Control Leg Research Articles

Design of a Bionic Spider Robot with a Two-Degrees-of-Freedom Leg Structure and Body Frame

Spiders have unique biological characteristics and excellent maneuverability, making them an ideal model for bionic robot design. However, traditional bionic spider robot designs usually have multiple degrees of freedom and confront many challenges. These challenges include complex control requirements, higher energy consumption, larger size and weight, higher risk of failure, and higher cost. This study proposes a leg design with two degrees of freedom to reduce its control and manufacturing costs. It can better control leg movement and improve leg force through a multi-link mechanism and a dual-motor system. In addition, the triangular gait and hexagonal body structure align the weight of the body with the support point, thereby enhancing stability. This study offers a comprehensive and organized approach to bio-inspired robot design, providing a valuable reference for future bionic robot development.

Porcine blast injury model achieves prolonged elevation of intra-compartmental pressures without exogenous pressure manipulation

BackgroundMost existing animal models of acute compartment syndrome (ACS) rely on exogenous manipulation of intra-compartmental pressures to model ACS. The purpose of the current study was to evaluate the endogenous effect of a blast injury on porcine lower leg intra-compartmental pressures (ICP).MethodsThe hindlimb of juvenile Landrace pigs was fractured at the diaphyseal tibia and subjected to blasts of compressed air to mimic a blast injury. Injured and control legs underwent pre-operative continuous ICP monitoring. At 4.5 h post injury, the fracture was stabilized followed by closure of the anterior compartment fascia (continued compartment pressure model, CCPM) or four compartment fasciotomy. Pressure measurements were made after operative fixation. Select pigs in CCPM were harvested between 48 and 72 h post-injury to evaluate the duration of ICP elevation.ResultsPost-injury, the model created significantly elevated ICP compared to control limbs (54.5 ± 18.2 vs. 18.2 ± 4.9 mmHg; p < 0.001). Operative fixation and anterior compartment fascial closure further increased the ICP (Mean: 87.4 ± 42.5 mmHg) relative to the pre-operative state (p = 0.037). Fasciotomy returned baseline compartment pressures (Mean: 13.7 ± 10.2 mmHg) which were equivalent to control limbs (p = 0.117). Pressure measurements at the time of delayed harvest (48–72 h) demonstrated that elevated ICP persisted following injury (69.7 ± 55.12 mmHg).ConclusionThe current study demonstrates that a pilot porcine blast model elevates ICP comparable to existing animal models of compartment syndrome without exogenous ICP manipulation. ICP remained elevated at 48–72 h in the absence of fasciotomy.

Quantitative Evaluation of Knee Cartilage in Professional Martial Arts Athletes Using T2 Mapping: A Comparative Study.

Although the relationship between high-impact sports like football and basketball and the development of knee osteoarthritis is well established, the effect of martial arts on the knee joint remains unclear. To compare the imaging abnormalities of knee joints and T2 relaxation times of cartilage in professional martial arts athletes and healthy controls. Cross-sectional study. Hospital imaging center. Nine asymptomatic professional martial arts athletes and 18 healthy volunteers. We performed 3T magnetic resonance imaging of the knee on both legs of athletes and the dominant leg of controls. The magnetic resonance imaging protocol included conventional sequences used for morphological assessment (cartilage, meniscus, ligaments, joint effusion, and bone marrow edema) and T2 mapping used for quantitatively evaluating the cartilage. Knee cartilage was manually divided into 8 regions, and T2 relaxation times of the corresponding subregions were measured. Fisher exact test and t test were used to compare the frequency of lesions and cartilage T2 values both between groups and between the athletes' limbs. P < .05 was considered significant. Professional martial arts athletes exhibited significantly higher frequencies of cartilage (55.6% vs 11.1%, P = .023) and ligament lesions (66.7% vs 16.7%, P = .026) compared with the control group. Athletes showed higher T2 values in 3 distinct cartilage segments: the central weight-bearing segment of the medial femoral condyle (P = .006), the medial tibial plateau (P = .012), and the trochlea (P = .032), when compared with the controls. Additionally, the dominant leg of athletes showed significantly higher T2 values compared with the nondominant leg. The findings demonstrated the impact of martial arts on the knee joint, characterized by higher prevalence of lesions and elevated cartilage T2 values, particularly in the medial compartment. The dominant legs of martial arts athletes seem to have higher risk of cartilage degeneration due to the observed interlimb differences in T2 values.

