Search

Introduction: The aim of the present study was to investigate the effects of eccentric phase tempo in squats on hypertrophy, strength, and contractile properties of the quadriceps femoris (QF) muscle. Methods: Eighteen participants (10 males and 8 females, age 24.0 ± 1.7 years) with no resistance training (RT) experience in the last 8 months were randomized into two groups, each following a 7 week squat resistance training (RT) protocol with either a fast eccentric (FE, 1 s eccentric/0 s isometric/1 s concentric/0 s isometric) or slow eccentric (SE, 4 s eccentric/0 s isometric/1 s concentric/0 s isometric) tempo. The training intensity (60%–70% RM), the number of sets (3–4), and the rest intervals (120 s) were consistent in both groups. The study measured changes in quadriceps cross-sectional area (CSA), one-repetition maximum (1RM) strength, and muscle contractile properties such as contraction time (Tc) and radial displacement (Dm), using tensiomyography (TMG). An ANCOVA model with baseline values as covariates was used to examine between-group differences. Results: Results showed significant strength gains in both groups, with the SE group achieving greater 1RM increases (effect size [ES] = 1.60 vs 0.99, p < 0.05). CSA increased for all QF muscles; however, the SE group exhibited significantly higher hypertrophy in the vastus lateralis (ES = 1.74 vs. 1.37, p < 0.05). TMG analysis revealed decreased Dm in the rectus femoris for both groups (p < 0.05), while Tc significantly (ES = 1.33, p < 0.01) increased in the SE group. Discussion: These findings suggest that slower eccentric tempo in RT may optimize vastus lateralis hypertrophy and enhance strength while promoting muscle fiber-type specificity, contributing to the understanding of eccentric training's role in muscle adaptation. [ABSTRACT FROM AUTHOR]

IntroductionThe aim of the present study was to investigate the effects of eccentric phase tempo in squats on hypertrophy, strength, and contractile properties of the quadriceps femoris (QF) muscle.MethodsEighteen participants (10 males and 8 females, age 24.0 ± 1.7 years) with no resistance training (RT) experience in the last 8 months were randomized into two groups, each following a 7 week squat resistance training (RT) protocol with either a fast eccentric (FE, 1 s eccentric/0 s isometric/1 s concentric/0 s isometric) or slow eccentric (SE, 4 s eccentric/0 s isometric/1 s concentric/0 s isometric) tempo. The training intensity (60%–70% RM), the number of sets (3–4), and the rest intervals (120 s) were consistent in both groups. The study measured changes in quadriceps cross-sectional area (CSA), one-repetition maximum (1RM) strength, and muscle contractile properties such as contraction time (Tc) and radial displacement (Dm), using tensiomyography (TMG). An ANCOVA model with baseline values as covariates was used to examine between-group differences.ResultsResults showed significant strength gains in both groups, with the SE group achieving greater 1RM increases (effect size [ES] = 1.60 vs 0.99, p < 0.05). CSA increased for all QF muscles; however, the SE group exhibited significantly higher hypertrophy in the vastus lateralis (ES = 1.74 vs. 1.37, p < 0.05). TMG analysis revealed decreased Dm in the rectus femoris for both groups (p < 0.05), while Tc significantly (ES = 1.33, p < 0.01) increased in the SE group.DiscussionThese findings suggest that slower eccentric tempo in RT may optimize vastus lateralis hypertrophy and enhance strength while promoting muscle fiber-type specificity, contributing to the understanding of eccentric training’s role in muscle adaptation.

The purpose of this study is a comparison of skeletal muscle characteristics in Slovenian gymnasts assessed by TMG and values of contraction properties of muscles, lateral symmetries, and the effect of aging on selected contraction properties of skeletal muscles in men's artistic gymnastics (MAG); women's artistic gymnastics (WAG) and rhythmic gymnastics (RG). A survey of 81 athletes from different disciplines was conducted as follows: MAG (n = 26), WAG (n = 28), and RG (n = 27). The athletes' average age was 15.41±5.03 years. In this study, the contraction times of ten skeletal muscles for Slovenian gymnasts on the right and left sides of the body were compared: m. biceps brachii BB, m. triceps brachii TB, m. biceps femoris BF, m. erector spinae ES, m. gastrocnemius lateralis GL, m. gastrocnemius medialis GM, m. rectus femoris RF, m. tibialis anteriror TA, m vastus lateralis VL, m. vastus medialis VM. Out of all twenty-nine pairs analyzed, there are differences only in six pairs, namely: BB_Tc_MAG_WAG, TB_Tc_MAG_WAG, BF_Tc_MAG_RG, BF_Tc_WAG_RG, ES_Tc_MAG_RG and VM_Tc_MAG_RG. [ABSTRACT FROM AUTHOR]

