Acute Effect of Ankle Kinesio™ Taping on Lower-Limb Biomechanics During Single-Legged Drop Landing.

CONTEXT: Chronic ankle instability is documented to be followed by a recurrence of giving away episodes due to impairments in mechanical support. The application of ankle Kinesiotaping (KT) as a therapeutic intervention has been increasingly raised among athletes and physiotherapists. OBJECTIVES: This study aimed to investigate the impacts of ankle KT on the lower-limb kinematics, kinetics, dynamic balance, and muscle activity of college athletes with chronic ankle instability. DESIGN: A crossover study design. PARTICIPANTS: Twenty-eight college athletes with chronic ankle sprain (11 females and 17 males, 23.46 [2.65] y, 175.36 [11.49] cm, 70.12 [14.11] kg) participated in this study. SETTING: The participants executed 3 single-leg drop landings under nontaped and ankle Kinesio-taped conditions. Ankle, knee, and hip kinematics, kinetics, and dynamic balance status and the lateral gastrocnemius, medial gastrocnemius, tibialis anterior, and peroneus longus muscle activity were recorded and analyzed. RESULTS: The application of ankle KT decreased ankle joint range of motion (P = .039) and angular velocities (P = .044) in the sagittal plane, ground reaction force rate of loading (P = .019), and mediolateral time to stability (P = .035). The lateral gastrocnemius (0.002) and peroneus longus (0.046) activity amplitudes also experienced a significant decrease after initial ground contact when the participants' ankles were taped, while the application of ankle KT resulted in an increase in the peroneus longus (0.014) activity amplitudes before initial ground contact. CONCLUSIONS: Ankle lateral supports provided by KT potentially decreases mechanical stresses applied to the lower limbs, aids in dynamic balance, and lowers calf muscle energy consumption; therefore, it could be offered as a suitable supportive means for acute usage in athletes with chronic ankle instability.

Differences in elbow extensor muscle characteristics between resistance-trained men and women.

PURPOSE: Muscular strength is suggested to be dependent upon muscle characteristics. Yet, sex-specific relationships of muscle characteristics to strength in the resistance-trained require investigation. Therefore, the purpose was to evaluate sex differences in muscle characteristics and isometric strength in the elbow extensors, as well as their respective associations. METHODS: Resistance-trained men (n = 15, mean ± SD 22 ± 4 years, 87.5 ± 12.8 kg, 16.9 ± 2.9% body fat) and women (n = 15, mean ± SD 25 ± 5 years, 59.3 ± 7.3 kg, 22.4 ± 4.2% body fat) were tested. B-mode ultrasound images assessed muscle thickness, pennation angle, and echo intensity. Muscle volume and fascicle length were estimated from previously validated equations. Maximal voluntary isometric contraction measured elbow extensors isometric strength. Independent samples t-tests and Fisher's r-to-z test examined differences between sexes. RESULTS: Sex differences existed in all muscle characteristics (p < 0.05). Men's absolute strength (27.86 ± 3.55 kg) was significantly greater than women (16.15 ± 3.15 kg), but no differences were noted when controlling for muscle volume (men 0.069 ± 0.017, women 0.077 ± 0.022 kg/cm3). Sex differences did not exist in the relationships of muscle characteristics to strength with muscle size having the largest correlations. However, the relationship between echo intensity and body fat was different in men (r = - 0.311) and women (r = 0.541, p = 0.0143). CONCLUSIONS: Sex differences in isometric elbow extensor strength are eliminated when expressed relative to muscle volume. Relationships of echo intensity and body fat were different between men and women and may be indicative of greater adipose infiltration in women.

Quantification and simulation of layer-specific mitral valve interstitial cells deformation under physiological loading.

