Evaluation of the strength-size relationship in vivo using various muscle size indices

Jump Performance and Its Relationship with Lower Body Joint Kinetics and Kinematics in Children with Cerebral Palsy

PURPOSE

The aim was to quantify jump performance in children with cerebral palsy (CP) and determine if the expected deficit is related to their lower body joint kinetics and kinematics.

METHODS

Twenty-four ambulatory ( n = 17 level I and 7 level II in the Gross Motor Function Classification System) children with spastic CP ( n = 13 unilateral and 11 bilateral) and 24 age-, sex-, and race-matched typically developing controls were studied. Jump height and peak power and range of motion at the hip, knee, and ankle of the more affected limb in children with CP and the nondominant limb in controls were assessed during a countermovement jump using three-dimensional motion capture and a force platform.

RESULTS

Compared with controls, children with CP had lower jump height (33%, Cohen's d ( d ) = 1.217), peak power at the knee (39%, d = 1.013) and ankle (46%, d = 1.687), and range of motion at the hip (32%, d = 1.180), knee (39%, d = 2.067), and ankle (46%, d = 3.195; all P < 0.001). Jump height was positively related to hip, knee, and ankle power and range of motion in children with CP ( rs range = 0.474-0.613, P < 0.05), and hip and ankle power and knee and ankle range of motion in controls ( rs range = 0.458-0.630, P < 0.05). The group difference in jump height was no longer detected when ankle joint power, ankle range of motion, or knee range of motion was statistically controlled ( P > 0.15).

CONCLUSIONS

Jump performance is compromised in children with CP and is associated with low power generation and range of motion in the lower limb, especially at the ankle.

Additional effect of neuromuscular electrical stimulation in a conservative intervention on morphology and strength of abductor hallucis muscle and correction of hallux valgus deformity: a randomized controlled trial

BACKGROUND

In hallux valgus, morphological changes and functional weakness of intrinsic foot muscles occur, especially in the abductor hallucis muscle.

OBJECTIVES

This study aimed to investigate how a conservative treatment with the addition of neuromuscular electrical stimulation affects the volume and strength of the muscle, the correction of deformity, passive range of motion, pain, and disability.

METHODS

Twenty-eight female participants (48 feet) were randomly assigned to two groups. The interventions included orthoses and exercise (Ortho) in both groups. One group received additional neuromuscular electrical stimulation of abductor hallucis muscle to activate it. Each group received the treatments for one month and was assessed two times, at baseline before starting and after one month of treatment. Mixed within-between ANOVA, analysis of covariance, and nonparametric tests were used for data analysis.

RESULTS

The muscle volume, abduction strength, goniometric angle, and passive hallux dorsi/plantar flexion showed significant changes in both groups (p < .001). Subscales of the foot and ankle ability questionnaire, significantly changed (p ≤ .05). Pain decreased significantly in the two groups (p < .001 and p = .02). Intermetatarsal angle did not significantly differ between the two groups (p = .86, partial eta effect size = 0.001). But, the hallux valgus angle mean (on MRI) in the Ortho group was less than that of the orthoNMES group (p = .007, partial eta effect size = 0.15).

CONCLUSION

Both groups showed nearly identical treatment effects in the primary volume and hallux valgus correction outcome measures. In this study, adding neuromuscular electrical stimulation did not have an additional effect compared to conservative in the treatment of hallux valgus.

TRIAL REGISTRATION NUMBER

The RCT Code is IRCT20200915048725N1.

Pectoralis major and triceps brachii cross-sectional area measured on different planes: the effect on the muscle size-strength relationship

BACKGROUND

Magnetic resonance imaging (MRI) is a well-used technique to assess muscle size and can be acquired on different planes. Pectoralis major (PM) and triceps brachii (TB) muscles are often acquired and analyzed on the axial plane, however it is unknown if anatomical cross-sectional area (CSA) calculated from different planes will affect the muscle size-strength relationship. Thus, the first aim of the present study was to identify if the CSA of the PM and TB measured on different planes presents a similar muscle size-strength relationship. A secondary aim was to investigate if the quantification of CSA of the PM and TB muscles are similar between sagittal and axial plane.

METHODS

Fifteen males underwent an MRI examination, and after that, one-repetition maximum (1RM) test was performed.

RESULTS

There was a significant relationship between 1RM and PM CSA measured on the axial and sagittal plane (r≤0.81), while the relationship with TB CSA was only good on the axial plane (r=0.65) and not significant on the sagittal plane (r=0.27). ICC between planes was excellent for PM CSA (0.96) with Bland-Altman procedure showing agreement between planes (d=0.376; P=0.612). Contrarily, TB CSA ICC was week (0.07), with Bland-Altman procedure showing no agreement between planes (d=-24.49; P=0.022).

CONCLUSIONS

CSA measured at axial plane from PM and TB muscles showed a significant relationship with 1RM, while only PM CSA on the sagittal plane showed a significant relationship with 1RM. Finally, it was demonstrated that PM images showed a great reliability between planes, which was not true for TB muscle.

Triceps surae muscle forces during dynamic exercises in patients with Achilles tendinopathy: A cross-sectional study

PURPOSE

The aim of this study was to investigate the individual triceps surae muscle forces during the execution of six different functional movements and rehabilitation exercises in patients with Achilles tendinopathy compared to a control group.

METHODS

Triceps surae muscle forces of 15 participants with Achilles tendinopathy (AT) and 15 healthy controls were estimated through a combination of experimental data and musculo-skeletal modeling. Three-dimensional motion capture and force plates were used to collect the ankle and knee joint angles and moments during three functional movements (walking, heel walking, and toe walking) and three rehabilitation exercises (bilateral heel drop, unilateral heel drop with extended knee and with flexed knee). A dynamic optimization method was used to obtain the modeled triceps surae muscle forces. Force-sharing strategies were calculated at the peak triceps surae muscle force and compared between groups.

RESULTS

Lower peak triceps surae forces were obtained for the AT group during dynamic exercises. Across all exercises, the average contribution of the soleus (SOL) to the total triceps surae muscle force was the largest (60.83 ± 13.89% [AT] > 56.90 ± 16.18% [healthy]), followed by the gastrocnemius medialis (29.87 ± 10.67% [AT] < 32.19 ± 12.90% [healthy]) and the gastrocnemius lateralis (9.30 ± 4.31% [AT] < 10.91 ± 4.66% [healthy]). The triceps surae force-sharing strategy was different for the toe walking, heel walking, and the bilateral and unilateral heel drop with extended knee.

CONCLUSION

This study provides evidence for altered triceps surae muscle force-sharing strategies during dynamic tasks in patients with AT. The influence of altered muscle force-sharing on the subtendon nonuniformity and/or the tendon loading should be explored in future work.

A longer Achilles tendon moment arm length is not associated with superior hopping performance

Variability in musculoskeletal and lower leg structure has the potential to influence hopping height. Achilles tendon moment arm length and plantarflexor muscle strength can influence ankle joint torque development and, consequently, hopping performance. While most studies have examined the connection of the Achilles tendon moment arm with hopping performance including the resting length, in this study we attempted to explore how the changes in Achilles tendon moment arm are related to hopping performance. Therefore, the purpose of this study was to test for correlations between foot and lower leg muscle structure parameters (i.e., muscle mass, volume, cross-sectional area and Achilles tendon moment arm length) and hopping height performance in relation to changes in Achilles tendon moment arm length. Eighteen participants (10 males 8 female) performed repetitive bilateral hopping on a force platform while sagittal plane kinematics of the lower leg were recorded. Additionally, maximal isometric plantarflexion was measured. To obtain structural parameters of the lower leg, the right lower leg of each participant was scanned with magnetic resonance imaging. The cross-sectional areas of the Achilles tendon, soleus, lateral and medial gastrocnemius were measured, while muscle volumes, muscle mass, and Achilles tendon moment arm length were calculated. Contrary to our initial assumption, longer Achilles tendon moment arm did not result in superior hopping performance. Interestingly, neither maximal isometric plantarflexion force nor muscle size correlated with repetitive bilateral hopping performance. We can assume that the mechanical characteristics of the tendon and the effective utilization of the stored strain energy in the tendon may play a more important role in repetitive hopping than the structural parameters of the lower leg.