PurposeStatic stretch training (SST) with long stretching durations seems to be sufficient to increase flexibility, maximum strength (MSt) and muscle thickness (MTh). However, changes in contraction properties and effects on muscle damage remain unclear. Consequently, the objective of the study was to investigate the effects of a 6-week self-performed SST on MSt, MTh, contractile properties, flexibility, and acute response of creatine kinase (CK) 3 days after SST.MethodsForty-four participants were divided into a control (CG, n = 22) and an intervention group (IG, n = 22), who performed a daily SST for 5 min for the lower limb muscle group. While isometric MSt was measured in leg press, MTh was examined via sonography and flexibility by functional tests. Muscle stiffness and contraction time were measured by tensiomyography on the rectus femoris. Additionally, capillary blood samples were taken in the pretest and in the first 3 days after starting SST to measure CK.ResultsA significant increase was found for MSt (p 0.310). Scheffé post hoc test did not show significant differences between the rectus femoris muscle inter- and intragroup comparisons for MTh nor for muscle stiffness and contraction time (p > 0.05, η2 0.05, η2 = 0.032.DiscussionIn conclusion, the increase in MSt cannot be exclusively explained by muscular hypertrophy or the increased CK-related repair mechanism after acute stretching. Rather, neuronal adaptations have to be considered. Furthermore, daily 5-min SST over 6 weeks does not seem sufficient to change muscle stiffness or contraction time. Increases in flexibility tests could be attributed to a stretch-induced change in the muscle–tendon complex.

Objective: The purpose of this study is a comparison of skeletal muscle characteristics in Slovenian gymnasts assessed by TMG and values of contraction properties of muscles, lateral symmetries, and the effect of aging on selected contraction properties of skeletal muscles in men's artistic gymnastics (MAG); women's artistic gymnastics (WAG) and rhythmic gymnastics (RG). This study is the first larger study to use the TMG method and in which top athletes from artistic and rhythmic gymnastics participated. Materials and Methods: A survey of 81 athletes from different disciplines was conducted as follows: MAG (n = 26), WAG (n = 28), and RG (n = 27). The athletes' average age was 15.41 ± 5.03 years. In this study, the contraction times of ten skeletal muscles for Slovenian gymnasts on the right and left sides of the body were compared: M. Biceps brachii, M. Triceps brachii, M. Biceps femoris, M. Erector spinae, M. Gastrocnemius lateralis, M. Gastrocnemius medialis, M. Rectus femoris, M. Tibialis anteriror, M Vastus lateralis, M. Vastus medialis. Results: In MAG, a statistically significant correlation between age and contraction time was found for m. VL and m. VM. In WAG, was found for m. GM. In RG was found for m. TA and m VL for all at p < 0.01. Conclusions: A comparison between the left and the right side body shows a slight asymmetry. With TMG, we can assess the discipline's demands and help improve gymnasts' performances along with the safety of training. Tensiomyography has a high predictive ability to discriminate between the left and right sides of the body functionally. [ABSTRACT FROM AUTHOR]

Toskić, LD, Dopsaj, MJ, Marković, MR, Toskić, DR, Ignjatović, AM. Mechanical and contractile properties of knee joint muscles measured by the method of tensiomyography in differently trained men and women. J Strength Cond Res 36(6): 1532–1539, 2022—The aim of this study was to investigate the differences in mechanical and contractile properties of knee joint flexor and extensor muscles between differently trained men and women, using tensiomyography (TMG). The sample consisted of 159 subjects (84 men and 75 women), who were assigned to one of 5 groups according to the following levels and types of their physical activity: physically inactive, physically active nonathletes, strength and power athletes, endurance athletes, and team sports athletes. Measurements were performed on the following knee flexor and extensor muscles of the dominant leg: rectus femoris, vastus medialis, vastus lateralis, biceps femoris, and semitendinosus. The results showed significant differences in contraction time—Tc (F = 1.911, p = 0.010) and delay time—Td (F = 1.989, p = 0.007) parameters between differently trained men and women, whereas in other TMG parameters, there were no differences between groups. It is indicated that physical activities characteristic of strength and power sports (combat sports and sprint disciplines) could lead to an increased speed of twitch force generation and fast twitch muscle fibers, and that almost any regular, systematic, and planned physical activity leads to increased muscle responsiveness. Obtained results also indicated that TMG parameters do not have enough specific discriminatory power for detecting differences between differently trained young adults. [ABSTRACT FROM AUTHOR]

