Arch Height Ratio Research Articles

Physical characteristics inducing Sever's disease in junior gymnasts

ObjectiveThis prospective cohort study aimed to determine characteristics contributing to the development of Sever's disease in junior gymnasts. MethodsThis study included 74 limbs from 37 junior gymnasts. The Baseline demographic data, flexibility measurements, foot alignments, trunk function tests, and functional balancing tests were used for evaluation. The incidence of Sever's disease among this cohort was assessed for six months after the first evaluations. We categorized those diagnosed by medical specialists as having Sever's disease into a Sever's disease group, while those with no foot pain or other diagnosed pathologies were in a no-symptom group. ResultsThe Junior gymnasts with Sever's disease had a lower arch height ratio and lower anterior star excursion balance test values. ConclusionsSever's disease in junior gymnasts may be potentially prevented through using a medial longitudinal arch support and/or undertaking dynamic postural balance training.

High Rate of Change of the Foot in Ecuadorian Children: The Need for Proper Shoe Design.

Physiological changes in the foot may be influenced by external factors such as shoe types or demographic parameters, leading to podiatric conditions in adulthood. The aim of this study was to assess the changes in morphological measurements of the feet of boys and girls during childhood and adolescence. A total of 1678 Ecuadorian children aged 8 to 17 years participated in the study. The length, width, and height of the foot were analyzed using a 3D scanner to obtain the arch height ratio for the diagnosis of pediatric flat foot. Statistical differences were observed for lengths, widths, and perimeters of the foot in boys aged 5 to 15-16 years and girls aged 5 to 12-13 years. Differences in the height of the navicular bone were found in all age groups, with changes from 2.8 to 4.1% in boys and from 1.3 to 1.5% in girls. The greatest differences between boys and girls of the same age were found at 14 years old onwards. The highest prevalence of flat foot was found in 8-year-old girls (64.9%) and in 12-year-old boys (82.5%). The feet of Ecuadorian children develop progressively during childhood and adolescence. Boys presented with longer and wider feet than girls of the same age. The highest prevalence of flat foot was found in 12-year-old boys and 8-year-old girls.

The effect of foot somatosensory loss in postural control during Functional reach test in patients with diabetic polyneuropathy: A controlled study

BackgroundIn patients with diabetic polyneuropathy (DPN), differences in postural control due to losing the lower limb somatosensory information were reported. However, it is still unclear by which mechanisms the dynamic postural instability is caused. ObjectivesThis study aimed to investigate postural control differences and neuromuscular adaptations resulting from foot somatosensory loss due to DPN. MethodsIn this controlled cross-sectional study, fourteen DPN patients and fourteen healthy controls performed the Functional Reach Test (FRT) as a dynamic task. The postural control metrics were simultaneously measured using force plate, motion capture system, and surface electromyography (sEMG). The main metrics including reach length (FR), FR to height ratio (FR/H), displacement of CoM and CoP, moment arm (MA), and arch height ratio. Also, kinematic (range of motion of ankle, knee, and hip joints), and sEMG metrics (latencies and root mean square amplitudes of ankle and hallux muscles) were measured. To compare variables between groups, the independent sample T-test for (normally distributed) and the Mann-Whitney U test (non-normally distributed) were used. ResultsThe subjects' reach length (FR), FR to height ratio, absolute MA, and displacement of CoM were significantly shorter than controls, while displacement of CoP was not significant. Arch height ratio was found significantly lower in DPN patients. We observed that CoM was lagging CoP in patients (MA = + 0.89) while leading in controls (MA = -1.60). Although, the muscles of patients showed significantly earlier activation, root mean square sEMG amplitudes were found similar. Also, DPN patients showed significantly less hip flexion, knee extension, and ankle plantar flexion. ConclusionsThis study presented that decreasing range of motion at lower limbs’ joints and deterioration in foot function caused poor performance at motor execution during FRT in DPN patients.

Effects of 10KM run on foot morphology and bilateral symmetry in male recreational runners.

