New Perspectives on Foot Segment Forces and Joint Kinetics-Integrating Plantar Shear Stresses and Pressures with Multi-segment Foot Modeling.

The role of the many small foot articulations and plantar tissues in gait is not well understood. While kinematic multi-segment foot models have increased our knowledge of foot segmental motions, the integration of kinetics with these models could further advance our understanding of foot mechanics and energetics. However, capturing and effectively utilizing segmental ground reaction forces remains challenging. The purposes of this study were to (1) develop methodology to integrate plantar pressures and shear stresses with a multi-segment foot model, and (2) generate and concisely display key normative data from this combined system. Twenty-six young healthy adults walked barefoot (1.3 m/s) across a pressure/shear sensor with markers matching a published 4-segment foot model. A novel anatomical/geometric template-based masking method was developed that successfully separated regions aligned with model segmentation. Directional shear force plots were created to summarize complex plantar shear distributions, showing opposing shear forces both between and within segments. Segment centers of pressure (CoPs) were shown to be primarily stationary within each segment, suggesting that forward progression in healthy gait arises primarily from redistributing weight across relatively fixed contact points as opposed to CoP movement within a segment. Inverse dynamics-based normative foot joint moments and power were presented in the context of these CoPs to aid in interpretation of tissue stresses. Overall, this work represents a successful integration of motion capture with direct plantar pressure and shear measurements for multi-segment foot kinetics. The presented tools are versatile enough to be used with other models and contexts, while the presented normative database may be useful as a baseline comparison for clinical work in gait energetics and efficiency, balance, and motor control. We hope that this work will aid in the advancement and availability of kinetic MSF modeling, increase our knowledge of foot mechanics, and eventually lead to improved clinical diagnosis, rehabilitation, and treatment.

The influence of bed height as a percentage of participant height on low back forces when boosting a patient up in bed.

BACKGROUND: Repositioning patients is a frequent task for healthcare workers causing substantial stress to the low back. Patient handling methodologies that reduce low back load should be used. Some studies have observed the effect of bed height on back forces using a limited range of heights. This study details a wider range. OBJECTIVE: The aim of this study was to discover an optimal bed height for reducing low back force when boosting a patient. METHODS: 11 university students and local residents participated by completing a series of boosts with a 91.6 kg research assistant acting as dependent. The bed was adjusted 3% of participant height and 3 boosts were completed at each height which resulted in 8-10 different bed heights depending on the height of the participant. Motion and force data were collected to estimate low back forces via 3DSSPP. Pearson's R was performed to observe the correlation between caregiver height and low back forces. RESULTS: There were significant negative correlations between bed height and low back compression force at L4-L5 (r = -0.676, p = <0.001) and L5-S1 (r = -0.704, p = <0.001). There were no significant correlations with any shear forces. CONCLUSION: The highest bed height led to decreased low back compression forces regardless of participant height, but there was not a significant difference in shear forces. Thus, healthcare workers may experience less low back stress with the bed at a higher height. There may be a force tradeoff between the low back and other parts of the body that needs further exploration. Healthcare workers need to be made aware of the implications of adjusting the environment when performing patient handling tasks.

Contributions of Intrinsic and Extrinsic Foot Muscles during Functional Standing Postures.

Purpose: Maintaining balance during static standing postures requires the coordination of many neuromuscular mechanisms. The role of the intrinsic and extrinsic foot muscles in this paradigm has yet to be clearly defined. The purpose of this study was to explore foot muscle activation during static phases on common weight-bearing tasks of varying loads and balance demands. Methods: Twenty healthy young adults performed 6 standing postures (single-limb and double-limb stand, squat, and heel raise) with one foot on a force plate. Muscle activity was recorded from the abductor hallucis, flexor hallucis longus and brevis, and tibialis posterior using intramuscular electrodes; surface electrodes were used to record activity from the peroneus longus and tibialis anterior. Two-way repeated measures ANOVA (2 loading conditions × 3 postures) were run to compare muscle activation and center of pressure velocity. Results: Intrinsic foot muscle activity increased as loading and postural demand increased; however, the specific effects varied for each of the extrinsic foot muscles. Conclusions: These results suggest that the intrinsic foot muscles play an important role in maintaining static balance. Strengthening intrinsic and extrinsic foot muscles may help increase stability in people who have weak toe flexors or who suffer from a variety of foot pathologies.

