Muscle Architecture Research Articles

Sedentary behaviour (especially accumulation pattern) has an independent negative impact on skeletal muscle size and architecture in community-dwelling older adults.

Prolonged sedentary behaviour (SB) i.e. longer bouts, is suggested to have a range of negative health effects, independent of habitual light and medium-to-vigorous physical activity (LIPA or MVPA). Any effect on musculoskeletal size, architecture or morphology has seldom been reported in older adults. Moreover, no study has yet determined if any association would persist following adjustment for covariates. Therefore, the aim of the present study was to investigate the associations between SB, and properties of the Gastrocnemius Medialis (GM) muscle, in a cross-sectional sample of older adults using compositional data analysis. 105 healthy older adults (73±6y) wore a thigh mounted tri-axial accelerometer for seven consecutive days, and underwent ultrasound [e.g. muscle length (Lm), anatomical cross-sectional area (ACSA), muscle volume (VM), fascicle length (LF), & physiological cross-sectional area (PCSA)], body composition (e.g. DEXA) and health (e.g. medical history) assessments. In-unadjusted models, SB time was negatively associated with ACSA at 75% of Lm (R2adj = 0.085), VM (R2adj = 0.020), and PCSA (R2adj = 0.039). Standing was positively associated with pennation angle (R2adj = 0.110), which persisted following co-variate adjustment (R2adj = 0.296). In fully adjusted models, both SB & LIPA time were associated with ACSA at 75% of Lm (Both R2adj = 0.393). Standing and light activity time were also associated with LF, VM, & PCSA (R2adj 0.116-0.573). In fully adjusted models, SB pattern parameters (i.e. the manner in which sedentary behaviour is accumulated daily throughout waking hours such as the timing, duration and frequency of sedentary bouts), were associated with GM muscle properties (R2adj 0.156-0.564) including LM, LF, and VM. The pattern, rather than accumulated daily SB time, was associated with the size and architecture of the GM. Our results suggest that regardless of co-existing habitual physical activities, SB bouts should be kept short and frequently interrupted to offset some of the deleterious ageing-related muscle architecture characteristics changes.

Multimodal and conventional resistance training interventions improve muscle function in older adults: Findings from the Training IMCT study

Age-associated remodeling processes affect the intramuscular connective tissue (IMCT) network, which may significantly impair muscle function. Thus, we aimed to test whether including exercises shown to efficiently target the IMCT to a conventional resistance exercise intervention (CONV) would result in greater functional gains as compared to CONV alone. Fifty-three men and women (66.2 ± 3.3 years) were assigned to either CONV (n = 15), multimodal training (MULTI; n = 17) or a control (CTRL; n = 21) group. All subjects were tested at baseline, and those assigned to CONV or MULTI underwent a 16-week training intervention. The CONV group followed a progressive resistance training program, in which the number of weekly training sessions gradually increased from 1 to 3. In the MULTI group, one of these sessions was replaced with plyometric training, followed by self-myofascial release. Testing included maximal strength and power, imaging-based muscle volume, architecture, and functional performance. The intervention effects were analyzed using two- or three-way repeated measures ANOVA models (α = 0.05). Briefly, the maximal knee extension isometric contraction, one-repetition maximum, and isokinetic peak torque increased in all groups (p < 0.05), albeit to a lesser extent in CTRL. On the other hand, quadriceps femoris muscle volume (p = 0.019) and vastus lateralis pennation angle (p < 0.001) increased only in the MULTI group. Handgrip strength did not change in response to the intervention (p = 0.312), whereas Sit-to-Stand performance improved in all groups after the first 8-wks, but only in MULTI and CONV after 16-wks (all p < 0.001). In conclusion, we found that a resistance training intervention in which one weekly training session is replaced by plyometric training is feasible and as effective as a program consisting solely of conventional strength training sessions for inducing gains in muscle strength and function in older adults. Muscle size and architecture improved only in the MULTI group. German Clinical Trials: DRKS00015750.

