Previous studies have used twitch electrical stimulation and accelerometer-based mechanomyography (aMMG) to evaluate muscle function in clinical populations. However, the reproducibility and validity of the methodology has not been defined. This study evaluated the reproducibility and validity of twitch electrical stimulation and aMMG as an assessment of muscle endurance. Participants were healthy males and females 21.8±1.9 years of age. Muscle twitch acceleration was measured using an accelerometer placed over the surface of the muscle. The relationship between acceleration and torque was measured during twitch stimulation of the vastus lateralis muscle. Muscle endurance of the forearm and gastrocnemius was measured during 9 minutes of twitch electrical stimulation, in three stages (3min/stage) of increasing frequency (2Hz, 4Hz, and 6Hz). An Endurance Index (EI) was calculated as the percent of acceleration at the end of each stimulation stage relative to the peak acceleration. Oxygen saturation was measured using near-infrared spectroscopy. Results showed that acceleration correlated with torque during twitch electrical stimulation of the vastus lateralis (mean R²= 0.96±0.04; p<0.05). Measures of forearm EI reproducibility were CV= 2.5-7.4%. EI was significantly higher (12.1%) in the gastrocnemius compared to the forearm (p<0.01). Muscle oxygen saturation was not reduced during stimulation of the forearm (72.6±9.8% at 2Hz, 73.2±11.6% at 4Hz, and 71.0±12.5% at 6Hz) compared to resting baseline (74.3±15.1%) (p>0.1). This study found that EI is a reproducible measure of muscle endurance that is not influenced by declines in oxygen saturation.

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This study investigated whether the repeated use of an active recovery (ACT) program is beneficial for promoting recovery of muscle function during an intensive training phase in elite Olympic weightlifters. Using a crossover design, eight competitive weightlifters (7 male; 1 female) from the German national Olympic team participated in a two-day microcycle, comprising of four high-intensity training sessions, with either ACT or passive recovery (PAS) following the session. Barbell velocity during the clean pull, countermovement jump (CMJ) height, muscle contractile properties using tensiomyography (TMG), creatine kinase activity (CK), muscle soreness (DOMS) and perceived overall recovery and stress were measured. After termination of the microcycle, the sport-specific performance during all clean pull intensities (85% 1RM, ACT: Effect size (ES) = -0.20, PAS: ES = -0.50; 90% 1RM, ACT: ES = -0.29, PAS: ES = -0.35; 95% 1RM, ACT: ES = -0.41, PAS: ES = -020; P > 0.05) decreased. Both CK (ACT: ES = 2.11, PAS: ES = 1.41; P = 0.001) and DOMS (ACT: ES = 1.65, PAS: ES = 2.33; P = 0.052) considerably increased. Similarly, ratings of perceived recovery and stress were adversely affected in ACT and PAS, whereas changes in CMJ height and TMG muscle contractile properties remained trivial in both conditions. No practically meaningful differences in changes of the outcome measures were found between ACT and PAS, however there were variable individual responses to ACT. In conclusion, the short-term implementation of an individualized ACT program does not seem to enhance recovery from training-induced fatigue more effectively than PAS. However, because of the inter-individual variability in responses to ACT, it may be beneficial at the individual level.

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The purpose of this study was to use TMG for the assessment of lateral symmetries (LS) and muscle response speed (Vrn) in elite futsal players in accordance with the specific position of the players. A total of 23 male elite futsal players competing in the Spanish elite championship were assessed. Five muscles were analysed: biceps femoris (BF), rectus femoris (RF), semitendinosus (ST), vastus lateralis (VL), and vastus medialis (VM). All assessments were carried out during the same period (i.e., inseason competition and on the recovery day of the microcycle). An analysis of variance of one factor for playing position and for muscle factor were performed on the parameter obtained (Vrn) for BF, RF, ST, VL, and VM. Cohen's d effect sizes were used to identify statistical differences. The results show that there are no muscle function differences between the dominant and non-dominant limb and no differences in lateral symmetries between muscles. Many differences were found between muscles but very few ones were found between playing positions. In conclusion, Vrn seems to be a useful parameter to assess the neuromuscular characteristics of the knee extensor and flexor musculature in futsal players during the season.

