Changes In Joint Stiffness Research Articles

Variation in the nonlinear stiffness of bolted joints due to tangential hysteresis behavior

Obtaining the stiffness variation characteristics of a bolted joint during service is essential for predicting the response of an entire structure. In this study, we propose a relationship between the macro deviation, microtopography of the bearing surface, and hysteretic characteristics of a bolted joint. We first analyze the stiffness variation caused by the hysteretic characteristics during the tightening and service processes. Next, we investigate the influence of non-parallel bearing surfaces and displacement loads on pressure distribution and stiffness, both at macro and micro scales, using Finite Element Modeling (FEM) and experiments. Finally, we compare data from a hysteresis behavior test of a single-bolt lap beam with the FEM simulation results. The comparison demonstrates that macro deviations in the bearing surface alter the preload after assembly, while the bearing surface experiences dynamic changes in pressure due to microtopography and cyclic displacement loads. Consequently, this leads to irregular dynamic changes in joint stiffness during the service process, significantly affecting the dynamic/static response of the bolted assembly structure.

Effects of muscular endurance and tendon extensibility on endurance of joint stiffness

ABSTRACT In some sporting events (e.g., long-distance running), the ability to maintain joint stiffness is considered an essential physical ability. However, the determinants of joint stiffness endurance remain unclear. This study aimed to examine the effects of muscular endurance and tendon extensibility on joint stiffness endurance. Thirteen males performed the fatigue task (5 sets of 50 hopping). Ankle joint stiffness during drop jump was measured before and after fatigue task. The maximum number of repetitions at 30% of one repetition maximum for plantar flexion was measured as muscular endurance. Maximal elongation of the Achilles tendon was measured during ramp (with a low strain rate of tendon) and ballistic (with a high strain rate of tendon) contractions as tendon extensibility. Joint stiffness significantly decreased by 7.5% after the fatigue task (p = 0.033). The maximum number of repetitions at 30% of 1RM (79.6 ± 48.7 repetitions) was not significantly correlated with the relative change in joint stiffness (r = 0.283, p = 0.348). The maximal elongation of the Achilles tendon measured during ramp and ballistic contractions were not significantly associated with the relative change in joint stiffness (r = 0.326, p = 0.277 for ramp contraction; r = 0.438, p = 0.135 for ballistic contraction). These results suggest that muscular endurance and tendon extensibility were unrelated to joint stiffness endurance.

Musculoskeletal Model Capable of Reproducing Lumbar Extension Motion Strategy Based on the Equilibrium Point Hypothesis

We considered the change in joint stiffness as a motion strategy in human lumbar extension movement. We developed a musculoskeletal model that can reproduce this motion strategy and attempted to clarify the individual characteristics and differences in motion strategy. This model reproduces changes in lumbar joint stiffness during movement by appropriately adjusting parameters such that they represent the motion strategy. Using this model, we identified parameters in lumbar extension exercises for six participants with differences in lumbar joint stiffness and examined changes in lumbar joint stiffness and motion strategies. The results showed that participants with similar changes in joint stiffness had commonalities in their motion strategies.