Musculotendon Parameters in Lower Limb Models: Simplifications, Uncertainties, and Muscle Force Estimation Sensitivity

Musculotendon parameters are key factors in the Hill-type muscle contraction dynamics, determining the muscle force estimation accuracy of a musculoskeletal model. Their values are mostly derived from muscle architecture datasets, whose emergence has been a major impetus for model development. However, it is often not clear if such parameter update indeed improves simulation accuracy. Our goal is to explain to model users how these parameters are derived and how accurate they are, as well as to what extent errors in parameter values might influence force estimation. We examine in detail the derivation of musculotendon parameters in six muscle architecture datasets and four prominent OpenSim models of the lower limb, and then identify simplifications which could add uncertainties to the derived parameter values. Finally, we analyze the sensitivity of muscle force estimation to these parameters both numerically and analytically. Nine typical simplifications in parameter derivation are identified. Partial derivatives of the Hill-type contraction dynamics are derived. Tendon slack length is determined as the musculotendon parameter that muscle force estimation is most sensitive to, whereas pennation angle is the least impactful. Anatomical measurements alone are not enough to calibrate musculotendon parameters, and the improvement on muscle force estimation accuracy will be limited if the source muscle architecture datasets are the only main update. Model users may check if a dataset or model is free of concerning factors for their research or application requirements. The derived partial derivatives may be used as the gradient for musculotendon parameter calibration. For model development, we demonstrate that it is more promising to focus on other model parameters or components and seek alternative strategies to further increase simulation accuracy.

Aging-related changes in knee flexor muscle strength and cross-sectional area

Weakening muscle strength around the knee tends to render it vulnerable to aging-related damage. This study aimed to examine the association between knee flexor muscle strength and its cross-sectional area (CSA). We also evaluated aging-related changes in flexor muscle strength and CSA. We retrospectively analyzed 252 patients with acute-onset knee pain (<1 month) between September 2006 and August 2009 in accordance with the Strengthening the Reporting of Observational studies in Epidemiology statement. The CSA of each knee flexor muscle (biceps femoris, sartorius, gracilis, semitendinosus (ST), and semimembranosus (SM)) was measured on magnetic resonance imaging axial images at the suprapatellar level. We evaluated flexor muscle strength (peak torque in N.m) using a Cybex dynamometer at 60°/second and 180°/second and its correlation with CSA. In total, 252 patients (mean age, 34.5 years; range, 11 to 66 years; 184 men and 68 women) were included in this study. No significant intergroup differences in demographic data such as sex or body mass index were found. Mean CSA was 605.4 mm2 for the SM, 444.7 mm2 for the biceps femoris, 282 mm2 for the sartorius, 55.4 mm2 for the ST, and 34.1 mm2 for the gracilis. Mean peak torques were 67.4 N.m and 52.7 N.m at 60°/second and 180°/second, respectively. CSA was positively correlated with flexion strengths of 60°/second (R = 0.363, P < .001) and 180°/second (R = 0.354, P < .001). Muscle strength was associated with CSA in all muscles but the gracilis (R = 0.056, P = .375). Flexion strength decreased significantly with aging from the thirties. Total CSA decreased with aging (r = -0.247, P < .001). The CSA of the biceps femoris, sartorius, SM, and ST decreased significantly, whereas that of the gracilis tended to decrease non-significantly with aging. Flexor muscle strength was associated with total muscle CSA on magnetic resonance imaging and the CSA of every muscle except the gracilis. Flexion strength decreased significantly with aging after the twenties, while total CSA decreased significantly with aging. The CSA of all flexor muscles decreased significantly with aging, whereas that of the gracilis decreased only slightly.

Partial Replacement of Soybean Meal with Canola Meal or Corn DDGS in Low-Protein Diets Supplemented with Crystalline Amino Acids-Effect on Growth Performance, Whole-Body Composition, and Litter Characteristics

A 42-day study was conducted to explore the application of supplemental amino acids (AA) in low-protein diets with soybean meal (SBM), canola meal (CM) or corn distillers dried grain with solubles (cDDGS) as the main protein feedstuffs. The responses of interest were growth performance, carcass yield, whole-body composition, litter ammonia and litter N. On d 0, a total of 540 Cobb 500 (off-sex) male broilers were allocated to 36 floor pens. All the birds received one starter diet that met nutrient requirements during the first 10d. Thereafter, six experimental diets were provided in grower and finisher phases. The diets included a positive control (PC): a corn−SBM diet with adequate protein. The protein level of the negative control (NC) was decreased by 45 g/kg relative to the PC. The next two diets had the same protein levels as the NC but with cDDGS added at 50 or 125 g/kg. The last two diets had the same CP as the NC but with CM added at 50 or 100 g/kg. All the low-protein diets had the same level of standardized ileal digestible indispensable AA according to Cobb 500 recommended level. Gly and Ser were added as sources of non-specific N. The dietary protein reduction in corn−SBM diets at both phases decreased (p < 0.05) weight gain and increased (p < 0.05) feed conversion ratio (FCR). Increasing levels of cDDGS or CM, at a constant CP level, linearly decreased (p < 0.05) the weight gain and feed intake, whereas increasing CM level linearly increased (p < 0.05) FCR in the grower and finisher phases. The eviscerated and carcass yields decreased, whereas the fat yield increased (p < 0.05) with reduced protein in corn−SBM diet. Increasing levels of cDDGS and CM at a constant CP level quadratically decreased (p < 0.05) the eviscerated weight, whereas the fat weight linearly decreased (p < 0.05) with increasing levels of cDDGS and CM. The birds receiving the PC diet had a lower (p < 0.05) lean muscle (%) and a higher fat (%) compared to birds receiving the NC diet at d 21. However, on d42, birds receiving the PC diet had decreased (p < 0.05) bone mineral density, bone mineral content and lean weight compared to those receiving the NC diet. The litter ammonia increased (p < 0.05) with the increasing levels of protein in the SBM diets. In conclusion, 50 g/kg inclusion levels of CM and cDDGS at the same low-protein levels as SBM produced a similar growth response to the NC, whereas higher levels were detrimental. Hence under the conditions of the current experiment, complete replacement of SBM with DDGS or CM in low-protein diets was not feasible.

The Relationship between Resistance Training Frequency and Muscle Quality in Adolescents

Previous research has established the role of resistance training (RT) on muscle function in adolescents, but a lack of evidence to optimize RT for enhancing muscle quality (MQ) exists. This study examined whether RT frequency is associated with MQ in a nationally representative adolescent cohort. A total of 605 adolescents (12−15 year) in NHANES were stratified based on RT frequency. MQ was calculated as combined handgrip strength divided by arm lean mass (via dual-energy X-ray absorptiometry). Analysis of covariance was adjusted for sex, race/ethnicity, and arm fat percentage; p < 0.05 was considered significant. RT frequency was associated with MQ for 2−7 day/week but not 1 day/week. When no RT was compared to 1−2 and 3−7 day/week, associations were present for 3−7 day/week but not 1−2 day/week. When comparing no RT to 1−4 and 5−7 day/week, associations existed for 5−7 day/week but not 1−4 day/week. Next, no RT was compared to 1, 2−3, and 4−7 day/week; associations were found for 4−7 day/week, while 2−3 day/week had a borderline association (p = 0.06); there were no associations for 1 day/week. Finally, no RT was compared to 1, 2, 3, 4, and 5−7 day/week; associations were present for all except 1 and 3 day/week. These prospective data suggest a minimum RT frequency of 2 day/week is associated with MQ in adolescents as indicated by the lack of differences in MQ between 1 day/week RT versus no RT.

Effect of Leg Half-Squat Training With Blood Flow Restriction Under Different External Loads on Strength and Vertical Jumping Performance in Well-Trained Volleyball Players

Purpose

To examine the effect of blood flow restriction resistance training under different external loads on the muscle strength and vertical jumping performance in volleyball players.

Methods

18 well-trained collegiate male volleyball players were randomly divided into 3 groups: high-load resistance training group (HL-RT, 70% 1RM, n = 6), low-load blood flow restriction resistance training group (LL-BFR-RT, 30% 1RM, 50% arterial occlusion, n = 6), and high-load blood flow restriction resistance training group (HL-BFR-RT, 70% 1RM, 50% arterial occlusion, n = 6). Participants performed leg half-squat exercise 3 times per week for 8 weeks. Measurements of Isokinetic peak torque of knee extension and flexion, 1RM leg half-squat, squat jump, and 3 footed take-off were obtained before and after training. A two-way repeated-measures analysis of variance was used to examine differences among the 3 groups and between the 2 testing time (pre-test vs post-test).

Results

(1) The HL-RT group was significantly greater in muscle strength than that in the LL-BFR-RT group (P < .05), but no improvement in vertical jumping performance (P >.05). (2) Improvement in muscle strength and vertical jumping performance was significantly greater in the HL-BFR-RT group than that in the LL-BFR-RT group (P <.05). (3) The HL-BFR-RT group had greater but not significant improvement in muscle strength and vertical jumping performance than that in the HL-RT group.

Conclusions

Although increases in muscle strength were observed between training groups, HL-BFR-RT increased not only muscle strength but vertical jumping performance to a greater extent compared to LL-BFR-RT and HL-RT.

