Rapid Force Research Articles

A Comparison of Catch Phase Force-Time Characteristics During Clean Derivatives From the Knee.

Comfort, P, Williams, R, Suchomel, TJ, and Lake, JP. A comparison of catch phase force-time characteristics during clean derivatives from the knee. J Strength Cond Res 31(7): 1911-1918, 2017-The aim of this study was to compare load-absorption force-time characteristics of the clean from the knee (CK), power clean from the knee (PCK), and clean pull from the knee (CPK). Ten collegiate athletes (age 27.5 ± 4.2 years; height 180.4 ± 6.7 cm; mass 84.4 ± 7.8 kg) performed 3 repetitions each of the CK, PCK, and CPK with 90% of their 1 repetition maximum power clean on a force platform. The CK load-absorption duration (0.95 ± 0.35 seconds) was significantly longer compared with the CPK (0.44 ± 0.15 seconds; p < 0.001, d = 2.53), but not compared with the PCK (0.56 ± 0.11 seconds; p > 0.05, d = 1.08), with no differences between PCK and CPK (p > 0.05, d = 0.91). The CPK demonstrated the greatest mean force (2,039 ± 394 N), which was significantly greater than the PCK (1,771 ± 325 N; p = 0.012, d = 0.83), but not significantly different to the CK (1,830 ± 331 N; p > 0.05, d = 0.60); CK and PCK were not different (p > 0.05, d = 0.18). Significantly more load-absorption work was performed during the CK (655 ± 276 J) compared with the PCK (288 ± 109 J; d = 1.75, p < 0.001), but not compared with the CPK (518 ± 132 J; d = 0.80, p > 0.05). Additionally, more load-absorption work was performed during the CPK compared with the PCK (d = 1.90, p = 0.032). Inclusion of the catch phase during the CK does not provide any additional stimulus in terms of mean force or work during the load-absorption phase compared with the CPK, although the CPK may be beneficial in training rapid force absorption because of high force and a short duration.

Delayed Effect of Blood Flow-restricted Resistance Training on Rapid Force Capacity.

The aim of the present study was to investigate the effect and time course of high-frequent low-load blood flow-restricted (BFR) resistance training on rapid force capacity (i.e., rate of torque development [RTD]). Ten male subjects (22.8 ± 2.3 yr) performed four sets of knee extensor exercise (20% one-repetition maximum) to concentric failure during concurrent BFR of the thigh (100 mm Hg), and eight work-matched controls (21.9 ± 3.0 yr) trained without BFR (CON). Twenty-three training sessions were performed within 19 d. Maximal slow and fast knee joint velocity muscle strength and rapid force capacity (e.g., RTD) and evoked twitch contractile parameters were assessed before (Pre) and 5 and 12 d after (Post5 and Post12) training. Muscle biopsies were obtained Pre, after 8 d (Mid8), and 3 and 10 d after (Post3 and Post10) training to examine changes in myofiber area and expression of myocellular proteins known to be modified by cellular stress (CaMKII, annexin A6, SNO-CYS). RTD remained unchanged after BFR training at Post5, while increasing 15%-20% Post12 (P < 0.01). Evoked muscle twitch parameters showed a general decline Post5 (P < 0.01) while returning to baseline levels at Post12. All contractile parameters essentially remained unchanged in CON. Elevated CaMKII was observed with BFR training at Post3 (57%) and Post10 (71%) (P < 0.05), whereas SNO-CYS increased in CON at Mid8 (P < 0.05). This study is the first to show that low-load resistance exercise performed with BFR leads to marked increases in rapid force capacity (RTD). However, a general delayed adaptive response was observed for voluntary contractile parameters (including RTD) in parallel with a decline and subsequent recovery in evoked contractile properties, suggesting the delayed gain in rapid force capacity mainly have a peripheral origin.

Effect of calf-raise training on rapid force production and balance ability in elderly men.