Angle-Specific Analysis of Isokinetic Quadriceps and Hamstring Strength at 6 and 12 Months After Unilateral ACL Reconstruction.

Quadriceps and hamstring strength deficits are related to the increased risk of reinjury after anterior cruciate ligament reconstruction (ACLR). Knee angle-specific quadriceps and hamstring strength differences would be observed in patients with ACLR 6 and 12 months after surgery. Case-series. Level 4. A total of 23 postprimary unilateral ACLR patients followed-up at 6 and 12 months postoperatively and 25 controls were included. Isokinetic knee extension and flexion strength were evaluated at 60 deg/s from 20° to 90°. Statistical parametric mapping were performed to explore the angle-specific strength and the limb symmetry index (LSI). At 6 months postoperatively, the reconstructed leg demonstrated lower knee extension and flexion strength than the contralateral (20°-77°, 24°-90°) (P < 0.01) and control legs (22°-90°, 40°-82°) (P < 0.01). From 6 months to 12 months, knee extension (60°-90°) and flexion (20°-79°) strength improved in the reconstructed leg (P < 0.05), while LSI remained unchanged (P > 0.02). At 12 months, knee extension strength differences persisted in the reconstructed leg compared with the contralateral (20°-81°) and controls (25°-63°) (P < 0.01). ACLR patients had lower LSI of knee extension strength at 6 (20°-59°) and 12 (24°-57°) months postoperatively than the controls (P < 0.02). The reconstructed leg exhibited differences in knee extension strength compared with the contralateral and control legs. Although bilateral knee extension strength increased from 6 to 12 months postoperatively, LSI did not show improvement during this period. Quadriceps restoration was observed only in knee flexion angles greater than 60° compared with controls. Future studies should investigate whether knee extension strength, especially in lower flexion angles, can be enhanced through rehabilitation programs. Furthermore, assessing the impact of this improvement on long-term outcomes and reinjury risk in ACLR patients is warranted.

Five days of bed rest in young and old adults: Retainment of skeletal muscle mass with neuromuscular electrical stimulation.

The consequences of short-term disuse are well known, but effective countermeasures remain elusive. This study investigated the effects of neuromuscular electrical stimulation (NMES) during 5 days of bed rest on retaining lower limb muscle mass and muscle function in healthy young and old participants. One leg received NMES of the quadriceps muscle (3 × 30min/day) (NMES), and the other served as a control (CON). Isometric quadriceps strength (MVC), rate of force development (RFD), lower limb lean mass, and muscle thickness were assessed pre-and post-intervention. Muscle thickness remained unaltered with NMES in young and increased in old following bed rest, while it decreased in CON legs. In old participants, mid-thigh lean mass (MTLM) was preserved with NMES while decreased in CON legs. In the young, only a tendency to change with bed rest was detected for MTLM. MVC and early-phase RFD decreased in young and old, irrespective of NMES. In contrast, late-phase RFD was retained in young participants with NMES, while it decreased in young CON legs, and in the old, irrespective of NMES. NMES during short-term bed rest preserved muscle thickness but not maximal muscle strength. While young and old adults demonstrated similar adaptive responses in preventing the loss of skeletal muscle thickness, RFD was retained in the young only.

Hamstring Muscle Stiffness in Athletes with and without Anterior Cruciate Ligament Reconstruction History: A Retrospective Study.

