Clinical walk tests may not predict the development of frailty in healthy older adults. With advancements in wearable technology, it may be possible to predict the development of frailty using loading asymmetry parameters during clinical walk tests. This prospective cohort study aimed to test the hypothesis that increased limb loading asymmetry predicts frailty risk in community-living older adults. Sixty-three independently ambulant community-living adults aged ≥ 65 years were recruited, and forty-seven subjects completed the ten-month follow-up after baseline. Loading asymmetry index of net and regional (forefoot, midfoot, and rearfoot) plantar forces were collected using force sensing insoles during a 10 m walk test with their maximum speed. Development of frailty was defined if the participant progressed from baseline at least one grading group of frailty at the follow-up period using the Kihon Checklist. Fourteen subjects developed frailty during the follow-up period. Increased risk of frailty was associated with each 1% increase in loading asymmetry of net impulse (Odds ratio 1.153, 95%CI 1.001 to 1.329). Net impulse asymmetry significantly correlated with asymmetry of peak force in midfoot force. These results indicate the feasibility of measuring plantar forces of gait during clinical walking tests and underscore the potential of using load asymmetry as a tool to augment frailty risk assessment in community-dwelling older adults.

OBJECTIVE: To investigate relationships between static foot posture, dynamic plantar foot forces and knee pain in people with medial knee osteoarthritis (OA).
METHODS: Data from 164 participants with symptomatic, moderate to severe radiographic medial knee OA were analysed. Knee pain was self-reported using a numerical rating scale (NRS; scores 0-10; higher scores worse) and the Knee Injury and Osteoarthritis Outcome Score pain subscale (KOOS; scores 0-100; lower scores worse). Static foot posture was assessed using clinical tests (foot posture index, foot mobility magnitude, navicular drop). Dynamic plantar foot forces (lateral, medial, whole foot, medial-lateral ratio, arch index) were measured using an in-shoe plantar pressure system while walking. Relationships between foot posture and plantar forces (independent variables) and pain (dependent variables) were evaluated using linear regression models, unadjusted and adjusted for sex, walking speed, Kellgren & Lawrence grade, shoe category, and body mass (for dynamic plantar foot forces).
RESULTS: No measure of static foot posture was associated with any knee pain measure. Higher medial-lateral foot force ratio at midstance, and a higher arch index during overall stance, were weakly associated with higher knee pain on the NRS (regression coefficient = 0.69, 95% confidence interval (CI) 0.09 to 1.28) and KOOS (coefficient=3.03, 95% CI 0.71 to 5.35) pain scales, respectively.
CONCLUSIONS: Dynamic plantar foot forces, but not static foot posture, were associated with knee pain in people with medial knee OA. However, the amount of pain explained by increases in plantar foot force was small; thus, these associations are unlikely to be clinically meaningful.

The purpose of this study was to determine if estimated center of pressure (COP) from plantar force data collected using three-sensor loadsol insoles was comparable to the COP from plantar pressure data collected using pedar insoles during walking and running. Ten healthy adults walked and ran at self-selected speeds on a treadmill while wearing both a loadsol and pedar insole in their right shoe. Plantar force recorded from the loadsol was used to estimate COP along mediolateral (COPx) and anteroposterior (COPy) axes. The estimated COPx and COPy were compared with the COPx and COPy from pedar using limits of agreement and Spearman\'s rank correlation. There were significant relationships and agreement within 5 mm in COPx and 20 mm in COPy between loadsol and pedar at 20-40% of stance during walking and running. However, loadsol demonstrated biases of 7 mm in COPx and 10 mm in COPy compared to pedar near initial contact and toe-off.

Patients with diabetic foot ulcers are instructed to be non-weight bearing on the affected limb to promote healing. Therefore, the aim of this study was to investigate the effect of different assistive devices on whole foot plantar loading, peak forefoot force, ankle range of motion, and locomotion speed during gait in patients with Type 2 Diabetes Mellitus.
Participants walked normally, with crutches, a walker, and a wheeled knee walker (WKW) in randomized order. Force sensitive insoles and 3D motion capture were used to record plantar normal force and ankle kinematics. Force sensitive pads were wrapped around handles of the crutches and walker to measure bodyweight offloaded onto the assistive device. An instrumented WKW was used to measure bodyweight offloaded onto the handlebars and knee cushion.
Locomotion with the WKW produced the lowest whole foot plantar loading and peak forefoot force in the propulsive limb, while also producing the greatest ankle range of motion and locomotion speed amongst assistive devices.
This pre-clinical study found that the WKW could be the preferred assistive device for total unilateral offloading of diabetic foot ulcers as it reduced propulsive limb whole foot and forefoot plantar loading while retaining ankle range of motion and locomotion speed.