EFFECTIVENESS OF PLATELET RICH PLASMA IN PAIN MANAGEMENT OF OSTEOARTHRITIS KNEE: RANDOMIZED COMPARATIVE STUDY

Background: Intra-articular injections of platelet-rich plasma to treat symptoms of knee osteoarthritis have been successfully used in young patients. However, in most of these studies the control and test knees were present in different patients thus incorporating a large amount of bias in the results. Therefore, the present study was designed in which patients with bilateral osteoarthritis knee were included and platelet-rich plasma was administered in one knee and normal saline in another knee of same patient. 20 patients aged 30---65 years with bilateral osteoar Methods: thritis knees (ASA class I and II) of either gender were included in the study. Patients were randomized to receive platelet-rich plasma and normal saline in one of the two knees. The primary outcome was VAS and WOMAC score at 6 months after procedure. The secondary outcome included changes in joint stiffness, physical function, any adverse effects noted during the course of study.p The baseline VAS score in platelet-rich plasma knee was 8.7±0.1which i Results: mproved significantly to 6.4±0.11 (p < 0.001) at 6 months as compared to normal saline knee (p = 0.017). The WOMAC pain score also improved from baseline (17.7±0.15) to over 6 month 14.0±0.11 ( < 0.001) in platelet-rich plasma knee while in the normal saline knee, no significant change occurred from baseline to six months (14.4±0.1 to 14.4±0.1). There was also significant decrease in stiffness and improvement of physical activity in the platelet-rich plasma knee as compared to normal saline knee. The present study showed significant decrease in pain and stiffness and improveme Conclusion: nt of physical functions of knee joint with intra-articular platelet-rich plasma injection as compared to normal saline.

Flexible joint parameters identification method based on improved tracking differentiator and adaptive differential evolution.

The assembly error of flexible joints and the change in joint stiffness during movement make the actual value of joint parameters inconsistent with the given value, which affects the joint control accuracy. In order to suppress the influence of parameters error, a parameters identification method for flexible joint combined offline identification and online compensation is proposed. First, the offline identification model of inertia, mass, and damping and the online identification model of joint stiffness are established, respectively. Then, a hybrid tracking differentiator based on an improved Sigmoid function is designed to track the differential signals of joint motion parameters, and the Lyapunov function is designed to prove its convergence. The adaptive differential evolution is used as the identification algorithm, and the improved adaptive crossover, mutation factor, and Metropolis acceptance criterion are designed to improve the convergence speed. Finally, a feedforward control structure based on identification is designed to compensate for the model deviation. Simulation and experimental results show that the improved differentiator can effectively improve the tracking speed and derivation accuracy of the signals. Compared with other algorithms, the proposed identification method has a faster convergence speed and higher identification accuracy, and feedforward compensation control can effectively correct model parameters and improve control accuracy.

Interaction Between Surface Stiffness and Lower Limb Stiffness and its Effects on the Performance and Injury

The purpose of this review study is to review the studies that have assessed the interaction between surface stiffness and lower limb stiffness. There is a general hypothesis that with the increase of surface stiffness, the lower limb stiffness decreases or vice versa. These interactions take place with the aim of maintaining the dynamics of the center of mass and reducing the energy consumption during movement. One of the mechanisms for these interactions is the change in joint stiffness and leg geometry. Some studies suggested that the stretch reflex has no role in changing the lower limb stiffness. Although interactions between lower limb stiffness and surface stiffness has been recognized, there is little evidence about neuromuscular mechanism of these interactions. More studies is needed in this filed.

Safety analysis of adapted battery-powered ride-on toy car for children with disabilities using a modified test dummy with varying joint stiffness

ABSTRACT Adaptive ride-on toy programs have increased in popularity in recent years and provide novel rehabilitation tools as developmental aids for children with disabilities. While the adaptations made to these toys are intended to provide a safer experience for children with disabilities, safety concerns still exist. Within this context, the purpose of this study was to use a model with varying joint stiffness as a first-order approximation of a child with disabilities and to investigate whether modifications to ride-on toys are sufficient to prevent common injuries. Because the population of children with disabilities who are receiving adaptive ride-on toys have a wide range of musculoskeletal disorders, those with both decreased and increased muscle stiffness were considered in this safety study. A 5-point harness reduced movement regardless of change in joint stiffness and therefore, results from this study indicate that the use of these harnesses is effective regardless of joint stiffness. Furthermore, as excursion-related injuries are considered more critical to the user than injuries relating to kinetic variables and no known injury thresholds were exceeded, the addition of a belt is considered a necessary trade-off with little-to-no added risk.