Foot morphology and arch integrity do not remain constant during a running bout. Previous studies have reported inconsistent changes in foot sizes and arch parameters and this discrepancy may be related to the variation in their test duration, e.g., 15-min treadmill run vs. 30KM trial. Hence, this study sought to evaluate the change in foot morphology, arch integrity and bilateral symmetry after a 10KM run among 19 male recreational runners. Before and after the run, a portable foot scanner was used to capture the 3-dimensional foot images and measure foot dimensions in both weight-bearing and non-weight-bearing conditions. Foot arch integrity was quantified by arch height ratio, arch height index, and arch stiffness index (ASI). Bilateral symmetry was evaluated by calculating the symmetry index. Increased foot length (p = 0.007; = 0.18) and decreased ball girth (p = 0.038; = 0.11) were demonstrated following the run with absolute differences of less than 2mm. Navicular height, dorsum height, arch height ratio and arch height index significantly decreased after the run (p < 0.001; ≥0.30) whereas ASI increased (p < 0.001, = 0.33) and navicular height drop reduced (p < 0.001, = 0.37). Significances of symmetry index were only demonstrated for navicular height (p = 0.019, effect size = 0.37) and arch height ratio (p = 0.019, effect size = 0.42). A few changes in foot morphology were detected but a reduction in foot arch height was demonstrated, which may give shoe manufacturers insights into shoe design. Male recreational runners were recommended to choose shoes with arch support for maintaining foot arch function during a 10KM run.

一本歯サンダルを着用して行う足踏み運動が内側縦アーチ高と足底表面温度に与える影響

Single-tooth sandals under new development have special material and shape characteristics. Exercises with single-tooth sandals can increase pressing stimulus on the soles of the feet, thereby suppressing a decline in medial longitudinal arch and elevating sole surface temperature. This study thus aimed to examine the effects of exercise with single-tooth sandals on medial longitudinal arch and sole surface temperature. Sixteen young adults (23 ± 5 years) participated in 20 min of stepping exercise on the spot. They randomly put on a regular normal sandal (N conditions) or a single-tooth sandal (Z conditions) on each left and right side. Before and after exercise, medial longitudinal arch and sole surface temperature were assessed by digital caliper and straightedge and thermography, respectively. No significant differences in baseline parameters were observed between N and Z conditions. After exercise, arch height and arch height ratio significantly reduced in N conditions, but not in Z conditions. Central sole surface temperature in Z conditions also increased significantly, and the changes in surface temperature were significantly higher in Z conditions than in N conditions. Therefore, these findings suggest that exercise with single-tooth sandals has a positive effect on a suppressing decline in medial longitudinal arch and an elevation in sole surface temperature.

Damage and recovery of the intrinsic and extrinsic foot muscles from running a full marathon.

To investigate the effects of full marathon running on intrinsic and extrinsic foot muscle damage and to determine the relationship with the height change of the longitudinal foot arch following full marathon completion. Magnetic resonance imaging-measured transverse relaxation time (T2 ) of the abductor hallucis (ABH), flexor digitorum brevis (FDB) and quadratus plantae (QP), flexor digitorum longus (FDL), tibialis posterior (TP), and flexor hallucis longus (FHL) from 22 collegiate runners were assessed before and 1, 3, and 8 days after full marathon running. The three-dimensional foot posture of 10 of the 22 runners was further obtained using a foot scanner system before and 1, 3, and 8 days after the marathon. Marathon-induced increases in T2 were observed in the QP, FDL, TP, and FHL 1 day after the marathon (+7.5%, +4.7%, +6.7%, and +5.9%, respectively), with the increased T2 of TP persisting until 3 days after the marathon (+4.6%). T2 changes of FDL and FHL from pre-marathon to DAY 1 showed direct correlations with the corresponding change in the arch height ratio (r = 0.823, p = 0.003, and r = 0.658, p = 0.038). The damage and recovery response from a full marathon differed among muscles; QP, FDL, TP, and FHL increased T2 after the marathon, whereas ABH and FDB did not. In addition, T2 changes in FDL and FHL and the arch height ratio change were correlated. Our results suggest that the extrinsic foot muscles could be more susceptible to damage than the intrinsic during marathon running.