Relationship between thigh muscle cross-sectional areas and single leg stand-up test in Japanese older women

In older adults, the quantitative decline of the quadriceps femoris is associated with the augmentation of difficulty in the execution of a stand-up task. However, it is unclear whether the cross-sectional areas (CSAs) of individual thigh muscles differ between older adults who can stand up from a 40-cm-height chair on a single leg and those who cannot. To investigate this, the present study determined the CSAs of individual mid-thigh muscles in 67 Japanese women aged 60–77 years by using a magnetic resonance imaging method. Participants were asked to stand up from a 40-cm-height chair on a single leg, and those who could and could not stand up without leaning back and maintain a standing posture for 3 seconds on a single leg were allocated into the successful group (SG, n = 40) and unsuccessful group (USG, n = 27), respectively. Only the CSA of the adductors (sum of the adductor longus and adductor magnus) was significantly smaller in USG compared to SG. When CSA was expressed relative to the two-third power of body mass, the values for the four heads of the quadriceps femoris and biceps femoris long head, as well as the adductors, were significantly lower in USG than in SG. The current results indicate that in terms of the value relative to body mass, the reduced CSAs of the adductors and biceps femoris long head, as well as the four heads of the quadriceps femoris, are associated with the failure of attempts to stand up from a 40-cm-height chair on a single leg in older women. This may be due to the anatomical function of the two muscle groups, which contributes to hip extension movement involved in transitioning from a sitting position to a standing position during the stand-up task.

Automatic MRI segmentation of pectoralis major muscle using deep learning

To develop and validate a deep convolutional neural network (CNN) method capable of selecting the greatest Pectoralis Major Cross-Sectional Area (PMM-CSA) and automatically segmenting PMM on an axial Magnetic Resonance Imaging (MRI). We hypothesized a CNN technique can accurately perform both tasks compared with manual reference standards. Our method is based on two steps: (A) segmentation model, (B) PMM-CSA selection. In step A, we manually segmented the PMM on 134 axial T1-weighted PM MRIs. The segmentation model was trained from scratch (MONAI/Pytorch SegResNet, 4 mini-batch, 1000 epochs, dropout 0.20, Adam, learning rate 0.0005, cosine annealing, softmax). Mean-dice score determined the segmentation score on 8 internal axial T1-weighted PM MRIs. In step B, we used the OpenCV2 (version 4.5.1, https://opencv.org) framework to calculate the PMM-CSA of the model predictions and ground truth. Then, we selected the top-3 slices with the largest cross-sectional area and compared them with the ground truth. If one of the selected was in the top-3 from the ground truth, then we considered it to be a success. A top-3 accuracy evaluated this method on 8 axial T1-weighted PM MRIs internal test cases. The segmentation model (Step A) produced an accurate pectoralis muscle segmentation with a Mean Dice score of 0.94 ± 0.01. The results of Step B showed top-3 accuracy > 98% to select an appropriate axial image with the greatest PMM-CSA. Our results show an overall accurate selection of PMM-CSA and automated PM muscle segmentation using a combination of deep CNN algorithms.

Associations between the size of individual plantar intrinsic and extrinsic foot muscles and toe flexor strength

Background

The size of the plantar intrinsic and extrinsic foot muscles has been shown to be associated with toe flexor strength (TFS). Previous studies adopted the size of limited plantar intrinsic foot muscles or a compartment containing several muscles as an independent variable for TFS. Among the plantar intrinsic and extrinsic foot muscles, therefore, it is unclear which muscle(s) primarily contributes to TFS production. The present study aimed to clarify this subject.

Methods

In 17 young adult men, a series of anatomical cross-sectional area of individual plantar intrinsic and extrinsic foot muscles was obtained along the foot length and the lower leg length, respectively, using magnetic resonance imaging. Maximal anatomical cross-sectional area (ACSA_max) and muscle volume (MV) for each constituent muscle of the plantar intrinsic foot muscles (flexor hallucis brevis; flexor digitorum brevis, FDB; abductor hallucis; adductor hallucis oblique head, ADDH-OH; adductor hallucis transverse head, ADDH-TH; abductor digiti minimi; quadratus plantae) and extrinsic foot muscles (flexor hallucis longus; flexor digitorum longus) were measured. TFS was measured with a toe grip dynamometry.

Results

TFS was significantly associated with the ACSA_max for each of the ADDH-OH (r = 0.674, p = 0.003), ADDH-TH (r = 0.523, p = 0.031), and FDB (r = 0.492, p = 0.045), and the MV of the ADDH-OH (r = 0.582, p = 0.014). As for the ADDH-OH, the correlation coefficient with TFS was not statistically different between ACSA_max and MV (p = 0.189). Stepwise multiple linear regression analysis indicated that ACSA_max and MV of the ADDH-OH alone explained 42 and 29%, respectively, of the variance in TFS.

Conclusion

The ADDH-OH is the primary contributor to TFS production among the plantar intrinsic and extrinsic foot muscles as the result of the stepwise multiple linear regression analysis.

Muscle volume vs. anatomical cross-sectional area: Different muscle assessment does not affect the muscle size-strength relationship

Muscle volume (MV) and anatomical cross-sectional area (CSA) are used as measures of muscle-size, but determining these from magnetic resonance imaging (MRI) is a very time-consuming process. Additionally, it is unclear if the use of different muscle size assessments (all vs. reduced number of slices images) would impact the muscle size-strength relationship. Thus, this study aimed to investigate if muscle size calculation by using a reduced or all slices images from pectoralis major (PM) would maintain a similar muscle size-strength relationship with bilateral maximal dynamic and isometric contractions on a bench press exercise. Twenty-four healthy males underwent an MRI examination to measure PM muscle size, and maximal isometric and dynamic contractions (by one repetition maximum, 1RM) were performed. Correlations between maximal isometric voluntary force (MVF) and dynamic strength (1RM) with muscle size variables [three images from the largest part of PM (CSA_3MAX), three images accounting for the shape -first image, middle image, final image- of the PM (CSA₃), and MV] were performed. The correlation between 1RM with MV, CSA₃, and CSA_3MAX were 0.84, 0.832, and 0.727 (p < 0.001), respectively. The correlation between MVF with MV, CSA₃, and CSA_3MAX were 0.738, 0.733, and 0.604 (p < 0.001), respectively. Overall, PM MV and CSA₃ exhibit a stronger and similar muscle size-strength relationship during maximal dynamic and isometric tests than CSA_3MAX. Therefore, a reduced number of slices (CSA₃) could be used as an alternative to considerably reduce the time of analysis without compromise muscle size-strength relationship.

Added value of combined acromiohumeral distance and critical shoulder angle measurements on conventional radiographs for the prediction of rotator cuff pathology

Purpose

Method

Results

Conclusions

•

Acromiohumeral distance (AHD) and critical shoulder angle (CSA) do not depend on age or sex.

•

CSA and AHD are significantly different in healthy and pathologic rotator cuffs.

•

Combining CSA and AHD into one index (PI_AHD-CSA) increases overall diagnostic performance.

•

A high PIAHD-CSA increases the risk of full thickness rotator cuff tear and critical fatty degeneration.

Gastrocnemius Muscle Architecture in Elite Basketballers and Cyclists: A Cross-Sectional Cohort Study

Eccentric and concentric actions produce distinct mechanical stimuli and result in different adaptations in skeletal muscle architecture. Cycling predominantly involves concentric activity of the gastrocnemius muscles, while playing basketball requires both concentric and eccentric actions to support running, jumping, and landing. The aim of this study was to examine differences in the architecture of gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) between elite basketballers and cyclists. A trained sonographer obtained three B-mode ultrasound images from GM and GL muscles in 44 athletes (25 basketballers and 19 cyclists; 24 ± 5 years of age). The images were digitized and average fascicle length (FL), pennation angle (θ), and muscle thickness were calculated from three images per muscle. The ratio of FL to tibial length (FL/TL) and muscle thickness to tibial length (MT/TL) was also calculated to account for the potential scaling effect of stature. In males, no significant differences were identified between the athletic groups in all parameters in the GM, but a significant difference existed in muscle thickness in the GL. In basketballers, GL was 2.5 mm thicker (95% CI: 0.7-4.3 mm, p = 0.011) on the left side and 2.6 mm thicker (95% CI: 0.6-5.7 mm, p = 0.012) on the right side; however, these differences were not significant when stature was accounted for (MT/TL). In females, significant differences existed in the GM for all parameters including FL/TL and MT/TL. Female cyclists had longer FL in both limbs (MD: 11.2 and 11.3 mm), narrower θ (MD: 2.1 and 1.8°), and thicker muscles (MD: 2.1 and 2.5 mm). For the GL, female cyclists had significantly longer FL (MD: 5.2 and 5.8 mm) and narrower θ (MD: 1.7 and 2.3°) in both limbs; no differences were observed in absolute muscle thickness or MT/TL ratio. Differences in gastrocnemius muscle architecture were observed between female cyclists and basketballers, but not between males. These findings suggest that participation in sport-specific training might influence gastrocnemius muscle architecture in elite female athletes; however, it remains unclear as to whether gastrocnemius architecture is systematically influenced by the different modes of muscle activation between these respective sports.