Within each of the four layers of mitral valve (MV) leaflet tissues there resides a heterogeneous population of interstitial cells that maintain the structural integrity of the MV tissue via protein biosynthesis and enzymatic degradation. There is increasing evidence that tissue stress-induced MV interstitial cell (MVIC) deformations can have deleterious effects on their biosynthetic states that are potentially related to the reduction of tissue-level maintenance and to subsequent organ-level failure. To better understand the interrelationships between tissue-level loading and cellular responses, we developed the following integrated experimental-computational approach. Since in vivo cellular deformations are not directly measurable, we quantified the in-situ layer-specific MVIC deformations for each of the four layers under a controlled biaxial tension loading device coupled to multi-photon microscopy. Next, we explored the interrelationship between the MVIC stiffness and deformation to layer-specific tissue mechanical and structural properties using a macro-micro finite element computational model. Experimental results indicated that the MVICs in the fibrosa and ventricularis layers deformed significantly more than those in the atrialis and spongiosa layers, reaching a nucleus aspect ratio of 3.3 under an estimated maximum physiological tension of 150N/m. The simulated MVIC moduli for the four layers were found to be all within a narrow range of 4.71-5.35kPa, suggesting that MVIC deformation is primarily controlled by each tissue layer's respective structure and mechanical behavior rather than the intrinsic MVIC stiffness. This novel result further suggests that while the MVICs may be phenotypically and biomechanically similar throughout the leaflet, they experience layer-specific mechanical stimulatory inputs due to distinct extracellular matrix architecture and mechanical behaviors of the four MV leaflet tissue layers. This also suggests that MVICs may behave in a layer-specific manner in response to mechanical stimuli in both normal and surgically modified MVs.

Standard isometric contraction has higher reliability than maximum voluntary isometric contraction for normalizing electromyography during level walking among older adults with knee osteoarthritis.

Introduction: Electromyography (EMG) normalization often relies on maximum voluntary isometric contraction (MVIC), which may not be suitable for knee osteoarthritis (KOA) patients due to difficulties in generating maximum joint torques caused by pain. This study aims to assess the reliability of standard isometric contraction (SIC) for EMG normalization in older adults with KOA, comparing it with MVIC. Methods: We recruited thirty-five older adults with KOA and collected root mean square EMG amplitudes from seven muscles in the affected limb during level walking, SIC, and MVIC tests. EMG data during level walking were normalized using both SIC and MVIC methods. This process was repeated after at least 1 week. We calculated intra-class correlation coefficients (ICCs) with 95% confidence intervals to evaluate between- and within-day reliabilities. Results: SIC tests showed higher between- (ICC: 0.75-0.86) and within-day (ICC: 0.84-0.95) ICCs across all seven muscles compared to MVIC tests. When normalized with SIC, all seven muscles exhibited higher between- (ICC: 0.67-0.85) and within-day (ICC: 0.88-0.99) ICCs compared to MVIC normalization. Conclusion: This study suggests that SIC may offer superior movement consistency and reliability compared to MVIC for EMG normalization during level walking in older adults with KOA.

Towards a comprehensive biomechanical assessment of the elderly combining in vivo data and in silico methods.

The aging process is commonly accompanied by a general or specific loss of muscle mass, force and/or function that inevitably impact on a person's quality of life. To date, various clinical tests and assessments are routinely performed to evaluate the biomechanical status of an individual, to support and inform the clinical management and decision-making process (e.g., to design a tailored rehabilitation program). However, these assessments (e.g., gait analysis or strength measures on a dynamometer) are typically conducted independently from one another or at different time points, providing clinicians with valuable yet fragmented information. We hereby describe a comprehensive protocol that combines both in vivo measurements (maximal voluntary isometric contraction test, superimposed neuromuscular electrical stimulation, electromyography, gait analysis, magnetic resonance imaging, and clinical measures) and in silico methods (musculoskeletal modeling and simulations) to enable the full characterization of an individual from the biomechanical standpoint. The protocol, which requires approximately 4 h and 30 min to be completed in all its parts, was tested on twenty healthy young participants and five elderlies, as a proof of concept. The implemented data processing and elaboration procedures allowing for the extraction of several biomechanical parameters (including muscle volumes and cross-sectional areas, muscle activation and co-contraction levels) are thoroughly described to enable replication. The main parameters extracted are reported as mean and standard deviation across the two populations, to highlight the potential of the proposed approach and show some preliminary findings (which were in agreement with previous literature).