This study examined whether home-based, high-speed calf-raise training changes the rate of torque development (RTD) during plantar flexion contractions and balance performance in elderly men. Thirty-four healthy elderly men (73 ± 5 yr) were randomly assigned to a training or control group (n = 17 in each group). The subjects in the training group completed 8 wk (3 times/wk) of home-based bilateral calf-raise training using body mass. Before and after the intervention, RTD during plantar flexion contractions and center-of-pressure (COP) displacement during single-leg standing were measured. Surface electromyographic amplitude of the triceps surae and tibialis anterior during the strength and single-leg standing was measured. Clinical magnitude-based inferences were used to interpret the training effect, with the smallest worthwhile effect assumed to be 0.2 of the baseline SD. The peak RTD increased 21% (90% confidence limits, ±19%) relative to the control group, which was accompanied by corresponding changes of the medial gastrocnemius (MG) and soleus (SOL) activations. The effect on COP displacement was possibly trivial (0%, ±13%), whereas substantial reduction in the MG (-19%, ±15%) and SOL (-25%, ±13%) activations during standing was observed. Our findings indicate that calf-raise training at home, performed without special equipment or venue, induces a substantial increase in the plantar flexors' rapid force-generating capability and triceps surae activations. Although the training effect on standing balance performance was not substantial, observed changes in the triceps surae activations during standing are expected to contribute to future balance performance improvement.NEW & NOTEWORTHY Calf-raise training with the intent to move rapidly, without special equipment or venue, induces an improvement of explosive plantar flexion force, which is attributable to neuromuscular rather than musculotendinous adaptations. Although the training effect on balance performance was trivial, we found a sign of improvement (i.e., neuromuscular adaptations during standing). In conclusion, functional neuromuscular capacity can be enhanced by home-based calf-raise exercise in elderly men, which may protect against mobility loss with aging.

Strength Training In Patients With Schizophrenia

Patients with schizophrenia are inactive, have impaired physical function and slowed performance in motor tasks. As a countermeasure, maximal strength training (MST) with high load and few repetitions improves muscle force generating capacity and physical function during daily activities. PURPOSE: Investigate the effect and feasibility of MST as a part of standard clinical treatment of patients with schizophrenia. METHODS: 11 male and 6 female outpatients (37±10(SD) yrs, ICD-10 schizophrenia, schizotypal or delusional disorders (F20-F29)) were randomized to either a training group (TG), performing leg press MST (4 repetitions, 4 sets, at ~90% of one repetition maximum (1RM)) twice a week for 12 weeks at the hospital exercise training clinic, or a control group (CG) following traditional guidelines for physical activity. RESULTS: 5/9 patients in the TG completed >85% of the training and were included in the statistical analysis. After MST, 1RM and muscle rapid force development (work/time with a load ~70% of 1RM) increased 43% (233±35 to 333±50 kg, p<0.05) and 36% (408±108 to 555±137 Nm·s-1, p<0.05), respectively. These improvements in muscle force generating capacity were ~twofold larger (p<0.05) compared to the CG which had improvements of 23% in 1RM (188±66 kg to 232±89 kg, p<0.05) and 16% in rapid force development (391±223 to 454±227 Nm·s-1, p<0.05). CONCLUSIONS: MST yielded larger improvements in functionally relevant muscle force generating capacity compared with conventional treatment, and suggest that MST should be implemented as a part of standard clinical practice for optimal exercise rehabilitation benefits. Supported by grants from the Norwegian ExtraFoundation for Health and Rehabilitation, The Liaison Committee between the Central Norway Regional Health Authority and the Norwegian University of Science and Technology, and The Norwegian Directorate of Health.

