Reliability and validity of depth camera 3D scanning to determine thigh volume

Gross thigh volume is a key anthropometric variable to predict sport performance and health. Currently, it is either estimated by using the frustum method, which is prone to high inter-and intra-observer error, or using medical imaging, which is expensive and time consuming. Depth camera 3D-imaging systems offer a cheap alternative to measure thigh volume but no between-session reliability or comparison to medical imaging has been made. This experiment established between-session reliability and examined agreement with magnetic resonance imaging (MRI). Forty-eight male cyclists had their thigh volume measured by the depth camera system on two occasions to establish between-session reliability. A subset of 32 participants also had lower body MRIs, through which agreement between the depth camera system and MRI was established. The results showed low between-session variability (CV = 1.7%; Absolute Typical Error = 112 cm³) when measuring thigh volume using the depth camera system. The depth camera systematically measured gross thigh volume 32.6cm³ lower than MRI. These results suggest that depth camera 3D-imaging systems are reliable tools for measuring thigh volume and show good agreement with MRI scanners, providing a cheap and time-saving alternative to medical imaging analysis.     

Validity and repeatability of a depth camera-based surface imaging system for thigh volume measurement

Complex anthropometrics such as area and volume, can identify changes in body size and shape that are not detectable with traditional anthropometrics of lengths, breadths, skinfolds and girths. However, taking these complex with manual techniques (tape measurement and water displacement) is often unsuitable. Three-dimensional (3D) surface imaging systems are quick and accurate alternatives to manual techniques but their use is restricted by cost, complexity and limited access. We have developed a novel low-cost, accessible and portable 3D surface imaging system based on consumer depth cameras. The aim of this study was to determine the validity and repeatability of the system in the measurement of thigh volume. The thigh volumes of 36 participants were measured with the depth camera system and a high precision commercially available 3D surface imaging system (3dMD). The depth camera system used within this study is highly repeatable (technical error of measurement (TEM) of <1.0% intra-calibration and ~2.0% inter-calibration) but systematically overestimates (~6%) thigh volume when compared to the 3dMD system. This suggests poor agreement yet a close relationship, which once corrected can yield a usable thigh volume measurement.     

Assessment of a Microsoft Kinect-based 3D scanning system for taking body segment girth measurements: a comparison to ISAK and ISO standards

Use of anthropometric data to infer sporting performance is increasing in popularity, particularly within elite sport programmes. Measurement typically follows standards set by the International Society for the Advancement of Kinanthropometry (ISAK). However, such techniques are time consuming, which reduces their practicality. Schranz et al. recently suggested 3D body scanners could replace current measurement techniques; however, current systems are costly. Recent interest in natural user interaction has led to a range of low-cost depth cameras capable of producing 3D body scans, from which anthropometrics can be calculated. A scanning system comprising 4 depth cameras was used to scan 4 cylinders, representative of the body segments. Girth measurements were calculated from the 3D scans and compared to gold standard measurements. Requirements of a Level 1 ISAK practitioner were met in all 4 cylinders, and ISO standards for scan-derived girth measurements were met in the 2 larger cylinders only. A fixed measurement bias was identified that could be corrected with a simple offset factor. Further work is required to determine comparable performance across a wider range of measurements performed upon living participants. Nevertheless, findings of the study suggest such a system offers many advantages over current techniques, having a range of potential applications.     