Simple Summary: The hamstring muscle group is the most frequently injured muscle group in non-contact muscle injuries involving high-speed running sports. The biceps femoris (BF) muscle has the highest injury incidence. Clinical assessments and magnetic resonance imaging (MRI) are routinely used to diagnose a given injury. We tested the possibilities of a new technology—tensiomyography—as a potential screening test (diagnostic and classification purposes) to assess the functional differences between injured and non-injured BF muscles. The results show that tensiomyography has a high predictive ability to discriminate between injured and non-injured BF non-invasively and functionally and that it can be reliably used as a complementary screening test in the diagnosis of BF injuries. The hamstring muscle group is the most frequently injured muscle group in non-contact muscle injuries in sports involving high-speed running. A total of 84% of hamstring injuries affect the biceps femoris (BF) muscle. Clinical assessments and magnetic resonance imaging (MRI) are routinely used for diagnosis and plan management. MRI-negative scans for clinically diagnosed hamstring injuries range from 14% to 45%. We tested the hypothesis that the functional differences between injured and non-injured BF assessed by tensiomyography can be used for diagnostic and classification purposes. We compared an injured group of 53 international-level soccer players and sprinters with 53 non-injured international-level soccer players and sprinters of both sexes. Comparing the injured vs. non-injured athletes and the left vs. right side in all of the athletes, we used the percentage of absolute differences in the BF contraction time (Tc) to classify non-injured and injured BF muscles. The receiver operating characteristic (ROC) curve and the area under the curve (AUC) and the precision–recall curve (PRC) were used to measure the classification accuracy and to identify cut-off limits using the Tc differences. There was a very high ROC AUC value of 0.981 (SE = 0.009, p < 0.000), with 98.11% of the injured muscles being correctly classified (cut-off point 12.50% on Tc differences), and an AUPRC value of 0.981, with association classification criteria at >9.87. Tensiomyography has a high predictive ability to discriminate between injured and non-injured BF non-invasively and functionally. [ABSTRACT FROM AUTHOR]

The deep tendon reflex (DTR) is a key component of the neurological examination. However, interpretation of the results is a challenge since there is a lack of knowledge on the important features of reflex responses such as the amount of hammer force, the strength of contraction, duration of the contraction and relaxation. The tools used to elicit the reflexes also play a role in the quality of the reflex contraction. Furthermore, improper execution techniques during the DTR assessment may alter the findings and cloud the true assessment of the nervous system. Therefore, understanding the basic principles and the key features of DTR allows for better interpretation of the reflex responses. This paper discusses the brief history of reflexes, the development of the reflex hammer, and also the key features of a reflex response encompassing the amplitude of force needed to elicit a reflex response, the velocity of contraction, the strength of contraction, and the duration of contraction and relaxation phases. The final section encloses the techniques of eliciting DTR in the upper extremities, trunk, and lower extremities, and the interpretation of these reflexes. [ABSTRACT FROM AUTHOR]

Localised signal voids in diffusion‐weighted (DW) images of skeletal muscle have been postulated to occur as a result of muscle fibre contraction and relaxation. We investigated the contrast mechanism of these signal voids using a combination of modelling and experimental measurements by employing DW and phase contrast (PC) imaging sequences. The DW signal and PC signal were simulated for each time point of a theoretical muscle twitch. The model incorporated compaction (simulating actively contracting muscle fibres) and translation (simulating passively moving surrounding fibres). The model suggested that the DW signal depended on contraction time and compaction whereas the PC signal depended on contraction time, compaction and translation. In a retrospective study, we tested this model with subgroup analyses on 10 healthy participants. Electrical nerve stimulation was used to generate muscle twitches in lower leg muscles; the resulting force was measured using an MR‐compatible force transducer. At current levels causing a visible muscle twitch (~13 mA), the width of the first signal drop in the DW signal (mean ± SD: 103 ± 20 ms) was comparable with the force contraction time (93 ± 34 ms; intraclass correlation coefficient [ICC] = 0.717, P =.010). At current levels activating single motor units (~9 mA), the contraction time determined from the DW signal was 75 ± 13 ms and comparable with the PC contraction time (81 ± 15 ms; ICC = 0.925, P =.001). The maximum positive velocity was 0.55 ± 0.26 cm/s and the displacement was 0.20 ± 0.10 mm. Voxel‐wise analysis revealed localised DW changes occurring together with more widespread phase changes. In conclusion, local signal attenuations in DW images following muscle fibre activation are primarily caused by compaction. The PC sequence also detects translating muscle tissue being passively pulled. The magnitude of the changes in DW and PC images depends on the twitch's contractile properties and percentage contraction. DW imaging and PC imaging can therefore measure twitch profiles of skeletal muscle fibres. [ABSTRACT FROM AUTHOR]