Abstract P4-10-08: Characterizing cannabidiol use in a breast cancer population

Abstract Background: Cannabidiol (CBD) is an exogenous cannabinoid found in the plant Cannabis sativa and is thought to have broad therapeutic value. It works via different receptors than Δ9-tetrahydrocannabinol (THC) and, as such, lacks the psychoactive effects associated with cannabis intoxication. While CBD is becoming more commonly used in preclinical and clinical research studies in patients with breast cancer, few studies have explored these patients’ attitudes toward CBD use outside of the research setting. This survey study aimed to characterize the rate of and benefits from CBD use in patients with breast cancer, while also identifying barriers and limitations to its use. Methods: Individuals being seen at the University of Michigan Rogel Cancer Center for a diagnosis of breast cancer were given a flyer inviting them to participate in an online survey characterizing current and former CBD use. The survey questions were adapted from a previously published questionnaire conducted in patients with chronic pain conditions. All data was collected anonymously. The survey was accessed between September 2020 and March 2021. Survey responses were excluded if a patient had no history of breast cancer diagnosis or if a majority of the survey was incomplete. Results: A total of 114 survey responses meeting criteria for inclusion were collected. Most respondents were female (n = 113), White (n = 101, 88.6%) and the average age was 55.7 years (range 30-96 years). 51 respondents (44.8%) reported an annual household income of over $100,000. 83 respondents (72.8%) were currently receiving treatment for breast cancer. 44 respondents (38.6%) had ever used CBD to manage pain or other symptoms, and 26 of the 44 (59%) reported current use of CBD. Of the 18 patients who no longer used CBD, the most common reasons reported for stopping its use were lack of efficacy (35%) and expense (25%). Negative side effects were reported by 5%. Respondents continuing to use CBD most often reported using it to manage pain (19%), anxiety (18%), insomnia (15%), and joint stiffness (15%). It was less commonly used to manage depression (8%), fatigue (7%), and memory (4%). On a continuous scale of 1 (very much worse) to 7 (very much improved), respondents reported a median change in pain with CBD use of 6 (range 4 - 7, n=17), a median change in anxiety of 5.6 (range 4.1 - 7, n=16), a median change in insomnia of 6.3 (range 4 - 7, n=13) and a median change in joint stiffness of 5.6 (range 3 - 7, n=13). 61 respondents (53.5%) reported never using CBD to manage pain or other symptoms; the most common reasons were lack of symptoms (12%) or well-controlled symptoms (13%), lack of research on CBD use (15%), lack of regulation and fear of production contamination (14%), worry about side effects associated with CBD use (14%), and interactions with other medications (12%). Few respondents were concerned about expense (2%), CBD’s legal status (4%), or family and friends’ opinions (3%). Conclusions: While less than half of patients in this survey study reported previous or current CBD use, breast cancer patients who are using CBD seem to derive symptomatic benefit from reduction in pain and improvement in insomnia. Barriers to use of CBD include expense, concern about lack of CBD research, and concern about its interaction with other medications. While negative side effects were rarely reported in former CBD users, this remained a top concern for patients who had never used CBD. As CBD becomes increasingly used in the clinical setting, it will be important for physicians to help navigate these concerns related to its use. Additional research is needed to determine which patient-reported symptoms are most likely to be impacted by CBD use, as use in this patient population could lead to improvement in quality of life. Citation Format: Nicole Grogan, Norah Lynn Henry. Characterizing cannabidiol use in a breast cancer population [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-10-08.

Analysis of Changes in Parameters of Free Vibration of Single and Multi-span Girders with Semi-rigid Joints

This study presents the analysis carried out for changes in parameters of free vibrations of single-span corrugated web girders with a semi-rigid joint at midspan and multi-span girders with spans connected by semi-rigid joints. Based on the experimental tests and the theoretical analysis, the behavior of six simply supported girders with the semi-rigid joint at midspan was analyzed. They were straight and double-slope girders with a span of 6.02 m, made of corrugated web sections WTA 500/300x15 with different types of semi-rigid end plate joints. It was demonstrated that the variable rotational stiffness Sj of the joint affected the equivalent concentrated mass of the girder mz, the frequency of damped free vibrations α, damping ρ, and the frequency of free vibrations ω. The theoretical analysis was conducted for a change in the equivalent concentrated mass of the single-span girders fixed at both ends and of the multi-span girders. It was described how the change in the support stiffness in the single-span girders fixed at both ends and the change in joint stiffness of spans affected the equivalent concentrated mass mz as a function of non-dimensional stiffness k. The equivalent concentrated mass mz of the girder was found to affect the values of maximum vibrations in the structure. A continuous change in the rotational stiffness of joints was taken into account from the pinned to the rigid joint.