Quadriceps Function is Associated with Running Kinetics Post Anterior Cruciate Ligament Reconstruction

PURPOSE: Individuals with anterior cruciate ligament reconstruction (ACLR) are at greater risk for knee osteoarthritis (KOA), partially due to chronic quadriceps dysfunction. Impaired quadriceps function contributes to higher loading rates during gait, and may exacerbate cartilage breakdown. The purpose of this study was to examine the association between indices of quadriceps function and ground reaction forces (GRF) characteristics linked to KOA development during running in individuals with ACLR. METHODS: Quadriceps function and running biomechanics were assessed in 20 individuals (5 M, 15 F) with unilateral ACLR (age=22.3±3.3 years, height=1.73±0.09m; mass=71.8±15.3kg). Indices of quadriceps function included isometric peak torque (PT) and rate of torque development (RTD), and isokinetic peak torque measured at 180°/s and 240°/s. Kinetic data included peak vertical impact force (PIF), average vertical loading rate (ALR), and instantaneous vertical loading rate (ILR) acquired from the ACLR limb while running at a self-selected pace. Partial correlations were used to assess the relationship between quadriceps function and running kinetics after accounting for self-selected running speed. RESULTS: Quadriceps RTD was negatively correlated with PIF (r=-0.40, p=0.04) and ALR (r=-0.48, p=0.03). A trend was observed between quadriceps RTD and ILR (r=-0.36, p=0.07). Neither isometric PT nor isokinetic PT at 180°/second or 240°/second were associated with any running biomechanics variable. CONCLUSIONS: Slower quadriceps RTD were associated with larger PIF and ALR during running. The ability of the quadriceps to generate rapid force prior to heel contact is necessary for GRF attenuation during gait. Since larger PIF and ALR have been linked to cartilage degradation in individuals with knee pathologies, the current results emphasize the role of quadriceps dysfunction in KOA development following ACLR. Improving quadriceps RTD may reduce loading characteristics that negatively influence cartilage health.

The Influence of Alkalosis on Muscle Force and Power in the Triceps Surae and Brachii

The effect of metabolic alkalosis on fibre-specific maximal force production and rates of force development (RFD) has been previously investigated in animal models, with evidence suggesting an improved capacity to rapidly develop force in fast- compared to slow-twitch muscle. To date, the fibre-type dependent findings related to pH and rapid force generation have not been replicated in the exercising human. PURPOSE: To model in vivo the fatigue profile of voluntary and involuntary maximal force and rate of force development in the triceps’ surae and brachii after sodium bicarbonate (NaHCO3) ingestion. METHODS: In a double-blind, 3-way repeated measures design participants (n=10) ingested either 0.3 g·kg-1 NaHCO3 (ALK) or equivalent calcium carbonate (PLA) prior to 2-min of continuous (1Hz) supramaximal stimulation (300ms at 40Hz) of the triceps’ surae or brachii, with maximal voluntary efforts (MVT) coupled with direct muscle stimulation also measured at baseline, 1-min and 2-min. RESULTS: Metabolic alkalosis was achieved in both ALK trials but was not different between muscle groups. Regardless of condition, involuntary torque declined nearly 60% in the triceps brachii (p < 0.001) and ~ 30% in the triceps surae (p < 0.001). In all trials there was a significant decline in normalised involuntary RFD (p < 0.05). MVT declined nearly 28% but was not different between conditions (p < 0.01), and although declining nearly 21% in voluntary RFD (p < 0.05) there was no difference between PLA and ALK in either muscle group (p = 0.93). CONCLUSION: NaHCO3 exhibited no effect on the fatigue observed between representative fibre-type muscle groups on maximal voluntary and involuntary torque or rates of torque development during and after 2-min of tetanic stimulation.

