functional significance of the ankle dorsiflexors, larger studies should be conducted to further investigate these concerns and explore reliable methods for measuring rapid force production in the hemiparetic dorsiflexor muscles.

Foot-dominance does not influence force variability during ankle dorsiflexion and foot adduction

ABSTRACT The aim of our study was to compare the force steadiness and the discharge characteristics of motor units in the tibialis anterior (TA) during ankle dorsiflexion and foot adduction produced by submaximal isometric contractions with the dominant and non-dominant foot. Fifteen young men performed maximal and submaximal contractions at five target forces with both legs, and motor unit activity in TA was recorded using high-density electromyography. Maximal force and the fluctuations in force during submaximal contractions were similar between the two legs (p > 0.05). Motor unit activity was characterized by measures of mean discharge rate (MDR), coefficient of variation for interspike interval (CoV for ISI), and standard deviation of the filtered cumulative spike train (SD of fCST). There were no statistically significant differences in motor unit activity between legs during ankle dorsiflexion. In contrast, the MDR and the CoV for ISI but not the SD of fCST, were greater for the non-dominant foot compared with the dominant foot during foot adduction. Nonetheless, these differences in motor unit activity were not sufficient to influence the force fluctuations during the submaximal contractions. These results indicate that control of the force produced by TA during the two actions was not influenced by limb dominance.

Design and Scalable Fast Fabrication of Biaxial Fabric Pouch Motors for Soft Robotic Artificial Muscle Applications

Soft pouch motors, engineered to mimic the natural movements of skeletal muscles, play a crucial role in advancing robotics and exoskeleton development. However, the fabrication techniques often involve multistage processes; they lack soft sensing capabilities and are sensitive to cutting and damage. This work introduces a new textile‐based pouch motors with the capacity for biaxial actuation and capacitive sensory functions, achieved through the application of computerized knitting technology using ultrahigh molecular weight polyethylene yarn (Spectra) and conductive silver yarns. This method enables the rapid and scalable mass fabrication of robust pouch motors. The resulting pouch motors exhibit maximum lifting capacity of 10 kg, maximum contraction of 53.3% along the y‐axis, and transverse extension of 41.18% along the x‐axis at 50 kPa pressure. Finite element analysis closely matches the experimental data. The capacitance signals in relation to contraction motion are well suited for detecting air pressure levels and hold promise for applications requiring robotic control. Notably, it effectively elevates an ankle joint simulator at a 20° angle, highlighting its potential for applications such assisting individuals with foot drop. This study presents a practical demonstration of the soft ankle exosuit designed to provide lifting support for individuals facing this mobility challenge.

Minimum Intensity of Daily Six Eccentric Contractions to Increase Muscle Strength and Size.

Our previous study showed that daily six maximal eccentric contractions that were performed 5 days a week for 4 weeks increased maximal voluntary isometric (MVC-ISO), concentric (MVC-CON), and eccentric contraction (MVC-ECC) strength of the elbow flexors and muscle thickness of biceps brachii and brachialis (MT) by 8.3 ± 4.9%, 11.1 ± 7.4%, 13.5 ± 11.5%, and 10.6 ± 5.1%, respectively. In the present study, we tested the hypothesis that the muscle strength and MT would still increase when the training intensity was reduced to 2/3 or 1/3 of the peak MVC-ECC torque. Thirty-six healthy young (19-24 years) adults who had not performed resistance training were placed to three groups (n = 12/group): 2/3MVC or 1/3MVC that performed six eccentric contractions with 2/3 or 1/3 MVC-ECC load using a dumbbell 5 days a week for 4 weeks or control group that did not perform any training. Changes in the MVC-ISO, MVC-CON, MVC-ECC torque, and MT before and after the 4-week period were compared among the groups and with the group of the previous study in which six maximal eccentric contractions were performed 5 days a week for 4 weeks (MVC group; n = 12). The control and 1/3MVC groups showed no significant changes in any measures. Significant (p < 0.05) increases in MVC-ISO (10.3 ± 11.4%), MVC-CON (10.9 ± 9.5%), and MVC-ECC (9.3 ± 8.8%) torque and MT (10.1 ± 9.2%) were observed for the 2/3MVC group. These changes were not significantly different from those of the MVC group. These results suggest that the 2/3-intensity eccentric contractions with a dumbbell are as effective as maximal-intensity isokinetic eccentric contractions to induce muscle adaptations.