Prediction of segmental lean mass using anthropometric variables in young adults

Abstract

The aim of the present study was to develop and cross-validate anthropometrical prediction equations for segmental lean tissue mass (SLM). One hundred and seventeen young healthy Caucasians (67 men and 50 women; mean age: 31.9 ± 10.0 years; Body Mass Index: 24.3 ± 3.2 kg · m^?2) were included. Body mass (BM), stretch stature (SS), 14 circumferences (CC), 13 skinfolds (SF) and 4 bone breadths (BB) were used as anthropometric measurements. Segmental lean mass of both arms, trunk and both legs were measured by dual energy X-ray absorptiometry as the criterion method. Three prediction equations for SLM were developed as follows: arms = 40.394(BM) + 169.836(CCarm-tensed) + 399.162(CCwrist) – 85.414(SFtriceps) – 39.790(SFbiceps) – 7289.190, where Adj.R ² = 0.97, P < 0.001, and standard error of estimate (SEE) = 355 g;trunk = 181.530(BM) + 155.037(SS) + 534.818(CCneck) + 175.638(CCchest) ? 88.359(SFchest) ? 147.232(SFsupraspinale) ? 46522.165, where Adj.R ² = 0.97, P < 0.001, and SEE = 1077g; and legs = 55.838(BM) + 88.356(SS) + 235.579(CCmid-thigh) + 278.595(CCcalf) + 288.984(CCankle) ? 84.954(SFfront-thigh) ? 53.009(SFmedial calf) ? 28522.241, where Adj.R ² = 0.96, P < 0.001, and SEE = 724 g. Cross-validation statistics showed no significant differences (P < 0.05) between observed and predicted SLM. Root mean squared errors were smallest for arms (362 g), followed by legs (820 g) and trunk (1477 g). These new prediction equations allow an accurate estimation of segmental lean mass in groups of young adults, but estimation errors of 8 to 14% can occur in certain individuals.     

Digit ratio (2D:4D) and competition level in world-class female gymnasts

Abstract

In this study the relationship between the digit ratio (2D:4D) and artistic gymnastics performance and competition level was investigated in a sample of Caucasian world-class female gymnasts (n = 145). The sample was divided into three competition events (compulsories, free work, final score). Within each event three performance groups (lowest, middle, and highest) were based on the competition scores gathered at the World Championships at Rotterdam, the Netherlands, in 1987. Lengths of the digits were measured on X-rays of the left hand. Several anthropometric dimensions were measured and from those measurements an androgyny index (Bayer & Bayley) and somatotype components (endomorphy, mesomorphy, ectomorphy) were calculated. Although significant differences in some anthropometric characteristics between the performance level groups within each competition event were observed, no significant differences in the 2D:4D ratios were found between the performance level groups, varying from 0.918 ± 0.020 to 0.924 ± 0.020. Also, no significant correlations were observed between the 2D:4D ratio and anthropometric, androgyny, and somatotype characteristics, r varying from r = –0.11 to r = +0.12. It can be concluded that in this sample the 2D:4D digit ratio, unlike other anthropometric characteristics, is not a discriminating factor for the performance in artistic gymnastics performance on a world-class level.     

Three-dimensional anthropometric analysis: Differences between elite Australian rowers and the general population

Abstract

The aim of this study was to quantify the anthropometric differences between elite senior Australian rowers and the Australian adult population using three-dimensional (3D) whole-body scanning. The dimensions of senior rowers competing at the 2007–2008 Australian Rowing Championships were compared with those of an age-matched sample of Australian adults. Mass, height, and sitting height were measured before the participants underwent a 3D whole-body scan, with lengths, breadths, girths, cross-sectional and surface areas, and volumes extracted from each scan. Differences in means and variability between the two groups were expressed as standardized effect sizes and ratios of coefficients of variation. Heavyweight rowers were generally much larger than the general population in absolute size, with 3D dimensions and height and mass showing the largest effects. In contrast, lightweight rowers were generally similar or smaller in absolute and proportional size. The dimensions of rowers, especially the lightweights, were also generally less variable than those of the general population. The greatest differences between elite rowers and the general population were seen in dimensions that could not be captured without 3D scanning, such as segmental volumes and cross-sectional areas.     