Activation Of Knee Extensor Muscles During Rapid Force Development In Men And Women

Adequacy of activation during rapid voluntary contractions is limited in young and old adults and can be shown by comparing the voluntary rate of force development (RFD) and electrically evoked RFD. Nonetheless, it is unknown whether the activation of rapid voluntary contractions differs between young men and women. PURPOSE: The purpose of this study was to compare the maximal RFD of young men and women during electrically evoked isometric contractions and rapid voluntary contractions with the knee extensor muscles across a range of torques. METHODS: Eight young adults (18-26 years; 4 men, 4 women) consented to sets of single and double pulse (10 ms interval) stimulations of the femoral nerve at maximal intensities followed by rapid voluntary isometric knee extensions at target torques matched to the electrically evoked torques. For the rapid voluntary isometric contractions, subjects were instructed to kick as fast as possible rather than as accurately as possible. Voluntary target torques ranged between 10-40% of maximal voluntary contraction (MVC) and were set to match the electrically evoked torques. Maximal RFD for each trial (voluntary and electrically evoked) was calculated as the peak values of the first derivative of the torque signal. RESULTS: Torques (between 10-40% MVC) were similar for the electrically evoked and voluntary contractions (F1,6=0.54, P=0.49) for both the men (25.0 ± 0.6 %MVC vs. 26.4 ± 0.7 %MVC) and women (26.0 ± 2.0 %MVC vs. 26.5 ± 2.7 %MVC). Although torques were similar, RFD from electrically evoked contractions in men (514.8 ± 30.4 % MVC.s−1) and women (475.1 ± 78.0 %MVC.s−1) was 36% greater than the voluntary contractions (men; 330.2 ± 18.8 vs. women; 305.9 ± 21.2 %MVC.s−1; F1.6 = 23.1, P = 0.003). The linear association between relative torque (%MVC) and electrically evoked RFD (R2 = 0.85, b = 0.92, P<0.001) was larger and steeper than the association with voluntary RFD (R2 = 0.72, b = 0.85, P<0.001) indicating that the difference in RFD between the electrically evoked and voluntary contractions increased at the higher forces. CONCLUSIONS: Young men and women had marked reductions in the ability to voluntarily generate isometric knee extension torque rapidly compared with electrically evoked contractions that were independent of the central nervous system. Supported by NIA R01 AG048262 to SKH

The Use of Maximum Strength Measures as a Predictor of Rapid Force Production and Strength Endurance

The ability to produce force rapidly and to maintain it is essential to sports performance. Although rapid force production and endurance are indispensable characteristics of optimal health and performance, assessing these qualities of strength is difficult because of clinician time constraints. The purpose of this study was to determine if peak force is a predictor of rate of force production and strength endurance. The results indicated peak force is a predictor of rate of force development, but not strength endurance. Clinicians should assess both maximum strength and endurance to gain a more complete picture of lower extremity strength deficits.

Kim jestem? Tożsamość jako zadanie w czasach gwałtownej zmiany społecznej

&lt;p&gt;Pytanie „kim jestem?” należy do najczęściej formułowanych pytań o charakterze&lt;br /&gt;egzystencjalnym. Nasuwa się coraz bardziej natarczywie w okresie gwałtownej zmiany społecznej. W ostatnich dziesięcioleciach zmiany w różnych dziedzinach życia przybrały wręcz charakter rewolucyjny. Do szczególnie widocznych należy globalizacja. Gwałtowna zmiana społeczna zmusza człowieka do ciągłego kształtowania własnego „ja”. Nie jest to zadanie łatwe, toteż wiele osób odczuwa dylematy tożsamościowe. Pogłębiają je różne, często niespójne, a nawet przeciwstawne standardy i oczekiwania instytucji i grup społecznych, w których funkcjonowaniu uczestniczą. Charakterystyczne dla nowoczesności i czasów ponowoczesnych wyzwolenie indywidualizmu zwiększa poczucie podmiotowości jednostek, a jednocześnie naraża je na stany niepewności i kryzysów. Anthony Giddens sądzi, że są one wyrażane przez takie opozycyjne wymiary współczesnej rzeczywistości, jak: unifikacja vs fragmentaryzacja, bezsilność vs kontrola, autorytet vs niepewność, doświadczenie osobiste vs doświadczenie urynkowione. Dlatego konstruowanie tożsamości staje się ważnym zadaniem jednostki i wymaga pedagogicznego wspomagania.&lt;/p&gt;

Doublet stimulation increases Ca2+ binding to troponin C to ensure rapid force development in skeletal muscle.