Tensiomyography detects the contraction time (Tc) and amplitude (Dm) of muscle belly thickening during maximal isometric twitch contraction. The assessment of both parameters is highly reliable; however, it seems that their calculation depends on the measurement point. The aim of the study was to determine spatial relative error distribution of Tc and/or Dm within a two-dimensional array of 27 (3 × 9) measurement points in comparison to the reference point (RP) in 12 male participants (22.5 ± 3.1 years). The RPs were determined as follows: in the biceps brachii (BB) at 50% of the humerus length; in the erector spinae (ES) at the height of the iliac crest; in the vastus lateralis (VL), vastus medalis (VM), and rectus femoris (RF) at 30%, 20%, and 50% of femur length above the patella, respectively. The surface area under the 3% relative error in Dm (BB: 4.0; VL: 3.8; VM; 8.2; RF: 6.2; ES: 2.4 cm2) was lower than in Tc (BB: 6.9; VL: 3.8; VM; 4.6; RF: 9.5; ES: 3.7 cm2), yielding merged values (BB: 3.9; VL: 3.7; VM; 4.8; RF: 5.1; ES: 2.4 cm2). Dm show twice as steep relative error rate when moving away from the RP in comparison to Tc, which seems to be less sensitive to spatial sensor positioning. [ABSTRACT FROM AUTHOR]

In young and older people, skeletal muscle mass is reduced after as little as 7 days of disuse. The declines in muscle mass after such short periods are of high clinical relevance, particularly in older people who show a higher atrophy rate and a slower or even a complete lack of muscle mass recovery after disuse. Ten men (24.3 yr; SD 2.6) underwent 35 days of 6° head-down tilt bed rest, followed by 30 days of recovery. During bed rest, a neutral energy balance was maintained, with three weekly passive physiotherapy sessions to minimize muscle soreness and joint stiffness. All measurements were performed in a hospital at days 1-10, 16, 28, and 35 of bed rest (BR1-BR10, BR16, BR28, and BR35, respectively) and days 1, 3, and 30 after reambulation (R + 1, R + 3, and R + 30, respectively). Vastus medialis obliquus (VMO), vastus medialis longus (VML), and biceps femoris (BF) thickness (d) and pennation angle (Θ) were assessed by ultrasonography, whereas twitch muscle belly displacement (Dm) and contraction time (Tc) were assessed with tensiomyography (TMG). After bed rest, d and Θ decreased by 13-17% in all muscles (P < 0.001) and had recovered at R + 30. Dm was increased by 42.3-84.4% (P < 0.001) at BR35 and preceded the decrease in d by 7, 5, and 3 days in VMO, VML, and BF, respectively. Tc increased only in BF (32.1%; P < 0.001) and was not recovered at R + 30. TMG can detect early bed-rest-induced changes in muscle with higher sensitivity before overt architectural changes, and atrophy can be detected. [ABSTRACT FROM AUTHOR]

BACKGROUND: Information regarding the relationship between methods for assessment of voluntary and involuntary muscle contractile properties is of importance in sport science and medicine. OBJECTIVE: To appraise the concurrent and predictive validity of isokinetic dynamometry and tensiomyography (TMG) in differently trained men and women. METHODS: Fifty men and 45 women were divided into three groups: physically inactive, physically active and athletes. Isokinetic testing was performed on knee muscles in concentric mode at 60 and 180 ∘ s while tensiomyographic measurements were obtained from the rectus and the biceps femoris muscles. RESULTS: A small, statistically significant correlation was detected between the peak moment and tensiomyography parameters relating to contraction time and maximal displacement (Adj. R = 2 0.086, p = 0.028). CONCLUSION: In general, isokinetic dynamometry and tensiomyography are not related and represent different technologies that measure different contractile properties of muscles. A hierarchical structure of predictive validity at the level of individual variables was detected as a function of gender and training level. [ABSTRACT FROM AUTHOR]

