Plantar Flexor Muscle Group Research Articles

Muscle and tendon morphology of a world strongman and deadlift champion.

This study compared the muscle and tendon morphology of an extraordinarily strong individual, a World's Strongest Man and deadlift champion (WSM), with that of various other athletic, trained, and untrained populations. The WSM completed the following: 1) 3.0-T MRI scans, to determine the volume of 22 individual lower limb muscles, 5 functional muscle groups, patellar tendon (PT) cross-sectional area (CSA), and PT moment arm; and 2) countermovement jumps (CMJ) and isometric midthigh pull (IMTP) contractions. The WSM was compared with previously assessed groups from our laboratory (muscle and tendon) and the wider research literature (CMJ and IMTP). The WSM's CMJ peak power (9,866 W) and gross (9,171 N) and net (7,480 N) IMTP peak forces were higher than any previously published values. The WSM's overall measured leg muscle volume was approximately twice that of untrained controls (+96%) but with pronounced anatomical variability in the extent of muscular development. The plantar flexor group (+120%) and the guy rope muscles (sartorius, gracilis, and semitendinosus: +140% to +202%), which stabilize the pelvis and femur, demonstrated the largest differences relative to that of untrained controls. The WSM's pronounced quadriceps size (greater than or equal to twofold vs. untrained) was accompanied by modest PT moment arm differences and, notably, was not matched by an equivalent difference in PT CSA (+30%). These results provide novel insight into the musculotendinous characteristics of an extraordinarily strong individual, which may be toward the upper limit of human variation, such that the WSM's very pronounced lower limb muscularity also exhibited distinct anatomical variability and with muscle size largely uncoupled from tendon size.NEW & NOTEWORTHY Lower-body muscle size of an extraordinarily strong individual, a World's Strongest Man and deadlift champion (WSM), was approximately twice that of controls but was underpinned by pronounced anatomical variability in the extent of muscular development (+23-202%): the plantar flexor group and guy rope muscles demonstrating the largest differences. The WSM's quadriceps size (more than or equal to twice that of controls) contrasted with modest differences in patella tendon moment arm (+18%) and was uncoupled from patellar tendon size (+30%).

The Relationship of Gastrocnemius-Soleus Muscle Architecture with Balance and Functional Strength in Acute Stroke Patients

Balance and functional impairment could occur due to the weakness of the gastrocsoleus muscles in acute stroke patients. This study was planned to determine the muscle architecture and its relationship to balance and functional strength functional ability in patients with acute stroke. A cross-sectional analysis of 22 stroke patients (68.59 ± 8.16) was performed in this study. Gastrocnemius muscle thickness and cross-sectional area were significantly greater on the non-paretic than on the paretic sides (p = 0.004, p = 0.005, respectively). Partial correlation analysis showed that soleus muscle thickness and cross-sectional area was significantly correlated with Berg Balance Scale, Single Leg Stance Test, Five Times Sit to Stand Test and Tandem test results in the paretic side (r = 0.49–0.77, p < 0.05). The gastrocnemius muscle thickness of the non-paretic side had a significant relationship with balance (r = 0.45–0.65, p < 0.05). The muscle thickness and cross-sectional area of the soleus muscle on the paretic sides was significantly related with the functional strength and balance after stroke. It may be beneficial to develop clinical assessment and intervention programs focusing on distal plantar flexor muscle groups in order to improve the functional status and balance.

Ischemic preconditioning increases spinal excitability and voluntary activation during maximal plantar flexion contractions in men.

The enigmatic benefits of acute limb ischemic preconditioning (IP) in enhancing muscle force and exercise performance have intrigued researchers. This study sought to unravel the underlying mechanisms, focusing on increased neural drive and the role of spinal excitability while excluding peripheral factors. Soleus Hoffmann (H)-reflex /M-wave recruitment curves and unpotentiated supramaximal responses were recorded before and after IP or a low-pressure control intervention. Subsequently, the twitch interpolation technique was applied during maximal voluntary contractions to assess conventional parameters of neural output. Following IP, there was an increase in both maximum normalized force and voluntary activation (VA) for the plantar flexor group, with negligible peripheral alterations. Greater benefits were observed in participants with lower VA levels. Despite greater H-reflex gains, soleus volitional (V)-wave and sEMG amplitudes remained unchanged. In conclusion, IP improves muscle force via enhanced neural drive to the muscles. This effect appears associated, at least in part, to reduced presynaptic inhibition and/or increased motoneuron excitability. Furthermore, the magnitude of the benefit is inversely proportional to the skeletal muscle's functional reserve, making it particularly noticeable in under-recruited muscles. These findings have implications for the strategic application of the IP procedure across diverse populations.