Mapping the relationships between joint stiffness, modeled muscle stiffness, and shear wave velocity.

Joint stiffness is often measured to make inferences about the stiffness of muscle groups, but little can be gleaned about individual muscles. Decomposing the muscular origins of joint stiffness may inform treatment targets for conditions like spasticity. To complement joint stiffness, shear wave ultrasound elastography has been used to estimate the material properties of individual muscles. If shear wave measures are to be used to assess the muscular origins of joint stiffness, then changes in shear wave velocity should strongly relate to changes in joint stiffness. Here, we estimated the relationships between shear wave velocity in the primary plantar flexors [soleus (SOL) and medial gastrocnemius (MG)] and ankle joint stiffness. Participants performed isometric plantar flexion tasks at a range of activations (0-40%), while joint stiffness and muscle shear wave velocities were obtained. We observed a strong, linear relationship between plantar flexor shear wave velocities and joint stiffness. Remarkably, the parameter estimates of this stiffness-shear wave relationship strongly agreed with theoretical and literature-based estimates [SOL:MG parameter ratios = 2.83 (observed) vs. 2.85 (expected from theoretical stiffness ratio)]. Finally, a musculoskeletal model of the plantar flexors was able to accurately reproduce joint stiffness estimates, and shear wave velocities could explain 80-95% of the variance in modeled muscle stiffness. These findings suggest that shear wave velocity may be used to infer the muscular origins of changes in joint stiffness.NEW & NOTEWORTHY Shear wave velocity is commonly assessed to infer the muscular origins of changes in joint stiffness, but the exact relationship between shear wave velocity changes in muscle and joint stiffness changes remains unknown. Here, we systematically evaluated and quantified this relationship in the plantar flexors. Our results provide evidence for the ability of shear wave velocity to elucidate the muscular origins of joint stiffness changes.

Changes in joint, muscle, and tendon stiffness following repeated hopping exercise.

The purpose of this study was to elucidate the mechanisms of decline in joint stiffness after repeated stretch‐shortening cycle exercises according to changes in both muscle‐tendon properties and neuromuscular activities. Eleven males performed fatigue task (5 sets of 50 hopping). Ankle joint stiffness and electromyographic activities (mEMG) of plantar flexor and tibial anterior muscles during drop jump were measured before and after fatigue task. Active muscle stiffness with (100 deg·sec−1) and without (250 deg·sec−1) stretch reflex were calculated according to changes in estimated muscle force and fascicle length during fast stretching after submaximal isometric contractions. Tendon stiffness was measured during ramp and ballistic contractions. After fatigue task, joint stiffness significantly decreased by 20.7 %, whereas mEMG of measured muscles during drop jump did not. After fatigue task, active muscle stiffness with and without stretch reflex significantly decreased by 15.7 % and 21.5 %, and tendon stiffness measured during ramp and ballistic contractions did not change. In addition, the relative change in joint stiffness was significantly correlated with that in active muscle stiffness with stretch reflex (r = 0.737, P = 0.009), but not with those in the other measured variables. These results suggested that the decline in joint stiffness after repeated hopping exercises would be caused by changes in active muscle stiffness, but not those in tendon properties or neuromuscular activities.