Up in the air: the efficacy of weighted gloves in figure skating jumps.

Successful performance of difficult, multi-revolution jumps is a critical aspect of singles and pairs figure skating. Key determinants of quality jumps include jump height, angular momentum at takeoff (L_BodyTO) and total body moment of inertia (I_Body). The purpose of this study was to determine the effect of weighted gloves on L_BodyTO of figure skating jumps. Kinematic data was collected from thirteen skaters during on-ice testing sessions conducted before and after one week of training with weighted gloves. A one-way repeated measures ANOVA was used to compare metrics from jumps performed pre-training without weights (PreNW), post-training without weights (PostNW) and post-training with weights (PostW). No significant differences were found between kinematics in PreNW and PostNW. Skaters did not pull their arms in as tightly while wearing the weighted gloves (distance from the wrists to the axis of rotation were 13.6% and 12.1% greater in PostW than PreNW and PreW, respectively). A post hoc simulation showed that the added mass affected I_Body in the air. While theoretical evidence supports the use of weighted gloves in figure skating jumps, compensations negated their effectiveness in jumps the skaters could already perform well. Optimal implementation may be when skaters are learning new jumps.

The influence of the windlass mechanism on kinematic and kinetic foot joint coupling.

BACKGROUND: Previous research shows kinematic and kinetic coupling between the metatarsophalangeal (MTP) and midtarsal joints during gait. Studying the effects of MTP position as well as foot structure on this coupling may help determine to what extent foot coupling during dynamic and active movement is due to the windlass mechanism. This study's purpose was to investigate the kinematic and kinetic foot coupling during controlled passive, active, and dynamic movements. METHODS: After arch height and flexibility were measured, participants performed four conditions: Seated Passive MTP Extension, Seated Active MTP Extension, Standing Passive MTP Extension, and Standing Active MTP Extension. Next, participants performed three heel raise conditions that manipulated the starting position of the MTP joint: Neutral, Toe Extension, and Toe Flexion. A multisegment foot model was created in Visual 3D and used to calculate ankle, midtarsal, and MTP joint kinematics and kinetics. RESULTS: Kinematic coupling (ratio of midtarsal to MTP angular displacement) was approximately six times greater in Neutral heel raises compared to Seated Passive MTP Extension, suggesting that the windlass only plays a small kinematic role in dynamic tasks. As the starting position of the MTP joint became increasingly extended during heel raises, the amount of negative work at the MTP joint and positive work at the midtarsal joint increased proportionally, while distal-to-hindfoot work remained unchanged. Correlations suggest that there is not a strong relationship between static arch height/flexibility and kinematic foot coupling. CONCLUSIONS: Our results show that there is kinematic and kinetic coupling within the distal foot, but this coupling is attributed only in small measure to the windlass mechanism. Additional sources of coupling include foot muscles and elastic energy storage and return within ligaments and tendons. Furthermore, our results suggest that the plantar aponeurosis does not function as a rigid cable but likely has extensibility that affects the effectiveness of the windlass mechanism. Arch structure did not affect foot coupling, suggesting that static arch height or arch flexibility alone may not be adequate predictors of dynamic foot function.

Healthcare worker choice and low back force between self-chosen and highest bed height when boosting a patient up in bed.

Healthcare workers have a high rate of low back injury due to patient handling tasks. These workers receive training in patient handling methods such as adjusting bed height, but often ignore them. In this study, 35 healthcare workers completed patient boosts at a self-chosen bed height and again with the bed in a higher standardised position. Motion capture and force data were collected for analysis. Given the choice, less than half of participants adjusted the bed at all and none of them moved the bed to the highest position (99.1 cm). The self-chosen bed position yielded significantly higher low back force than the higher position at L4-L5 and L5-S1 (p = 0.02, p = 0.01 respectively). Low back forces can be reduced by raising the bed prior to engaging in patient handling tasks, which is a simple step that can reduce forces placed on healthcare workers' low backs. Practitioner summary: Healthcare workers experience high rates of low back pain secondary to patient handling tasks. In this cross-sectional crossover study, healthcare workers consistently chose a low bed height when boosting a patient, which resulted in higher low back loads compared to the highest bed height.

Stepping Back to Minimal Footwear: Applications Across the Lifespan.