Although master athletes maintain high levels of physical activity, they also suffer from an age-related decline in skeletal muscle function. There are indications of disproportional age- and physical inactivity-induced muscle wasting between muscles. Tensiomyography is a noninvasive tool that has been used to study the effects of a variety of sports on the contraction time (Tc) in different skeletal muscles. The aim of this cross-sectional study was to assess age-related changes in the Tc of the vastus lateralis, gastrocnemius medialis, and biceps femoris muscles with Tensiomyography in older nonathletes (age = 62.1 ± 12.7 years; NMALES = 133; NFEMALES = 246), and power (age = 56.9 ± 13.5 years; NMALES = 100; NFEMALES = 78) and endurance master athletes (age = 56.5 ± 14.5 years; NMALES = 76; NFEMALES = 73). We found an age-related slowing in all muscles, irrespective of discipline, where endurance master athletes had the longest and power master athletes had the shortest Tc. The longer Tc in endurance master athletes than in nonathletes suggests that regular endurance sport activity aggravates slowing of skeletal muscles during aging. [ABSTRACT FROM AUTHOR]

Purpose Adolescents with patellofemoral pain (PFP) do not comply with their exercise prescription, performing too few and too fast repetitions, compromising recovery. We investigated if real-time feedback on contraction time would improve the ability of adolescents with PFP to perform exercises as prescribed. Methods A randomized, controlled, participant-blinded, superiority trial with a 6-wk intervention of three weekly sessions of three elastic band exercises was undertaken. Forty 15- to 19-yr-old adolescents with PFP were randomized to real-time BandCizer™-iPad feedback on contraction time or not by a physiotherapist. The primary outcome was the mean deviation from the prescribed contraction time of 8 s per repetition. Secondary outcomes included isometric hip and knee strength, Kujala Patellofemoral Scale, and Global Rating of Change. Results The mean deviation from prescribed 8 s per repetition contraction time was 1.5 ± 0.5 s for the feedback group, compared with 4.3 ± 1.0 s for the control group (mean difference: 2.7 s (95% confidence interval = 2.2-3.2, P < 0.001). On the basis of total contraction time during the intervention, the feedback group received 35.4% of the prescribed exercise dose whereas the control group received 20.3%. Isometric hip and knee strength increased significantly more in the feedback group compared with controls (mean difference = 1.35 N⋅kg-1, 95% confidence interval = 0.02-2.68, P = 0.047). There were no significant differences in Kujala Patellofemoral Scale and Global Rating of Change between groups, but the study was not powered for this. Conclusion Real-time feedback on contraction time resulted in the ability to perform exercises closer to the prescribed dose and also induced larger strength gains. [ABSTRACT FROM AUTHOR]

While there are numerous data on the skeletal muscle fiber type composition in adults, little is known about the changes in fiber type composition and contractile properties during maturational growth in children. Using noninvasive tensiomyography, we measured contraction time (Tc), an indirect estimate of the myosin heavy chain I (MHC-I) proportion, to assess the longitudinal changes of the biceps brachii (BB), biceps femois (BF), vastus lateralis (VL), and erector spinae (ES) muscles in 53 boys and 54 girls. The children were 9 years at the start of the study and returned for 5 follow-up measurements until the age of 14 years. The ES has the shortest and the BF has the longest Tc. The VL and ES of boys have shorter Tc than those of girls. When applying the relationship between proportion of MHC-I and Tc established in adults to children's TMG data, we found a slow-to-fast transition in the VL between, at least, the ages of 6 to 10 years, when it stabilized to adult proportions. Regular participation in sports was associated with a faster BF, but not in the VL. Our data represents a first non-invasive indication of the developmental changes in muscle fiber type composition in children. [ABSTRACT FROM AUTHOR]