Introduction: Sports requiring sprinting, jumping, and kicking tasks frequently lead to hamstring strain injuries (HSI). One of the structural risk factors of HSI is the increased passive stiffness of the hamstrings. Anterior cruciate ligament (ACL) injury history is associated with a 70% increase in the incidence of HSI, according to a recent meta-analysis. The same report recommended that future research should concentrate on the relationships between the HSI risk factors. Hence, the present study aimed to retrospectively compare changes in the passive stiffness of the hamstrings in athletes with and without ACL reconstruction history. Methods: Using ultrasound-based shear-wave elastography, the mid-belly passive muscle stiffness values of the biceps femoris long head, semimembranosus, and semitendinosus muscles were assessed and compared amongst athletes with and without a history of ACL reconstruction. Results: There were no significant differences in the biceps femoris long head (injured leg (IL): 26.19 ± 5.28 KPa, uninjured contralateral (UL): 26.16 ± 7.41 KPa, control legs (CL): 27.64 ± 5.58 KPa; IL vs. UL: p = 1; IL vs. CL: p = 1; UL vs. CL: p = 1), semimembranosus (IL: 24.35 ± 5.58 KPa, UL: 24.65 ± 8.35 KPa, CL: 22.83 ± 5.67 KPa; IL vs. UL: p = 1; IL vs. CL: p = 1; UL vs. CL, p = 1), or semitendinosus (IL: 22.45 ± 7 KPa, UL: 25.52 ± 7 KPa, CL: 22.54 ± 4.4 KPa; IL vs. UL: p = 0.487; IL vs. CL: p = 1; UL vs. CL, p = 0.291) muscle stiffness values between groups. Conclusions: The passive mid-muscle belly stiffness values of the biceps femoris long head, semitendinosus, and semimembranosus muscles did not significantly differ between previously injured and uninjured athletes; therefore, further assessment for other muscle regions of hamstrings may be necessary. To collect more comprehensive data related to the structural changes that may occur following ACL reconstructions in athletes, a future study should examine the passive stiffness of wider muscle regions from origin to insertion.

Endurance Training Improves Leg Proton Release and Decreases Potassium Release During High-Intensity Exercise in Normoxia and Hypobaric Hypoxia.

To assess the impact of endurance training on skeletal muscle release of H+ and K+. Nine participants performed one-legged knee extension endurance training at moderate and high intensities (70%-85% of Wpeak), three to four sessions·week-1 for 6 weeks. Post-training, the trained and untrained (control) leg performed two-legged knee extension at low, moderate, and high intensities (40%, 62%, and 83% of Wpeak) in normoxia and hypoxia (~4000 m). The legs were exercised simultaneously to ensure identical arterial inflow concentrations of ions and metabolites, and identical power output was controlled by visual feedback. Leg blood flow was measured (ultrasound Doppler), and acid-base variables, lactate- and K+ concentrations were assessed in arterial and femoral venous blood to study K+ and H+ release. Ion transporter abundances were assessed in muscle biopsies. Lactate-dependent H+ release was similar in hypoxia to normoxia (p = 0.168) and was lower in the trained than the control leg at low-moderate intensities (p = 0.060-0.006) but similar during high-intensity exercise. Lactate-independent and total H+ releases were higher in hypoxia (p < 0.05) and increased more with power output in the trained leg (leg-by-power output interactions: p = 0.02). K+ release was similar at low intensity but lower in the trained leg during high-intensity exercise in normoxia (p = 0.024) and hypoxia (p = 0.007). The trained leg had higher abundances of Na+/H+ exchanger 1 (p = 0.047) and Na+/K+ pump subunit α (p = 0.036). Moderate- to high-intensity endurance training increases lactate-independent H+ release and reduces K+ release during high-intensity exercise, coinciding with increased Na+/H+ exchanger 1 and Na+/K+ pump subunit α muscle abundances.