Tibial bone strength is negatively affected by volumetric muscle loss injury to the adjacent muscle in male mice.

This study's objective was to investigate how contractile strength loss associated with a volumetric muscle loss (VML) injury affects the adjacent tibial bone structural and functional properties in male C57BL/6J mice. Mice were randomized into one of two experimental groups: VML-injured mice that were injured at age 12 weeks and aged to 20 weeks (8 weeks postinjury, VML) and 20-week-old age-matched uninjured mice (Uninjured-20). Tibial bone strength, mid-diaphysis cortical geometry, intrinsic material properties, and metaphyseal trabecular bone structure were assessed by three-point bending and microcomputed tomography (µCT). The plantar flexor muscle group (gastrocnemius, soleus, plantaris) was analyzed for its functional capacities, that is, peak-isometric torque and peak-isokinetic power. VML-injured limbs had 25% less peak-isometric torque and 31% less peak-isokinetic power compared to those of Uninjured-20 mice (p < 0.001). Ultimate load, but not stiffness, was significantly less (10%) in tibias of VML-injured limbs compared to those from Uninjured-20 (p = 0.014). µCT analyses showed cortical bone thickness was 6% less in tibias of VML-injured limbs compared to Uninjured-20 (p = 0.001). Importantly, tibial bone cross-section moment of inertia, the primary determinant of bone ultimate load, was 16% smaller in bones of VML-injured limbs compared to bones from Uninjured-20 (p = 0.046). Metaphyseal trabecular bone structure was also altered up to 23% in tibias of VML-injured limbs (p < 0.010). These changes in tibial bone structure and function after a VML injury occur during a natural maturation phase between the age of 12 and 20 weeks, as evidenced by Uninjured-20 mice having greater tibial bone size and strength compared to uninjured-aged 12-week mice.

Effects of Motor-Cognitive Dual-Task Standing Balance Exergaming Training on Healthy Older Adults' Standing Balance and Walking Performance.

Objective: This study examined the effects of motor-cognitive dual-task exergaming standing balance training on healthy older adults' static, dynamic, and walking balance. Methods: Twenty-four adults older than 70 years (control group: n = 9, males = 6, balance training group: n = 15, males = 8) completed the experiment. Dual-tasking standing balance training comprised the accurate control of a ping-pong ball on a tray held with both hands, while standing on one leg (analog training) and three modules of Wii Fit™ exergaming (digital training). The duration of balance training was ∼15 minutes per day, 2 days per week for 8 weeks, in total 16 sessions. We measured one-leg standing time, functional reach distance, walking balance evaluated by the distance walked on a narrow beam (4-cm long, 4-cm wide, and 2-cm high) with single and dual tasking, habitual and maximal walking speed, and muscle strength of the hip extensor, hip abductor, hip adductor, knee extensor, and plantarflexor muscle groups in the right leg at baseline and after 8 weeks. Results: Control group decreased, but balance training group increased one-leg standing time. Only the balance training group improved functional reach distance and hip and knee extensor strength. There was no change in walking speed and walking balance in either group. In the balance training group, changes in maximal speed correlated with changes in dual-tasking walking balance and changes in one-leg standing time correlated with changes in single-tasking walking balance. Conclusion: These results suggest that 16 sessions of motor-cognitive dual-task standing exergaming balance training substantially improved healthy older adults' static and dynamic balance and leg muscle strength but failed to improve walking speed and walking balance. Balance exercises specific to walking balance need to be included in balance training to improve walking balance.

EFFECT OF FOOTBALL ON REHABILITATION OF ANKLE INJURY PATIENTS

ABSTRACT Introduction: Brief introduction: Ankle tendon and ligament sports injuries are common in football players. Objective: To continue to improve special strength training related to the characteristics of football after rehabilitation of injured ankle tendons and ligaments. Methods: Two master football sportsmen were rehabilitated by multi-point equal-length, short-arc and long-arc equal-speed training combined with balance ability exercises. Results: There were two long muscle L be maintain muscle tone plantar flexors force four times of 96 n/m, n/m 121, 140 n/m, 145 n/m than back flexors force of 63 n/m, 52 n/m, 60 n/m, 74 n/m tall. Plantar flexor fatigue was 57%, 30%, 29%, 12%, 28%, 18%, 20%, 21%. Conclusions: With the passing of time, the relative peak moment value of the right ankle plantar flexor muscle group of the two patients kept rising, the dorsiflexor muscle was basically flat, and the work fatigue index decreased step by step, indicating that the right ankle muscle strength level was significantly improved, the anti-fatigue ability was improved, and the rehabilitation treatment had a good effect. Level of evidence II; Therapeutic studies - investigation of treatment results.