The Role of the Nordic Hamstring Curl in the Rehabilitation of Hamstring Injuries: A Narrative Review

Background: Hamstring injuries are common in sports requiring high speed and power, such as soccer, football, and field. Prevention and rehabilitation strategies are essential to address the economic and performance-related consequences of hamstring injuries in sports. A state-of-the-art review provides a comprehensive and up-to-date summary of knowledge on hamstring muscle injuries in athletes. Purpose: To review the literature to verify the effectiveness of Nordic hamstring curls exercise in managing and preventing hamstring injuries during sports activity. Method: Electronic databases used for relevant trials: Google Scholar, Pubmed, Cochrane, NCBI, Science Direct, and CINAHLI. All the articles are taken from 2017 to 2022. On Nordic hamstring curls in sports, players were kept as inclusion criteria. One hundred forty articles were searched, which includes NHE in sports players. After screening, 39 studies were finally included in the review. Result: A total of 39 studies were finally included in the review, of which 17 were Randomized controlled trials, 16 were Systemic Reviews, 2 were Quasi-experimental Studies, and 4 were Observational studies. The hamstring injury rate was substantially lower in groups that included the Nordic Hamstring curl exercise in their daily regime. NHE significantly increases eccentric strength, eccentric peak torque, H: Q ratio, muscle fascicle length, and muscle architecture. Conclusion: There was a significant relation between hamstring injuries and Nordic hamstring curl exercise. NHE is found to be effective in the prevention and rehabilitation of hamstring injuries in athletes. Clinicians should be encouraged to incorporate NHE into their prevention strategies, and players and coaches should be more aware of and encourage the use of NHE. Keywords: Hamstring Injuries, Nordic hamstring exercise, Nordic curl, eccentric strength, injury prevention.

Anatomic variations of the deltoid muscle insertion: a cadaveric study

The deltoid is a trisegmented muscle with anterior, middle, and posterior components. While the clinical relevance of the presence of anatomic variations of the deltoid origin and insertion continues to be debated, the architecture of the deltoid muscle is more complex than initially believed. This study aimed to evaluate the gross anatomy of the deltoid muscle insertion by qualitatively and quantitatively characterizing the insertion and location of the deltoid muscle's anterior, middle, and posterior components. This information is valuable to surgeons as it raises awareness of potential variants that could be encountered during surgery, promotes mindfulness of neurovascular proximities, and reduces the likelihood of confusion between adjacent muscle fibers. Eight nonpaired, fresh-frozen clavicle-to-fingertip cadaveric shoulders were acquired for the study (6 left, 2 right). The average age of the cadavers was 79.5 years (range: 64-92). The standard deltopectoral approach was carried out on all specimens. The planes dividing the anterior, middle, and posterior deltoid were identified and marked. Once complete exposure had been achieved, digital calipers were used to record the size of the deltoid insertion. The specimens were qualitatively assessed to characterize the style of insertion they demonstrated. The average length of the deltoid insertion was 39.45±9.33 mm (n=8). Six of the eight shoulders demonstrated an insertion style previously characterized in the literature. The remaining two shoulders highlighted an insertion pattern not previously described. The current study demonstrates a novel insertion pattern for the deltoid muscle that has not been previously characterized. This "step-off" insertion pattern shows that the anterior, middle, and posterior tendons are inserted superior-medial, directly on, and inferior-lateral to the deltoid tuberosity and was found in 2/8 of our cadaveric specimens.

Musculoaponeurotic architecture of the human masseter muscle: an in vivo ultrasonographic study of architectural changes during mandibular protrusion and lateral excursions

ObjectiveThe present study evaluated the in vivo musculoaponeurotic architecture of the superficial head (SH) of the masseter muscle (MM) of asymptomatic participants in excursive mandibular movements compared to the relaxed state as examined with ultrasound imaging. It was hypothesized that the mean fiber bundle length (FBL) and mean height of the aponeurosis (HA) of the laminae of the SH would differ significantly between the relaxed state and protrusion, ipsilateral excursion, and contralateral excursion. Study DesignThe MM was studied volumetrically in 12 female and 12 male asymptomatic participants bilaterally by using ultrasound imaging. Mean FBL and HA in protrusion and ipsilateral and contralateral excursion were compared to these values in the relaxed state using paired t-tests (P < .05). The intraclass correlation coefficient was used to assess intraexaminer reliability. ResultsThe SH exhibited multiple laminae. Fiber bundles were found to attach to bone and the superior and inferior aponeuroses. Mean FBL was significantly shorter and mean HA significantly longer in protrusion and the excursions than in the relaxed state although the pattern of altered laminae and aponeuroses differed among the mandibular movements. Intraexaminer reliability was excellent. ConclusionSpecific changes in mean FBL and mean HA suggest differential contraction of the SH of the MM based on laminar morphology. These findings provide a baseline to investigate musculoaponeurotic changes in patients with myogenic masseter muscle pain.