Fast-twitch skeletal muscle fibers are often exposed to motor neuron double discharges (≥200 Hz), which markedly increase both the rate of contraction and the magnitude of the resulting force responses. However, the mechanism responsible for these effects is poorly understood, likely because of technical limitations in previous studies. In this study, we measured cytosolic Ca2+ during doublet activation using the low-affinity indicator Mag-Fluo-4 at high temporal resolution and modeled the effects of doublet stimulation on sarcoplasmic reticulum (SR) Ca2+ release, binding of Ca2+ to cytosolic buffers, and force enhancement in fast-twitch fibers. Single isolated fibers respond to doublet pulses with two clear Ca2+ spikes, at doublet frequencies up to 1 KHz. A 200-Hz doublet at the start of a tetanic stimulation train (70 Hz) decreases the drop in free Ca2+ between the first three Ca2+ spikes of the transient, maintaining a higher overall free Ca2+ level during first 20-30 ms of the response. Doublet stimulation also increased the rate of force development in isolated fast-twitch muscles. We also modeled SR Ca2+ release rates during doublet stimulation and showed that Ca2+-dependent inactivation of ryanodine receptor activity is rapid, occurring ≤1ms after initial release. Furthermore, we modeled Ca2+ binding to the main intracellular Ca2+ buffers of troponin C (TnC), parvalbumin, and the SR Ca2+ pump during Ca2+ release and found that the main effect of the second response in the doublet is to more rapidly increase the occupation of the second Ca2+-binding site on TnC (TnC2), resulting in earlier activation of force. We conclude that doublet stimulation maintains high cytosolic Ca2+ levels for longer in the early phase of the Ca2+ response, resulting in faster saturation of TnC2 with Ca2+, faster initiation of cross-bridge cycling, and more rapid force development.

Piezoelectric BaTiO3/alginate spherical composite beads for energy harvesting and self-powered wearable flexion sensor

A simple, large-scale fabrication of spherical composite (BaTiO3 nanoparticle/Ca-alginate) beads was developed using the ionotropic gelation (IG) method. The energy harvesting performance of a composite bead-based nanogenerator (CBNG) was studied using various device areas (3 cm2, 11.25 cm2), different mechanical pressures (170 Pa–1.77 kPa) and bending angles, rapid hand force, capacitive loadings and electrical poling. High output (82 V, 227 μA) was generated with a simple low mechanical pressure of 1.70 kPa, which is enough to drive low power electronic devices. We demonstrate that the strip-based CBNG (S-CBNG) device can act as a self-powered wearable flexion sensor for decoding right arm finger flexion/extension movements in a periodic manner without any external battery and additional sensory circuit. It is highly desirable to classify and detect finger movements for in-patient rehabilitation, finger Braille typing and directional bending of the human body. In this work, the average peak power of the flexible S-CBNG varied from 1.23 pW to 0.4 nW for flexion/extension movements of the right arm fingers. The reliability of the sensor depends on the generated electric potential, the location of the device on the forearm, the strain applied by the fingers, and the flexibility of the S-CBNG device. The proposed work is non-invasive, robust, cost-effective and it does not require external power for wearable and smart devices.

A new era for labour migration in the GCC?

The six Gulf Cooperation Council (GCC) countries, Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates (UAE), are among the most dependent on foreign workers to fill private-sector jobs. A combination of lower oil prices and rapid native labour force growth has given new impetus to efforts to diversify GCC economies away from oil and encourage natives to fill private sector jobs. This article summarizes the current status of foreigners and foreign workers in GCC countries and considers several scenarios, including maintaining the status quo, improving protections for foreign workers in countries of destination (CODs) and countries of origin (COOs), and changing the current migration system to employ fewer and more skilled workers.