Characteristics of hindfoot morphology and ankle range of motion in young women with hallux valgus

BackgroundHallux valgus occurs more frequently in women as they age; therefore, it is beneficial to prevent hallux valgus in younger women. The purpose of this study was to clarify the characteristics of hindfoot morphology and the range of motion of the ankle joint with hallux valgus in young women.MethodsThe participants were 140 young women (mean age 18.8 ± 0.6 years). A three-dimensional footprint automatic measurement apparatus was used to measure the hallux valgus angle in the standing position and the arch-height ratio and heel-floor angle (HFA) in the standing and chair-sitting positions. The amount of change in foot morphology owing to differences in posture was calculated. The range of motion of the ankle joint dorsiflexion, plantarflexion, inversion, and eversion was measured. Participants were classified into two groups according to the presence of hallux valgus. Statistical analysis was used to compare hindfoot morphology and range of motion between the two groups, and the correlation between foot morphology and range of motion was investigated depending on the presence of hallux valgus.ResultsWith hallux valgus, the HFA tilted inwards (p = 0.010), and the change in the arch-height ratio due to the difference in posture was large (p = 0.021). There was no difference in the range of motion of the ankle joints with or without hallux valgus. In women with hallux valgus, the amount of change in arch height and HFA was correlated with the range of motion of eversion (r = 0.391, p = 0.027; r = -0.362, p = 0.042).ConclusionsWith hallux valgus, the hindfoot pronated, and the arch height decreased from sitting to standing. Furthermore, the amount of change in the hindfoot and midfoot due to posture was related to the range of motion of eversion.

Relationship between foot morphology, muscle strength, and physical performance test in women aged 65 years and older: a cross-sectional study

BackgroundHallux valgus is a foot deformity that may affect gait, thus increasing the risk of falls among older people. We investigated the relationship between foot morphology, muscle strength, and physical performance.MethodsIn this study, community-dwelling older people aged ≥65 years were included. A three-dimensional footprint automatic measurement apparatus was used to measure the hallux valgus angle, arch height ratio, and heel-floor angle. Furthermore, the toe flexor strength and ankle plantar flexion strength were measured. Physical performance tests included the five-repetition sit-to-stand test, one-leg standing time, maximal step length, functional reach test, and 5-m fastest walking time (walking time). The relationship between the hallux valgus angle and foot morphology and muscle strength was examined. In addition, factors affecting physical performance testing were assessed. Two-group comparisons, correlation, and multiple comparisons were used for statistical analyses.ResultsOf the 133 women (age 77.7 ± 6.2 years), 57 had hallux valgus and 76 had no hallux valgus. There was a significant difference in the arch height ratio and heel-floor angle between women with and without hallux valgus (p < 0.001). A correlation was found between the hallux valgus angle and the heel-floor angle (r = 0.468, p < 0.001) and arch height ratio (r = − 0.337, p < 0.001), respectively. Multiple regression analysis showed that the hallux valgus angle was related to functional reach (β = − 0.162, p = 0.042), and toe flexor strength was related to five-repetition sit-to-stand (β = − 0.182, p = 0.036), maximal step length (β = 0.328, p < 0.001), and walking time (β = − 0.219, p = 0.006).ConclusionsA relationship was found between the hallux valgus angle, arch height rate, and inward inclination angle of the calcaneus. Functional reach was predicted based on the hallux valgus angle, whereas the five-repetition sit-to-stand, maximal step length, and walking time were predicted based on toe flexor strength. Hallux valgus predicted not only the forefoot but also the foot morphology and was related to physical performance. From the perspective of motor function and fall prevention, efforts should be made to better understand and prevent the onset and progression of hallux valgus.