Lower Limb Muscle Forces in Table Tennis Footwork during Topspin Forehand Stroke Based on the OpenSim Musculoskeletal Model: A Pilot Study

Introduction: Footwork is one of the training contents that table tennis players and coaches focus on. This study aimed to gain a thorough understanding of the muscle activity of the table tennis footwork and creating a musculoskeletal model to investigate the muscle forces, joint kinematic, and joint kinetic characteristics of the footwork during topspin forehand stroke. Methods: Six male table tennis athletes (height: 171.98 ± 4.97 cm; weight: 68.77 ± 7.86 kg; experience: 10.67 ± 1.86 years; age: 22.50 ± 1.64 years) performed chasse step and one-step footwork to return the ball from the coach by topspin forehand stroke. The kinematics, kinetics, and muscle activity of the lower limb were recorded by the motion capture, force platform, and Electromyography (EMG) system. Statistical parametric mapping (SPM) analysis was used to investigate any difference between the chasse step and one-step footwork during the stroke. Results and Conclusion: The muscle force of the biceps femoris long head (p < 0.001), lateral gastrocnemius (p < 0.001), vastus lateralis (p < 0.001), vastus medial (p < 0.001), rectus femoris (p < 0.001), and tibia anterior (p < 0.001) of the chasse step were significantly greater than the one-step footwork during the early stroke phase (stance). At the end of the stroke phase (push-off), the muscle force of the biceps femoris long head (p < 0.001), medial gastrocnemius (p < 0.001), lateral gastrocnemius (p < 0.001), rectus femoris (p < 0.001), and tibias anterior (p < 0.001) in the chasse step footwork was significantly greater than the one-step footwork. The muscle force of the ankle plantar flexor and valgus muscle groups in the one-step was significantly greater than in the chasse step. Besides, the moment and angle of hip flexion (p = 0.001) and axial rotation (p = 0.009) were significantly greater for the chasse step than the one-step footwork, as well as the ankle plantarflexion angle (p < 0.001) and moment (p < 0.001) of the one-step footwork were significantly higher than the chasse step footwork. The results of this study can be applied to movement control and injury prevention in table tennis footwork.

Intra- and Intermuscular Coherence and Body Acceleration Control in Older Adults during Bipedal Stance.

Our aim was to clarify the effect of aging on the coherence of electromyograms of plantar flexor pairs during bipedal stance and to clarify the relationship between coherence and center-of-mass acceleration (COMacc). The subjects were 16 adults and 18 older adults. Intra- and intermuscular coherence and phase analyses were used to analyze the muscle pairs of bilateral and unilateral plantar flexor muscle groups. The relationship between coherence value and anterior–posterior COMacc of the plantar flexor muscle pairs was also examined to determine whether the connectivity of the lower limb muscle pairs is functionally important. The older adults showed higher coherence in the frequency range of 0–4 Hz for muscle pairs than the younger adults. In phase analysis, the older adults showed a phase difference between bilateral heteronymous muscle pairs in the frequency range of 0–6 Hz, which was one of the characteristics not seen in the younger adults. Correlation analysis showed that all the muscle pairs were moderately correlated with COMacc in the older adults. Not only does aging affects the organization of the bilateral and unilateral postural muscle activity of the plantar flexors during bipedal stance, but such organization may also be related to the increased COMacc characteristics of older adults.

