Skeletal muscle accumulates intramuscular fat through age and obesity. Muscle quality, a measure of muscle strength per unit size, decreases in these conditions. It is not clear how fat influences this loss in performance. Changes to structural parameters (e.g. fibre pennation and connective tissue properties) affect the muscle quality. This study investigated the mechanisms that lead to deterioration in muscle performance due to changes in intramuscular fat, pennation and aponeurosis stiffness. A finite-element model of the human gastrocnemius was developed as a fibre-reinforced composite biomaterial containing contractile fibres within the base material. The base-material properties were modified to include intramuscular fat in five different ways. All these models with fat generated lower fibre stress and muscle quality than their lean counterparts. This effect is due to the higher stiffness of the tissue in the fatty models. The fibre deformations influence their interactions with the aponeuroses, and these change with fatty inclusions. Muscles with more compliant aponeuroses generated lower forces. The muscle quality was further reduced for muscles with lower pennation. This study shows that whole-muscle force is dependent on its base-material properties and changes to the base material due to fatty inclusions result in reductions to force and muscle quality.

Skeletal muscle can contain neuromuscular compartments that are spatially distinct regions that can receive relatively independent levels of activation. This study tested how the magnitude and direction of the force developed by a whole muscle would change when the muscle activity was regionalized within the muscle. A 3D finite element model of a muscle with its bounding aponeurosis was developed for the lateral gastrocnemius, and isometric contractions were simulated for a series of conditions with either a uniform activation pattern, or regionally distinct activation patterns: in all cases the mean activation from all fibers within the muscle reached 10%. The models showed emergent features of the fiber geometry that matched physiological characteristics: with fibers shortening, rotating to greater pennation, adopting curved trajectories in 3D and changes in the thickness and width of the muscle belly. Simulations were repeated for muscle with compliant, normal and stiff aponeurosis and the aponeurosis stiffness affected the changes to the fiber geometry and the resultant muscle force. Changing the regionalization of the activity resulted to changes in the magnitude, direction and center of the force vector from the whole muscle. Regionalizing the muscle activity resulted in greater muscle force than the simulation with uniform activity across the muscle belly. The study shows how the force from a muscle depends on the complex interactions between the muscle fibers and connective tissues and the region of muscle that is active.

Background: Foot problems are prevalent in older adults, which may increase the risk and concern for falls. Ankle-foot orthoses (AFO) have been shown to be effective in the stabilization of lower extremities, but their long-term effectiveness in improving balance and their potential to encourage older adults to become more physically active are still debated. Objective: This randomized controlled trial investigated the effectiveness of daily use of a custom-made AFO on balance, fear of falling, and physical activity in older adults. Study Design: Forty-four older adults with concern about or at risk for falling were randomly allocated to either the control group (CG; 77.3% female, age 75.6 ± 6.5 years, BMI 29.3 ± 6.4) or the intervention group (IG; 63.6% female, age 73.7 ± 6.3 years, BMI = 27.8 ± 4.8). The IG received walking shoes and bilateral custom-made AFO. The CG received only walking shoes. At the baseline and 6-month follow-ups, balance and physical activity were assessed using validated wearable instrumentation and fear of falling was assessed using the Fall Efficacy Scale-International (FES-I). Adherence and acceptability toward wearing the AFO were assessed using self-reported questionnaires at the 6-month follow-up. Results: No significant between-group difference was observed at baseline (p = 0.144–0.882). Compared to baseline and the CG, hip, ankle, and center-of-mass (COM) sways were significantly reduced at the 6-month follow-up in the IG while standing with the feet together during the eyes-open condition (p = 0.005–0.040). Within the IG, the FES-I was reduced significantly (p = 0.036) and there was an increasing trend in the number of walking bouts with a medium effect size (d = 0.52, p = 0.440) compared to baseline. However, there were no significant changes in FES-I and physical activity measures in the CG (p = 0.122–0.894). The reduction in COM sway in the IG was moderately correlated with adherence (r = –0.484, p = 0.047) and strongly correlated with baseline COM sway (r = –0.903, p < 0.001). Conclusion: Results suggest that bilateral custom-made AFO plus walking shoes is effective in improving balance compared to walking shoes alone, and it significantly reduces the fear of falling, with a nonsignificant but noticeable positive trend in physical activity, compared to baseline. The results also suggest that older adults with poor balance at baseline and higher daily adherence to using the AFO will gain more benefit from the AFO intervention.