Elliptical-Shaped Fresnel Lens Design through Gaussian Source Distribution

A novel three-dimensional elliptical-shaped Fresnel lens (ESFL) analytical model is presented to evaluate and maximize the solar energy concentration of Fresnel-lens-based solar concentrators. AutoCAD, Zemax and Ansys software were used for the ESFL design, performance evaluation and temperature calculation, respectively. Contrary to the previous modeling processes, based on the edge-ray principle with an acceptance half-angle of ±0.27° as the key defining parameter, the present model uses, instead, a Gaussian distribution to define the solar source in Zemax. The results were validated through the numerical analysis of published experimental data from a flat Fresnel lens. An in-depth study of the influence of several ESFL factors, such as focal length, arch height and aspect ratio, on its output performance is carried out. Moreover, the evaluation of the ESFL output performance as a function of the number/size of the grooves is also analyzed. Compared to the typical 1–16 grooves per millimeter reported in the previous literature, this mathematical parametric modeling allowed a substantial reduction in grooves/mm to 0.3–0.4, which may enable an easy mass production of ESFL. The concentrated solar distribution of the optimal ESFL configuration was then compared to that of the best flat Fresnel lens configuration, under the same focusing conditions. Due to the elliptical shape of the lens, the chromatic aberration effect was largely reduced, resulting in higher concentrated solar flux and temperature. Over 2360 K and 1360 K maximum temperatures were found for ESFL and flat Fresnel lenses, respectively, demonstrating the great potential of the three-dimensional curved-shaped Fresnel lens on renewable solar energy applications that require high concentrations of solar fluxes and temperatures.

Upper body gait deviations in children with Duchenne muscular dystrophy

Previous studies have successfully used the longitudinal arch angle (LAA) to assess foot posture, but the measurement consistency and ability of the LAA to predict dynamic foot posture during activity in a variety of foot types have not been evaluated. The purpose of this study was to determine the reliability of the LAA as well as if the clinical method of assessing the LAA could be used to predict the LAA at midstance during walking for supinated, normal, and pronated foot types. The Arch Height Ratio was used to select 35 participants with 12 supinated, 46 normal, and 12 pronated feet. A standard goniometer was used to measure the LAA (CLINIC_LAA) on both feet while standing. Both feet were then filmed using a high speed camera while walking on a treadmill. The LAA was determined by the angle formed by two lines drawn between the markers placed on the first metatatarsal and medial malleolus with the apex the navicular tuberosity. The LAA in midstance (WALK_LAA) was determined using the mean of five walking trials. The reliability of the CLINIC_LAA assessed on both feet by two raters over two days were excellent. There was no difference between the left and right foot for the CLINIC_LAA. The Pearson correlation between CLINIC_LAA and WALK_LAA for all 70 feet was r = 0.96 (r2 = 0.92). The results indicate the LAA is highly predictive of foot posture at midstance in walking explaining over 90% of the variance for a wide range of foot types.

Increase in foot arch asymmetry after full marathon completion

ABSTRACT Long-distance running results in lowering of the foot medial longitudinal arch, but it is unknown whether the left and right arches decrease equally. This study aimed to determine whether foot arch asymmetry increases upon completion of a full marathon and to identify factors capable of explaining the degree of asymmetry of navicular height and navicular height displacement. The three-dimensional foot posture data of 74 collegiate runners were obtained using an optical foot scanner system before (PRE) and immediately after (POST) a full marathon. The navicular height and arch height ratio (normalised navicular height by foot length) of both feet significantly decreased from PRE to POST full marathon completion (44.3 ± 6.3 mm versus 40.8 ± 6.5 mm, 17.8 ± 2.5 versus 16.6 ± 2.7, respectively; p < 0.001, both). The asymmetry of the arch height ratio was significantly greater POST than PRE marathon. Multiple linear regression analysis indicated that the POST-race Asymmetry Index (AI) of navicular height was significantly predicted by the PRE-race AI of navicular height; navicular height displacement was predicted by PRE-race navicular height and the marathon time. Full marathon running induced increasing asymmetry and lowering of the medial longitudinal arch in runners.