Hair removal with a clipper and microbial colonisation prior to knee arthroplasty: a randomised controlled trial

Despite the widely reported success of knee arthroplasty, studies show that 1.6-3 % of patients undergo revision within the first postoperative year predominantly due to infection. Preoperative skin preparation may potentially decrease the bacterial load and consequently, the risk of periprosthetic joint infections. The effects of hair removal on prosthetic joint infection are inconsistent. Our primary aim was to investigate if hair removal with a clipper influenced skin colonisation and bacterial composition. Forty Caucasian male participants who were planned to undergo knee arthroplasty, (mean age 63.8 years), were included. Patients were randomised to hair removal in a within-person study design. As a control, the opposite leg of the patient was used. Swabs were collected prior to hair removal (baseline), immediately after hair removal (Day 0), and with follow-up after one and seven days. The intervention showed significant decrease in mean log colony-forming units per. cm2 from baseline 2.97 to 2.67 (P<0.01) immediately after hair removal and sustained at Day 1 (P=0.01). At Day 7, the mean was non-significant compared to baseline. The control group did not show any decrease of skin microbiota at follow-up on Day 0, 1 or 7.No significant differences within the bacterial composition were found between the intervention and control leg at baseline among the six most prevalent detected bacterialspecies: Staphylococcus epidermidis, Micrococcus luteus, S. hominis, S. capitis, S. haemolyticus and S. aureus. The study did not find any changes in the bacterial composition over time. Hair removal with a clipper within 24 hours prior to surgery causes a significant non-selective reduction in skin colonisation.

Positron Emission Tomography of Nitric Oxide by a Specific Radical-Generating Dihydropyridine Tracer.

Nitric oxide (NO) plays a pivotal role as a biological signaling molecule, presenting challenges in its specific detection and differentiation from other reactive nitrogen and oxygen species within living organisms. Herein, a 18F-labeled (fluorine-18, t1/2 = 109.7 min) small-molecule tracer dimethyl 4-(4-(4-[18F]fluorobutoxy)benzyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate ([18F]BDHP) is developed based on the dihydropyridine scaffold for positron emission tomography (PET) imaging of NO in vivo. [18F]BDHP exhibits a highly sensitive and efficient C-C cleavage reaction specifically triggered by NO under physiological conditions, leading to the production of a 18F-labeled radical that is readily retained within the cells. High uptakes of [18F]BDHP are found within and around NO-generating cells, such as macrophages treated with lipopolysaccharide or benzo(a)pyrene. MicroPET/CT imaging of arthritic animal model mice reveals distinct tracer accumulation in the arthritic legs, showcasing a higher distribution of NO compared with the control legs. In summary, a specific radical-generating dihydropyridine tracer with a unique radical retention strategy has been established for the marking of NO in real-time in vivo.

Noninvasive estimation of skeletal muscle oxygen consumption rate and microvascular reactivity in chronic stroke survivors using near-infrared spectroscopy.

Understanding post-stroke changes in skeletal muscle oxidative metabolism and microvascular reactivity could help create therapeutic targets that optimize rehabilitative interventions. Due to disuse atrophy, we hypothesized that basal muscle oxygen consumption rate and microvascular endothelial function would be impaired in the tibialis anterior (TA) muscle of the affected leg of chronic stroke survivors compared with the nonaffected leg and versus matched controls. Fifteen chronic stroke survivors (10 females) and 15 matched controls (9 females) completed this study. A near-infrared spectroscopy oximeter measured tissue oxygen saturation (StO2) of the TA in both legs of stroke survivors and the dominant leg of controls. A cuff was placed around the thigh and inflated to 225 mmHg for 5 min while StO2 was continuously measured. The rate of change in StO2 was calculated during cuff occlusion and immediately post-cuff release. The rate of oxygen desaturation was similar between the legs of the stroke survivors (paretic -0.12 ± 0.04%·s-1 vs. nonparetic -0.16 ± 011%·s-1; P = 0.49), but the paretic leg had a reduced desaturation rate versus controls (-0.25 ± 0.18%·s-1; P = 0.007 vs. paretic leg). After cuff release, there was a greater oxygen resaturation rate in the nonparetic leg compared with the paretic leg (3.13 ± 2.08%·s-1 vs. 1.60 ± 1.11%·s-1, respectively; P = 0.01). The control leg had a similar resaturation rate versus the nonparetic leg (control = 3.41 ± 1.79%·s-1; P = 0.69) but was greater than the paretic leg (P = 0.003). The TA in the paretic leg had an impaired muscle oxygen consumption rate and reduced microvascular endothelial function compared with controls.NEW & NOTEWORTHY Secondary consequences of stroke are not well described. In this study, we show that basal muscle oxidative consumption and microvascular endothelial function are reduced in the paretic tibialis anterior muscle of chronic stroke survivors compared with matched controls using near-infrared spectroscopy and the vascular occlusion technique. There was a moderately strong correlation between microvascular endothelial function and paretic leg strength.