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Purpose: This study was designed to: a) examine the influence of elbow joint angle and contraction intensity on electromyographic (EMG) and mechanomyographic (MMG) responses using linear slope coefficients and, b) further describe these relationships utilizing polynomial regression. Methods: 14 male subjects (mean ± SD, age 22.1 ± 2.3 years) performed maximal voluntary isometric contractions (MVC) at elbow flexion angles of 60°, 90°, and 120°. Subjects then performed 35 second contractions at two MVC levels (50%, 75%) for each joint angle. EMG and MMG were recorded simultaneously from the biceps brachii. The center 30 second segment of the signal was utilized to determine the root-mean-square (RMS). Results: No significant effect of elbow joint angle was found for the EMG (p = 0.52) and MMG (p = 0.12) slope coefficient analysis, as well as contraction intensity (EMG: p = 0.61; MMG: p = 0.50). Composite polynomial regression revealed that the MMG-Time relationships were best fit with linear models at 120° (50% MVC: p = 0.025; 75% MVC: p = 0.019), while non-linear relationships best described the 60° (50% MVC, 75% MVC: p < 0.001) and 90° (50% MVC, 75% MVC: p < 0.001) joint angles. Conclusions: Results indicate that motor control strategies are not significantly different between elbow joint angles when utilizing linear regression models. However, polynomial regression revealed elbow joint angle specific MMG-Time relationships. Non-linear, MMG-Time relationships are influenced by elbow joint angle during short-term, sustained isometric contractions.

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Tensiomyography is used to measure skeletal muscle contractile properties, most notably muscle displacement (Dm) and contraction time (Tc). Professional football medical departments are currently using the equipment to profile the muscle function of their squad and subsequently evaluate change due to injury or intervention. However, at present there are no published standardised operating procedures for identifying probe position for muscle assessment. In this technical report we propose standardised operating procedures for the identification of precise probe position as part of an on-going study in male professional footballers.

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Tensiomyography (TMG) can estimate the intrinsic contractile potential of a muscle using data between 10 and 90% of the displacement-time curve. However, it is yet to be determined whether this data represents the greatest rate of displacement i.e. the most valid estimate of the maximal shortening velocity of a muscle. The aim of this secondary analysis of data gathered from 10 participants who had maximal displacement (Dm) of the rectus femoris assessed using TMG, was to compare the rate of displacement using data from 0 – 100% of Dm; 10 – 90% of Dm and the most linear phase of the displacement-time curve. One-way analysis of variance (ANOVA) indicated that rate of displacement increased as data bands narrowed towards the most linear phase of the displacement-time curve (P<0.001). Rate of displacement explained the greatest proportion of variance in total Tc when estimated from the linear phase (R²=0.601; P=0.008). Rate of displacement estimated from data points between 10 – 90% of Dm had a strong association with rate of displacement estimated from the linear phase (r=0.996; P<0.001). The most valid estimate of maximal rate of displacement comes from the linear phase of the displacement-time curve.

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The aim of this study was to determine the contractile properties and muscle stiffness to assess lateral symmetry in competitive female surfers. Fifteen competitive female surfers volunteered to participate in the study. Tensiomyography was used to derive maximum muscle belly displacement, and time delay duration of the Biceps Brachiis, Biceps Femoris, Deltoid, Gastrocnemius lateral head, Rectus Femoris, Tibialis Anterior, Triceps Brachii and Vastus Medialis. No significant differences between right and left limbs at in any of the tested muscles were observed (p > 0.05). Competitive female surfers showed that upper body muscles had the ability to generate force rapidly during contractions, while the lower body muscles generated force at a slower rate. Surf specific training seems to have had an influence on the contractile properties, and stiffness of these muscles. The neuromuscular profile provided here provides further normative data to this unique population.

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This study aimed to measure contractile rate of torque development (RTD) from maximal voluntary isometric contractions (MVC) of the knee extensors and flexors in order to determine reliability of the measure, report age-related difference in RTD, determine the association between RTD and selected functional tasks and determine the effect of progressive resistance training (PRT) on RTD in healthy 50-70y women. 136 women performed MVC's of the knee extensors and flexors. Maximal RTD was determined from the slope of the most linear phase of the torque-time trace. RTD was also determined at 0-50 ms; 0-100 ms and 0-200 ms from the onset of contraction in a subsample (n=26) of knee extensor MVC's. Functional capability was determined based on the ability to complete a 900 m gait speed test (n=128) and the number of chair rises completed in 30 seconds (n=68). 57 participants were randomised into a protein supplementation (PRO) control group or a PRO + PRT group for 12 weeks. Maximal RTD had a coefficient of variance of . 17%. RTD became more dependent on maximal strength as the time from the onset of contraction increased as did its association with maximal RTD. On average, participants in the 7th decade of life had a lower (~23%; P<0.01) RTD than their younger counterparts in the 6th decade. RTD had a weak association with extended gait speed (r=-0.234; P=0.008) and was not associated with chair rise performance (r=0.076; P=0.540). RTD did not change in response to 12 weeks of PRT and PRO compared to a PRO only group (+9% vs. +13%; P>0.05). Maximal RTD cannot be measured reliably in healthy 50-70 year old women from the most linear slope of the torque-time trace of an isometric MVC. Age-related difference in maximal RTD appears to be greater than that of maximal strength. Maximal RTD has a weak association with functional capability and does not change in response to PRT in healthy 50-70 year old women.

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