Correlation of medial longitudinal arch morphology with body characteristics and locomotive function in community-dwelling older women: A cross-sectional study.

This cross-sectional study aimed to investigate the effects of foot arch deformities on physical characteristics, muscular strength, and motor function in older women depending on the presence or absence of pain. Overall, 145 community-dwelling women aged 65 to 90 years were included in this study. We measured the foot arch height ratio (AHR, dorsal height/truncated foot length) and classified participants with AHR values above, below, or within 1.5 standard deviations into the high-arched group (HAG), Low-Arched Group (LAG), or normal-arched group (NAG), respectively. We also compared body characteristics (age, height, weight, body mass index (BMI), and skeletal mass index), muscle strength (handgrip strength and intrinsic foot strength (IFS)), and locomotive function (two-step value and gait speed) among the three groups. Locomotive examination and muscle strength showed significant differences among the three groups only in the presence of pain; in the two-step test, HAG, NAG, and LAG values were 0.98 cm/cm, 1.19 cm/cm, and 1.18 cm/cm, respectively. The IFS measured 19.2 N, 24.2 N, 31.0 N, respectively, in the HAG, NAG, and LAG. This study suggests that decreased IFS affects the mobility function of high-arched feet in older women. Although there was no significant difference in the evaluation of pain, HAG showed the highest average value, which is considered to contribute to the decreased two-step value. It has been suggested that a high-arched foot in the presence of pain is associated with IFS weakness and may affect the decline of mobility function in older women.

The effect of pads on foot morphology in athletes with medial tibial stress syndrome.

Evaluation of the effect of a pad on foot morphologies in patients with medial tibial stress syndrome (MTSS) requires more reliable and objective methods, rather than conventional subjective observations. The objective of this study was to investigate the effect of pads on foot morphologies during quiet standing in athletes with MTSS. We measured three-dimensional foot morphologies in 30 feet with MTSS and 40 healthy feet. The analysis showed that Hallux valgus degree, calcaneal angle, arch height, and arch height ratio differed significantly as a result of the pad support, compared to no pad support in the MTSS group. The pad support only resulted in significant differences in arch height, compared to no support in the control group. Furthermore, thumb side angle, calcaneal angle, and arch height ratio were significantly different between the MTSS and control groups. Our study results suggest that changes in foot morphologies because of the use of a pad can be measured objectively in patients with MTSS.

Use of malleoli as an indicator for flatfoot in patients with Down syndrome: development of a simple and non-invasive evaluation method through medial longitudinal arch.

[Purpose] Flatfoot often presents in patients with Down syndrome, and it can be diagnosed using a simple radiograph. Consequently, due to radiograph limitations, alternative non-invasive testing must be determined. Conventionally, arch height ratio can be used for evaluation of the medial longitudinal arch, where the foot is evaluated by detecting the navicular bone on the foot surface. However, detection of the navicular tuberosity is difficult and even though the detection is relatively straightforward for patients without intellectual disability, measuring navicular bone is more difficult in patients with intellectual disability, such as those who have Down syndrome and are uncooperative with a tester. Therefore, we evaluated arch height ratio using the malleoli instead of the navicular bone to determine whether malleoli testing was appropriate for patients with Down syndrome that have an intellectual disability. [Participants and Methods] We conducted a retrospective study of 16 pairs of feet in 16 patients with Down syndrome, diagnosed with flatfoot. The height to the centre of the talo-navicular joint and that of the malleoli from the sole were measured on radiographs using weight-bearing conditions. [Results] The age range was 5.2 to 25.3 years. There was a correlation between the height of the navicular bone and that of the medial and lateral malleoli. [Conclusion] We conclude that the medial and lateral malleoli can substitute navicular bone as a landmark diagnosis test for flatfoot. Considering the close physical distance between the medial malleolus and navicular bone, and the association between the tibia and medial longitudinal arch, the medial malleolus may provide a better landmark in patients with Down syndrome with it being potentially less invasive for uncooperative patients.