Mechanomyogram amplitude vs. isometric ankle plantarflexion torque of human medial gastrocnemius muscle at different ankle joint angles

The purpose of this study was to investigate the influence of changes in ankle joint angle on the mechanomyogram (MMG) amplitude of the human medial gastrocnemius (MG) muscle during voluntary isometric plantarflexion contractions. Ten healthy individuals were asked to perform voluntary isometric contractions at six different contraction intensities (from 10% to 100%) and at three different ankle joint angles (plantarflexion of 26°; plantarflexion of 10°; dorsiflexion of 3°). MMG signals were recorded from the surface over the MG muscle, using a 3-axis accelerometer. The relations between root mean square (RMS) MMG and isometric plantarflexion torque at different ankle joint angles were characterized to evaluate the effects of altered muscle mechanical properties on RMS MMG. We found that the relation between RMS MMG and plantarflexion torque is changed at different ankle joint angles: RMS MMG increases monotonically with increasing the plantarflexion torque but decreases as the ankle joint became dorsiflexed. Moreover, RMS MMG shows a negative correlation with muscle length, with passive torque, and with maximum voluntary torque, which were all changed significantly at different ankle joint angles. Our findings demonstrate the potential effects of changing muscle mechanical properties on muscle vibration amplitude. Future studies are required to explore the major sources of this muscle vibration from the perspective of muscle mechanics and muscle activation level, attributable to changes in the neural command.

A limited number of slices yields comparable results to all slices in foot intrinsic muscle deterioration ratio on computed tomography and magnetic resonance imaging

Diagnostic imaging modalities, like computed tomography (CT) and magnetic resonance imaging (MRI), can be used to assess in vivo muscle quality. Quantitative assessment using these techniques is time-intensive and costly due in part to extensive post-processing needs. The purpose of this study was to identify whether a subset of slices on CT and MRI would yield comparable results to the full number of slices for a measure of muscle quality (muscle deterioration ratio = fat volume/muscle volume) in the foot intrinsic muscles of people with diabetes and peripheral neuropathy. CT (0.6 mm slice thickness) and MRI (3.5 mm slice thickness) scans were obtained using previously described methods. The total number of slices acquired during the scan was compared to several conditions using a portion of slices. Bland-Altman plots and Lin's concordance correlation coefficient were used to test agreement. Any condition using at least three slices yielded substantial to almost perfect agreement with the total number of slices on both CT and MRI (Range of Lin's concordance correlation coefficient: 0.947-0.999). Using a single slice in the middle of the region of interest demonstrated poor to moderate agreement with the total number of slices. The findings of this study suggest that using a limited number of slices to quantify muscle deterioration ratio on CT or MRI is a viable way to balance the combined need for measurement accuracy with feasibility in research and clinical settings.

Skeletal Muscle Quality: A Biomarker for Assessing Physical Performance Capabilities in Young Populations

Muscle quality (MQ), defined as the amount of strength and/or power per unit of muscle mass, is a novel index of functional capacity that is increasingly relied upon as a critical biomarker of muscle health in low functioning aging and pathophysiological adult populations. Understanding the phenotypical attributes of MQ and how to use it as an assessment tool to explore the efficacy of resistance exercise training interventions that prioritize functional enhancement over increases in muscle size may have implications for populations beyond compromised adults, including healthy young adults who routinely perform physically demanding tasks for competitive or occupational purposes. However, MQ has received far less attention in healthy young populations than it has in compromised adults. Researchers and practitioners continue to rely upon static measures of lean mass or isolated measures of strength and power, rather than using MQ, to assess integrated functional responses to resistance exercise training and physical stress. Therefore, this review will critically examine MQ and the evidence base to establish this metric as a practical and important biomarker for functional capacity and performance in healthy, young populations. Interventions that enhance MQ, such as high-intensity stretch shortening contraction resistance exercise training, will be highlighted. Finally, we will explore the potential to leverage MQ as a practical assessment tool to evaluate function and enhance performance in young populations in non-traditional research settings.

Sex and posture dependence of neck muscle size-strength relationships

Neck muscle size and strength have been linked to lower injury risk and reduced pain. However, prior findings have been inconclusive and have failed to clarify whether there are sex differences in neck muscle size-strength relationships. Such differences may point to an underlying cause for the reported sex difference in neck pain prevalence. Thirty participants (13 males, 17 females) who underwent neck strength testing and MR imaging were analyzed. Strength was measured in three conditions that differed in posture and exertion direction. Muscle size was quantified by three metrics: anatomical cross-sectional area (ACSA), muscle volume (MV), and an estimate of physiological cross-sectional area-reconstruction-based cross-sectional area (RCSA). Inter-posture strength correlations, muscle size-strength correlations, and sex differences were analyzed with linear regression. Males were approximately 65% stronger and had significantly larger muscles. Strength varied significantly across postures, but only female strength values for different postures were significantly correlated. Observed in males only, the sternocleidomastoid (SCM) was a strong predictor of flexion strength in the neutral posture while the anterior scalene (AS) was more involved in the extended. No extensor's size was significantly linked to extension strength. A greater amount of force variation is unexplained by muscle size alone in females than in males. Males and females exhibited distinct size-strength relationships, highlighting the need for sex-specific models and analyses and the greater potential effect of non-morphometric factors on force generating capacity in females. No advantage of one muscle size metric over another in strength prediction was evidenced.

Corticomotor excitability of gluteus maximus and hip extensor strength: The influence of sex

PURPOSE

To compare hip extensor strength and corticomotor excitability (CME) of gluteus maximus (GM) between males and females. A secondary purpose was to determine if CME of GM is predictive of hip extensor strength.

METHOD

Thirty-two healthy individuals participated (15 males and 17 females). CME of GM was assessed using the input-output curve (IOC) procedure acquired from transcranial magnetic stimulation (average slope). Hip extensor strength was measured by a dynamometer during a maximal voluntary isometric contraction. Independent t-tests were used to compare CME of GM and peak hip extensor torque between males and females. Linear regression analysis was used to determine whether peak hip extensor torque was predicted by CME of GM.

RESULT

Compared to males, females demonstrate lower peak hip extensor torque (4.42 ± 1.11 vs. 6.15 ± 1.72 Nm/kg/m2, p < 0.01) and lower CME of GM (1.36 ± 1.07 vs. 2.67 ± 1.30, p < 0.01). CME of GM was a significant predictor of peak hip extensor torque for males and females combined (r² = 0.36, p < 0.001).

CONCLUSION

Our findings support the premise that corticomotor excitability plays a role in the ability of a muscle to generate torque.

The Human Muscle Size and Strength Relationship: Effects of Architecture, Muscle Force, and Measurement Location

PURPOSE

This study aimed to determine the best muscle size index of muscle strength by establishing if incorporating muscle architecture measurements improved the human muscle size-strength relationship. The influence of calculating muscle force, and the location of anatomical cross-sectional area (ACSA) measurements on this relationship were also examined.

METHODS

Fifty-two recreationally active males completed unilateral isometric knee extension strength assessments and MRI scans of the dominant thigh and knee to determine quadriceps femoris (QF) size variables (ACSA along the length of the femur, maximum ACSA [ACSAMAX] and volume [VOL]) and patellar tendon moment arm. Ultrasound images (2 sites per constituent muscle) were analyzed to quantify muscle architecture (fascicle length, pennation angle), and when combined with VOL (from MRI), facilitated calculation of QF effective PCSA (EFFPCSA) as potentially the best muscle size determinant of strength. Muscle force was calculated by dividing maximum voluntary torque (MVT) by the moment arm and addition of antagonist torque (derived from hamstring EMG).

RESULTS

The associations of EFFPCSA (r=0.685), ACSAMAX (r=0.697), or VOL (r=0.773) with strength did not differ, although qualitatively VOL explained 59.8% of the variance in strength, ~11-13% greater than EFFPCSA or ACSAMAX. All muscle size variables had weaker associations with muscle force than MVT. The association of strength-ACSA at 65% of femur length (r=0.719) was greater than for ACSA measured between 10-55% and 75-90% (r=-0.042-0.633) of femur length.

CONCLUSIONS

In conclusion, using contemporary methods to assess muscle architecture and calculate EFFPCSA did not enhance the muscle strength-size association. For understanding/monitoring muscle size, the major determinant of strength, these findings support the assessment of muscle volume, that is independent of architecture measurements, and was most highly correlated to strength.