Bioimpedance patterns and bioelectrical impedance vector analysis (BIVA) of road cyclists

Bioelectrical impedance vector-analysis (BIVA) describes cell-mass, cell function and hydration status of an individual or a group. The goal of the present investigation was to provide bioelectrical impedance data for 525 male road cyclists (155 professionals, 79 elite, 59 elite-youth, and 232 amateurs) at the time of their optimal performance level. Data were plotted on the resistance-reactance (R-Xc) graph to characterize cyclists group vectors using BIVA. Compared to the general male population, the mean vector position of the road cyclists indicates a higher body cell mass (BCM) and phase angle (p<0.001). The vector position of the high-performance, compared to the amateur cyclists showed similar patterns with higher BCM and phase angles and higher reactance values for the high-performance athletes (p<0.001). The bio-impedance data were used to calculate the 50%, 75%, and 95% tolerance ellipses of each group of cyclists. The characteristic vector positions of the road cyclists indicate normal hydration and greater muscle mass and function of the high-performance cyclists compared to amateur cyclists and the normal population. The cyclists specific tolerance ellipses, particularly the high-performance cyclists might be used for classifying a cyclist according to the individual vector position and to define target vector regions for lower level cyclists.     

Determination of thigh volume in youth with anthropometry and DXA: Agreement between estimates

Abstract

This study examined the agreement between estimates of thigh volume (TV) with anthropometry and dual-energy x-ray absorptiometry (DXA) in healthy school children. Participants (n=168, 83 boys and 85 girls) were school children 10.0–13.9 years of age. In addition to body mass, height and sitting height, anthropometric dimensions included those needed to estimate TV using the equation of Jones & Pearson. Total TV was also estimated with DXA. Agreement between protocols was examined using linear least products regression (Deming regressions). Stepwise regression of log-transformed variables identified variables that best predicted TV estimated by DXA. The regression models were then internally validated using the predicted residual sum of squares method. Correlation between estimates of TV was 0.846 (95%CI: 0.796–0.884, S_y·x=0.152L). It was possible to obtain an anthropometry-based model to improve the prediction of TVs in youth. The total volume by DXA was best predicted by adding body mass and sum of skinfolds to volume estimated with the equation of Jones & Pearson (R=0.972; 95%CI: 0.962–0.979; R ²=0.945).     

America's Cup yacht racing: Race analysis and physical characteristics of the athletes

Abstract

The America's Cup is the oldest competing trophy in sport, yet little is known of the nature and intensity of racing or the physical characteristics of the athletes. In this study, aspects of the physical demands of America's Cup yacht racing were analysed, including the intensity of exercise and activity pattern of “grinding”. Anthropometric data were collected from 92 professional male America's Cup sailors, and fitness data from a top-4 and a lower-7 ranking team during the 32nd America's Cup. Over the 135 races, mean race duration was 82 min (s = 9), with 20 tacks (s = 10) and 8 gybes (s = 3) per race. Grinding bouts were 5.5 s (s = 5.4; range: 2.2–66.3) long, with 143 exercise bouts per race and an exercise-to-rest ratio of 1:6. Mean and peak heart rate was 64% and 92% of maximum for all positions, with bowmen highest (71% and 96%). Grinders were taller, heavier, and stronger than all other positions. Body fat was similar between positions (13%, s = 4). The higher-standard team was stronger and had greater strength endurance, which probably contributed to their quicker manoeuvres. Intensity of exercise was dependent on the similarity of competing boats and the role of the athlete. The short duration and intermittent nature of grinding is indicative of predominantly anaerobic energy provision.     

Effect of Weight Training on Self-Concept: A Profile of those Influenced Most

Abstract

This study was conducted to determine the effect of weight training on the self-concepts of college males. Another purpose was to identify the types of males, relative to measures of extroversion, neuroticism, body cathexis, somatotype, and muscular strength, who experience the most improvement in self-concept during a lifting program. Subjects of the experimental group (n = 113) trained with weights twice each week for 16 weeks, while controls (n = 127) were educated relative to personal health concepts. The results revealed significant posttest differences in global, internal, and external self-concept between the groups, confirming the hypothesis that regular weight training is positively associated with the improvement of self-concept. Pretest body cathexis, self-concept, and neuroticism scores were significant predictors of global self-concept change from the pretest to the posttest, whereas pretest measures of extroversion, somatotype, and muscular strength were not. Changes in neuroticism, body cathexis, and muscular strength scores were significant predictors of self-concept change, while extroversion change was not, indicating that the positive association between weight training and self-concept enhancement is multivariately determined, and that some types of males experience more improvement of self-concept than others during a weight training regime.     