Musculoskeletal modelling based estimates of load dependent relative muscular effort during resistance training exercises

ABSTRACT The purpose of this study was to investigate the relative muscular effort (RME) of the hip and knee extensor and ankle plantarflexor muscle groups during the back squat (BS) and split squat (SS) exercises across four external load conditions. Motion capture and force plate data were collected as participants performed the BS and SS at 0%, 25%, 50%, and 75% of their body-mass. These data were used to calculate net joint moments (NJM) at the hip, knee, and ankle of the front leg during the SS and the matched leg during the BS. A musculoskeletal model, which accounted for force-length-velocity properties of 52 muscles, was used to estimate the maximal possible NJM (NJMmax) of the hip and knee extensor and ankle plantarflexor muscle groups. RME was calculated as the ratio between NJM and NJMmax, and compared across exercises and loads. The results indicated that while hip extensor RME increased across all loads, the increases in hip extensor RME were disproportionately greater during the SS at loads of 50% and 75%. Knee extensor RME increased linearly across loads and did not differ between exercises. These results provide coaches and athletes with detailed information about how to optimise resistance training specificity.

Hind foot drumming: Volumetric micro-computed tomography investigation of the hind limb musculature of three African mole-rat species (Bathyergidae).

Several species of African mole-rats use seismic signalling by means of hind foot drumming for communication. The present study aimed to create three-dimensional reconstructions and compare volumetric measurements of 27muscles of the hind limb of two drumming (Georychus capensis and Bathyergus suillus) and one non-drumming (Cryptomys hottentotus natalensis) species of African mole-rats. Diffusible iodine contrast-enhanced micro-computed tomography (diceCT) scans were performed on six specimens per species. Manual segmentation of the scans using VGMAX Studio imaging software allowed for individual muscles to be separated while automatically determining the volume of each muscle. The volume of the individual muscles was expressed as a percentage of the total hind limb volume and statistically compared between species. Subsequently, three-dimensional reconstructions of these muscles were created. Musculus gracilis anticus had a significantly larger percentage of the total hind limb muscle volume in both drumming species compared to the non-drumming C. h. natalensis. Furthermore, several hip and knee extensors, namely mm. gluteus superficialis, semimembranosus, gluteofemoralis, rectus femoris and vastus lateralis, had significantly larger muscle volume percentages in the two drumming species (G. capensis and B. suillus) compared to the non-drumming species. While not statistically significant, G. capensis had larger muscle volume percentages in several key hip and knee extensors compared to B. suillus. Additionally, G capensis had the largest summed percentage of the total hind limb volume in the hip flexor, hip extensor, knee extensor and ankle plantar flexor muscle groups in all the three species. This could be indicative of whole muscle hypertrophy in these muscles due to fast eccentric contractions that occur during hind foot drumming. However, significantly larger muscle volume percentages were observed in the scratch digging B. suillus compared to the other two chisel tooth digging species. Moreover, while not statistically significant, B. suillus had larger muscle volume percentages in several hip extensor and knee flexor muscles compared to G. capensis (except for m. vastus lateralis). These differences could be due to the large relative size of this species but could also be influenced by the scratch digging strategy employed by B. suillus. Therefore, while the action of hind foot drumming seems to influence certain key muscle volumes, digging strategy and body size may also play a role.

ACUTE EFFECTS OF INTRAMUSCULAR STRETCHING AND PASSIVE STRETCHING ON SPASTICITY IN CHILDREN WITH CEREBRAL PALSY

Purpose: Several methods are used to reduce spasticity in cerebral palsy (CP) rehabilitation. One of these methods is stretching. This study aimed to compare the acute effects of intramuscular stretching and passive stretching on spasticity in children with bilateral spastic CP.Methods: The study included a total of 22 children (12 boys and 10 girls) with bilateral CP, between the ages of 5 and 13 years (mean age=6.45±1.96 years), who had spasticity in the plantar flexor muscle groups. All children were under an individualized physiotherapy program. In addition to the physiotherapy program, intramuscular stretching was applied to the plantar flexor muscles on one side, whereas passive manual stretching was applied to the other side. The Modified Ashworth Scale (MAS), Modified Tardieu Scale (MTS), and Silfverskiold test were used to assess the spasticity. Evaluations were performed before and after the applications.Results: There was a significant difference between pre and post-treatment comparisons in the intramuscular stretching side (MAS p=0.024, MTS R2-R1 p&amp;lt;0.001, Silfverskiold test p=0.002) and the passive stretching side (MAS p=0.014, MTS R2-R1 p=0.001, and the Silfverskiold test p=0.003). On the other hand, there was no difference between the intramuscular and passive stretching sides (p&amp;gt;0.05).Conclusion: Both intramuscular and passive stretching are effective methods for reducing spasticity in children with bilateral spastic CP, and their acute effects are similar.

Acute Effects of Static and Ballistic Stretching on Muscle-Tendon Unit Stiffness, Work Absorption, Strength, Power, and Vertical Jump Performance.