Free-Weight Resistance Training in Youth Athletes: A Narrative Review

Generating high levels of muscular strength and power are important for success in sport and may have long-term implications for sporting careers in youth athletes. Importantly, maturation may confound the neuromuscular adaptations to resistance training when attempting to differentiate between training- vs. growth-induced strength and power gains; thus, potentially leading to erroneous conclusions regarding the efficacy of resistance training in youth athletes. The aim of this review was to critically appraise the literature concerning the efficacy of externally loaded free-weight resistance training on strength and power measures in youth athletes at different stages of maturity. Strength underpins power production; thus, developing strength through traditional resistance training methods can positively influence powerful sporting movements. In addition, weightlifting has the capacity to improve muscular power via explosive lower-body triple extension, which is essential for many sports. Despite the complexity of the techniques involved, it can be a safe and effective method to improve athletic qualities in young athletes, potentially more so than plyometric training. While low-load, high-velocity training can have a positive effect influence on high speed movements such as sprinting, the reduced intensity appears to be disadvantageous post peak-height velocity. Irrespective of age, well-coached progressive strength training adhering strictly to correct technique can then be periodised within a long-term athletic development program. It is important to primarily develop muscular strength, while concurrently refining the technical skill required for weightlifting. Physically mature athletes should undertake high-intensity resistance training to maximise neuromuscular adaptations, leading to positive changes in strength and power.

The effect of regional quadriceps anatomical parameters on angle-specific isometric torque expression

The length–tension relationship affects knee extension performance; however, whether anatomical variations in different quadriceps regions affect this relationship is unknown. Regional (proximal, middle, distal) quadriceps thickness (MT), pennation angle, and fascicle length of 24 males (48 limbs) were assessed via ultrasonography. Participants also performed maximal voluntary isometric torque (MVIT) assessments at 40°, 70°, and 100° of knee flexion. Measures were recorded on 3 separate occasions. Linear regression models predicting angle-specific torque from regional anatomy provided adjusted simple and multiple correlations (√adjR2) with bootstrapped compatibility limits to assess magnitude. Middle vastus lateralis MT and MVIT at 100° (√adjR2 = 0.64) was the largest single correlation, with distal vastus lateralis MT having the greatest mean correlations regardless of angle (√adjR2 = 0.61 ± 0.05, mean ± SD). Lateral distal MT and architecture had larger (Δ√adjR2 = 0.01 to 0.43) single and multiple correlations with MVIT than the lateral proximal (√adjR2 = 0.15 to 0.69 vs −0.08 to 0.65). Conversely, middle anterior MT had greater (Δ√adjR2 = 0.08 to 0.38) single and multiple correlations than proximal MT (√adjR2 = 0.09 to 0.49 vs −0.21 to 0.14). The length–tension relationship was trivially affected by regional quadriceps architecture. The middle and distal quadriceps were the strongest predictors of MVIT at all joint angles. Therefore, researchers may wish to focus on middle and distal lateral quadriceps anatomy when performing ultrasonographic evaluations.

Novelty: The length–tension relationship is minimally affected by regional quadriceps anatomical parameters. Middle and distal vastus lateralis and lateral vastus intermedius anatomy were consistently the best predictors of torque. Practitioners may focus their assessments on the middle and distal regions of the lateral quadriceps’ musculature.

Evaluation of functional muscle anatomy scalability in the canine hind limb

In contrast to other mammals, the large variation in dog sizes is not accompanied by any significant genetic re-organization. In order to study the relationship between body mass, limb length and the functional anatomical muscle parameters of the canine hind limb, a large dataset comprising of muscle masses, optimal muscle fibre lengths and physiological cross-sectional area's (PCSA) were acquired for twenty-five muscles in ten dogs of sizes varying between 20 kg and 52 kg. The potential of body mass and limb length for reliably scaling individual muscle masses, optimal muscle fibre lengths and PCSA's were examined. For the majority of the muscles of the canine hind limb, neither body mass nor limb length were reliable scaling parameter for either muscle masses, PCSA's and optimal fibre length. These results indicate the need of a breed-specific approach to musculoskeletal modelling in future canine musculoskeletal research.

Maniraptoran pelvic musculature highlights evolutionary patterns in theropod locomotion on the line to birds

Locomotion is a fundamental aspect of palaeobiology and often investigated by comparing osteological structures and proportions. Previous studies document a stepwise accumulation of avian-like features in theropod dinosaurs that accelerates in the clade Maniraptora. However, the soft tissues that influenced the skeleton offer another perspective on locomotory adaptations. Examination of the pelvis for osteological correlates of hind limb and tail musculature allowed reconstruction of primary locomotory muscles across theropods and their closest extant relatives. Additionally, the areas of pelvic muscle origins were quantified to measure relative differences within and between taxa, to compare morphological features associated with cursoriality, and offer insight into the evolution of locomotor modules. Locomotory inferences based on myology often corroborate those based on osteology, although they occasionally conflict and indicate greater complexity than previously appreciated. Maniraptoran pelvic musculature underscores previous studies noting the multifaceted nature of cursoriality and suggests that a more punctuated step in caudal decoupling occurred at or near the base of Maniraptora.

Muscle Quality, Measured by Ultrasound-Derived Corrected Echo Intensity, Does not Affect Changes in Cross-sectional Area of the Vastus Lateralis Following Recumbent Rest

Objective:

Recumbent rest elicits a decrease in muscle size of the lower extremity, but the extent of decrease may be related to differences in muscle quality. This could have implications for ultrasound-derived measures of muscle size, particularly in individuals with a large proportion of intramuscular contractile elements. The research objective was to determine whether decreases in muscle size following recumbent rest are related to ultrasound-derived corrected echo intensity in resistance-trained males.

Methods:

Cross-sectional area (CSA), echo intensity (EI), subcutaneous fat thickness (SFT), and EI corrected for SFT (EICor) of the vastus lateralis (VL) were measured via ultrasonography in 30 resistance-trained males. Measures were obtained immediately following recumbency (T0) and 15 minutes after recumbency (T15). The association between EICor and percentage change in CSA (%ΔCSA) from T0 to T15 was examined. Comparisons of morphological characteristics were examined between a subset of participants with the lowest (LO; n = 10; <33rd percentile) and highest (HI; n = 10; >66th percentile) EICor.

Results:

EICor was not correlated with %ΔCSA ( P = .151), and the decrease in CSA from T0 to T15 did not differ between the LO and HI groups.

Conclusions:

Muscle quality (EICor) is not related to the decrease in CSA of the VL following recumbent rest among resistance-trained, young males. The time frame of muscle CSA acquisition should not differ based solely on differences in muscle quality.

Predicting muscular strength using demographics, skeletal dimensions, and body composition measures

The purpose of this study was to develop an equation to predict strength for seven common resistance training exercises using anthropometric and demographic measures. One-hundred forty-seven healthy adults (74 males, 73 females, 35 ± 12 yr, 174 ± 10 cm, 88 ± 19 kg) volunteered to participate. Body composition values (regional/total) and body dimensions were assessed using dual-energy x-ray absorptiometry (DEXA). Subjects underwent the following maximal strength assessments: Leg Press, Chest Press, Leg Curl, Lat Pulldown, Leg Extension, Triceps Pushdown, and Biceps Curl. Multiple linear regression with stepwise removal was used to determine the best model to predict maximal strength for each exercise. Independent predictor variables identified (p < 0.05) were height (cm); weight (kg); BMI; age; sex (0 = F,1 = M); regional lean masses (LM,kg); fat mass (FM,kg); fat free mass (FFM,kg); percent fat (%BF); arm, leg, and trunk lengths (AL, LL, TL; cm); and shoulder width (SW,cm). Analyses were performed with and without regional measures to accommodate scenarios where DEXA is unavailable. All models presented were significant (p < 0.05, R² = 0.68–0.83), with regional models producing the greatest accuracy. Results indicate that maximal strength for individual resistance exercises can be reasonably estimated in adults.

Muscle architecture and morphology as determinants of explosive strength

PURPOSE

Neural drive and contractile properties are well-defined physiological determinants of explosive strength, the influence of muscle architecture and related morphology on explosive strength is poorly understood. The aim of this study was to examine the relationships between Quadriceps muscle architecture (pennation angle [Θ_P] and fascicle length [F_L]) and size (e.g., volume; Q_VOL), as well as patellar tendon moment arm (PT_MA) with voluntary and evoked explosive knee extension torque in 53 recreationally active young men.

METHOD

Following familiarisation, explosive voluntary torque at 50 ms intervals from torque onset (T₅₀, T₁₀₀, T₁₅₀), evoked octet at 50 ms (8 pulses at 300-Hz; evoked T₅₀), as well as maximum voluntary torque, were assessed on two occasions with isometric dynamometry. B-mode ultrasound was used to assess Θ_P and F_L at ten sites throughout the quadriceps (2-3 sites) per constituent muscle. Muscle size (Q_VOL) and PT_MA were quantified using 1.5 T MRI.