Effects of foam rolling on hamstrings stiffness in damaged and non-damaged muscle states.

Introduction: The aim of this study was to examine the effects of foam rolling (FR) on hamstring muscles stiffness in both non-damaged and exercise-induced muscle damage (EIMD) states, using shear wave ultrasound elastography to measure changes in shear modulus. Methods: Fourteen healthy adults (25.5 ± 4.7 years) participated in a within-participant repeated measures design, with a 2-minute FR intervention applied on one leg and contralateral leg serving as a control. The damaging protocol encompassed maximal eccentric knee extensions performed on an isokinetic dynamometer and the Nordic hamstring exercise, consisting of 3 sets of 10 and 6 repetitions, respectively. Measurement were taken at baseline and then 1h, 24h and 48h after the damaging protocol. Results: The results indicated no significant time × leg interaction for shear modulus in biceps femoris, semimembranosus, and semitendinosus muscles in both non-damaged and damaged states. Notably, there was a significant increase in biceps femoris (p = 0.001; η2 = 0.36) and semitendinosus (p < 0.001; η2 = 0.44) shear modulus after EIMD, but no significant differences were found between the FR and control leg, which was also the case for muscle soreness, range of motion, and passive resistive torque (p = 0.239-0.999 for interactions). Discussion: The absence of significant changes post-FR intervention suggests a limited role of short-duration FR in altering muscle stiffness during recovery from EIMD. These findings contribute to the understanding of FR's role in muscle recovery. Although this was not directly investigated, our results suggest a predominance of central mechanisms rather than direct mechanical modifications in muscle properties. This research highlights the necessity for additional investigations to explore how FR interventions influence muscles in different states and to elucidate the mechanisms underlying these influences.

Quadriceps and Hamstrings Activation Peaks Earlier as Athletes Repeatedly Hop, but There are Differences Depending on ACL Reconstruction Technique.

After Anterior Cruciate Ligament Reconstruction (ACLR) athletes face the challenge of regaining their previous competitive level while avoiding re-injury and early knee joint cartilage degeneration. Quadriceps and hamstrings strength reductions and neuromuscular alterations potentially related to risk of re-injury are present after ACLR and relate to deficits in muscle activation. Cross-sectional laboratory study. To examine quadriceps and hamstrings muscle activation during repeated hops in healthy pivoting-sport athletes and those who had undergone ACLR (bone-tendon-bone and semitendinosus graft) who had met functional criteria allowing return to training. Surface electromyography (SEMG) was recorded from vastus medialis and lateralis and medial and lateral hamstrings bilaterally during 30 seconds' repeated hopping in male athletes on average eight months after ACLR surgery (5-12 months). All patients underwent hamstring (HS) (n=24) or bone-tendon-bone (BTB) reconstruction (n=20) and were compared to healthy controls (n=31). The SEMG signals were normalized to those obtained during maximal voluntary isometric contraction. A significant time shift in peak muscle activation (earlier) was seen for: vastus medialis and vastus lateralis activation in the control group, in the BTB group's healthy (but not injured) leg and both legs of the HS group. A significant time shift in peak muscle activation was seen for lateral hamstrings (earlier) in all but the BTB group's injured leg and the medial hamstrings in the control group only. Lower peak activation levels of the vastus lateralis (p\<0.001) and vastus medialis (p\<0.001) were observed in the injured compared to healthy legs and lower peak lateral hamstrings activity (p\<0.009) in the injured leg compared to control leg. Decline in medial hamstring peak activation (p\<0.022) was observed between 1st and 3rd phase of the hop cycle in all groups. Repeated hop testing revealed quadriceps and hamstring activation differences within ACLR athletes, and compared to healthy controls, that would be missed with single hop tests. 3.