Minimal footwear has existed for tens of thousands of years and was originally designed to protect the sole of the foot. Over the past 50 yr, most footwear has become increasingly more cushioned and supportive. Here, we review evidence that minimal shoes are a better match to our feet, which may result in a lower risk of musculoskeletal injury.

Leg muscle cross-sectional area measured by ultrasound is highly correlated with MRI.

BACKGROUND: The leg muscles are important for balance, posture, and movement during static and dynamic activity. Obtaining cross-sectional area measurements (CSA) of the leg muscles helps researchers understand the health and force production capability of individual leg muscles. Therefore, having an easy to use and readily available method to assess leg muscle CSA is needed. Thus, the purpose of this study was to compare the magnitude, repeatability, and validity of CSA measurements of select leg muscles from ultrasound (US) and the current gold standard, magnetic resonance imaging (MRI). METHODS: 20 healthy volunteers participated in this study. Each participant was imaged via US and MRI. The muscles of interest obtained on each participant consisted of the tibialis anterior at both 30 and 50% of the shank length, tibialis posterior at both 30 and 50% of the shank length, the flexor digitorum longus, the fibularis (peroneus) longus, and the fibularis (peroneus) brevis. RESULTS: Strong Pearson correlations were seen for all of the muscles when comparing US to MRI with a range from .7840 to .9676. For all measurements, standard error of the measurement ranged from .003 to 0.260 cm2. Minimum detectable difference for muscle measurements ranged from .008 cm2 for MRI fibularis longus and fibularis brevis to .693 cm2 for MRI of tibialis anterior at 30%. US minimum detectable difference ranged from .125 cm2 for the tibialis posterior muscle at 30% to .449 cm2 for the tibialis anterior muscle at 50%. CONCLUSIONS: Based on these results ultrasound is a valid method to obtain CSA of muscles of the leg when compared with MRI.

Ultrasound Imaging Is Reliable for Tibialis Posterior Size Measurements.

OBJECTIVES: The tibialis posterior (TP) is a vital muscle for controlling the medial longitudinal arch of the foot during weight-bearing activities. Dysfunction of this muscle is associated with a variety of pathologic conditions; thus, it is important to reliably assess its morphologic characteristics. Ultrasound (US) has been used to assess characteristics of TP tendons but not the muscle cross-sectional area (CSA). The purpose of this study was to establish a reliable US technique to measure the TP CSA and thickness. METHODS: Twenty-three healthy volunteers participated. We evaluated the CSA and thickness at 4 measurement locations (anterior and posterior views at both 30% and 50% of the shank length). RESULTS: The participants included 12 female and 11 male volunteers (mean age ± SD, 31.23 ± 14.93 years). Excellent reliability was seen for the CSA and thickness at all locations (intraclass correlation coefficients, 0.988-0.998). Limits of agreement (LoA) and standard errors of the measurement (SEMs) were slightly lower at the 30% locations (LoA at 30%, 4.6-9.2; LoA at 50%, 6.4-9.7; SEM at 30%, 0.03-0.05; SEM at 50%, 0.04-0.07). Strong correlations were seen between anterior and posterior measurements of the CSA (30%, r = 0.99; P < .0001; 50%, r = 0.94; P < .0001) and thickness (30%, r = 0.98; P < .0001; 50%, r = 0.95; P = .0001). CONCLUSIONS: Based on these results, the TP can be measured accurately with US at any of the tested locations. Due to the ease of collection and the quality of the data, we recommend the anterior view at 30% of the shank length to measure the CSA. The ability to assess muscle size of the TP will aid in a variety of medical and research applications.

Early-Stage Diabetic Neuropathy Reduces Foot Strength and Intrinsic but Not Extrinsic Foot Muscle Size.