Early neuromechanical outcomes of the triceps surae muscle-tendon after an Achilles' tendon repair.

OBJECTIVES: To compare the neuromechanical and functional characteristics of the legs of athletes who underwent unilateral Achilles' tendon repair and their controls, and to determine any correlation between the characteristics. DESIGN: A case-control and cross-sectional study. SETTING: A university institute. PARTICIPANTS: Male athletes (N=33) were recruited; 23 in the ≥3- and <12-month postsurgical group (median age, 29.8y; age range, 21.9-40.0y) and 10 in the control group (median age, 30.0y; age range, 21.1-39.5y) who had not undergone any surgery. INTERVENTION: Surgical Achilles' tendon repair in the study group. MAIN OUTCOME MEASURES: Bilateral measurements of activation strategy involving the triceps surae and tibialis anterior muscles, mechanical properties of the Achilles' tendon, and explosive performance tests were conducted. RESULTS: Compared with the noninjured legs and the control legs, the repaired legs showed lower normalized rates of electromyographic rise (RER) in the soleus, gastrocnemius medialis, and gastrocnemius lateralis (P ranged between .006 and .001); and less tendon stiffness, greater hysteresis, and less rates of force development (RFD) (P ranged between .006 and <.001). Repaired legs had less ankle dorsiflexion, a shorter 1-leg hopping distance, and lower balance scores (P≤.001). The noninjured legs of the athletes who underwent surgical Achilles' tendon repair had a lower normalized RER (0-50 ms) in the soleus and lateral gastrocnemius when compared with the legs of the healthy controls (P=.011). The neuromechanical outcomes and explosive performances showed correlations with RFD, 1-leg hopping distance, and balance score. CONCLUSIONS: The athletes who underwent unilateral Achilles' tendon repair demonstrated bilateral neuromechanical deficits within the 1-year postsurgical period.

Do the Testing Posture and the Grip Modality Influence the Shoulder Maximal Voluntary Isometric Contraction?

Assessing and monitoring shoulder strength is extremely important during rehabilitation. A fixed dynamometer represents a valid and inexpensive assessment method. However, it has not been studied whether posture and grip modality influence shoulder muscle strength. The aim of this study was to compare shoulder strength values between sitting and standing positions and between the handle and cuff grip modalities. A total of 40 volunteers were divided into a posture (PG) and a handle-cuff group (HCG). Participants in the PG were asked to perform a maximum voluntary isometric contraction (MVIC) for shoulder flexion, extension, ab-adduction, and intra-extra rotation in standing and sitting positions. The HCG participants were tested in a standing position while holding a handle or with a cuff around their wrist. PG showed higher forces in the standing position for shoulder flexion (p = 0.009); internal rotation showed higher values in the sitting position (p = 0.003). ER/IR ratio was significantly higher in the standing position (p < 0.001). HCG showed higher significant forces during cuff modality in all positions and grip modalities, including the ER/IR ratio (p < 0.05). Different body positions and grip modalities influenced the assessment of shoulder strength as recorded by a fixed dynamometer; therefore, these factors should be carefully considered when carrying out a shoulder strength assessment, and we encourage the development of assessment guidelines to make future clinical trial results comparable.

Topical Cannabidiol and the Progression Rate of Delayed Onset Muscle Soreness.