A New and Improved View of Force Production

A central question in muscle contraction is “How is the energy release in ATP hydrolysis converted into mechanical force and work?” With the elucidation of the actomyosin ATPase reaction in the 1970s (1,2) and the fact that a large amount of free energy is produced during Pi release from an actomyosin-ADP-Pi species (3), the Pi release step from actomyosin-ADP-Pi must be associated with the generation of force and shortening. It was also known that increases in the [Pi] concentration in isometrically contracting skinned muscle fibers reduced isometric force (4).

Experimental Verification for Cable Force Estimation Using Handheld Shooting of Smartphones

Currently, due to the rapid development and popularization of smartphones, the usage of ubiquitous smartphones has attracted growing interest in the field of structural health monitoring (SHM). The portable and rapid cable force measurement for cable-supported structures, such as a cable-stayed bridge and a suspension bridge, has an important and practical significance in the evaluation of initial damage and the recovery of transportation networks. The extraction of dynamic characteristics (natural frequencies) of cable is considered as an essential issue in the cable force estimation. Therefore, in this study, a vision-based approach is proposed for identifying the natural frequencies of cable using handheld shooting of smartphone camera. The boundary of cable is selected as a target to be tracked in the region of interest (ROI) of video image sequence captured by smartphone camera, and the dynamic characteristics of cable are identified according to its dynamic displacement responses in frequency domain. The moving average is adopted to eliminate the noise associated with the shaking of smartphone camera during measurement. A laboratory scale cable model test and a pedestrian cable-stayed bridge test are carried out to evaluate the proposed approach. The results demonstrate the feasibility of using smartphone camera for cable force estimation.

On Land Warfare and Motor Vehicles: From Biblical Times, Through Tomorrow

For the past three millennia or so, land warfare has been based upon three types of fighting forces, infantry, rapid deploy forces (such as horse-based cavalry) and armoured vehicular forces. This article discusses aspects of the latter. We examine a bit of the history and attempt some extrapolation to conceive where this force may be headed. In that sense, the article is also speculative. Basically, where are armoured fighting vehicles going (pardon the pun)? At present, it appears that they may have reached a technological impasse, as motor technology has not advanced significantly for the past century-fuel use today is remarkably similar to that of the original Ford Model T. We begin the discussion with historical aspects emphasising the difficulty of powering mechanisms, continue with electronic vulnerabilities that are not well-known and then finish with powering issue for the future. Tanks historical success has been firstly based upon their power-source, with vulnerabilities coming into play primarily when the issue is tank-to-tank; this may change. Today’s vulnerabilities may be more profound than is generally perceived.

The time has come to incorporate a greater focus on rate of force development training in the sports injury rehabilitation process.

V.

Effects of oncoming target velocities on rapid force production and accuracy of force production intensity and timing

ABSTRACTThe present study aimed to clarify the effects of oncoming target velocities on the ability of rapid force production and accuracy and variability of simultaneous control of both force production intensity and timing. Twenty male participants (age: 21.0 ± 1.4 years) performed rapid gripping with a handgrip dynamometer to coincide with the arrival of an oncoming target by using a horizontal electronic trackway. The oncoming target velocities were 4, 8, and 12 m · s−1, which were randomly produced. The grip force required was 30% of the maximal voluntary contraction. Although the peak force (Pf) and rate of force development (RFD) increased with increasing target velocity, the value of the RFD to Pf ratio was constant across the 3 target velocities. The accuracy of both force production intensity and timing decreased at higher target velocities. Moreover, the intrapersonal variability in temporal parameters was lower in the fast target velocity condition, but constant variability in 3 target velocities was observed in force intensity parameters. These results suggest that oncoming target velocity does not intrinsically affect the ability for rapid force production. However, the oncoming target velocity affects accuracy and variability of force production intensity and timing during rapid force production.