Effect of patellofemoral pain on foot posture and walking kinematics

Background Excessive pronation has been implicated in patellofemoral pain (PFP) aetiology and foot orthoses are commonly prescribed for PFP patients. Pronation can be assessed using foot posture tests, however, the utility of such tests depends on their association with foot and lower-limb kinematics.Research questions Do PFP participants compared with healthy participants (1) have a more pronated foot measured with static foot tests and a kinematic multi-segmental foot model and (2) is there an association between static foot posture and foot and lower limb kinematics during walking?Methods A case-control study including 22 participants (n = 11 PFP, 5 females per group, aged 24 ± 3 (mean ± SD) years) was conducted. Foot posture measures included Arch Height Ratio, Navicular Drop (ND), and Foot Posture Index. Between-group comparisons of foot posture, segment and joint angle magnitudes, and associations between foot posture and kinematic data during gait were evaluated.Results There were no group differences in foot posture tests and mean joint angles. PFP participants had greater internal rotation of the shank and rearfoot segments, and adduction of the mid- and forefoot in the transverse plane (all p < 0.05). Greater ND was associated with increased forefoot abduction (rho=-0.68, p = 0.02) in healthy participants but no relationships were found between foot posture and kinematics in PFP participants.Significance Foot posture and kinematic data did not indicate excessive pronation in PFP participants questioning the use of orthoses to correct pronation. Larger studies are needed to determine the utility of foot posture tests as indicators of gait abnormalities in PFP.

Intra-rater reliability of arch height ratio measurement using the navicular tuberosity on the surface of the body in children with Down syndrome.

[Purpose] Flat feet frequently present in children with Down syndrome, necessitating a clinical evaluation and diagnosis. Therefore, a simple, low cost diagnostic method that can avoid radiation exposure is needed. This study was performed to investigate the intra-rater reliability of arch height ratio measurement using bone markers of the foot on the surface of the body in children with Down syndrome. [Participants and Methods] In total, 27 feet of 27 children with Down syndrome (16 male, 11 female) were included. We measured the length of each foot and the height of the navicular tuberosity on the surface of the body. The arch height ratio was calculated using the length and height. The same examiner performed three consecutive measurements of each of the two parameters. We calculated the arch height ratio using each of these measurements. The intraclass correlation coefficient [ICC(1,3)] of the length of the foot, height of the navicular tuberosity, and arch height ratio among the three measurements was obtained. [Results] The ICC of the height of the navicular tuberosity, length of the foot, and arch height ratio were quite high at 0.998, 0.999, and 0.997, respectively. [Conclusion] This study showed high intra-rater reliability of arch height ratio measurement using the length of the foot and height of the navicular tuberosity on the surface of the body in children with Down syndrome.

Relationship between foot morphology and toe muscle strength in female university students.

[Purpose] The purpose was to clarify the relationship between foot morphology and toe muscle strength in female university students. [Participants and Methods] Data from 103 female university students (age, 20.4 ± 1.6 years) on height, body weight, pain in the foot and toes, heel height (cm) of shoes worn in everyday life, and the number of times (per week) shoes with heels ≥3 cm were worn were collected. The hallux valgus angle and medial longitudinal arch height ratio of the foot were measured, and toe muscle strength was evaluated according to the strength of the toe flexor and abductor hallucis muscles. [Results] Arch height ratio was significantly lower with hallux valgus angle ≥16°. In the 206 feet, a very weak negative correlation was found between hallux valgus angle and arch height ratio. In 150 feet with hallux valgus angle <16°, a very weak correlation was found between toe flexor strength and arch height ratio. [Conclusion] Body mass index was within the normal range, and the period of wearing high-heeled shoes was short; these factors have no effect on hallux valgus angle. Hallux valgus may be prevented by increasing toe flexor strength to prevent downward movement of the navicular and first cuneiform bones.