Gesel, FJ, Morenz, EK, Cleary, CJ, and LaRoche, DP. Acute effects of static and ballistic stretching on muscle-tendon unit stiffness, work absorption, strength, power, and vertical jump performance. J Strength Cond Res 36(8): 2147-2155, 2022-The purpose of this study was to evaluate the effects of static and ballistic stretching on muscle-tendon unit (MTU) stiffness, work absorption (WA), strength, power, and countermovement vertical jump (CMJ) performance. Using a within-subject design, 22 subjects performed 3 separate experimental conditions: no-stretching, ballistic stretching, and static stretching for the quadriceps, hamstrings, gluteus, and plantarflexor muscle groups. After each condition, plantarflexor MTU stiffness, WA, isometric strength, and power were measured, followed by a CMJ on a force plate to obtain peak center of mass velocity, peak power, rate of force development, peak force, work, and vertical jump height. Repeated measures analysis of variance with Bonferroni corrected post-hoc tests were used to detect differences between conditions for plantarflexor and CMJ measures. An acute bout of static stretching significantly reduced WA by 12% ( p = 0.049) and isokinetic power by 8% ( p = 0.047) compared with the control condition but ballistic stretching did not ( p = 0.624, p = 0.692, respectively). Significant positive correlations existed between MTU stiffness, WA, strength, and power ( r = 0.64-0.77, p < 0.001). Despite significant positive correlations between MTU stiffness, WA, and CMJ performance measures ( r = 0.40-0.72, p < 0.001), neither static nor ballistic stretching affected CMJ performance ( p > 0.05). These data show that stiffer MTU that absorb more work (energy) are associated with greater muscle force, power, and CMJ performance. Although an acute bout of static stretching impaired MTU passive-elastic properties and power production, neither static nor ballistic stretching impaired isometric strength or CMJ performance.

Tibial stress during running following a repeated calf-raise protocol.

Tibial stress fractures are a problematic injury among runners. Increased loading of the tibia has been observed following prolonged weight-bearing activity and is suggested to be the result of reduced activity of the plantar flexor muscles. The musculature that spans the tibia contributes to bending of the bone and influences the magnitude of stress on the tibia during running. Participant-specific models of the tibia can be used as a non-invasive estimate of tibial stress. This study aimed to quantify tibial stress during running using participant-specific bone geometry and to compare tibial stress before and after a protocol of repeated muscular contractions of the plantar flexor muscle group. Fourteen participants who run recreationally were included in the final analysis of the study. Synchronized force and kinematic data were collected during overground running before and after an exhaustive, weighted calf-raise protocol. Bending moments and stress at the distal third of the tibia were estimated using beam theory combined with inverse dynamics and musculoskeletal modeling. Bone geometry was obtained from magnetic resonance images. There was no difference in stress at the anterior, posterior, medial, or lateral peripheries of the tibia after the calf-raise protocol compared with before. These findings suggest that an exhaustive, repeated calf-raise protocol did not alter tibial stress during running.

Muscle length: A new feature to investigate neural control of lengthening contractions.

Muscle length: A new feature to investigate neural control of lengthening contractions.

Interplay Between Whole Body Metabolism, Physical Activity, and Muscle Function Following Volumetric Muscle Loss Injury