Objective: Recent research has reported that lower maximal rate of torque development (dτ/dt max) exhibited by females, relative to males, during knee extension can be accounted for by normalization to a maximal voluntary contraction (MVC); however, this was not seen in the upper limb.Purpose: The aim of the current work was to examine the contribution of maximum strength (τmax), twitch contraction time (CT), muscle fiber condition velocity (MFCV), and rate of muscle activation (Q30) to sex-differences in the dτ/dt max during maximal isometric dorsiflexion.Methods: Thirty-eight participants (20 males; 18 females) performed both maximal voluntary and evoked isometric contractions of the tibialis anterior across 3 days. Ten maximal compound muscle action potentials were elicited and subsequently followed by three, 5-s contractions. From the recordings, MFCV, dτ/dt max, τmax, CT, electromechanical delay (EMD), root-mean squared (RMS) amplitude, peak-to-peak voltage (Vpp), and Q30 were calculated.Results: An ANCOVA showed that τmax accounted for all the sex-differences in dτ/dt max (p = 0.96). There were no significant differences between groups with respect to MFCV, RMS amplitude, Vpp amplitude, or CT. However, there was a significant sex-difference in dτ/dt max, τmax, and Q30. Females had longer evoked EMD times compared with males (15.69 ± 10.57 ms versus 9.95 ± 3.46 ms; p = 0.01), but the voluntary EMD times were not different.Conclusion: The current research supports the work by Hannah et al. Exp Physiol 97:618-629, (2012) that normalization to MVC in the quadriceps is able to account for all sex-differences in rate of toque development in the lower limb. [ABSTRACT FROM AUTHOR]

• When walking speed is kept constant, it not only maintains healthy body composition but also causes positive changes in muscle contractility, which can serve as a way to slow sarcopenia. • Walking can improve the immunocyte function in the elderly by improved muscle contractility. • This study found that moderate to fast walking helps elderly people to maintain a healthy body composition and muscle contractility and to change the immune cells positively. This study investigated the changes in body composition, muscle contractility and immunocytes of the elderly using three types of walking. Seventy-six participants were randomly assigned to control group (CON), slow walking group (SWG), moderate walking group (MWG), or fast walking group (FWG). Muscle mass in CON decreased (-2.55 ± 3.63%; P < 0.05), while it increased in FWG (1.92 ± 4.46%; P < 0.05). Fat mass in CON increased, whereas it decreased in MWG and FWG (-18.71 ± 14.22%; P < 0.001). Tc (contraction time) of biceps femoris (BF) decreased in CON, while a decreasing tendency was seen in SWG. Although Tc of BF increased in MWG, it showed a marked increase in FWG (21.19 ± 24.53%; P < 0.05). A similar tendency was observed in the rectus femoris. Leukocytes did not change in CON, but they showed an increasing tendency in MWG and FWG. Neutrophils decreased in CON, whereas the other groups showed an increasing tendency. Lymphocytes (10.25 ± 19.48%; P < 0.01) and helper T cells (14.32 ± 17.99%; P < 0.05) showed an increase in FWG, and NK cell was improved in SWG, but showed a clear increase in MWG (38.45 ± 96.96%; P < 0.05) and FWG (52.69 ± 58.37%; P < 0.05). This study concludes that fast walking by the elderly improves the muscle contractility, which can also be expected to improve the function of immunocytes by increased or maintained muscle mass and decreased fat mass after 12 weeks. [ABSTRACT FROM AUTHOR]

Introduction: Mechanomyography (MMG) has recently shown promise in monitoring recovery of injured muscles. However, delivering a maximal percutaneous neuromuscular stimulus (PNS) could potentially be painful on severely damaged muscles. The aim of this paper was to determine whether delivering a sub-maximal PNS could still obtain accurate MMG recordings of muscle contraction time (Tc). The effect of muscle architecture on determining the minimal level of current was also investigated. Methods: Six muscles were investigated; 5 lower limb and the 1st dorsal interosseous. A ‘current ramp’ procedure was performed to determine minimal stimulus intensity required for accurate Tc recordings. A current ramp entails beginning at a low current (30 mA) and increasing in increments of 10 mA until a maximal muscle contraction is observed. Results: For lower limb muscles, 130 mA was the largest current required to obtain accurate Tc recordings in at least 95% of the population. This was up to a 50% reduction in the amount of current delivered for some muscles. Fibre type distribution showed the greatest relationship with mean minimum current. Discussion: Future studies investigating injured or uninjured muscles via MMG, could use these submaximal currents to obtain accurate MMG recordings, whilst improving patient comfort and reducing experiment duration. [ABSTRACT FROM AUTHOR]

Background The tensiomyography assessment offers information, in the time domain, regarding the following parameters: maximal radial deformation or displacement of the muscle belly, contraction time, reaction time, sustain time and relaxation time. The aim of this study is to provide information about muscle stiffness, the mechanic and contractile properties using the TMG muscles after 4 months rehabilitation process gymnast. Material/Methods Four muscles were chosen on both lateral sides involved in artistic gymnastics performance: biceps femoris, erector spinae, gluteus maximus, rectus femoris. The testing sample in this study was taken from the Croatian Republic's senior representative who won third place 2012 and eighth place 2015 in the floor routine at the ECh. Results The testing and measuring took place after the subject injured the lumbar region of the spinal cord and after a four-month prevention exercise program. After the first two stages of measuring, the differences can be found in: BF: -7%; ES: +17%; GM: -8%; RF: +11%. Generally speaking, a dependent t-test did not reveal significant differences in between the first and second measurement point (t = 1.941, df = 39, P < 0.059). Conclusions This approach can be used to investigate top athletes who are in the process of training for muscle recovery as a result of skeletal muscle injury. [ABSTRACT FROM AUTHOR]