BACKGROUND: Tracking progression of diabetic peripheral polyneuropathy (DPN) is usually focused on sensory nerves and subjective testing methods. Recent studies have suggested that distal muscle atrophy may precede sensation loss. Methods to objectively measure distal muscle size and strength are needed to help understand how neuropathy affects muscle function. PURPOSE: To evaluate individual intrinsic and extrinsic foot muscle sizes and functional foot strength in participants with DPN. METHODS: Thirty individuals participated in this cross-sectional study (15 DPN and 15 matched controls). Sizes of 10 separate muscles of the lower leg and foot were measured using ultrasound imaging. Functional foot strength was also quantified using custom great toe and lateral toe flexion tests along with a doming test. Muscle size and strength metrics were compared between groups using ANOVAs and paired t-tests (α = 0.05). Correlations between strength and relevant muscle sizes were also evaluated. RESULTS: The sizes of all four intrinsic foot muscles were smaller in individuals with DPN (p ≤ 0.03), while only one (toe extensor) of the six extrinsic muscles was smaller (p ≤ 0.03), while only one (toe extensor) of the six extrinsic muscles was smaller (p ≤ 0.03), while only one (toe extensor) of the six extrinsic muscles was smaller (p ≤ 0.03), while only one (toe extensor) of the six extrinsic muscles was smaller (r ≤ 0.80) with several corresponding intrinsic muscle sizes. The doming strength test did not show any difference between groups and was moderately correlated with one muscle size (r ≤ 0.80) with several corresponding intrinsic muscle sizes. The doming strength test did not show any difference between groups and was moderately correlated with one muscle size (. CONCLUSION: Diabetic peripheral polyneuropathy affects intrinsic muscles before extrinsics. Ultrasound imaging of individual muscles and functional toe flexion tests can be used clinically to monitor DPN progression and foot function. Participants need to be trained in the doming test before a relationship can be established between this test and DPN foot function. Future studies should include muscle quality measurements to better understand characteristics of affected muscles.

Use of Cine Loops and Structural Landmarks in Ultrasound Image Processing Improves Reliability and Reduces Error in the Assessment of Foot and Leg Muscles.

OBJECTIVES: Foot and leg muscle strength and size are crucial to proper function. It is important to assess these characteristics reliably. Our primary objective was to compare the measurement of still images to cine loops. The secondary purpose was to determine interoperator and intraoperator reliability between operators of different experience levels using video clips and internal and external landmarks. METHODS: Twelve healthy volunteers participated in our study. Internal (navicular tuberosity) and external (lateral leg length at 30% and 50% from the knee joint line) landmarks were used. Two operators each captured and later measured still and cine loop images of selected foot and leg muscles. RESULTS: The 12 participants included 8 male and 4 female volunteers (mean age ± SD, 23.5 ± 1.9 years). Good to excellent intraoperator and interoperator reliability was seen (intraclass correlation coefficient range of 0.946-0.998). The use of cine loops improved the intraclass correlation coefficients for both intraoperator and interoperator reliability (0.5%-4% increases). The use of cine loops decreased the intraoperator standard error of the measurement and limits of agreement of the novice operator (decreases of 45%-73% and 24%-51%, respectively), and these became comparable to those of experienced operators using still images. The interoperator standard errors of the measurement dropped by 42% to 53%, whereas the limits of agreement dropped by 27% to 40%. No substantial changes were noted in the tibialis anterior across reliability metrics. CONCLUSIONS: Improved protocols that take advantage of using internal bony landmarks and cine loops during both the image-gathering and measurement processes improve the reliability of research examining muscle size changes in the lower leg or foot associated with muscle changes due to exercise, injury, disuse, or disease.

Diabetic Gait Is Not Just Slow Gait: Gait Compensations in Diabetic Neuropathy.

BACKGROUND: Neuropathic complications from diabetes mellitus affect multiple nerve types and may manifest in gait. However, gait compensations are still poorly understood, as narrow analyses and lack of speed controls have contributed to conflicting or equivocal results. PURPOSE: To evaluate gait mechanics and energetics in diabetic peripheral polyneuropathy. METHODS: Instrumented gait analysis was performed on 14 participants with diabetic peripheral polyneuropathy and 14 matched controls, walking at 1.0 m/s. A full-body model with a multisegment foot was used to calculate inverse dynamics and analyze sagittal plane metrics and time series waveforms across stance phase. RESULTS: Alterations included increased hip and knee flexion in early stance followed by a prolonged hip extension moment in midstance. Late stance ankle dorsiflexion and power absorption were increased, and final push-off was delayed and truncated. CONCLUSION: A neuropathic diabetic gait shares important similarities to a mild crouch gait with weakness/dysfunction in the foot and ankle. This study highlights two main compensation mechanisms that have been overlooked in previous literature. First, increased triceps surae stretch in terminal stance may be used to increase proprioception and/or energy storage, while a prolonged hip extension moment in midstance compensates for a limited push-off. These result in an overall workload shift from distal to proximal joints. Clinical assessment, monitoring, and treatment of neuropathy may benefit by focusing on these specific functional alterations.