Volumetric muscle loss (VML) injury occurs when a substantial volume of skeletal muscle is abruptly removed and results in significant long‐term functional limitations. Following VML injury, patients likely undergo periods of low or no mobility and are expected to have reduced physical activity. Immobility and lack of physical activity leads to impaired muscle function, and increased all‐cause mortality and risk for chronic disease. It is plausible that inactivity and immobility negatively affect outcomes following VML injury, exacerbating functional impairments. Our previous work supports an ~25% lower oxygen consumption rate in permeabilized muscle fibers of the muscle remaining after VML up to 4 months post‐injury, but how this may impact whole body metabolism is unclear. Therefore, the purpose of this study was to characterize whole body metabolic and physical activity following VML injury. We hypothesized that metabolism and physical activity would be impaired following VML. To elucidate the interplay between metabolism, activity, and muscle function following VML injury, adult male C57BL/6 mice (n=7) underwent a full‐thickness multi‐muscle VML injury (removal of ~22mg) to the gastrocnemius, soleus, and plantaris, or sham surgery (n=7). Twenty‐four hour whole body metabolic and physical activity was assessed pre‐, and 2 and 6 weeks post‐VML (or sham) injury. Contractile activity of the ankle plantarflexors was assessed terminally at 8 weeks post‐VML. Prior to randomization into experimental groups metabolic rate was ~18.5kcal/kg/hr and there was no difference in any metabolic or activity measure (p≥0.21), and both groups gained ~3g over the 8 week period. Whole body metabolism was evaluated for the 24‐hour period and isolated by the 12 hours of active and inactive time; respiratory exchange ratio (RER), an indirect measure of muscle oxidative capacity, was not different across experimental groups (p≥0.76) but was significantly decreased with time (main effect p≤0.01). Two weeks post‐VML mice tended to become hypermetabolic with a metabolic rate ~14% greater than sham. On average, mice ambulated ~1.2 km per 24‐hour period and contrary to the hypothesis, there was no difference in activity levels (p≥0.23) between sham and VML injured mice. Terminally the plantarflexor muscle group of the VML‐injured mice had ~1.4 fold greater maximal passive torque (indicator of muscle stiffness) and ~40% less maximal active isometric torque. These findings indicate limited changes whole body metabolic and physical activity levels in a model of VML injury, contrary to our hypothesis. Future studies will limit physical activity levels in this model to better recapitulate the low or no mobility expected following VML injury clinically.Support or Funding InformationSupported by W81XWH‐18‐1‐0710 &amp; T32AR050938

Comparing the acute effect of myofascial release techniques and passive stretching on hind foot dynamic loading in patients with multiple sclerosis: A cohort-blinded study

Summary Study aim: It is important for therapists to incorporate new practical methods into therapy programs when they have demonstrable efficacy in the treatment of multiple sclerosis. Investigating the acute effects of myofascial release techniques (MFR) and passive stretching (PS) on hind foot loading and the severity of spasticity in individuals with multiple sclerosis (MS) was the aim of the study. Material and methods: Following the initial evaluation, 10 participants with MS (n = 20 feet) were given MFR for the plantar flexor muscle group. After the day following the first visit, participants were asked to come again and PS was applied to the plantar flexor muscle groups after the evaluation. The severity of spasticity was assessed with the Modified Ashworth Scale (MAS). Dynamic loading parameters of the hind foot – medial and lateral maximum pressure (N/cm2), active contact areas (cm2), contact percentiles (%) – were evaluated with dynamic pedobarography. Participants of the study were evaluated four times: (1) at the initial evaluation, (2) after MFR application, (3) 24 hours after the initial evaluation (pre-PS), (4) after PS. Results: There were no differences in MAS (p &gt; 0.05) according to time-dependent analyses (p &gt; 0.05). After MFR, the maximum pressure of the medial heel and active contact area were increased (p &lt; 0.05) and there was a carryover effect on the maximum pressure of the right foot. Conclusions: This study showed that MFR was an effective method for management of plantar flexor spasticity in patients with multiple sclerosis in the short term and there was a carryover effect in favor of MFR. There was no additional effect of PS.

Estimation of the force-velocity properties of individual muscles from measurement of the combined plantarflexor properties.

The force-velocity (F-V) properties of isolated muscles or muscle fibers have been well studied in humans and other animals. However, determining properties of individual muscles in vivo remains a challenge because muscles usually function within a synergistic group. Modeling has been used to estimate the properties of an individual muscle from the experimental measurement of the muscle group properties. While this approach can be valuable, the models and the associated predictions are difficult to validate. In this study, we measured the in situ F-V properties of the maximally activated kangaroo rat plantarflexor group and used two different assumptions and associated models to estimate the properties of the individual plantarflexors. The first model (Mdl1) assumed that the percent contributions of individual muscles to group force and power were based upon the muscles' cross-sectional area and were constant across the different isotonic loads applied to the muscle group. The second model (Mdl2) assumed that the F-V properties of the fibers within each muscle were identical, but because of differences in muscle architecture, the muscles' contributions to the group properties changed with isotonic load. We compared the two model predictions with independent estimates of the muscles' contributions based upon sonomicrometry measurements of muscle length. We found that predictions from Mdl2 were not significantly different from sonomicrometry-based estimates while those from Mdl1 were significantly different. The results of this study show that incorporating appropriate fiber properties and muscle architecture is necessary to parse the individual muscles' contributions to the group F-V properties.