Effectiveness of platelet rich plasma in pain management of osteoarthritis knee: double blind, randomized comparative study

BackgroundIntra-articular injections of platelet-rich plasma to treat symptoms of knee osteoarthritis have been successfully used in young patients. However in most of these studies the control and test knees were present in different patients thus incorporating a large amount of bias in the results. Therefore, the present study was designed in which patients with bilateral osteoarthritis knee were included and platelet-rich plasma was administered in one knee and normal saline in another knee of same patient. Methods20 patients aged 30–65 years with bilateral osteoarthritis knees (ASA class I and II) of either gender were included in the study. Patients were randomized to receive platelet-rich plasma and normal saline in one of the two knees. The primary outcome was VAS and WOMAC score at 6 months after procedure. The secondary outcome included changes in joint stiffness, physical function, any adverse effects noted during the course of study. ResultsThe baseline VAS score in platelet-rich plasma knee was 8.4±0.88 which improved significantly to 4.85±2.48 (p<0.001) at 6 months as compared to normal saline knee (p=0.017). The WOMAC pain score also improved from baseline (14.5±1.3) to over 6 month 7.00±4.24 (p<0.001) in platelet-rich plasma knee while in the normal saline knee, no significant change occurred from baseline to six months (10.2±1.2 to 10.05±1.23). There was also significant decrease in stiffness and improvement of physical activity in the platelet-rich plasma knee as compared to normal saline knee. ConclusionThe present study showed significant decrease in pain and stiffness and improvement of physical functions of knee joint with intra-articular platelet-rich plasma injection as compared to normal saline.

Efetividade do plasma rico em plaquetas no tratamento da dor em osteoartrite de joelho: estudo comparativo randômico e duplo‐cego

BackgroundIntra‐articular injections of platelet‐rich plasma to treat symptoms of knee osteoarthritis have been successfully used in young patients. However in most of these studies the control and test knees were present in different patients thus incorporating a large amount of bias in the results. Therefore, the present study was designed in which patients with bilateral osteoarthritis knee were included and platelet‐rich plasma was administered in one knee and normal saline in another knee of same patient. Methods20 patients aged 30‐65 years with bilateral osteoarthritis knees (ASA class I and II) of either gender were included in the study. Patients were randomized to receive platelet‐rich plasma and normal saline in one of the two knees. The primary outcome was VAS and WOMAC score at 6months after procedure. The secondary outcome included changes in joint stiffness, physical function, any adverse effects noted during the course of study. ResultsThe baseline VAS score in platelet‐rich plasma knee was 8.4 ± 0.88 which improved significantly to 4.85 ± 2.48 (p < 0.001) at 6months as compared to normal saline knee (p = 0.017). The WOMAC pain score also improved from baseline (14.5 ± 1.3) to over 6month 7.00 ± 4.24 (p < 0.001) in platelet‐rich plasma knee while in the normal saline knee, no significant change occurred from baseline to six months (10.2 ± 1.2 to 10.05 ± 1.23). There was also significant decrease in stiffness and improvement of physical activity in the platelet‐rich plasma knee as compared to normal saline knee. ConclusionThe present study showed significant decrease in pain and stiffness and improvement of physical functions of knee joint with intra‐articular platelet‐rich plasma injection as compared to normal saline.

Study of age-related changes in Middle ear transfer function

Osteoporosis (OP) is common with advancing age. Several studies have shown a strong correlation between OP and otosclerosis. However, no studies have investigated OP of the malleus, incus or stapes in the human middle ear, its effect on middle ear transfer function. Here, we investigate whether these three ossicles develop OP, and how this affects middle ear transfer function. The effect of OP on middle ear transfer function was investigated in simulations based on a finite element (FE) method. First, the FE model used in our previous study was refined, and optimized by introducing viscoelastic properties to selected soft tissues of the middle ear. Then, the FE model was used to simulate OP of the three ossicles and assess its influence on middle ear transfer function. Other possible age-related changes, such as stiffness of the joints or ligaments in the middle ear, were also investigated. The results indicated that OP of the ossicles could increase the high frequency displacement of both the umbo and stapes footplate (FP). However, the stiffness of the middle ear soft tissue can lead to the decrease of middle ear gain at lower frequencies. Furthermore, loosening of these joints or ligaments could increase displacement of the umbo and stapes FP. In conclusion, although age-related hearing loss is most commonly conceived of as sensorineural hearing loss (SNHL), we found that age-related changes may also include OP and changes in joint stiffness, but these will have little effect on middle ear transfer function in elderly people.