Magnetic resonance lymphangiography: Establishing normal

BackgroundDespite an increased interest in visualizing the lymphatic vessels with magnetic resonance lymphangiography (MRL), little literature is available describing their appearance in nonlymphedematous individuals. To determine lymphatic abnormalities, an understanding of how healthy lymphatic vessels appear and behave needs to be established. Therefore, in this study, MRL of individuals without a history of lymphatic disease was performed. MethodsA total of 25 individuals (15 women) underwent MRL of their lower limbs using a 3.0 T Philips magnetic resonance imaging scanner (Philips Medical Systems). The first nine participants were recruited to establish the concentration of gadolinium-based contrast agent (GBCA) to administer, with the remainder imaged before and after interdigital forefoot GBCA injections at the optimized dose. Outcomes, including lymphatic vessel diameter, tortuosity, and frequency of drainage via particular drainage routes, were recorded. ResultsHealthy lymphatic vessels following the anteromedial pathway were routinely observed in post-contrast T1-weighted images (average tortuosity, 1.09 ± 0.03), with an average of 2.16 ± 0.93 lymphatic vessels with a diameter of 2.47 ± 0.50 mm crossing the anterior ankle. In six limbs, vessels following the anterolateral pathways were observed. No vessels traversing the posterior of the legs were seen. In a subset of 10 vessels, the lymphatic signal, measured at the ankle, peaked 29 minutes, 50 seconds ± 9 minutes, 29 seconds after GBCA administration. No lymphatic vessels were observed in T2-weighted images. ConclusionsContrast-enhanced MRL reliably depicts the lymphatic vessels in the legs of healthy controls. Following interdigital contrast injection, anteromedial drainage appears dominant. Quantitative measures related to lymphatic vessel size, tortuosity, and drainage rate are readily obtainable and could be beneficial for detecting even subtle lymphatic impairment.

Daily blood flow restriction does not preserve muscle mass and strength during 2weeks of bed rest.

We measured the impact of blood flow restriction on muscle protein synthesis rates, muscle mass and strength during 2weeks of strict bed rest. Twelve healthy, male adults (age: 24±3years, body mass index: 23.7±3.1kg/m2 ) were subjected to 14days of strict bed rest with unilateral blood flow restriction performed three times daily in three 5min cycles (200mmHg). Participants consumed deuterium oxide and we collected blood and saliva samples throughout 2weeks of bed rest. Before and immediately after bed rest, lean body mass (dual-energy X-ray absorptiometry scan) and thigh muscle volume (magnetic resonance imaging scan) were assessed in both the blood flow restricted (BFR) and control (CON) leg. Muscle biopsies were collected and unilateral muscle strength (one-repetition maximum; 1RM) was assessed for both legs before and after the bed rest period. Bed rest resulted in 1.8±1.0kg lean body mass loss (P<0.001). Thigh muscle volume declined from 7.1±1.1 to 6.7±1.0L in CON and from 7.0±1.1 to 6.7±1.0L in BFR (P<0.001), with no differences between treatments (P=0.497). In addition, 1RM leg extension strength decreased from 60.2±10.6 to 54.8±10.9kg in CON and from 59.2±12.1 to 52.9±12.0kg in BFR (P=0.014), with no differences between treatments (P=0.594). Muscle protein synthesis rates during bed rest did not differ between the BFR and CON leg (1.11±0.12 vs. 1.08±0.13%/day, respectively; P=0.302). Two weeks of bed rest substantially reduces skeletal muscle mass and strength. Blood flow restriction during bed rest does not modulate daily muscle protein synthesis rates and does not preserve muscle mass or strength. KEY POINTS: Bed rest, often necessary for recovery from illness or injury, leads to the loss of muscle mass and strength. It has been postulated that blood flow restriction may attenuate the loss of muscle mass and strength during bed rest. We investigated the effect of blood flow restriction on muscle protein synthesis rates, muscle mass and strength during 2weeks of strict bed rest. Blood flow restriction applied during bed rest does not modulate daily muscle protein synthesis rates and does not preserve muscle mass or strength. Blood flow restriction is not effective in preventing muscle atrophy during a prolonged period of bed rest.