Functional assessments of foot strength: a comparative and repeatability study.

BACKGROUND: Evaluating the strength of the small muscles of the foot may be useful in a variety of clinical applications but is challenging from a methodology standpoint. Previous efforts have focused primarily on the functional movement of toe flexion, but clear methodology guidelines are lacking. A novel foot doming test has also been proposed, but not fully evaluated. The purposes of the present study were to assess the repeatability and comparability of several functional foot strength assessment techniques. METHODS: Forty healthy volunteers were evaluated across two testing days, with a two-week doming motion practice period between them. Seven different measurements were taken using a custom toe flexion dynamometer (seated), custom doming dynamometer (standing), and a pressure mat (standing). Measurements from the doming dynamometer were evaluated for reliability (ICCs) and a learning effect (paired t-tests), while measurements from the toe flexion dynamometer and pressure mat were evaluated for reliability and comparability (correlations). Electromyography was also used to descriptively assess the extent of muscle isolation in all measurements. RESULTS: Doming showed excellent within-session reliability (ICCs > 0.944), but a clear learning effect was present, with strength (p < 0.001) and muscle activity increasing between sessions. Both intrinsic and extrinsic muscles were engaged during this test. All toe flexion tests also showed excellent reliability (ICCs > 0.945). Seated toe flexion tests using the dynamometer were moderately correlated to standing toe flexion tests on a pressure mat (r > 0.54); however, there were some differences in muscle activity. The former may better isolate the toe flexors, while the latter appeared to be more functional for many pathologies. On the pressure mat, reciprocal motion appeared to display slightly greater forces and reliability than isolated toe flexion. CONCLUSIONS: This study further refines potential methodology for foot strength testing. These devices and protocols can be duplicated in the clinic to evaluate and monitor rehabilitation progress in clinical populations associated with foot muscle weakness.

Passive hallux adduction decreases lateral plantar artery blood flow: a preliminary study of the potential influence of narrow toe box shoes.

BACKGROUND: Blood flow is essential in maintaining tissue health. Thus, compromised blood flow can prevent tissue healing. An adducted hallux, as seen inside a narrow shoe, may put passive tension on the abductor hallucis, compressing the lateral plantar artery into the calcaneus and restricting blood flow. The purposes of this study were to compare lateral plantar artery blood flow before and after passive hallux adduction and to compare blood flow with arch height. METHODS: Forty-five healthy volunteers (20 female, 25 male; age = 24.8 ± 6.8 yr; height = 1.7 ± 0.1 m; weight = 73.4 ± 13.5 kg) participated in this cross-over design study. Arch height index (AHI) was calculated, and blood flow measurements were obtained using ultrasound (L8-18i transducer, GE Logiq S8). The lateral plantar artery was imaged deep to abductor hallucis for 120 s: 60 s at rest, then 60 s of passive hallux adduction. Maximal passive hallux adduction was performed by applying pressure to the medial side of the hallux. Blood flow was calculated in mL/min, and pre-passive hallux adduction was compared to blood flow during passive hallux adduction. RESULTS: Log transformed data was used to run a paired t-test between the preadduction and postadduction blood flow. The volume of blood flow was 22.2% lower after passive hallux adduction compared to before (- 0.250 ± 0.063, p < 0.001). As AHI decreased, there was a greater negative change in blood flow. As baseline blood flow increased, there was also a greater negative change in blood flow. CONCLUSIONS: Our preliminary findings of decreased blood flow through passive hallux adduction indicate conditions that elicit passive hallux adduction (e.g. wearing narrow-toed shoes) may have important effects on foot blood flow. Individuals with lower AHI appear to have a greater risk of decreased blood flow with passive hallux adduction.

Validity and Reliability of Standing Posture Measurements Using a Mobile Application.