The Impact of Aging and Hand Dominance on the Passive Wrist Stiffness of Squash Players: Pilot Study

Background: Passive joint stiffness can influence the risk of injury and the ability to participate in sports and activities of daily living. However, little is known about how passive joint stiffness changes over time with intensive repetitive exercise, particularly when performing unilateral activities using the dominant upper limb.

Effects of repeated eccentric and isometric contractions with relatively low loading dose on joint stiffness.

The purpose of the present study was to compare changes in joint stiffness after repeated eccentric (ECC; leading to muscle fatigue) and isometric (ISO; leading to tendon fatigue) contractions and to elucidate the mechanisms responsible for decline in joint stiffness after repeated stretch-shortening cycle exercises reported previously. Ankle joint stiffness (change in joint torque divided by change in joint angle during braking phase) and electromyographic activity (mEMG) of the plantar flexor muscles during drop jump using the ankle joint were measured before and after ECC, ISO, and control conditions. Peak ankle joint torque, range of motion, and joint stiffness during drop jump did not change after ECC or ISO. However, relative changes in joint stiffness correlated with those in range of motion, but not peak torque. In ECC and ISO, mEMG during pre-landing, braking, and push-off phases did not change after endurance tests, except for braking phase in ISO. Furthermore, relative change in joint stiffness correlated with that in mEMG during braking phase in ISO, but not in ECC. Under control conditions, no significant changes were noted in the measured variables. These results suggest that relative changes in joint stiffness (but not decrease in average values) after ECC and ISO were related to change in range of motion, but not exerted force levels. Furthermore, changes in range of motion after repeated contractions were relevant to those in muscle activation in ISO and other factors (probably muscle stiffness under passive and active conditions) in ECC.

A study of the role of platelet rich plasma in the treatment of knee osteoarthritis

A study of the role of platelet rich plasma in the treatment of knee osteoarthritis

Efficacy and safety of a compound supplement containing glucosamine, chondroitin, and five bioactive ingredients in volunteers with knee joint pain

Abstract Purpose This study was designed to evaluate the efficacy and safety of a compound supplement containing glucosamine (GS), chondroitin sulfate (CS), and five bioactive ingredients for improvement of knee osteoarthritis (OA). Methods Sixteen volunteers aged ≥40 years with knee pain and without ambulant treatment participated in a 6-week randomized, double-blind, placebo-controlled study. They were assigned to the dietary supplement or placebo groups (n = 8, respectively) and ingested six capsules twice daily. The OA symptoms of each subject were determined in pre- and post-treatment periods using a visual analog scale for pain (VAS pain) and four Japanese Knee Osteoarthritis Measure (JKOM) subscales (joint stiffness, daily living, social activities, and general health condition). For safety and biomarker assessments, blood and urine samples were tested. Results In the treatment group, the subjective symptoms of VAS pain and three JKOM subscale scores except for social activities were significantly improved compared to pre-treatment. Among them, the pattern of change in joint stiffness and total JKOM scores showed a significant difference between groups (p = 0.008 and 0.041, respectively). The serum level of interleukin-6, a systemic inflammation biomarker, was significantly decreased in the treatment group after 6 weeks (p = 0.019), whereas the level remained stable in the placebo group (p = 0.690). Diagnostic urine and hematological parameters revealed no serious adverse differences following dietary supplementation over the 6-week study. Conclusion These findings suggest that the compound supplementation of functional food ingredients has potential as an adjunctive and safe therapy for knee OA.