Influence of muscle length on the three-dimensional architecture and aponeurosis dimensions of rabbit calf muscles

The function of a muscle is highly dependent on its architecture, which is characterized by the length, pennation, and curvature of the fascicles, and the geometry of the aponeuroses. During in vivo function, muscles regularly undergo changes in length, thereby altering their architecture. During passive muscle lengthening, fascicle length (FL) generally increases and the angle of fascicle pennation (FP) and the fascicle curvature (FC) decrease, while the aponeuroses increase in length but decrease in width.Muscles are differently structured, making their change during muscle lengthening complex and multifaceted. To obtain comprehensive data on architectural changes in muscles during passive length, the present study determined the three-dimensional fascicle geometry of rabbit M. gastrocnemius medialis (GM), M. gastrocnemius lateralis (GL), and M. plantaris (PLA). For this purpose, the left and right legs of three rabbits were histologically fixed at targeted ankle joint angles of 95° (short muscle length [SML]) and 60° (long muscle length [LML]), respectively, and the fascicles were tracked by manual three-dimensional digitization. In a second set of experiments, the GM aponeurosis dimensions of ten legs from five rabbits were determined at varying muscle lengths via optical marker tracking.The GM consisted of a uni-pennated compartment, whereas the GL and PLA contained multiple compartments of differently pennated fascicles. In the LML compared to the SML, the GM, GL, and PLA had on average a 41%, 29%, and 41% increased fascicle length, and a 30%, 25%, and 33% decrease in fascicle pennation and a 32%, 11%, and 35% decrease in fascicle curvature, respectively. Architectural properties were also differentiated among the different compartments of the PLA and GL, allowing for a more detailed description of their fascicle structure and changes. It was shown that the compartments change differently with muscle length. It was also shown that for each degree of ankle joint angle reduction, the proximal GM aponeurosis length increased by 0.11%, the aponeurosis width decreased by 0.22%, and the area was decreased by 0.20%. The data provided improve our understanding of muscles and can be used to develop and validate muscle models.

Muscle geometry and its relevance for sports performance? A perspective of current findings and future opportunities

Muscle geometry and its relevance for sports performance? A perspective of current findings and future opportunities

The temperature sensitivity of motor units in rat soleus

Temperature has a significant impact on the performance of the neuromuscular system and motor control processes. The smallest functional components of these systems are motor units (MUs), which may differ significantly between different muscles. The influence of temperature on the contractile properties of slow-twitch (S) MUs from soleus (SOL) muscles in rats was investigated under hypothermia (25 °C), normothermia (37 °C), and hyperthermia (41 °C). Hypothermia prolonged the twitch time parameters, decreased the rate of force development, increased the twitch-to-tetanus ratio, enhanced twitch force, and abolished post-tetanic depression. In contrast, hyperthermia did not alter twitch time parameters. Moreover, there was no effect on force despite the noted increase in post-tetanic depression and the twitch-to-tetanus ratio. Therefore, hypothermia induced more profound changes in S MUs compared with hyperthermia. The temperature effects in SOL MUs were compared to the effects previously reported for S MUs in the medial gastrocnemius (MG). The major differences between the S MUs of both muscles were the effects of temperature on twitch force, post-tetanic force modulation, twitch-to-tetanus ratio, and the slope of the force-frequency curve under hypothermia. Hyperthermia shortened twitch time parameters solely in the MG. In contrast, post-tetanic depression, twitch-to-tetanus ratio, and the slope of the force-frequency curve were influenced by hyperthermia only in SOL MUs. The different temperature effects of S MUs probably corresponded to differences in muscle architecture and their diverse functional tasks and enzyme activity. In summary, S MUs in SOL are more thermal-sensitive than their counterparts in MG.