OBJECTIVE: The purpose of this study was to evaluate the validity and reliability of standing posture assessments in asymptomatic men using the PostureScreen Mobile (PSM) iOS application. METHODS: The standing posture of 50 asymptomatic male participants (24.04 ± 1.81 years) was measured during 3 trials on the same day. The following 10 measurements using the PSM app were compared to the criterion VICON 3-dimensional analysis: from the frontal plane, shift and tilt of the head, shoulders, and hips; and from the sagittal plane, shift of the head, shoulders, hips, and knees. We used Bayesian methods to analyze the data. RESULTS: Compared with the VICON measurements, PSM assessments of head tilt, shoulder tilt and shift, and hip tilt and shift in the frontal plane were biased. In the sagittal plane, PSM measurements of shoulder, hip, and knee shift were biased. Only head shift in the frontal and sagittal planes were comparable between the VICON and the PSM. The VICON and PSM had similar intraclass correlations in 6 of 10 measurements. The PSM assessments of head shift and tilt and shoulder tilt in the sagittal plane were significantly less reliable than with VICON. CONCLUSION: The use of the PSM app introduced significant bias in postural measurements in the frontal and sagittal plane. Until further research reports additional validity and reliability data of the PSM app, we suggest caution in the use of PSM app when highly accurate postural assessments are necessary.

Walking in Minimalist Shoes Is Effective for Strengthening Foot Muscles.

INTRODUCTION: Weakness of foot muscles may contribute to a variety of loading-related injuries. Supportive footwear may contribute to intrinsic foot muscle weakness by reducing the muscles' role in locomotion (e.g., absorbing forces and controlling motion). Increased stimulus to the foot muscles can be provided through a variety of mechanisms, including minimalist footwear and directed exercise. PURPOSE: To determine the effect of walking in minimalist footwear or performing foot strengthening exercises on foot muscle size and strength. METHODS: Fifty-seven runners were randomly assigned to one of three groups-minimalist shoe walking (MSW), foot strengthening (FS) exercise, or control (C). All groups maintained their prestudy running mileage throughout the study. The MSW group walked in provided footwear, increasing weekly the number of steps per day taken in the shoes. The FS group performed a set of progressive resistance exercises at least 5 d·wk. Foot muscle strength (via custom dynamometers) and size (via ultrasound) were measured at the beginning (week 0), middle (week 4), and end (week 8) of the study. Mixed model ANOVA were run to determine if the interventions had differing effects on the groups. RESULTS: There were significant group-time interactions for all muscle size and strength measurements. All muscle sizes and strength increased significantly from weeks 0 to 8 in the FS and MSW groups, whereas there were no changes in the C group. Some muscles increased in size by week 4 in the FS and MSW groups. CONCLUSIONS: Minimalist shoe walking is as effective as foot strengthening exercises in increasing foot muscle size and strength. The convenience of changing footwear rather than performing specific exercises may result in greater compliance.

The Role of the Midfoot in Drop Landings.

PURPOSE: The midfoot is instrumental to foot function; however, quantifying its roles in human movement has been difficult. A forceful dynamic activity like landing may help elucidate the midfoot's contribution to foot energetics and function. The main purpose of this study was to measure midtarsal joint kinematics and kinetics during a barefoot single-leg landing task. A secondary aim of this study was to explore the relationship between static foot posture and dynamic midfoot function. METHODS: In a cross-sectional study design, 48 females (age = 20.4 ± 1.8 yr, body mass index = 21.6 ± 1.7 kg·m) performed drop landings from a height of 0.4 m onto split force platforms. Subjects hung from wooden rings and landed on their dominant leg. Midtarsal joint kinematic and kinetic data were recorded using a 14-camera optical motion capture system in conjunction with two in-ground force platforms and a custom kinetic three-segment foot model. Foot structure was measuring using the arch height index (AHI) and the static midtarsal joint angle from motion capture. RESULTS: Kinematic data revealed an average sagittal plane midtarsal joint range of motion of 27° through the landing phase. Kinetic data showed that between 7% and 22% of the total lower extremity joint, work during the landing was performed by the midtarsal joint. Both standing AHI and static midtarsal joint angle (static MA) were correlated with sagittal plane midtarsal joint range of motion (standing AHI: r = -0.320, P = 0.026; static MA: r = 0.483, P < 0.001) and with midtarsal joint work (standing AHI: r = 0.332, P = 0.021; static MA: r = -0.323, P = 0.025). CONCLUSION: The midfoot contributes substantially to landing mechanics during a barefoot single-leg landing task. Static foot posture measures have limited value in predicting midfoot kinematics and kinetics during sportlike landings.

A sport-specific wearable jump monitor for figure skating.