This study investigated the efficacy of topical cannabidiol (CBD) ointment in reducing localized inflammation, minimizing performance detriments, and attenuating soreness associated with delayed onset muscle soreness (DOMS). In a double blind randomized control trial, upper-arm circumferences, maximal voluntary isometric contractions (MVICs) for elbow flexion at 90° and 30° for college-aged participants (n = 21, age 20.8 ± 1.9 years) were assessed at baseline. Participants then performed a DOMS-inducing protocol for the biceps brachii. Topical CBD ointment and placebo (P) ointment were randomly assigned and applied 30 minutes, 24, 48 and 72 hours post the DOMS protocol. The baseline parameters and a visual analog scale (VAS) to assess perceived soreness were assessed 24, 48 and 72 hours post DOMS protocol. A 4x2 repeated measures factorial ANOVA (P < 0.05) analyzed both within and between subject differences. No changes were statistically significant on any days between conditions: Upper-arm circumferences in the CBD arm (7.1 ± 5.8 cm) and in the P arm (7.3 ± 5.8 cm). MVICs were reduced at both the 90° and 30° positions (-5.9 ± 9.0 Nm (90°)); (-4.8 ± 6.5 Nm (30°)) and the P arm (-5.0 ± 10.0 Nm (90°)); (-4.6 ± 5.3 Nm (30°)). Soreness increased in both the CBD arm (6.1 ± 2.1) and the P arm (5.5 ± 2.6) over time. Topical CBD therefore did not alter any parameters vs the P treatment, thus the use of topical CBD does not attenuate the effects of DOMS.

A meta-analysis of post-exercise outcomes in people with amyotrophic lateral sclerosis.

Objective: To systematically evaluate post-exercise outcomes related to function and quality of life in people with ALS. Methods: PRISMA guidelines were used for identifying and extracting articles. Levels of evidence and quality of articles were judged based on The Oxford Centre for Evidence-based Medicine Levels of Evidence and the QualSyst. Outcomes were analyzed with Comprehensive Meta-Analysis V2 software, random effects models, and Hedge's G. Effects were examined at 0-4 months, up to 6 months, and > 6 months. Pre-specified sensitivity analyses were performed for 1) controlled trials vs. all studies and 2) ALSFRS-R bulbar, respiratory, and motor subscales. Heterogeneity of pooled outcomes was computed with the I2 statistic. Results: 16 studies and seven functional outcomes met inclusion for the meta-analysis. Of the outcomes explored, the ALSFRS-R demonstrated a favorable summary effect size and had acceptable heterogeneity and dispersion. While FIM scores demonstrated a favorable summary effect size, heterogeneity limited interpretations. Other outcomes did not demonstrate a favorable summary effect size and/or could not be reported due to few studies reporting outcomes. Conclusions: This study provides inconclusive guidance regarding exercise regimens to maintain function and quality of life in people with ALS due to study limitations (e.g., small sample size, high attrition rate, heterogeneity in methods and participants, etc.). Future research is warranted to determine optimal treatment regimens and dosage parameters in this patient population.

Gluteal muscle activation during rehabilitation exercises in female field hockey players.

BACKGROUND: Field hockey, a team sport played by both men and women at both recreational and professional levels, requires maintaining a forward flexed posture putting stress on the lumbar spine. Hence, it is necessary to assess the muscles supporting the lumbar spine, especially those surrounding the hip, to inform strengthening exercises for this population. OBJECTIVES: To establish the best body weight rehabilitation exercises shown to produce high muscle activation (≥ 61%MVIC - maximal voluntary isometric contraction) for both the gluteus maximus (Gmax) and medius (Gmed) muscles. Four exercises fell into this category. METHOD: Surface electromyography (sEMG) was used to record the muscle activation of Gmax and Gmed of four body weight rehabilitation exercises in 26 high-performance female field hockey players. The %MVIC activation data of both Gmax and Gmed were analysed using a three-way ANOVA. RESULTS: The single-leg squat generated the highest %MVIC activation of both Gmax (125.65%MVIC) and Gmed (126.30%MVIC). The only statistically significant difference for Gmax was between the single-leg squat and plank with hip extension (p = 0.0487). No statistically significant difference was observed for Gmed between the four body weight rehabilitation exercises (p = 0.6285). CONCLUSION: The four exercises generated similar %MVIC activation levels. The single-leg squat produced the highest observed %MVIC of Gmax and Gmed in high-performance female field hockey players and is, therefore, recommended. CLINICAL IMPLICATIONS: Implementation of the findings could result in benefits during prehabilitation, injury prevention programmes and the later stages of rehabilitation for high-performance female field hockey players.