A clinically applicable tool for rapidly estimating muscle volume using ultrasound images

PurposeThis study aimed to identify a safe, rapid, and accessible method of estimating muscle volume of key lower limb muscle groups to reduce the time-demand of acquiring this measurement and potentially facilitate its application as a clinical monitoring tool.MethodsUnilateral MRI images were acquired from the 12th thoracic vertebrae to the base of the foot in 18 recreationally active males. Panoramic B-mode ultrasound images were acquired from the same leg at the mid-hip, 25%, 50%, and 75% of thigh length, and 25% of shank length. Body mass, height, limb lengths, and circumferences at the sites corresponding to the ultrasound images were acquired. A single investigator manually analysed all images. Regression analyses were conducted to identify models for estimating volume of the hip extensor, knee extensor and flexor, and ankle plantarflexor muscle groups.ResultsModels were developed for estimating hip extensor (SEE = 8.92%, R2 = 0.690), knee extensor (SEE = 5.24%, R2 = 0.707) and flexor (SEE = 7.89%, R2 = 0.357), and ankle plantarflexor (SEE = 10.78%, R2 = 0.387) muscle group volumes. The hip and knee extensor models showed good potential for generalisation. Systematic error was observed for the knee flexor and ankle plantarflexor models.ConclusionsHip extensor, knee extensor and flexor, and ankle plantarflexor muscle group volumes can be estimated using B-mode ultrasound images and anthropometric measurements. The error shown for each of the models was sufficient to identify previously reported differences in muscle volume due to training or injury, supporting their clinical application.

COMPARISON OF EFFECT OF BALANCE DISC AND BOSU BALL ON ANKLE DORSIFLEXOR AND PLANTARFLEXOR MUSCLE STRENGTH

Purpose of this study is to compare effect of balance disc (duradisk, dynadisk, balance ball, inflatable disc, etc.) and bosu ball on the strength development of ankle dorsiflexor and plantarflexor muscles of sedentary children. 74 sedentary children with a mean age of 9.71 years (sd =0,370) were granted permission from their parents in accordance with the Helsinki Declaration. In the study, a balance disk group and a bosu group were formed by random sampling. Balance disk group with the balance disk to the bosu group with bosu balls, three days a week, the same training program was applied for 8 weeks. The pre and post test ankle strength measurements of all groups were measured using the ’Lafayette’ digital hand dynamometer and the differences between the groups were examined. The participants were asked to perform a right-left foot dorsiflexion, and right-left foot plantarflexion force measurements were performed for 5 seconds. Each measurement is repeated twice and the best result was recorded. Two-way analysis of variance was used for parametric results and Kruskall Wallis test for non-parametric results. Before the study, it was seen that there was no significant difference between the groups in the measurements (p>.05). Therefore, gender difference is not considered. After the research, both groups showed improvement according to the pre-tests. There was a significant difference between the balance disk group and the bosu group in favor of the balance disk group (p <.05). In our study, it was found that the training performed with balance disk and bosu ball significantly improved the strength of both ankle dorsiflexor muscle groups and ankle plantarflexor muscle groups. This result shows that the exercises with balance disc and bosu can increase the strength development of dorsiflexor and plantarflexor muscle groups in sedentary children. Therefore, it may be suggested that training with balance disc and bosu can be used as an alternative method for strength development for these muscle groups. Article visualizations:

The Contributions of Individual Muscle-Tendon Units to the Plantarflexor Group Force-Length Properties.

The combined force-length (F-L) properties of a muscle group acting synergistically at a joint are determined by several aspects of the F-L properties of the individual musculotendon units. Namely, misalignment of the optimal lengths of the individual muscles will affect the group F-L properties. This misalignment, which we named [Formula: see text], arises from the properties of the muscles (i.e., optimum fiber length and pennation angle) and of their tendons (i.e., compliance and slack length). The aim of this study was to measure the F-L properties of kangaroo rat plantarflexors as a group and individually and determine the effects of [Formula: see text] on the group F-L properties. Specifically, we performed a sensitivity analysis to quantify how [Formula: see text] influences the tradeoff between maximizing the peak force vs. having a wider group F-L curve. In the kangaroo rat, we found that the optimal lengths of two bi-articular musculotendon units, the plantaris and the gastrocnemius, were misaligned by 1.8mm, but this amount favored maximal peak force rather than increasing F-L curve width. Because we measured the misalignment in situ, we could directly assess the tradeoff between maximizing peak force vs. a wider F-L curve without making modeling assumptions about the individual muscle or tendon properties.