BACKGROUND: Young adults often tolerate the increased energy expenditure, coordination, and stance limb discomfort associated with walking aids for nonweightbearing ambulation. Adults aged ≥50 years may not have the same tolerance. Therefore, the objective of this study was to determine how walking aid selection affects stance limb plantar force, walking speed, perceived exertion, and device preference in adults aged ≥50 years.
METHODS: A prospective randomized crossover study was performed using healthy adults, aged ≥50 years, with no use of walking aids within 5 years. Participants walked 200 m in 4 randomized conditions: single nonweightbearing ambulation using crutches, a walker, a wheeled knee walker, and unaided walking. An in-shoe sensor measured stance limb plantar force, a stopwatch timed each walk, perceived exertion was reported using the BORG CR-10 scale, and device preference was identified.
RESULTS: Twenty-one participants (7 male; age: 56 ± 5 years; BMI: 26.6 ±1.9) showed stance limb plantar force was lowest when using a wheeled knee walker (P < .001). Walking speed was similar in unaided and wheeled knee walker conditions (1.41 and 1.31 m/s), but slower with crutches or a walker (42%-68%, P < .001). Perceived exertion was similar in unaided and wheeled knee walker conditions (1.6 and 2.8), but higher with crutches or a walker (5.7 and 6.1, P < .001). Most (20/21) participants preferred the wheeled knee walker.
CONCLUSIONS: Using a wheeled knee walker for nonweightbearing ambulation reduced stance limb plantar force, maintained unaided walking speed and perceived exertion, and was preferred to crutches or a walker.
METHODS: Level II, comparative study.

BACKGROUND: Anti-gravity treadmills are used to decrease musculoskeletal loading during treadmill running often in return to play rehabilitation programs. The effect different gradients (uphill/downhill running) have on kinetics and spatiotemporal parameters when using an AlterG® treadmill is unclear with previous research focused on level running only.
METHODS: Ten well-trained healthy male running athletes ran on the AlterG® treadmill at varying combinations of bodyweight support (60, 80, and 100% BW), speed (12 km/hr., 15 km/hr., 18 km/hr., 21 km/hr., and 24 km/hr), and gradients (- 15% decline, - 10, - 5, 0, + 5, + 10 + 15% incline), representing a total of 78 conditions performed in random order. Maximum plantar force and contact time were recorded using a wireless in-shoe force sensor insole system.
RESULTS: Regression analysis showed a linear relationship for maximum plantar force with bodyweight support and running speeds for level running (p < 0.0001, adj. R2 = 0.604). The linear relationship, however, does not hold for negative gradients at speeds 12 & 15 km/h, with a relative \'dip\' in maximum plantar force across all assisted bodyweight settings.
CONCLUSIONS: Maximum plantar force peaks are larger with faster running and smaller with more AlterG® assisted bodyweight support (athlete unweighing). Gradient made little difference except for a downhill grade of - 5% decreasing force peaks as compared to level or uphill running.