RESULT

There were no relationships with absolute early phase explosive voluntary torque (≤ 50 ms), but θ_P (weak), Q_VOL (moderate to strong) and PT_MA (weak) were related to late phase explosive voluntary torque (≥ 100 ms). Regression analysis revealed only Q_VOL was an independent variable contributing to the variance in T₁₀₀ (34%) and T₁₅₀ (54%). Evoked T₅₀ was also related to Q_VOL and θ_P. When explosive strength was expressed relative to MVT there were no relationships observed.

CONCLUSION

It is likely that the weak associations of θ_P and PT_MA with late phase explosive voluntary torque was via their association with MVT/Q_VOL rather than as a direct determinant.

Morphological study of the vastus medialis oblique in recurrent patellar dislocation based on magnetic resonance images

Background

To investigate the morphological parameters of the vastus medialis obliquus (VMO) muscle and delineate its importance in the maintenance of patellofemoral joint stability.

Methods

The magnetic resonance imaging data of seventy-five knees (fifty-four patients) with recurrent lateral patella dislocation (LPD) and seventy-five knees (seventy patients) without recurrent LPD were retrospectively analysed. Five morphological parameters related to the VMO (elevation in the sagittal plane and coronal plane, craniocaudal extent, muscle-fibre angulation, cross-sectional area ratio) and two patella tilt parameters (patella tilt angle, bisect offset ratio) were measured in MR images. The independent-samples t test or chi-square test was used for statistical comparisons.

Results

The mean ages of the patients in the recurrent LPD group and control group were 22.1 ± 9.9 years and 24.0 ± 6.5 years, respectively. Eighteen out of seventy-five (24%) patients MRI showed VMO injuries. Compared with the control group, the patients with recurrent LPD showed significantly higher sagittal VMO elevation (10.4 ± 2.3 mm vs. 4.1 ± 1.9 mm), coronal VMO elevation (15.9 ± 5.7 mm vs. 3.9 ± 3.7 mm), muscle-fibre angulation (35.4 ± 8.0° vs. 27.9 ± 6.3°), patella tilt angle (25.9 ± 10.7° vs. 9.1 ± 5.2°), and bisect offset ratio values (0.9 ± 0.3 vs. 0.5 ± 0.1) and significantly lower craniocaudal extent (13.7 ± 5.3 mm vs. 16.7 ± 5.1 mm) and cross-sectional area ratio values (0.05 ± 0.02 vs. 0.07 ± 0.02).

Conclusions

The results showed that abnormalities in the VMO and patella tilt were clearly present in recurrent LPD patients compared with normal people.

Influence of Changes in Soft Tissue Composition on Changes in Bone Strength in Peripubertal Girls: The STAR Longitudinal Study

Obesity and osteoporosis remain two major public health concerns. Soft tissue composition and bone are interrelated; however, it is still not well understood how changes in adiposity during adolescence affect bone development. The aim of this study was to assess how changes in DXA-derived total body lean mass (TBLM) and total body fat mass (TBFM) associate with 2-year changes in bone outcomes at the 20% femur, 66% tibia, 66% radius, and 4% tibia, as measured by pQCT, during the years surrounding the onset of menarche in a cohort of 9- to 12-year-old (baseline) adolescent girls (70% Hispanic). From baseline to 2-year follow-up, girls showed statistically significant increases in all bone outcomes, except radial endosteal circumference. In separate linear regression models, change in TBLM and change in TBFM were both positively associated with 2-year changes in bone outcomes at all measured bone sites, after controlling for relevant covariates. However, when change in TBLM and change in TBFM were included in the same model, change in TBLM was the predominant predictor of bone outcomes, explaining 4% to 14% of the variance in bone strength outcomes. Change in TBFM remained a positive predictor of tibia polar strength strain index (SSI_p) (2% variance explained). A significant interaction between change in TBFM and menarcheal status was identified at the radius for SSI_p and indicated that greater gains in TBFM were beneficial for SSI_p in girls that were premenarcheal at baseline but detrimental for girls who were postmenarcheal at baseline. The overall findings suggest that changes in TBLM during the peripubertal years have a greater influence on bone outcomes than changes in TBFM. While gains in TBFM might benefit the weight bearing 66% tibia, greater gains in TBFM may be detrimental to bone development at the non-weight bearing 66% radius after the onset of menarche. © 2020 American Society for Bone and Mineral Research (ASBMR).

Intramuscular Fat Influences Neuromuscular Activation of the Gluteus Medius in Older Adults

The amount of tissue between the muscle and surface electromyography (sEMG) electrode influences the sEMG signals. Increased intramuscular adipose tissue (IMAT) of the hip abductor muscles negatively impacts balance in older individuals, but it is unknown if this is related to the ability to activate the muscles. The aim of this preliminary study was to investigate the influence of gluteus medius (GM) IMAT on sEMG amplitude during maximal voluntary isometric contractions (MVIC) of the hip abductors in older adults. We recruited 12 healthy community-dwelling older adults that underwent a spiral computerized tomography scan. High density lean (HDL), IMAT, and subcutaneous adipose tissue (SUBFAT) cross-sectional area of the GM were assessed. sEMG signal from the GM was recorded while participants performed an MVIC of the hip abductors. There was a negative correlation between GM activation and IMAT (r = -0.58, P = 0.046), and also SUBFAT (r = -0.78, P = 0.002) and a positive correlation with HDL (r = 0.73, P = 0.006). When controlling for SUBFAT, the partial correlations demonstrated a consistent negative correlation between GM activation and IMAT (r = -0.60, P = 0.050) but no relationship with HDL. The current results are important for helping to interpret the results from sEMG by accounting for IMAT. In conclusion, the neuromuscular activation of the GM may be reduced by the quantity of IMAT.

Lower leg muscle-tendon unit characteristics are related to marathon running performance

The human ankle joint and plantar flexor muscle–tendon unit play an important role in endurance running. It has been assumed that muscle and tendon interactions and their biomechanical behaviours depend on their morphological and architectural characteristics. We aimed to study how plantar flexor muscle characteristics influence marathon running performance and to determine whether there is any difference in the role of the soleus and gastrocnemii. The right lower leg of ten male distance runners was scanned with magnetic resonance imagining. The cross-sectional areas of the Achilles tendon, soleus, and lateral and medial gastrocnemius were measured, and the muscle volumes were calculated. Additional ultrasound scanning was used to estimate the fascicle length of each muscle to calculate the physiological cross-sectional area. Correlations were found between marathon running performance and soleus volume (r = 0.55, p = 0.048), soleus cross-sectional area (r = 0.57, p = 0.04), soleus physiological cross-sectional area (PCSA-IAAF r = 0.77, p < 0.01, CI± 0.28 to 0.94), Achilles tendon thickness (r = 0.65, p < 0.01), and soleus muscle-to-tendon ratio (r = 0.68, p = 0.03). None of the gastrocnemius characteristics were associated with marathon performance. We concluded that a larger soleus muscle with a thicker Achilles tendon is associated with better marathon performance. Based on these results, it can be concluded the morphological characteristics of the lower leg muscle–tendon unit correlate with running performance.

Clinical utility of measuring the size of the lumbar multifidus and quadratus lumborum muscles in the Australian football league setting: A prospective cohort study

OBJECTIVES

Test the odds of factors previously associated with lower limb injury (decreased size of the multifidus (MF) and increased size of the quadratus lumborum (QL) muscle) in an independent sample of Australian Rules Football (ARF) players.

DESIGN

Prospective cohort study.

SETTING

Professional ARF.

PARTICIPANTS

Forty-three male ARF players.

MAIN OUTCOME MEASURES

Cross-sectional areas (CSAs) of MF and QL muscles measured from pre-season ultrasound images. Playing season injuries were recorded by club personnel. A multivariable logistic regression model was used to evaluate the usefulness of MF and QL muscle size for predicting playing season lower limb injuries.

RESULTS

Fifteen players (35%) sustained a playing season lower limb injury. The multivariable model indicated that the odds of sustaining a lower limb injury during the season was 2.38 (95% CI: 1.18, 5.00; P = 0.017) times less likely for a one cm² increase from the mean value in MF muscle CSA at the L5 vertebral level after adjusting for CSA of the QL, age and BMI. The main effect and interaction models positively predicted 75% of players that sustained a lower limb injury during the season (sensitivity 80%, specificity 85%).

CONCLUSION

Future studies could examine the efficacy, feasibility and adherence of 'at risk' players to a pre-season training program aimed at increasing MF muscle size and monitor playing season injuries.