Abstract P131: Associations Between Joint Symptoms and Prospective Changes in Physical Activity in First-degree Relatives of Rheumatoid Arthritis (RA) Patients

Background: CVD is accelerated in RA, and risk of CVD death is 50% higher in RA patients. Physical activity (PA) mitigates increased CVD risk, but RA patients typically have less PA. It is not known whether PA declines prior to RA onset, or whether joint symptoms (sxs) contribute to PA decline. We sought to determine whether RA-related joint sxs were associated with PA over time in first-degree relatives (FDRs) of RA patients, a population at increased risk for future RA. Methods: In the Studies of the Etiology of RA (SERA), we evaluated associations between presence of joint sxs and hours of PA in 878 FDRs; of whom, 376 had ≥2 visits. A physician confirmed joint swelling; participants self-reported stiffness and pain in the wrist, elbow, or any MCP, PIP, or MTP joints. Hours sleeping, sitting, and performing slight, moderate, or heavy activity during a typical 24-hour day were obtained through questionnaire, weighted to reflect metabolic expenditure, and calculated as follows: PA = (1.0*h sleep + 1.1*h sedentary + 1.5*h slight + 2.4*h moderate + 5.0*h heavy ). Linear mixed models were used to evaluate associations between joint sxs and change in PA over time, adjusting for age, sex, race, BMI, smoking, and positivity for RA-related autoantibodies Results: Mean baseline age was 50±16 years. 74% were female, 78% were White, 7% had joint swelling, 15% had joint stiffness, and 24% had joint pain. Average PA was 37±7. At baseline, PA was higher in FDRs with joint stiffness (B=1.27±0.64, p=0.05) and joint pain (B=1.43±0.54, p=0.01), and lower in FDRs with joint swelling (B=-1.50±0.91, p=0.10). Adjusting for baseline PA, baseline joint swelling, stiffness, and pain were not significantly associated with changes in PA. However, change in joint swelling was associated with increased PA; and changes in joint stiffness and pain were associated with decreased PA. (Table) Conclusion: Joint sxs may not predict future PA, but PA may be lower at the time joint sxs occur. Clinicians should address joint sxs as part of their PA intervention in CVD prevention.

Multiscale biomechanical responses of adapted bone–periodontal ligament–tooth fibrous joints

Reduced functional loads cause adaptations in organs. In this study, temporal adaptations of bone-ligament-tooth fibrous joints to reduced functional loads were mapped using a holistic approach. Systematic studies were performed to evaluate organ-level and tissue-level adaptations in specimens harvested periodically from rats (N=60) given powder food for 6months over 8,12,16,20, and 24weeks. Bone–periodontal ligament (PDL)–tooth fibrous joint adaptation was evaluated by comparing changes in joint stiffness with changes in functional space between the tooth and alveolar bony socket. Adaptations in tissues included mapping changes in the PDL and bone architecture as observed from collagen birefringence, bone hardness and volume fraction in rats fed soft foods (soft diet, SD) compared to those fed hard pellets as a routine diet (hard diet, HD). In situ biomechanical testing on harvested fibrous joints revealed increased stiffness in SD groups (SD:239–605N/mm) (p<0.05) at 8 and 12weeks. Increased joint stiffness in early development phase was due to decreased functional space (at 8weeks change in functional space was −33μm, at 12weeks change in functional space was −30μm) and shifts in tissue quality as highlighted by birefringence, architecture and hardness. These physical changes were not observed in joints that were well into function, that is, in rodents older than 12weeks of age. Significant adaptations in older groups were highlighted by shifts in bone growth (bone volume fraction 24weeks: Δ–0.06) and bone hardness (8weeks: Δ–0.04GPa, 16weeks: Δ–0.07GPa, 24weeks: Δ–0.06GPa). The response rate (N/s) of joints to mechanical loads decreased in SD groups. Results from the study showed that joint adaptation depended on age. The initial form-related adaptation (observed change in functional space) can challenge strain-adaptive nature of tissues to meet functional demands with increasing age into adulthood. The coupled effect between functional space in the bone–PDL–tooth complex and strain-adaptive nature of tissues is necessary to accommodate functional demands, and is temporally sensitive despite joint malfunction. From an applied science perspective, we propose that adaptations are registered as functional history in tissues and joints.