Performance of an adjustable compression wrap in occupational leg swelling.

Edema in some subjects worsens over time and wraps help to reduce the leg volume. An adjustable compression wrap was tried on volunteers for 5 h and volumes measured in each limb before and after wrapping using a 3D surface scanner (HandySCAN 3D®) to estimate the volume of the leg. The contralateral leg was used as control. We observed a significant decrease in volume in the wrap legs and an increase in the control legs (p < .001), both in the lower part of leg (p = .001) and in the upper part (p = .001). Using the Readywrap® for 5hours significantly reduces the leg volume. This study enables Readywrap to be studied in a population that is easy to observe in the context of a research program. The Handyscan3D® was shown accurate and reproducible to assess leg volume in future studies.

Effects of preconditioning with heat stress on acute exercise-induced intracellular signaling in male rat gastrocnemius muscle.

Heat stress (HS) induces Akt/mTOR phosphorylation and FoxO3a signaling; however, whether a prior increase in heat shock protein 72 (HSP72) expression affects intracellular signaling following eccentric exercise remains unclear. We analyzed the effects of HS pretreatment on intramuscular signaling in response to acute exercise in 10-week-old male Wistar rats (n = 24). One leg of each rat was exposed to HS and the other served as an internal control (CT). Post-HS, rats were either rested or subjected to downhill treadmill running. Intramuscular signaling responses in the red and white regions of the gastrocnemius muscle were analyzed before, immediately after, or 1 h after exercise (n = 8/group). HS significantly increased HSP72 levels in both deep red and superficial white regions. Although HS did not affect exercise-induced mTOR signaling (S6K1/ERK) responses in the red region, mTOR phosphorylation in the white region was significantly higher in CT legs than in HS legs after exercise. Thr308 phosphorylation of Akt showed region-specific alteration with a decrease in the red region and an increase in the white region immediately after downhill running. Overall, a prior increase in HSP72 expression elicits fiber type-specific changes in exercise-induced Akt and mTOR phosphorylation in rat gastrocnemius muscle.

Custom-made 3D-printed boot as a model of disuse-induced atrophy in murine skeletal muscle.

Skeletal muscle atrophy is characterized by a decrease in muscle mass and strength caused by an imbalance in protein synthesis and degradation. This process naturally occurs upon reduced or absent physical activity, often related to illness, forced bed rest, or unhealthy lifestyles. Currently, no treatment is available for atrophy, and it can only be prevented by overloading exercise, causing severe problems for patients who cannot exercise due to chronic diseases, disabilities, or being bedridden. The two murine models commonly used to induce muscle atrophy are hindlimb suspension and ankle joint immobilization, both of which come with criticalities. The lack of treatments and the relevance of this atrophic process require a unilateral, safe, and robust model to induce muscle atrophy. In this work, we designed and developed a 3D-printed cast to be used for the study of disuse skeletal muscle atrophy. Applying two halves of the cast is non-invasive, producing little to no swelling or skin damage. The application of the cast induces, in 2-weeks immobilized leg, the activation of atrophy-related genes, causing a muscle weight loss up to 25% in the gastrocnemius muscle, and 31% in the soleus muscle of the immobilized leg compared to the control leg. The cross-sectional area of the fibers is decreased by 31% and 34% respectively, with a peculiar effect on fiber types. In the immobilized gastrocnemius, absolute muscle force is reduced by 38%, while normalized force is reduced by 16%. The contralateral leg did not show signs of overload or hypertrophy when compared to free roaming littermates, offering a good internal control over the immobilized limb. Upon removing the cast, the mice effectively recovered mass and force in 3 weeks.