Age-related changes in force control under different task contexts.

We investigated age-related differences in motor behavior under different task contexts of isometric force control. The tasks involved rapid force production and force maintenance, either separately or in combination. For the combined context, we used Fitts-like tasks, in which we scaled either the force level (D manipulation, i.e., manipulation of the amplitude of the force to be produced) or the tolerance range (W manipulation, i.e., manipulation of the target width in which force is allowed to fluctuate). We studied two age groups and analyzed mainly variables that quantify behavioral variability (SD), information processing (signal-to-noise ratio and efficiency functions), and age-related slowing (slowing ratio). For rapid force control, age-related differences were more pronounced when preplanned processes were primarily involved, that is, in the rapid force production and Fitts-D manipulation tasks. Further, older adults were comparable to the younger adults in terms of end-point variability at the cost of being slower and more variable in timing. For force maintenance control, requiring mainly online control, age-related differences were the most visible in the stabilized phase of Fitts-D manipulation, followed by Fitts-W manipulation for SD, and then the force maintenance task. In sum, our findings reveal an age-related reorganization of how preplanned and online control processes are combined under different force control contexts. Indeed, both behavioral slowing and the overreliance on online control processes seem to be dependent on the task. In this respect, beyond the study of force control, we show the interest of investigating age effects using functionally different tasks.

Recovery of lower extremity muscle strength and functional performance in middle-aged patients undergoing arthroscopic partial meniscectomy.

To investigate lower extremity muscle strength and functional performance before and after arthroscopic partial meniscectomy in middle-aged patients with degenerative meniscal tears. We hypothesized that patients would experience deficiencies in the affected leg at 3months post-surgery, and that this deficiency would be normalized at 12months following surgery. Twenty-three patients (46±6.5years) meniscectomized in 2012 and 2013 were examined for knee extension, knee flexion, and hip abduction maximal isometric muscle strength (iMVC), rate of force development (RFD200), and knee function (single-leg hop for distance and single-leg knee bends in 30s.) before surgery, 3 and 12months after surgery. Functional performance, knee extension iMVC and RFD200 were impaired in the affected leg compared to the contralateral leg (p<0.05) prior to surgery. A significant (Knee extension RFD200, p=0.033) or borderline significant improvement was observed in the affected leg compared to the contralateral leg from before to 12months after surgery in most variables (leg×time interaction, n.s.). Middle-aged patients undergoing surgery for degenerative medial meniscal tears show significant reductions in muscle strength, rapid force production, and functional performance in the leg undergoing surgery compared to the contralateral leg prior to surgery. These deficits in muscle strength and knee function were still present at 3months post-surgery but were no longer observed at 12months following surgery. III.

Tunable assembly of hydrophobic protein nanoparticle at fluid interfaces with tannic acid

Interparticle forces that govern the assembly of particles adsorbed at fluid interfaces determine the rheology and microstructure of particle laden interface. In this study, natural small molecule, tannic acid (TA), was used to modify particle-particle interactions and assembly behaviors of food grade hydrophobic protein particle (zein nanoparticle) at air-water interface. For bare zein particle (ZP), the rapid adsorption and high interparticle forces led to the low coverage and formation of large ZP aggregates at the interface. The hydrogen-bonding of TA weakened the particle hydrophobicity and thus interparticle forces at fluid interfaces. Therefore, the adsorption process and assembly rate of ZTP at the interface obviously reduced, which also provided enough time for ZTP to rearrange into orderly interfacial networks. Furthermore, the Lissajous plots of surface pressure versus deformation are used to understand the surface rheological response to large mechanical deformation in terms of interfacial microstructure. The rheological response of interface stabilized by ZTP showed strain hardening during extension and strain softening during compression. These findings indicate that the interfacial rheology and microstructure of zein particle-laden interface can be tuned by changing the TA content.