Hydrogen sulfide inhibits aortic valve calcification in heart via regulating RUNX2 by NF-κB, a link between inflammation and mineralization.

INTRODUCTION: Hydrogen sulfide (H2S) was revealed to inhibit aortic valve calcification and inflammation was implicated in the pathogenesis of calcific aortic valve disease (CAVD). OBJECTIVES: We investigate whether H2S inhibits mineralization via abolishing inflammation. METHODS AND RESULTS: Expression of pro-inflammatory cytokines, interleukin-1ß (IL-1ß) and tumor necrosis factor α (TNF-α) were increased in patients with CAVD and in calcified aortic valve of ApoE-/- mice. Administration of H2 2S releasing donor (4-methoxyphenyl piperidinylphosphinodithioc acid (AP72)) exhibited inhibition on both calcification and inflammation in aortic valve of apolipoprotein E knockout mice (ApoE-/-) mice is reflected by lowering IL-1ß and TNF-α levels. Accordingly, AP72 prevented the accumulation of extracellular calcium deposition and decreased nuclear translocation of nuclear factor-κB (NF-κB) in human valvular interstitial cells (VIC). This was also accompanied by reduced cytokine response. Double-silencing of endogenous H2S producing enzymes, Cystathionine gamma-lyase (CSE) and Cystathionine beta-synthase (CBS) in VIC exerted enhanced mineralization and higher levels of IL-1ß and TNF-α. Importantly, silencing NF-κB gene or its pharmacological inhibition prevented nuclear translocation of runt-related transcription factor 2 (Runx2) and subsequently the calcification of human VIC. Increased levels of NF-κB and Runx2 and their nuclear accumulation occurred in ApoE-/- mice with a high-fat diet. Administration of AP72 decreased the expression of NF-κB and prevented its nuclear translocation in VIC of ApoE-/- mice on a high-fat diet, and that was accompanied by a lowered pro-inflammatory cytokine level. Similarly, activation of Runx2 did not occur in VIC of ApoE-/- mice treated with H2S donor. Employing Stimulated Emission Depletion (STED) nanoscopy, a strong colocalization of NF-κB and Runx2 was detected during the progression of valvular calcification. CONCLUSIONS: Hydrogen sulfide inhibits inflammation and calcification of aortic valve. Our study suggests that the regulation of Runx2 by hydrogen sulfide (CSE/CBS) occurs via NF-κB establishing a link between inflammation and mineralization in vascular calcification.

Effects of caffeine and sex on muscle performance and delayed-onset muscle soreness after exercise-induced muscle damage: a double-blind randomized trial.