Muscle Strength Preservation During Repeated Sets of Fatiguing Resistance Exercise: A Secondary Analysis.

Nuzzo, JL. Muscle strength preservation during repeated sets of fatiguing resistance exercise: A secondary analysis. J Strength Cond Res 38(6): 1149-1156, 2024-During sustained or repeated maximal voluntary efforts, muscle fatigue (acute strength loss) is not linear. After a large initial decrease, muscle strength plateaus at approximately 40% of baseline. This plateau, which likely reflects muscle strength preservation, has been observed in sustained maximal isometric and repeated maximal isokinetic contractions. Whether this pattern of fatigue occurs with traditional resistance exercise repetitions with free weights and weight stack machines has not been overviewed. Here, the aim was to determine whether the number of repetitions completed across 4 or more consecutive repetitions-to-failure tests exhibits the same nonlinear pattern of muscle fatigue. A secondary analysis was applied to data extracted as part of a recent meta-analysis on repetitions-to-failure tests. Studies were eligible if they reported mean number of repetitions completed in 4-6 consecutive repetitions-to-failure tests at a given relative load. Twenty-nine studies were included. Overall, the results show that the number of repetitions completed in consecutive repetitions-to-failure tests at a given load generally decreases curvilinearly. The numbers of repetitions completed in sets 2, 3, 4, 5, and 6 were equal to approximately 70, 55, 50, 45, and 45% of the number of repetitions completed in set 1, respectively. Longer interset rest intervals typically attenuated repetition loss, but the curvilinear pattern remained. From the results, a chart was created to predict the number of repetitions across 6 sets of resistance exercise taken to failure based on the number of repetitions completed in set 1. The chart is a general guide and educational tool. It should be used cautiously. More data from a variety of exercises, relative loads, and interset rest intervals are needed for more precise estimates of number of repetitions completed during repeated sets of fatiguing resistance exercise.

Impact of pelvic floor muscle training on sexual function in women affected by stress urinary incontinence.

Pelvic floor muscle training can effectively improve pelvic floor muscle strength and activities; however, its impact on sexual function in women with stress urinary incontinence remains unclear. The study sought to investigate the impact of pelvic floor muscle training on pelvic floor muscle and sexual function in women with stress urinary incontinence. This was a retrospective observational study involving women who visited a urogynecologic clinic at a tertiary medical center. Patients with stress urinary incontinence without pelvic organ prolapse underwent pelvic floor muscle training programs that included biofeedback and intravaginal electrostimulation. Other evaluations included pelvic floor manometry, electromyography, and quality-of-life questionnaires, including the short forms of the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire, Urogenital Distress Inventory, and Incontinence Impact Questionnaire. Clinical characteristics, vaginal squeezing and resting pressure, maximal pelvic floor contraction, duration of sustained contraction, quality-of-life scores, and sexual function were compared between baseline and after the pelvic floor muscle training programs. There were 61 women included in the study. The mean number of treatment sessions was 12.9 ± 6.3, and the mean treatment duration was 66.7 ± 32.1days. The short forms of the Urogenital Distress Inventory (7.7 ± 3.8 vs 1.8 ± 2.1; P < .001) and Incontinence Impact Questionnaire (5.9 ± 4.3 vs 1.8 ± 2.0; P < .001) scores significantly improved after the pelvic floor muscle training program. In addition, all pelvic floor muscle activities significantly improved, including maximal vaginal squeezing pressure (58.7 ± 20.1 cmH2O vs 66.0 ± 24.7 cmH2O; P = .022), difference in vaginal resting and maximal squeezing pressure (25.3 ± 14.6 cmH2O vs 35.5 ± 16.0 cmH2O; P < .001), maximal pelvic muscle voluntary contraction (24.9 ± 13.8 μV vs 44.5 ± 18.9 μV; P < .001), and duration of contraction (6.2 ± 5.7 s vs 24.9 ± 14.6s; P < .001). Nevertheless, the short form of the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire score demonstrated no significant improvement (28.8 ± 9.7 vs 29.2 ± 12.3; P = .752). Pelvic floor muscle training programs may not improve sexual function in women with stress urinary incontinence. The strength of this study is that we evaluated sexual function with validated questionnaires. The small sample size and lack of long-term data are the major limitations. Pelvic floor muscle training can improve pelvic floor muscle activities and effectively treat stress urinary incontinence; however, it may not improve sexual function.