Motor functions are deteriorated by aging. Some conditions may magnify this deterioration. This study examined whether hemodialysis (HD) process would negatively impact gait and balance beyond diabetes condition among mid-age adults (48–64 years) and older adults (65+ years). One hundred and ninety-six subjects (age = 66.2 ± 9.1 years, body-mass-index = 30.1 ± 6.4 kg/m2, female = 56%) in 5 groups were recruited: mid-age adults with diabetes undergoing HD (Mid-age HD+, n = 38) and without HD (Mid-age HD−, n = 40); older adults with diabetes undergoing HD (Older HD+, n = 36) and without HD (Older HD−, n = 37); and non-diabetic older adults (Older DM−, n = 45). Gait parameters (stride velocity, stride length, gait cycle time, and double support) and balance parameters (ankle, hip, and center of mass sways) were quantified using validated wearable platforms. Groups with diabetes had overall poorer gait and balance compared to the non-diabetic group (p < 0.050). Among people with diabetes, HD+ had significantly worsened gait and balance when comparing to HD− (Cohen’s effect size d = 0.63–2.32, p < 0.050). Between-group difference was more pronounced among older adults with the largest effect size observed for stride length (d = 2.32, p < 0.001). Results suggested that deterioration in normalized gait speed among HD+ was negatively correlated with age (r = −0.404, p < 0.001), while this correlation was diminished among HD−. Interestingly, results also suggested that poor gait among Older HD− is related to poor ankle stability, while no correlation was observed between poor ankle stability and poor gait among Older HD+. Using objective assessments, results confirmed that the presence of diabetes can deteriorate gait and balance, and this deterioration can be magnified by HD process. Among HD− people with diabetes, poor ankle stability described poor gait. However, among people with diabetes undergoing HD, age was a dominate factor describing poor gait irrespective of static balance. Results also suggested feasibility of using wearable platforms to quantify motor performance during routine dialysis clinic visit. These objective assessments may assist in identifying early deterioration in motor function, which in turn may promote timely intervention.

Frailty assessment is dependent on the availability of trained personnel and it is currently limited to clinic and supervised setting. The growing aging population has made it necessary to find phenotypes of frailty that can be measured in an unsupervised setting for translational application in continuous, remote, and in-place monitoring during daily living activity, such as walking. We analyzed gait performance of 161 older adults using a shin-worn inertial sensor to investigate the feasibility of developing a foot-worn sensor to assess frailty. Sensor-derived gait parameters were extracted and modeled to distinguish different frailty stages, including non-frail, pre-frail, and frail, as determined by Fried Criteria. An artificial neural network model was implemented to evaluate the accuracy of an algorithm using a proposed set of gait parameters in predicting frailty stages. Changes in discriminating power was compared between sensor data extracted from the left and right shin sensor. The aim was to investigate the feasibility of developing a foot-worn sensor to assess frailty. The results yielded a highly accurate model in predicting frailty stages, irrespective of sensor location. The independent predictors of frailty stages were propulsion duration and acceleration, heel-off and toe-off speed, mid stance and mid swing speed, and speed norm. The proposed model enables discriminating different frailty stages with area under curve ranging between 83.2–95.8%. Furthermore, results from the neural network suggest the potential of developing a single-shin worn sensor that would be ideal for unsupervised application and footwear integration for continuous monitoring during walking.

The results from this study suggest that shoelace closure technique can have a profound effect on TSR. It therefore stands to reason that optimal lace closure may have an impact in reducing risk of plantar ulcers in people with DPN. Interestingly, results revealed that even a self-adjusted lace closure may not be necessarily optimal and a preset closure setting like reel clutch might ultimately be recommended to minimize risk. Further study is warranted to confirm or refute these interesting results.

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