Reduced oxygen desaturation in the vastus lateralis of chronic stroke survivors during graded muscle contractions

ABSTRACT Background Few studies have examined changes in skeletal muscle physiology post-stroke. This study examined changes in tissue oxygen saturation (StO2) of the vastus lateralis (VL) muscle of stroke survivors and age-matched control participants during maximal and submaximal isometric contractions of the knee extensor muscles. Objectives We hypothesized that tissue oxygen desaturation (ΔStO2) during knee extensor muscle contractions would be less in the VL in the paretic vs. the non-paretic and control legs. Methods Ten chronic stroke survivors (>6 months post-stroke) with lower extremity muscle weakness and 10 age-matched controls completed this prospective cohort study. Maximum voluntary contractions (MVCs) of the knee extensor muscles were assessed with a Biodex dynamometer and StO2 of the VL was measured using near-infrared spectroscopy. Results In the paretic leg of the stroke survivors little change in StO2 of the VL was observed during an MVC (ΔStO2 = -1.7 ± 1.8%) compared to the non-paretic (ΔStO2 = -5.1 ± 6.1%; p < 0.05) and control legs (ΔStO2 = -14.4 ± 8.8%; p < 0.05 vs. paretic and non-paretic leg). These differences remained when normalizing for strength differences between the legs. Compared to controls, both the paretic and non-paretic VL showed pronounced reductions in ΔStO2 during ramp and hold contractions equal to 20%, 40%, or 60% of the MVC (p < 0.05 vs. controls at all load levels). Conclusions These results indicate that oxygen desaturation in response to isometric muscle contractions is impaired in both the paretic and non-paretic leg muscle of stroke survivors compared to age-matched controls, and these differences are independent of differences in muscle strength.

Progressive submaximal effort hamstring muscle endurance is reduced after reconstruction of the anterior cruciate ligament

BackgroundEndurance capability in the muscles controlling the knee is poorly understood post anterior cruciate ligament (ACL) reconstruction, despite many sporting activities requiring notable muscle endurance. The hamstring muscles, when active, provide important anatomical support to protect the reconstructed graft. In the absence of good hamstring endurance, fatigue may predispose individuals to re-injury. ObjectiveTo assess whether ACL reconstruction (ACLR) with a hamstring graft leads to reduced hamstring endurance 9–13 months post-surgery. Study designA cross-sectional inter-limb comparison study was undertaken with participants 9–13 months after an ACLR with a hamstring graft, and a group of age, sex, and activity-matched controls. There were 22 participants in each group. MethodSubmaximal hamstring endurance was measured using a progressive fatigue test on an isokinetic dynamometer at a joint angular velocity of 120°/second. The dependant variable was the maximum number of repetitions performed. Statistical comparisons were made across injured, uninjured and control group limbs. ResultsThere was a significant (p < 0.05) deficit in hamstring endurance observed between the injured leg (mean: 111 repetitions, SD 49) and uninjured leg (mean: 136 repetitions, SD 67) of the ACL group, but not between the uninjured and control group legs (mean: 124 repetitions, SD 50). ConclusionThe 18% deficit in submaximal hamstring endurance across the ACL-reconstructed individual's limbs is indicative of a notable loss in muscle performance at 9–13 months post-surgery. These results provide initial evidence for supporting further research examining the inclusion of hamstring endurance training in ACL rehabilitation programmes post-surgery.

Chemical component of differences in the endosperm of Gleditsia species seeds revealed based on comparative metabolomics

To investigate the chemical composition and interfunctional differences among the endosperm of Gleditsia species seeds (EGS), this study was conducted to determine the metabolic profiles in three EGSs based on the metabolomics approach of UPLC–ESI–MS/MS. A total of 505 metabolites were identified, of which 156 metabolites of EGS were annotated as pharmaceutical ingredients for six human diseases. A total of 110, 146, and 104 metabolites showed different accumulation patterns in the three control groups, LEGS vs. MEGS, LEGS vs. SEGS, and MEGS vs. SEGS, respectively. The metabolic profiles of EGSs differed significantly, and KEGG annotation and enrichment analyses indicated aminoacyl-tRNA biosynthesis as the key metabolic pathway of EGSs. This study enriches the understanding of the chemical composition of EGSs and provides theoretical support for the development and application of EGSs.