Exercise and Muscle Atrophy

The incidence of muscle atrophy is increasing with each passing year, which imposes a huge burden on the quality of life of patients. It is a public health issue that causes a growing concern around the world. Exercise is one of the key strategies to prevent and treat various diseases. Appropriate exercise is conducive to compensatory muscle hypertrophy, to improve muscle strength and elasticity, and to train muscle coordination, which is also beneficial to the recovery of skeletal muscle function and the regeneration of muscle cells. Sequelae of paralysis of patients with limb dyskinesia caused by muscle atrophy will be significantly alleviated after regular exercise therapy. Furthermore, exercise therapy can slow down or even reverse muscle atrophy. This article aims to introduce the characteristics of muscle atrophy and summarize the role and mechanism of exercise in the treatment of muscle atrophy in the existing studies, in order to further explore the mechanism of exercise to protect muscle atrophy and provide protection for patients with muscular atrophy.

Effects of Changes in Ankle Joint Angle on the Relation Between Plantarflexion Torque and EMG Magnitude in Major Plantar Flexors of Male Chronic Stroke Survivors

The slope of the EMG-torque relation is potentially useful as a parameter related to muscular contraction efficiency, as a greater EMG-torque slope has often been reported in stroke-impaired muscles, compared to intact muscles. One major barrier limiting the use of this parameter on a routine basis is that we do not know how the EMG-torque slope is affected by changing joint angles. Thus, the primary purpose of this study is to characterize the EMG-torque relations of triceps surae muscles at different ankle joint angles in both paretic and non-paretic limbs of chronic hemispheric stroke survivors. Nine male chronic stroke survivors were asked to perform isometric plantarflexion contractions at different contraction intensities and at five different ankle joint angles, ranging from maximum plantarflexion to maximum dorsiflexion. Our results showed that the greater slope of the EMG-torque relations was found on the paretic side compared to the non-paretic side at comparable ankle joint angles. The EMG-torque slope increased as the ankle became plantarflexed on both sides, but an increment of the EMG-torque slope (i.e., the coefficient a) was significantly greater on the paretic side. Moreover, the relative (non-paretic/paretic) coefficient a was also strongly correlated with the relative (paretic/non-paretic) maximum ankle plantarflexion torque and with shear wave speed in the medial gastrocnemius muscle. Conversely, the relative coefficient a was not well-correlated with the relative muscle thickness. Our findings suggest that muscular contraction efficiency is affected by hemispheric stroke, but in an angle-dependent and non-uniform manner. These findings may allow us to explore the relative contributions of neural factors and muscular changes to voluntary force generating-capacity after stroke.

Are body circumferences able to predict strength, muscle mass and bone characteristics in obesity? A preliminary study in women

Measurement of body circumferences (BCs) is widely used as an anthropometric tool to assess body composition and health risk in obese individuals. In this preliminary work we evaluated the association of several BCs with Dual-energy X-ray Absorptiometry (DXA)-measured lean mass as well as leg press test scores with an aim at exploring the potential of BCs as predictor of body composition and muscle strength. A total of 34 female participants aged 47.3±7.6 y who were obese (BMI, 30.4-43.7 kg/m2) were recruited. The upper arm (relaxed), wrist, chest, waist, hip, thigh, and calf circumferences were measured. The skinfold-corrected muscle (including bone) circumferences at the arm, thigh, and calf site were also calculated. Lean mass components were measured by DXA with a Hologic QDR Explorer scanner according to the manufacturer's procedures. Lower limbs strength was assessed with the 1-Repetition Maximum leg press. Bivariate association between variables was assessed with the Spearman's correlation coefficient after the Benjamini and Hochberg False Discovery Rate procedure. Predictive equations were developed using stepwise multiple regression analysis. Several statistically significant correlations (Benjamini and Hochberg corrected P [Pc] < 0.05) were present between BCs and DXA-measured body composition variables, and leg press test scores with special regard to the chest, arm, waist, and hip circumferences. Multiple regression analysis yielded statistically significant predictive models (Pc < 0.05 for all; adjusted R2 ranging 0.123 - 0.504; standard error of the estimate ranging 4.0% - 11% of the mean measured value) for all body composition as well as leg press outcomes. The current findings show that BCs represent a simple, suitable anthropometric measurement with a potential to predict several lean mass components as well as lower limbs strength in obese females. The proposed predictors need to be validated in a larger sample of participants and in obese males.

Reliability and Validity of Ultrasonography for Measurement of Hamstring Muscle and Tendon Cross-Sectional Area

The purpose of this study was to determine the reliability and validity of ultrasonography for measurement of hamstring muscle and semitendinosus (ST) tendon cross-sectional area (CSA). On two consecutive days, muscle anatomical CSA (ACSA) and ST tendon CSA were measured at standardized positions (30%-80% of thigh length; half the distance from the distal muscle-tendon junction to the popliteal crease) on 12 legs using ultrasonography and compared with corresponding magnetic resonance imaging measures. Inter-day intraclass correlation coefficients were good-to-excellent (0.882-0.996) for all assessed muscle and tendon sites. The limits of agreement widths were narrowest (range: 17%-52%) when muscle ACSA was large but were wide at sites with relatively small ACSA (≤184%) and for ST tendon CSA (range: 72%). Results suggest ultrasound-based measures of individual hamstring muscle maximal ACSA are reliable and valid and ST tendon CSA measures are reliable but require comparison with cadaveric or intra-operative measurements to verify validity.

Efficacy of whole-body suspension training on enhancing functional movement abilities following a supervised or home-based training program

BACKGROUND

The purpose of this study was to determine the effects of suspension training on functional movement and body composition, and to compare the effectiveness of home-based training to supervised training.

METHODS

Seventeen healthy subjects (8 males, 9 females, age=21.8±3.4 y) with no recent history of resistance training were randomly assigned to a home-based or supervised training group. Subjects performed an 8-week suspension training program consisting of 10 exercises targeting major muscle groups, twice per week for the duration of the study. Pre- and post-intervention testing included body composition using air displacement plethysmography, and a functional movement screen (FMS) to measure functional movement abilities.

RESULTS

The 8-week training program significantly improved total FMS scores across the whole sample of subjects (Pre=16.4; Post=17.5; P=0.004), with no differences in improvements between groups. When compared separately, only the supervised group significantly improved FMS scores. There was also a significant increase in lean mass across the total sample of subjects (Pre=52.4 kg; Post=53.3 kg; P=0.03) with no differences between groups. But when compared independently, neither group exhibited a significant increase in lean mass.

CONCLUSIONS

When completed as a whole-body exercise program over an 8-week period, suspension training can improve functional ability and increase lean mass in both a supervised and a home-based setting.

The relationship between cross-sectional area of multifidus muscle and disability index in patients with chronic non-specific low back pain

BACKGROUND

Nonspecific low back pain (NSLBP) is a common problem that may have an effect on the level of functional ability. Imaging techniques indicated the degeneration of multifidus muscles in patients with low back pain. But its relationship with disability in NSLBP is unclear.

OBJECTIVE

To assess the relationship between changes in multifidus muscle morphology in MRI as paraclinical data with changes in the level of disability as clinical data in patients with CNLBP, whose MRI studies are normal. Moreover, the relationship between multifidus CSA and its thickness was determined.

DESIGN

Cross-sectional study.

METHODS

A total of 45 subjects with CNLBP participated in this study. Multifidus muscle thickness and cross-sectional area (CSA) for both sides in L4-L5 and L5-S1 levels were measured with MRI and Image J software. Level of disability was assessed with Roland-Morris disability index.

RESULTS

There was no significant relationship between multifidus muscle's CSA or thickness variations among the L4-L5 and L5-S1 levels and disability index score. Furthermore, Pearson's test showed significant positive relationship between thickness and CSA of muscles (p˂0.05).

CONCLUSION

The relationship between lumbar multifidus Thickness and disability in CNLBP with normal MRI study, is not proven in this study. Multifidus muscle thickness in L4-L5 or L5-S1 level can be representative of its CSA in patients with CNLBP and normal MRI.