Advancements in wearable technology have facilitated performance monitoring in a number of sports. Figure skating may also benefit from this technology, but the inherent movements present some unique challenges. The purpose of this study was to evaluate the feasibility of using an inertial measurement unit (IMU) to monitor three aspects of figure skating jumping performance: jump count, jump height, and rotation speed. Seven competitive figure skaters, outfitted with a waist-mounted IMU, performed a total of 59 isolated multi-revolution jumps and their competition routines, which consisted of 41 multi-revolution jumps along with spins, footwork, and other skills. The isolated jumps were used to develop a jump identification algorithm, which was tested on the competition routines. Four algorithms to estimate jump height from flight time were then evaluated using calibrated video as a gold standard. The identification algorithm counted 39 of the 41 program jumps correctly, with one false positive. Flight time and jump height errors under 7% and 15% respectively were found using a peak-to-peak scaling algorithm. Rotation speeds up to 1,500°/s were noted, with peak speeds occurring just over halfway between takeoff and landing. Overall, jump monitoring via IMUs may be an efficient aid for figure skaters training multi-revolution jumps.

Running decreases knee intra-articular cytokine and cartilage oligomeric matrix concentrations: a pilot study.

INTRODUCTION: Regular exercise protects against degenerative joint disorders, yet the mechanisms that underlie these benefits are poorly understood. Chronic, low-grade inflammation is widely implicated in the onset and progression of degenerative joint disease. PURPOSE: To examine the effect of running on knee intra-articular and circulating markers of inflammation and cartilage turnover in healthy men and women. METHODS: Six recreational runners completed a running (30 min) and control (unloaded for 30 min) session in a counterbalanced order. Synovial fluid (SF) and serum samples were taken before and after each session. Cytokine concentration was measured in SF and serum using a multiplexed cytokine magnetic bead array. Ground reaction forces were measured during the run. RESULTS: There were no changes in serum or SF cytokine concentration in the control condition. The cytokine GM-CSF decreased from 10.7 ± 9.8 to 6.2 ± 5.9 pg/ml pre- to post-run (p = 0.03). IL-15 showed a trend for decreasing concentration pre- (6.7 ± 7.5 pg/ml) to post-run (4.3 ± 2.7 pg/ml) (p = 0.06). Changes in IL-15 concentration negatively correlated with the mean number of foot strikes during the run (r 2 = 0.67; p = 0.047). The control condition induced a decrease in serum COMP and an increase in SF COMP, while conversely the run induced an increase in serum COMP and a decrease in SF COMP. Changes in serum and SF COMP pre- to post-intervention were inversely correlated (r 2 = 0.47; p = 0.01). CONCLUSIONS: Running appears to decrease knee intra-articular pro-inflammatory cytokine concentration and facilitates the movement of COMP from the joint space to the serum.

The Effect of Training in Minimalist Running Shoes on Running Economy.

The purpose of this study was to examine the effect of minimalist running shoes on oxygen uptake during running before and after a 10-week transition from traditional to minimalist running shoes. Twenty-five recreational runners (no previous experience in minimalist running shoes) participated in submaximal VO2 testing at a self-selected pace while wearing traditional and minimalist running shoes. Ten of the 25 runners gradually transitioned to minimalist running shoes over 10 weeks (experimental group), while the other 15 maintained their typical training regimen (control group). All participants repeated submaximal VO2 testing at the end of 10 weeks. Testing included a 3 minute warm-up, 3 minutes of running in the first pair of shoes, and 3 minutes of running in the second pair of shoes. Shoe order was randomized. Average oxygen uptake was calculated during the last minute of running in each condition. The average change from pre- to post-training for the control group during testing in traditional and minimalist shoes was an improvement of 3.1 ± 15.2% and 2.8 ± 16.2%, respectively. The average change from pre- to post-training for the experimental group during testing in traditional and minimalist shoes was an improvement of 8.4 ± 7.2% and 10.4 ± 6.9%, respectively. Data were analyzed using a 2-way repeated measures ANOVA. There were no significant interaction effects, but the overall improvement in running economy across time (6.15%) was significant (p = 0.015). Running in minimalist running shoes improves running economy in experienced, traditionally shod runners, but not significantly more than when running in traditional running shoes. Improvement in running economy in both groups, regardless of shoe type, may have been due to compliance with training over the 10-week study period and/or familiarity with testing procedures. Key pointsRunning in minimalist footwear did not result in a change in running economy compared to running in traditional footwear prior to 10 weeks of training.Both groups (control and experimental) showed an improvement in running economy in both types of shoes after 10 weeks of training.After transitioning to minimalist running shoes, running economy was not significantly different while running in traditional or minimalist footwear.