Differences and similarities in muscle architecture of fibularis longus and brevis—An observational descriptive cross-sectional and feasibility study

BackgroundThe fibularis longus (FL) muscle is larger in volume than fibularis brevis (FB) and is therefore claimed to be the stronger evertor of the two. Clinical observation of FL and FB tendon rupture show that injury to the FB has a serious negative effect on hindfoot eversion. This implies that the FB is the stronger and more important evertor. The strength of a muscle is not purely based on its volume, and the observed discrepancy between the FB and FL may be due to differences in muscle architecture. This study compares the muscle architecture of FL with FB.MethodsSixteen legs from eight formaldehyde-fixed human specimens, mean age 83 (range 72–89) years, were dissected. The volume, fibre lengths and fibre pennation angles for both muscles were measured and the physiological cross-sectional area (PCSA) was calculated.ResultsThe FL was always larger than the FB, with an individual difference in volume that varied from 1.4 to 4.6 times larger with a mean difference of 17 ml (95% CI 14–20; p < 0.001). Mean fibre lengths were 9 mm (95% CI 2–16; p = 0.015) longer in FL than in FB. The mean pennation angle was 9.6 degrees in FL and 8.8 degrees in FB, this difference was not significant (p = 0.32). The mean PCSA for FL was 3 cm2 (95% CI 2–4) larger than for FB (p < 0.001).ConclusionsWith our sample set, the hypothesis that the muscle architecture can explain the clinical discrepancy between the FL and FB, was not supported. The difference in hindfoot eversion might instead depend on the different moment arms of FL and FB and the effect forefoot abduction has on hindfoot eversion.

Specific Changes in Contractile Functions and Skeletal Muscle Architecture in Humans in Response to the Use of Two Protocols of Unmodulated Neuromuscular Electrical Stimulation

Specific Changes in Contractile Functions and Skeletal Muscle Architecture in Humans in Response to the Use of Two Protocols of Unmodulated Neuromuscular Electrical Stimulation

Quantitative assessment of grasping strength in platyrrhine monkeys.

Despite the longstanding importance of grasping adaptations in theories of primate evolution, quantitative data on primate grasping strength remain rare. We present the results of two studies testing the prediction that callitrichines-given their comparative retreat from a small-branch environment and specialization for movement and foraging on tree trunks and large boughs-should be characterized by weaker grasping forces and underdeveloped digital flexor muscles relative to other platyrrhines. First, we directly measured manual grasping strength in marmosets (Callithrix jacchus) and squirrel monkeys (Saimiri boliviensis), using a custom-constructed force transducer. Second, we reanalyzed existing datasets on the fiber architecture of forearm and leg muscles in 12 platyrrhine species, quantifying digital flexor muscle physiological cross-sectional area (i.e., PCSA, a morphometric proxy of muscle strength) relative to the summed PCSA across all forearm or leg muscles. Callithrix was characterized by lower mean and maximum grasping forces than Saimiri, and callitrichines as a clade were found to have relatively underdeveloped manual digital flexor muscle PCSA. However, relative pedal digital flexor PCSA did not significantly differ between callitrichines and other platyrrhines. We found partial support for the hypothesis that variation in predominant substrate usage explains variation in empirical measurements of and morphological correlates of grasping strength in platyrrhines. Future research should extend the work presented here by (1) collecting morphological and empirical metrics of grasping strength in additional primate taxa and (2) extending performance testing to include empirical measures of primate pedal grasping forces as well.

Reliability of assessing skeletal muscle architecture and tissue organization of the gastrocnemius medialis and vastus lateralis muscle using ultrasound and spatial frequency analysis.