The present study aims to investigate effects of caffeine ingestion and sex difference on muscle performance, delayed-onset muscle soreness (DOMS), and various biomarkers under exercise-induced muscle damage (EIMD). Twenty (10 male and 10 female) healthy elite college athletes were recruited. Participants ingested either caffeine (6 mg/kg) or a placebo in a randomized, double-blind, and counterbalanced fashion at 24 and 48 h following EIMD. Muscle performance, DOMS, and blood samples were taken an hour before and an hour after supplementation. Caffeine ingestion restored impaired maximal voluntary isometric contractions (MVIC: 10.2%; MVICpost: 7.2%, both P < 0.05) during EIMD across both sexes. Following caffeine ingestion during MVIC, while affected by EIMD, an interaction was found in DOMS and serum K+ (both P < 0.05), with males showing greater attenuation (21.5 and 16.9%, respectively) compared with females (4.6 and 1.3%, respectively). DOMS demonstrated an inverse correlation with MVIC after caffeine ingestion both overall and among male athletes (r = -0.34 and -0.54, respectively; P < 0.05) but not among female athletes (r = -0.11; P > 0.05) under EIMD. In addition, caffeine ingestion increased postexercise serum glucose and lactate concentrations across both sexes (both P < 0.05). This is the first study to show that male athletes, compared with female athletes, experience a greater reduction in DOMS during enhanced MVIC when caffeine was consumed, suggesting men might receive greater ergogenic effects from caffeine when affected by EIMD. Furthermore, caffeine ingestion was able to restore impaired muscle power among elite collegiate athletes across both sexes.NEW & NOTEWORTHY Exercise-induced muscle damage (EIMD) reduces anaerobic/aerobic performance and increases delayed-onset muscle soreness (DOMS) during exercise. We show that acute caffeine supplementation at a dosage of 6 mg/kg seems to facilitate recovery of anaerobic muscle power and attenuate DOMS after EIMD across both sexes. Furthermore, male athletes, compared with female athletes, when caffeine was prescribed, experience a greater reduction in DOMS with better restoration of impaired maximal voluntary isometric contractions. This suggests that male athletes might benefit from the ergogenic effect of acute caffeine supplementation after the onset of EIMD.

Global electromyographic signal characteristics depend on maximal isometric contraction method in the knee extensors.

OBJECTIVE: To determine if maximal isometric contraction (MVIC) method (i.e., ramp (MVICRAMP) versus traditional MVIC) influences (1) maximal voluntary isometric torque (MVIT) production of the knee extensors, (2) electromyographic signal amplitude (EMGAMP), and (3) EMG mean power frequency (EMGMPF) of the rectus femoris and vastus lateralis in moderately-to highly-activated subjects. We hypothesized that EMGAMP would be greater during the MVICRAMP than MVIC muscle contractions, but that there would be no difference in MVIT. APPROACH: Twenty-five males (23.4 ±â€¯3.4 y; % voluntary activation = 93.9 ±â€¯5.1%) visited the laboratory and completed MVICRAMPs and MVICs. During all contractions, leg extensor torque and sEMG signals from the vastus lateralis (VL) and rectus femoris (RF) were recorded. MAIN RESULTS: There was no significant difference in the MVIT produced (p = 0.65) or in EMGMPF (p = 0.052) during MVICRAMP versus MVIC. However, EMGAMP was 18.1% higher during the MVICRAMP than MVIC (p = 0.004). SIGNIFICANCE: Maximal isometric muscle contraction method significantly influenced EMGAMP, and had a moderate effect on EMGMPF (d = 0.49). Investigators who utilize MVICs to determine maximal EMG signal amplitude and frequency to normalize their EMG signals should be aware of these differences.

Maximal voluntary isometric contraction tests for normalizing electromyographic data from different regions of supraspinatus and infraspinatus muscles: Identifying reliable combinations.

This study aimed to identify optimal sets of maximal voluntary isometric contractions (MVICs) for normalizing EMG data from anterior and posterior regions of the supraspinatus, and superior, middle and inferior regions of the infraspinatus. 31 right-handed young healthy individuals (15 males, 16 females) participated. EMG activity was obtained from two regions of supraspinatus and three regions of infraspinatus muscles via fine wire electrodes. Participants performed 15 MVIC tests against manual resistance. The EMG data were normalized to the maximum values. Optimal sets of MVIC combinations, defined as those which elicited >90% MVIC activation in the muscles of interest in >80% and >90% of the population, were obtained. EMG data from the inferior region of infraspinatus were removed from analysis due to technical problem. No single test achieved maximal activation of both regions of either the supraspinatus or infraspinatus. Instead, a combination of 6-8 MVICs were required to reach >90% MVIC activation in both parts of those muscles. In all regions of the rotator cuff muscles, the optimal combination was obtained with 8-10 MVICs. The proposed combinations can reduce inter-participant variability in generating maximal activation from different regions of the supraspinatus and infraspinatus muscles.