Foot Characteristics and Falls among Community-dwelling Independent Elderly Women Who Can Walk Outdoors.

We examined the toe flexor strength, foot morphology, and falls in community-dwelling elderly women who could walk outdoors independently without aids. The presence or absence of falls in 1 year, the toe flexor strength, and foot morphology were recorded in 70 women. Hallux valgus was defined as a first phalangeal angle ≥16°. Falls were compared based on the presence or absence of hallux valgus using the chi-squared test. The toe flexor strength, arch height ratio (medial longitudinal arch), and spread ratio (lateral arch) were compared using the Mann-Whitney U-test according to the presence or absence of hallux valgus. Spearman's correlation coefficient was used to compare toe flexor strength and foot morphology. No difference in the fall rate was noted between those with hallux valgus on at least one foot and those without hallux valgus. No difference in toe flexor strength was noted between feet with and without hallux valgus. Correlations were found between the hallux valgus angle and the arch height (r=-0.228, P<0.01) and spread ratios (r=0.494, P<0.001). Among community-dwelling elderly women who can walk independently outdoors without aids, the presence or absence of hallux valgus does not affect the incidence of falls. The lack of correlation between toe flexor strength and foot morphology may support this conclusion.

Factor Analysis of Individual Factors Associated with Low Arch Height Ratio of the Foot by SVM-RFE

Factor Analysis of Individual Factors Associated with Low Arch Height Ratio of the Foot by SVM-RFE

Slam Loads and Kinematics of Wave-Piercing Catamarans During Bow Entry Events in Head Seas

Centre bow (CB) design for wave-piercing catamarans (WPCs) is a critical compromise between minimization of slamming and protection against deck diving. To inform the design process, this article investigates the slam loads and kinematics during bow entry events in regular head seas for a 112-m WPC with systematic variations to its CB and wet-deck geometry. Model tests using a 2.5-m hydroelastic segmented catamaran considered five different CB configurations, designated as the parent, high, low, long, and short CB. The results indicated that changes in the CB length had little effect on the general kinematic trends obtained for the pitch, heave, and bow vertical displacement at the instant of slamming, but increasing the wet-deck height resulted in an increase in heave (but not pitch) at slamming. Two new design ratios are proposed. The CB immersion depth to arch height ratio showed slamming occurring in the range of 0.3–0.6 depending on the wave encounter frequency and the CB configuration. The CB buoyancy in the encountered waves was estimated by considering both immersion depth and area along the CB in waves through relative motion analyses. It was found that the buoyancy to slam force ratio increased with increasing wet-deck height but not with increasing CB length. This suggests that an optimal CB configuration could be achieved by first modifying the arched cross-structure to reduce the arch filling effect on slamming severity and then maximizing the CB buoyancy to slam force ratio by increasing either the wet-deck height or the CB length. 1. Introduction An above-water centre bow (CB) for improving seakeeping is a feature of modern wave-piercing catamarans (WPCs) (Soars 1993; Boulton 1998; Fang &amp; Chan 2007; Dubrovsky 2014). Figure 1 shows a 112-m Incat WPC with the CB located between the two demihulls. There are several important factors to be considered when designing such a central bow. First, the reserve buoyancy offered by the CB is the primary design factor for providing a pitchrestoring moment and eliminating deck diving in the following waves (Davis &amp; Whelan 2007). Second, the CB configuration can influence the slamming loads in WPCs during bow entry in waves (Lavroff et al. 2013). This is due to the complex fluid-structure interaction in the CB area. When the CB enters waves, the water gradually fills the spaces between the CB and demihulls, referred to here as archways, and may result in complete closure of the archways and slamming in excessive pitch conditions. Finally, the frequency of slamming occurrence is, to some extent, related to the CB design as it contributes to lateral jet flow during the CB entry. As a result, slamming may occur in even partial water entrapment below the arch wet-deck cross-structure, which could be the case in small pitch motions (Lavroff &amp; Davis 2015).