The purpose of this study was to investigate inter- and intra-rater reliability as well as the inter-rater interpretation error of ultrasound measurements assessing skeletal muscle architecture and tissue organization of the gastrocnemius medialis (GM) and vastus lateralis (VL) muscle. The GM and VL of 13 healthy adults (22 ± 3 years) were examined thrice with sagittal B-mode ultrasound: intraday test-retest examination by one investigator (intra-rater) and separate examinations by two investigators (inter-rater). Additionally, images from one investigator were analysed by two interpretators (interpretation error). Muscle architecture was assessed by muscle thickness [MT], fascicle length [FL], as well as superior and inferior pennation angle [PA]. Muscle tissue organization was determined by spatial frequency analysis (SFA: peak spatial frequency radius, peak -6 dB width, PSFR/P6, normalized peak value of amplitude spectrum [Amax], power within peak [PWP], peak power percent). Reliability of ultrasound examination and image interpretation are presented as intraclass correlation coefficient (ICC), test-retest variability, standard error of measurement as well as bias and limits of agreement. GM and VL demonstrated excellent ICCs for inter- and intra-rater reliability, along with excellent ICCs for interpretation error of MT (0.91-0.99), showing minimal variability (<5%) and SEM% (<5%). Systematic bias for MT was less than 1 mm. For PA and FL poor to good ICCs for inter- and intra-rater reliability were revealed (0.41-0.90), with moderate variability (<12%), low SEM% (<10%) and systematic bias between 0.1-1.4°. Tissue organization analysis indicated moderate to good ICCs for inter- and intra-rater reliability. Notably, Amax and PWP consistently held the highest ICC values (0.77-0.87) across all analyses but with higher variability (<24%) and SEM% (<18%), compared to lower variability (<9%) and SEM% (<8%) in other tissue organization parameters. Interpretation error of all muscle tissue organization parameters showed excellent ICCs (0.96-0.999) with very low variability (≤1%) and SEM% (<2%), except Amax & PWP (TRV%: <6%; SEM%: <7%). Our findings demonstrated excellent inter- and intra-rater reliability for MT. However, agreement for PA, FL, and SFA parameters was not as strong. Additionally, MT and all SFA parameters exhibited excellent agreement for inter-rater interpretation error. Therefore, the SFA seems to offer the possibility of objectively and reliably evaluating ultrasound images.

Cranial muscle architecture in wild boar: Does captivity drive ontogenetic trajectories?

The jaw system in mammals is complex and different muscle morphotypes have been documented. Pigs are an interesting group of animals as they are omnivorous and have a bunodont crushing dentition. Moreover, they have interacted with humans for over 10,000 years and grow nearly two orders of magnitude in size. Despite being a model system for studies on cranial form and function, data on the growth of the jaw adductor muscles are scant. Moreover, whether captivity impacts the growth and architecture of the jaw adductors remains unknown. Based on dissection data of the jaw adductors of 45 animals ranging from less than 1 kg to almost 100 kg, we show that muscle masses, muscle fiber lengths, and cross-sectional areas scale as predicted for geometrically similar systems or with slight negative allometry. Only the fiber length of the lateral pterygoid muscle grew with slight positive allometry. Animals raised in captivity in stalls or in an enclosure were overall very similar to wild animals. However, some muscles were larger in captive animals. Interestingly, variation in bite force in captive animals was well predicted by the variation in the size of the superficial masseter muscle relative to the overall jaw adductor mass.

Correlations between Achilles tendon moment arm and plantarflexor muscle architecture variables.

The production of triceps surae plantarflexion moment is complex in that the Achilles tendon moment arm affects the Achilles tendon force by determining the muscle length change and shortening velocity during ankle rotation. In addition, there is evidence for associations between the sizes of muscles and their moment arm at the joints they span. These relationships between muscle architecture and tendon moment arm ultimately affect the muscle's force generating capacity and are thus important for understanding the roles played by muscles in producing locomotion. The purpose of this study was to investigate in vivo the relationship between architecture of two plantarflexors and the Achilles tendon moment arm in a healthy adult population. Ultrasound-based measurements were made of the architecture (fascicle length, muscle volume, physiological cross-sectional area, and anatomical cross-sectional area) of the lateral and medial gastrocnemius and the Achilles tendon moment arm was assessed using a technique that combined ultrasound imaging and motion analysis. Positive correlations were observed between the length (r = 0.499, p = 0.049) and size variables (muscle volume r = 0.621, p = 0.010; ACSA r = 0.536, p = 0.032) of the lateral gastrocnemius and the Achilles tendon moment arm, but correlations were only observed for size variables (muscle volume r = 0.638, p = 0.008; PCSA r = 0.525, p = 0.037; ACSA r = 0.544, p = 0.029), and not the length, of the medial gastrocnemius. These findings suggest lateral gastrocnemius adapts to moment arms to maintain force production throughout the range of motion across individuals, while the medial gastrocnemius does not and is thus better suited for static force generation.