Contractile properties of skeletal muscle are studied for various purposes and mainly by means of force or torque twitch responses. This study compared contractile properties estimated from isometric longitudinal and transversal vastus lateralis twitch mechanical actions using torque and tensiomyography (TMG) as assessment methods, respectively. We calculated delay, contraction, sustain, half relaxation time and peak amplitude from the maximal twitch response obtained by both methods in 19 healthy males (age 46.1±17.8 years). Results indicated a shorter delay (Δ=-23.4%; p<.001) and contraction time (Δ=-42.7%; p<.001) when calculated from the transversal tensiomyographic actions, and shorter half relaxation time (Δ=-26.2%; p=.025) when calculated from the longitudinal torque actions, while no difference in sustain time was found. Delay and contraction time did not correlate significantly when correlated between longitudinal and transversal actions; however, sustain time (r=.478; p=.038) and half relaxation time (r=.608; p=.006) did. In conclusion, the tensiomyography and torque gives different information reflecting that different mechanisms affect longitudinal and transversal twitch skeletal muscle deformations. Tensiomyographic response of skeletal muscle's transversal actions likely reflects more intrinsic contractile properties. [ABSTRACT FROM AUTHOR]

Fatigue in forearm muscles may be critical for motorcycle riders in relation to performance and forearm disorders. Force-time course parameters were examined to better characterize the reduction in the maximal force generating capacity ( MVC) during an intermittent fatigue protocol ( IFP) specifically designed for motorcycle riders. Also, a mathematical force fatigue model is proposed. Forty motorcyclists (aged 27.6 ± 6.8 years) performed an IFP that simulated the braking gesture and posture of a rider. Fatigue was confirmed by a 40% decrement of the normalized MVC in comparison with basal value. Contraction time increased in comparison with basal condition ( P ≤ 0.034). Relaxation kinetics presented two phases: (a) a pre-fatigue phase where half relaxation time ( HRTraw) and normalized ( HRTnor) decreased ( P ≤ 0.013) while relaxation rate ( RRraw) remained unchanged; and (b) a fatiguing phase where HRTraw, HRTnor increased and RRraw decreased ( P ≤ 0.047). Normalized RRraw ( RRnor) declined progressively ( P ≤ 0.016). The proposed nonlinear force fatigue model confirmed a satisfactory adjustment ( R2 = 0.977 ± 0.018). This mathematical expression derived three patterns of force fatigue: three-phase, exponential and linear, representing 70%, 13%, and 17% of the participants, respectively. Overall, these results provided further support to force fatigue theoretical and applied proposals. [ABSTRACT FROM AUTHOR]

In this study, we tested the hypothesis that skeletal muscle from pigeons would display age-related alterations in isometric force and contractile parameters as well as a shift of the single muscle fiber cross-sectional area (CSA) distribution toward smaller fiber sizes. Maximal force output, twitch contraction durations and the force-frequency relationship were determined in tensor propatagialis pars biceps muscle from young 3-year-old pigeons, middle-aged 18-year-old pigeons, and aged 30-year-old pigeons. The fiber CSA distribution was determined by planimetry from muscle sections stained with hematoxylin and eosin. Maximal force output of twitch and tetanic contractions was greatest in muscles from young pigeons, while the time to peak force of twitch contractions was longest in muscles from aged pigeons. There were no changes in the force-frequency relationship between the age groups. Interestingly, the fiber CSA distribution in aged muscles revealed a greater number of larger sized muscle fibers, which was verified visually in histological images. Middle-aged and aged muscles also displayed a greater amount of slow myosin containing muscle fibers. These data demonstrate that muscles from middle-aged and aged pigeons are susceptible to alterations in contractile properties that are consistent with aging, including lower force production and longer contraction durations. These functional changes were supported by the appearance of slow myosin containing muscle fibers in muscles from middle-aged and aged pigeons. Therefore, the pigeon may represent an appropriate animal model for the study of aging-related alterations in skeletal muscle function and structure. [ABSTRACT FROM AUTHOR]