Surgeon symptoms, strain, and selections: Systematic review and meta-analysis of surgical ergonomics.

BACKGROUND: Many surgeons experience work-related pain and musculoskeletal symptoms; however, comprehensive reporting of surgeon ailments is lacking in the literature. We sought to evaluate surgeons' work-related symptoms, possible causes of these symptoms, and to report outcomes associated with those symptoms. MATERIALS AND METHODS: Five major medical indices were queried for articles published between 1980 and 2014. Included articles evaluated musculoskeletal symptoms and ergonomic outcomes in surgeons. A meta-analysis using a fixed-effect model was used to report pooled results. RESULTS: Forty articles with 5152 surveyed surgeons were included. Sixty-eight percent of surgeons surveyed reported generalized pain. Site-specific pain included pain in the back (50%), neck (48%), and arm or shoulder (43%). Fatigue was reported by 71% of surgeons, numbness by 37%, and stiffness by 45%. Compared with surgeons performing open surgery, surgeons performing minimally invasive surgery (MIS) were significantly more likely to experience pain in the neck (OR 2.77 [95% CI 1.30-5.93]), arm or shoulder (OR 4.59 [2.19-9.61]), hands (OR 2.99 [1.33-6.71], and legs (OR 12.34 [5.43-28.06]) and experience higher odds of fatigue (8.09 [5.60-11.70]) and numbness (6.82 [1.75-26.65]). Operating exacerbated pain in 61% of surgeons, but only 29% sought treatment for their symptoms. We found no direct association between muscles strained and symptoms. CONCLUSIONS: Most surgeons report work-related symptoms but are unlikely to seek medical attention. MIS surgeons are significantly more likely to experience musculoskeletal symptoms than surgeons performing open surgery. Symptoms experienced do not necessarily correlate with strain.

Dynamic versus isometric electromechanical delay in non-fatigued and fatigued muscle: A combined electromyographic, mechanomyographic, and force approach.

This study used a combined electromyographic, mechanomyographic, and force approach to identify electromechanical delay (EMD) from the onsets of the electromyographic to force signals (EMDE-F), onsets of the electromyographic to mechanomyogrpahic signals (EMDE-M), and onsets of mechanomyographic to force signals (EMDM-F). The purposes of the current study were to examine: (1) the differences in EMDE-F, EMDE-M, and EMDM-F from the vastus lateralis during maximal, voluntary dynamic (1 repetition maximum [1-RM]) and isometric (maximal voluntary isometric contraction [MVIC]) muscle actions; and (2) the effects of fatigue on EMDE-F, EMDM-F, and EMDE-M. Ten men performed pretest and posttest 1-RM and MVIC leg extension muscle actions. The fatiguing workbout consisted of 70% 1-RM dynamic constant external resistance leg extension muscle actions to failure. The results indicated that there were no significant differences between 1-RM and MVIC EMDE-F, EMDE-M, or EMDM-F. There were, however, significant fatigue-induced increases in EMDE-F (94% and 63%), EMDE-M (107%), and EMDM-F (63%) for both the 1-RM and MVIC measurements. Therefore, these findings demonstrated the effects of fatigue on EMD measures and supported comparisons among studies which examined dynamic or isometric EMD measures from the vastus lateralis using a combined electromyographic, mechanomyographic, and force approach.

POWER training in chronic stroke individuals: differences between responders and nonresponders.