Relationship in Children with Unilateral Cerebral Palsy Between Muscle Architecture and Functional Motor Skills

Relationship in Children with Unilateral Cerebral Palsy Between Muscle Architecture and Functional Motor Skills

Role of microenvironment on muscle stem cell function in health, adaptation, and disease.

The role of the cellular microenvironment has recently gained attention in the context of muscle health, adaption, and disease. Emerging evidence supports major roles for the extracellular matrix (ECM) in regeneration and the dynamic regulation of the satellite cell niche. Satellite cells normally reside in a quiescent state in healthy muscle, but upon muscle injury, they activate, proliferate, and fuse to the damaged fibers to restore muscle function and architecture. This chapter reviews the composition and mechanical properties of skeletal muscle ECM and the role of these factors in contributing to the satellite cell niche that impact muscle regeneration. In addition, the chapter details the effects of satellite cell-matrix interactions and provides evidence that there is bidirectional regulation affecting both the cellular and extracellular microenvironment within skeletal muscle. Lastly, emerging methods to investigate satellite cell-matrix interactions will be presented.

Fabrication of 3D Biomimetic Smooth Muscle Using Magnetic Induction and Bioprinting for Tissue Regeneration.

Smooth muscles play a vital role in peristalsis, tissue constriction, and relaxation but lack adequate self-repair capability for addressing extensive muscle defects. Engineering scaffolds have been broadly proposed to repair the muscle tissue. However, efforts to date have shown that those engineered scaffolds focus on cell alignment in 2-dimension (2D) and fail to direct muscle cells to align in 3D area, which is irresolvable to remodel the muscle architecture and restore the muscle functions like contraction and relaxation. Herein, we introduced an iron oxide (Fe3O4) filament-embedded gelatin (Gel)-silk fibroin composite hydrogel in which the oriented Fe3O4 self-assembled and functioned as micro/nanoscale geometric cues to induce cell alignment growth. The hydrogel scaffold can be designed to fabricate aligned or anisotropic muscle by combining embedded 3D bioprinting with magnetic induction to accommodate special architectures of muscular tissues in the body. Particularly, the bioprinted muscle-like matrices effectively promote the self-organization of smooth muscle cells (SMCs) and the directional differentiation of bone marrow mesenchymal stem cells (BMSCs) into SMCs. This biomimetic muscle accelerated tissue regeneration, enhancing intercellular connectivity within the muscular tissue, and the deposition of fibronectin and collagen I. This work provides a novel approach for constructing engineered biomimetic muscles, holding significant promise for clinical treatment of muscle-related diseases in the future.

Саркопения и болезнь Крона у детей

Sarcopenia is a significant health problem in developed countries as it increases the risk of fractures, impairs the ability to move independently and perform daily activities, relates to cardiovascular and respiratory diseases, cognitive impairment, reduces the quality of life, and imposes a financial burden on health care systems. Sarcopenia is characterized by progressive and generalized loss of muscle mass, deterioration in the quality of muscle architecture, and a decrease in muscle functionality, which predicts an unfavorable outcome. Recently, reports have appeared in the literature about the development of sarcopenia in patients with Crohn's disease. However, the mechanism of muscle loss in this inflammatory bowel disease is not fully understood. In this review, we present the possible pathophysiological mechanisms of Crohn's disease that contribute to the development of functional muscle failure and low performance. The literature review also presents potential treatments that may alleviate the development of sarcopenia in Crohn's disease. Key words: sarcopenia, Crohn's disease, inflammatory bowel disease, muscle mass, gut-muscle axis

Exploring the utility of bedside tests for predicting cardiorespiratory fitness in older adults.