Normal aging is characterized by muscular atrophy and a loss of force-generating capacity. The goal of this research was to investigate the age and sport activity type on postural (vastus lateralis) and non postural (biceps femoris) muscles’ contraction time in 170 master athletes (athletic events) and 51 non athletes. We found significant age effect in postural muscle (P = 0.032) and also in non postural muscle (P < 0.001). However, we found sport activity type effect significant just in non postural muscle (P < 0.001). The interaction effect of age * sport was significant in both observed muscles. Sprinters/jumpers deteriorate with age the most in postural muscle, while non athletes in non postural muscle. We could conclude that non postural muscle deteriorate the most without regular sport activity, while postural muscle have enough daily stimuli to be prevented from major deterioration.

Different muscle functions require different muscle contraction properties. Saccade-generating extraocular muscles (EOMs) are the fastest muscles in the human body, significantly faster than limb skeletal muscles. Muscle contraction speed is subjected to plasticity, i.e., contraction speed can be adjusted to serve different demands, but little is known about the molecular mechanisms that control contraction speed. Therefore, we examined whether myogenic growth factors modulate contractile properties, including twitch contraction time (onset of force to peak force) and half relaxation time (peak force to half relaxation). We examined effects of three muscle-derived growth factors: insulin-like growth factor 1 (IGF1), cardiotrophin-1 (CT1), and glial cell line-derived neurotrophic factor (GDNF). In gain-of-function experiments, CT1 or GDNF injected into the orbit shortened contraction time, and IGF1 or CT1 shortened half relaxation time. In loss-of-function experiments with binding proteins or neutralizing antibodies, elimination of endogenous IGFs prolonged both contraction time and half relaxation time, while eliminating endogenous GDNF prolonged contraction time, with no effect on half relaxation time. Elimination of endogenous IGFs or CT1, but not GDNF, significantly reduced contractile force. Thus, IGF1, CT1, and GDNF have partially overlapping but not identical effects on muscle contractile properties. Expression of these three growth factors was measured in chicken and/or rat EOMs by real-time PCR. The 'fast' EOMs express significantly more message encoding these growth factors and their receptors than skeletal muscles with slower contractile properties. Taken together, these findings indicate that EOM contractile kinetics is regulated by the amount of myogenic growth factors available to the muscle. [ABSTRACT FROM AUTHOR]

Copyright of Kinesiologia Slovenica is the property of Faculty of Sport and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Peripheral muscle dysfunction often occurs in patients with chronic obstructive pulmonary disease (COPD). The muscle dysfunction may be caused by a loss of force-generating capacity, resulting from a loss of muscle mass, as well as by other alterations in contractile properties of skeletal muscle. The maximal isometric voluntary strength and fatigability were determined in hand-grip and quadriceps muscles from nine male COPD patients (FEV1 30–50% predicted) and control subjects matched for fat-free mass (FFM), physical activity level and age. Contractile properties and fatigability of the quadriceps muscle were also studied with electrically evoked isometric contractions. The maximal voluntary force (MVC) and fatigability of the handgrip muscle did not differ between the COPD patients and control subjects. Also the MVC of the quadriceps muscle and the rate of force rise, contraction time, force–frequency relationship and fatigability, as determined with electrically evoked contractions, were similar in patients with COPD and control subjects. Skeletal muscle strength, contractile properties and fatigability are preserved in patients with moderate COPD and a normal FFM and activity level. This suggests that skeletal muscle dysfunction does not take place during moderate COPD until cachexia and/or a decline in physical activity occur. [ABSTRACT FROM AUTHOR]

Copyright of Italian Journal of Neurological Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mammalian slow and fast muscles are incompletely differentiated at birth, and their specific characteristics emerge gradually during the early postnatal period. The pattern of activity received by young muscles may be instrumental in bringing about their differentiation. Hind limb muscles of rats were stimulated via the sciatic nerve in order to test the influence of different patterns of activity on their development. Slow frequency stimulation (10 Hz) prevented the development of fast contraction times in 'fast' muscles. The slow soleus became slightly faster when stimulated a 25 Hz. Stimulation of muscles of rats between 4 and 12 days at 40 Hz apparently resulted in some denervation in both fast and slow muscles, although stimulation at this frequency in older rats resulted in shortening of slow muscle contractions. [ABSTRACT FROM AUTHOR]

Copyright of Zeitschrift Für Neurologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)