BACKGROUND: Lower extremity muscle weakness is a primary contributor to post-stroke dysfunction. Resistance training is an effective treatment for hemiparetic weakness and improves walking performance. Post-stroke subject characteristics that do or do not improve walking speed following resistance training are unknown. OBJECTIVE: The purpose of this paper was to describe baseline characteristics, as well as responses to training, associated with achieving a minimal clinically important difference (MCID) in walking speed (≥0.16 m/s) following Post-stroke Optimization of Walking Using Explosive Resistance (POWER) training. METHODS: Seventeen participants completed 24 sessions of POWER training, which included intensive progressive leg presses, jump training, calf raises, sit-to-stands, step-ups, and over ground fast walking. Outcomes included SSWS, FCWS, DGI, FMA-LE, 6-MWT, paretic knee power, non-paretic knee power, and paretic step ratio. RESULTS: Specific to those who reached MCID in SSWS (e.g. "responders"), significant improvements in SSWS, FCWS, 6-MWT, paretic knee power, and non-paretic knee power was realized. Paretic knee power and non-paretic knee power significantly improved in those who did not achieve MCID for gait speed (e.g. "non-responders"). CONCLUSION: The potential for POWER training to enhance general locomotor function was confirmed. Baseline paretic knee strength/power may be an important factor in how an individual responds to this style of training. The lack of change within the non-responders emphasizes the contribution of factors other than lower extremity muscle power improvement to locomotor dysfunction.

A comparison of two gluteus maximus EMG maximum voluntary isometric contraction positions.

Background. The purpose of this study was to compare the peak electromyography (EMG) of the most commonly-used position in the literature, the prone bent-leg (90°) hip extension against manual resistance applied to the distal thigh (PRONE), to a novel position, the standing glute squeeze (SQUEEZE). Methods. Surface EMG electrodes were placed on the upper and lower gluteus maximus of thirteen recreationally active females (age = 28.9 years; height = 164 cm; body mass = 58.2 kg), before three maximum voluntary isometric contraction (MVIC) trials for each position were obtained in a randomized, counterbalanced fashion. Results. No statistically significant (p < 0.05) differences were observed between PRONE (upper: 91.94%; lower: 94.52%) and SQUEEZE (upper: 92.04%; lower: 85.12%) for both the upper and lower gluteus maximus. Neither the PRONE nor SQUEEZE was more effective between all subjects. Conclusions. In agreement with other studies, no single testing position is ideal for every participant. Therefore, it is recommended that investigators employ multiple MVIC positions, when possible, to ensure accuracy. Future research should investigate a variety of gluteus maximus MVIC positions in heterogeneous samples.

The Gluteus Medius Vs. Thigh Muscles Strength Ratio and Their Relation to Electromyography Amplitude During a Farmer's Walk Exercise.

The strength ratio between hamstrings and quadriceps (H/Q) is associated with knee injuries as well as hip abductor muscle (HAB) weakness. Sixteen resistance trained men (age, 32.5 ± 4.2 years) performed 5 s maximal isometric contractions at 75° of knee flexion/extension and 15° of hip abduction on a dynamometer. After this isometric test they performed a Farmer's walk exercise to find out if the muscle strength ratio predicted the electromyography amplitude expressed as a percentage of maximum voluntary isometric contraction (%MVIC). The carried load represented a moderate intensity of 75% of the exercise six repetitions maximum (6RM). Electromyography data from the vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF) and gluteus medius (Gmed) on each leg were collected during the procedure. The groups selected were participants with H/Q ≥ 0.5, HQ < 0.5, HAB/H ≥ 1, HAB/H < 1, HAB/Q ≥ 0.5 and HAB/Q < 0.5. One way ANOVA showed that Gmed activity was significantly greater in the group with HAB/H < 1 (42 ± 14 %MVIC) as compared to HAB/H ≥ 1 (26 ± 10 %MVIC) and HAB/Q < 0.5 (47 ± 19 %MVIC) compared to HAB/Q ≥ 0.5 (26 ± 12 %MVIC). The individuals with HAB/H < 1 were found to have greater activation of their Gmed during the Farmer's walk exercise. Individuals with HAB/Q < 0.5 had greater activation of the Gmed. Gmed strength ratios predict the muscle involvement when a moderate amount of the external load is used. The Farmer's walk is recommended as an exercise which can strengthen the gluteus medius, especially for individuals with a HAB/H ratio < 1 and HAB/Q < 0.5.