Cardiorespiratory fitness (CRF) declines with advancing and has also, independent of age, been shown to be predictive of all-cause mortality, morbidity, and poor clinical outcomes. In relation to the older patient, there is a particular wealth of evidence highlighting the relationship between low CRF and poor surgical outcomes. Cardiopulmonary exercise testing (CPET) is accepted as the gold-standard measure of CRF. However, this form of assessment has significant personnel and equipment demands and is not feasible for those with certain age-associated physical limitations, including joint and cardiovascular comorbidities. As such, alternative ways to assess the CRF of older patients are very much needed. Sixty-four participants (45% female) with a median age of 74 (65-90) years were recruited to this study via community-based advertisements. All participants completed three tests of physical function: (1) a step-box test; (2) handgrip strength dynamometry; and (3) a CPET on a cycle ergometer; and also had their muscle architecture (vastus lateralis) assessed by B-mode ultrasonography to provide measures of muscle thickness, pennation angle, and fascicle length. Multivariate linear regression was then used to ascertain bedside predictors of CPET parameters from the alternative measures of physical function and demographic (age, gender, body mass index (BMI)) data. There was no significant association between ultrasound-assessed parameters of muscle architecture and measures of CRF. VO2peak was predicted to some extent from fast step time during the step-box test, gender, and BMI, leading to a model that achieved an R 2 of 0.40 (p < 0.001). Further, in aiming to develop a model with minimal assessment demands (i.e., using handgrip dynamometry rather than the step-box test), replacing fast step time with non-dominant HGS led to a model which achieved an R 2 of 0.36 (p < 0.001). Non-dominant handgrip strength combined with the step-box test parameter of fast step time and BMI delivered the most predictive model for VO2peak with an R 2 of 0.45 (p < 0.001). Our findings show that simple-to-ascertain patient characteristics and bedside assessments of physical function are able to predict CPET-derived CRF. Combined with gender and BMI, both handgrip strength and fast step time during a step-box test were predictive for VO2peak. Future work should apply this model to a clinical population to determine its utility in this setting and to explore if simple bedside tests are predictive of important clinical outcomes in older adults (i.e., post-surgical complications).

Effect of isokinetic eccentric training on the human shoulder strength, flexibility, and muscle architecture in physically active men: A preliminary study.

Strengthening the rotator cuff muscles is important for injury prevention and rehabilitation. Since muscle fascicle length improves motor performance and is suggested to reduce the risk of injury for the hamstring, it may be an important variable to promote multidirectional changes in the function and macroscopic structure for the shoulder. Recent literature reviews overwhelmingly suggest that eccentric exercises improve fascicle length and functional measures for the lower limb. However, there is a research gap for the shoulder. Since ultrasound imaging is the most commonly used imaging technique to quantify muscle structure, but has yielded heterogeneous results in different studies, there is another issue and a research gap for the imaging method. Based on the research gaps, the purpose of this study was to evaluate the effects of standardized eccentric strength training on the function and structure of the external rotator cuff muscles using an isokinetic dynamometer and MRI. Therefore, a preliminary pre-post intervention study was conducted and 16 physically active men were recruited in October 2021. For the right shoulder, an eccentric isokinetic training was performed twice a week for almost six weeks. The primary outcome measures (external rotators) were active and passive range of motion, eccentric and concentric torque at 30, 60, and 180°/s isokinetic speed, and fascicle length and fascicle volume for the supraspinatus and infraspinatus muscles. The findings show a training effect for the absolute mean values of eccentric strength (+24%, p = .008). The torque-angle relationship increased, especially in the final phase of range of motion, although a 4% (p = .002) decrease in passive range of motion was found in the stretch test. Positive changes in muscle structure were shown for the supraspinatus muscle fascicle length (+16%, p = .003) and fascicle volume (+19%, p = .002). Based on the study results, we can conclude that eccentric isokinetic training has a significant positive effect on the shoulder. To our knowledge, this is the first eccentric training study using both isokinetic dynamometer and muscle diffusion tensor imaging to access functional and structural changes in the human shoulder rotator cuff muscles. The methods were shown to be applicable for interventional studies. Based on these results, populations such as high-performance handball players with highly trained shoulders should be included in future studies.