Mobility aids are commonly prescribed to offload an injured lower extremity. Device selection may impact stance foot loading patterns and foot health in clinical populations at risk of foot ulceration.
Two questions motivated this study: How does device selection influence peak plantar and regional (rearfoot, mid foot and forefoot) foot forces on the stance foot? Does device selection influence peak, cumulative, and regional plantar forces within a 200 m walking trial?
Twenty-one older adults walked 200 m at self-selected pace in four randomized conditions for this prospective crossover study. Participants used a walker, crutches, wheeled knee walker (WKW), and no assistive device (control condition). Plantar forces were measured using a wireless in-shoe system (Loadsol, Novel Inc., St. Paul, MN). Repeated measures analyses of variance were used to determine differences in peak and cumulative total and regional forces among walking conditions. Paired sample t-tests compared forces during first and last 30 s epochs of each condition to determine device influence over time.
The WKW reduced peak net forces by 0.29 and 0.35 bodyweight (BW) when compared to the walker or control condition with similar trends in all foot regions. Crutch use had similar peak forces as control. There were no differences in the number of steps taken within devices comparing first and last epochs. Crutches had a 0.04 and 0.07 BW increase in peak net and forefoot forces during the last epoch. Walker use had 66.44 BW lower cumulative forefoot forces in the last epoch.
Crutches had similar stance foot loading as normal walking while a walker lowered forefoot forces at the expense of increased steps. A WKW may be the best choice to \'protect\' tissues in the stance foot from exposure to peak and cumulative forces in the forefoot region.

The purpose of this study was to explore the immediate effects of running speed and midsole type on foot loading during heel-toe running. Fifteen healthy male college students were required to complete 3 running trials on an indoor 45-m tartan runway at 4 different speeds (3, 4, 5, and 6 m/s) using 2 different running footwear types (engineering thermoplastic polyurethane elastomer, polyurethane elastomer; and ethylene vinyl acetate, vinyl acetate). The ground reaction force and plantar pressure data were quantified. Significant speed effects were detected both in ground reaction force and plantar pressure-related data (P < .05). Vertical average loading rate was significantly less, and time to first peak occurred later for the polyurethane elastomer compared with vinyl acetate footwear (P < .05). The peak pressure of the heel, medial forefoot, central forefoot, lateral forefoot, and big toe was significantly less when subjects wore a polyurethane elastomer than vinyl acetate footwear (P < .05). Overall, our results suggested that, compared with the vinyl acetate footwear, the special polyurethane elastomer footwear that is adhered with thousands of polyurethane elastomer granules was effective at reducing the mechanical impact on the foot.

BACKGROUND: Pes planus is a prevalent chronic condition that causes foot pain, disability, and impaired plantar load distribution. Short-foot exercises are often recommended to strengthen intrinsic foot muscles and to prevent excessive decrease of medial longitudinal arch height.
OBJECTIVE: To investigate the effects of short-foot exercises on navicular drop, foot posture, pain, disability, and plantar pressures in pes planus.
METHODS: Quasi-experimental study.
METHODS: Biomechanics laboratory.
METHODS: A total of 41 participants with pes planus were assigned to the short-foot exercises group (n = 21) or the control group (n = 20).
METHODS: Both groups were informed about pes planus, usual foot care, and appropriate footwear. Short-foot exercises group performed the exercises daily for 6 weeks.
METHODS: Navicular drop, Foot Posture Index, foot pain, disability, and plantar pressures were assessed at the baseline and at the end of 6 weeks.
RESULTS: Navicular drop, Foot Posture Index, pain, and disability scores were significantly decreased; maximum plantar force of midfoot was significantly increased in short-foot exercises group over 6 weeks (P < .05). No significant differences were determined between the baseline and the sixth week outcomes in control group (P > .05).
CONCLUSIONS: Six-week short-foot exercises provided a reduction in navicular drop, foot pronation, foot pain, and disability and increment in plantar force of medial midfoot in pes planus.

Transducers for spatial plantar force measurements have numerous applications in biomechanics, rehabilitation medicine, and gait analysis. In this work, the design of a novel, tri-axial transducer for plantar force measurements was presented. The proposed design could resolve both the normal and the shear forces applied at the foot\'s sole. The novelty of the design consisted in using a rotating bump to translate the external loads into axial compressive forces which could be measured effectively by conventional pressure sensors. For the prototype presented, multilayer polydimethylsiloxane (PDMS) thin-film capacitive stacks were manufactured and used as sensing units, although in principle the design could be extended to various types of sensors. A quasi-static analytic solution to describe the behavior of the transducer was also derived and used to optimize the design. To characterize the performance of the transducer, a 3 cm diameter, 1 cm tall prototype was manufactured and tested under various combination of shear and normal loading scenarios. The tests confirmed the ability of the transducer to generate strong capacitive signals and measure both the magnitude and direction of the normal and shear loads in the dynamic range of interest.