Greek Yogurt and 12 Weeks of Exercise Training on Strength, Muscle Thickness and Body Composition in Lean, Untrained, University-Aged Males

Milk and/or whey protein plus resistance exercise (RT) increase strength and muscle size, and optimize body composition in adult males and females. Greek yogurt (GY) contains similar muscle-supporting nutrients as milk yet it is different in several ways including being a semi-solid food, containing bacterial cultures and having a higher protein content (mostly casein) per serving. GY has yet to be investigated in the context of a RT program. The purpose of this study was to assess the effects of GY consumption plus RT on strength, muscle thickness and body composition in lean, untrained, university-aged males. Thirty untrained, university-aged (20.6 ± 2.2 years) males were randomized to 2 groups (n = 15/group): fat-free, plain GY or a Placebo Pudding (PP; isoenergetic carbohydrate-based pudding) and underwent a combined RT/plyometric training program 3 days/week for 12 weeks. They consumed either GY (20 g protein/dose) or PP (0 g protein/dose) daily, 3 times on training days and 2 times on non-training days. After 12 weeks, both groups significantly increased strength, muscle thickness and fat-free mass (FFM) (p < 0.05). The GY group gained more total strength (GY; 98 ± 37 kg, PP; 57 ± 15 kg), more biceps brachii muscular thickness (GY; 0.46 ± 0.3 cm, PP; 0.12 ± 0.2 cm), more FFM (GY; 2.4 ± 1.5 kg, PP; 1.3 ± 1.3 kg), and reduced % body fat (GY; −1.1 ± 2.2%, PP; 0.1 ± 2.6%) than PP group (p < 0.05 expressed as absolute change). Thus, consumption of GY during a training program resulted in improved strength, muscle thickness and body composition over a carbohydrate-based placebo. Given the results of our study, the general benefits of consuming GY and its distinctiveness from milk, GY can be a plausible, post-exercise, nutrient-rich alternative for positive strength, muscle, and body composition adaptations.

Identification of genetic variants associated with skeletal muscle function deficit in childhood acute lymphoblastic leukemia survivors

Background: Although 80% of childhood acute lymphoblastic leukemia (ALL) cases are cured with current treatment protocols, exposure to chemotherapeutics or radiation therapy during a vulnerable period of child development has been associated with a high frequency of late adverse effects (LAE). Previous observations suggest important skeletal muscle size, density and function deficits in ALL survivors.

Purpose: Given that only a fraction of all patients will suffer from this particular complication, we investigated whether it could be predicted by genetic markers. 

Patients and methods: We analysed associations between skeletal muscle force (Fmax) and power (Pmax) and germline genetic variants from 1039 genes derived through whole-exome sequencing. Top-ranking association signals retained after correction for multiple testing were confirmed through genotyping, and further analysed through stratified analyses and multivariate models. 

Results: Our results show that skeletal muscle function deficit is associated with two common single nucleotide polymorphisms (SNPs) (rs2001616DUOX2, P=0.0002 (Pmax) and rs41270041ADAMTS4, P=0.02 (Fmax)) and two rare ones located in the ALOX15 gene (P=0.001 (Pmax)). These associations were further modulated by sex, body mass index and risk groups, which reflected glucocorticoid dose and radiation therapy (P≤0.02). 

Conclusion: Occurrence of muscle function deficit in childhood ALL is thus strongly modulated by variations in the DUOX2, ADAMTS4 and ALOX15 genes, which could lead to personalized prevention strategies in childhood ALL survivors.

Selective motor control and gross motor function in bilateral spastic cerebral palsy

AIM

To investigate the relationship between selective motor control (SMC), muscle volume, and spasticity with gross motor function in adolescents and young adults with bilateral spastic cerebral palsy (CP).

METHOD

Eleven male participants with CP (mean age 15y 7mo, standard deviation 3y 6mo, range 12y 1mo-23y 1mo) in Gross Motor Function Classification System (GMFCS) levels I to IV took part in this cross-sectional study. Magnetic resonance imaging (MRI) of both lower limbs of all participants were acquired, from which 18 muscles were manually segmented and muscle volume calculated by a single assessor. Muscle volumes were normalized to body mass and averaged between limbs for each individual. SMC was assessed using Selective Control Assessment of the Lower Extremity (SCALE). Spasticity was assessed using the Modified Ashworth Scale (MAS), and gross motor functional ability was assessed using the Gross Motor Function Measure (GMFM-66).

RESULTS

GMFM-66 was strongly positively correlated to SCALE (r=0.901, p≤0.001) and lower limb muscle volume normalized to body mass (r=0.750, p=0.008). MAS was significantly correlated with GMFM-66 (r=-0.691, p=0.018).

INTERPRETATION

SMC is a major factor influencing gross motor function in individuals with CP. Lower limb muscle volume and spasticity also influence gross motor function.

WHAT THIS PAPER ADDS

Selective motor control is a major factor of gross motor function in adolescents and young adults with bilateral cerebral palsy (CP). Gross motor function is related to muscle size and level of spasticity in adolescents and young adults with bilateral CP.

Associations of Body Mass and Fat Indexes With Cardiometabolic Traits

BACKGROUND

Body mass index (BMI) is criticized for not distinguishing fat from lean mass and ignoring fat distribution, leaving its ability to detect health effects unclear.

OBJECTIVES

The aim of this study was to compare BMI with total and regional fat indexes from dual-energy x-ray absorptiometry in their associations with cardiometabolic traits. Duration of exposure to and change in each index across adolescence were examined in relation to detailed traits in young adulthood.

METHODS

BMI was examined alongside total, trunk, arm, and leg fat indexes (each in kilograms per square meter) from dual-energy x-ray absorptiometry at ages 10 and 18 years in relation to 230 traits from targeted metabolomics at age 18 years in 2,840 offspring from the Avon Longitudinal Study of Parents and Children.

RESULTS

Higher total fat mass index and BMI at age 10 years were similarly associated with cardiometabolic traits at age 18 years, including higher systolic and diastolic blood pressure, higher very low-density lipoprotein and low-density lipoprotein cholesterol, lower high-density lipoprotein cholesterol, higher triglycerides, and higher insulin and glycoprotein acetyls. Associations were stronger for both indexes measured at age 18 years and for gains in each index from age 10 to 18 years (e.g., 0.45 SDs [95% confidence interval: 0.38 to 0.53] in glycoprotein acetyls per SD unit gain in fat mass index vs. 0.38 SDs [95% confidence interval: 0.27 to 0.48] per SD unit gain in BMI). Associations resembled those for trunk fat index. Higher lean mass index was weakly associated with traits and was not protective against higher fat mass index.

CONCLUSIONS

The results of this study support abdominal fatness as a primary driver of cardiometabolic dysfunction and BMI as a useful tool for detecting its effects.

The Contributions of Fiber Atrophy, Fiber Loss, In Situ Specific Force, and Voluntary Activation to Weakness in Sarcopenia

The contributions of fiber atrophy, fiber loss, in situ specific force, and voluntary activation to weakness in sarcopenia remain unclear. To investigate, 40 older (20 women; age 72 ± 4 years) and 31 younger adults (15 women, age 22 ± 3 years) completed measurements. The knee extensor maximal voluntary torque (MVC) was measured as well as voluntary activation, patella tendon moment arm length, muscle volume, and fascicle architecture to estimate in situ specific force. Fiber cross-sectional area (FCSA), fiber numbers, and connective tissue contents were also estimated from vastus lateralis biopsies. The MVC, quadriceps volume, and specific force were 39%, 28%, and 17% lower, respectively, in old compared with young, but voluntary activation was not different. The difference in muscle size was due in almost equal proportions to lower type II FCSA and fewer fibers. Five years later (n = 23) the MVC, muscle volume and voluntary activation in old decreased an additional 12%, 6%, and 4%, respectively, but there was no further change in specific force. In situ specific force declines relatively early in older age and reduced voluntary activation occurs later, but the overall weakness in sarcopenia is mainly related to loss of both type I and II fibers and type II fiber atrophy.

High doses of anti-inflammatory drugs compromise muscle strength and hypertrophic adaptations to resistance training in young adults

AIMS

This study tested the hypothesis that high doses of anti-inflammatory drugs would attenuate the adaptive response to resistance training compared with low doses.

METHODS

Healthy men and women (aged 18-35 years) were randomly assigned to daily consumption of ibuprofen (IBU; 1200 mg; n = 15) or acetylsalicylic acid (ASA; 75 mg; n = 16) for 8 weeks. During this period, subjects completed supervised knee-extensor resistance training where one leg was subjected to training with maximal volitional effort in each repetition using a flywheel ergometer (FW), while the other leg performed conventional (work-matched across groups) weight-stack training (WS). Before and after training, muscle volume (MRI) and strength were assessed, and muscle biopsies were analysed for gene and protein expression of muscle growth regulators.

RESULTS

The increase in m. quadriceps volume was similar between FW and WS, yet was (averaged across legs) greater in ASA (7.5%) compared with IBU (3.7%, group difference 34 cm³ ; P = 0.029). In the WS leg, muscle strength improved similarly (11-20%) across groups. In the FW leg, increases (10-23%) in muscle strength were evident in both groups yet they were generally greater (interaction effects P < 0.05) for ASA compared with IBU. While our molecular analysis revealed several training effects, the only group interaction (P < 0.0001) arose from a downregulated mRNA expression of IL-6 in IBU.

CONCLUSION

Maximal over-the-counter doses of ibuprofen attenuate strength and muscle hypertrophic adaptations to 8 weeks of resistance training in young adults. Thus, young individuals using resistance training to maximize muscle growth or strength should avoid excessive intake of anti-inflammatory drugs.