Countermovement jump performance assessment using a wearable 3D inertial measurement unit

The aim of this study was to validate a wearable inertial measurement unit (IMU), containing a 3D accelerometer and gyroscope, for the estimation of countermovement jump height. The absolute vertical acceleration of the IMU positioned on the back of the participant at L5 level, compensated for trunk rotations, was used to obtain jump height by applying the equation of free-fall to the motion of the IMU. The methodology was tested on 28 participants performing five countermovement jumps each. A reference value for this quantity was obtained using stereophotogrammetry (35.4 cm, s = 4.9). Jump height scores obtained using the proposed methodology (35.9 cm, s = 5.5) presented no significant difference with respect to stereophotogrammetry (P = 0.61). A low bias of 0.6 cm confirmed the accuracy of the estimate, which also showed a high (r = 0.87) and significant (P < 0.0001) correlation with reference values. Furthermore, without compensating accelerations for trunk rotation, jump height was largely underestimated (P < 0.0001) (bias: -12.7 cm) and poorly associated (r = 0.31) with stereophotogrammetry. The results of this study show that the estimation of jump height using inertial sensors leads to accurate results when the measured accelerations are corrected for trunk rotations.     

Whole-body vibration can reduce calciuria induced by high protein intakes and may counteract bone resorption: A preliminary study

Abstract

Excess protein intake can adversely affect the bone via an increase in calcium excretion, while suitable mechanical loading promotes osteogenesis. We therefore investigated whether vibration exposure could alleviate the bone mineral losses associated with a metabolic acidosis. Ten healthy individuals aged 22 – 29 years (median = 25) underwent three 5-day study periods while monitoring their dietary intake. The study consisted of recording the participants' usual dietary intake for 5 consecutive days. Participants were then randomly divided into two groups, one of which received a protein supplement (2 g · kg^?1 body mass · day^?1; n = 5) and the other whole-body low-magnitude (3.5 g), low-frequency (30 Hz) mechanical vibration (WBV) delivered through a specially designed vibrating plate for 10 min each day (n = 5). Finally, for the third treatment period, all participants consumed the protein supplement added to their normal diet and were exposed to WBV exercise for 10 min per day. Daily urine samples were collected throughout the experimental periods to determine the excretion of calcium, phosphate, titratable acid, urea, and C-telopeptide. As expected, when the participants underwent the high protein intake, there was an increase in urinary excretion rates of calcium (P < 0.001), phosphate (P < 0.003), urea (P < 0.001), titratable acid (P < 0.001), and C-telopeptide (P < 0.05) compared with baseline values. However, high protein intake coupled with vibration stimulation resulted in a significant reduction in urinary calcium (P = 0.006), phosphate excretion (P = 0.021), and C-telopeptide (P < 0.05) compared with protein intake alone, but did not affect titratable acid and urea output. The participants showed no effect of WBV exercise alone on urinary excretion of calcium, phosphate, urea, titratable acid, or C-telopeptide. The results indicate that vibration stimulation can moderate the increase in bone resorption and reduction in bone formation caused by a metabolic acidosis.     

Promoting physical activity using a wearable activity tracker in college students: A cluster randomized controlled trial

This study examined the effects of utilizing a wearable activity tracker in a credit-based physical activity instructional program (PAIP) for promoting physical activity (PA) in college students. Fourteen PAIP courses in a large public university were randomly assigned into intervention (k = 7; n = 101) and control (k = 7; n = 86) groups. All courses focused on a core curriculum that covers basic exercise and behavioral science contents through lectures and activity sessions. A Misfit Flash activity tracker was provided to students in the intervention group. Objective PA assessments occurred at baseline, mid-, and end-of-semester during a 15-week academic semester. The control group showed a significant reduction in moderate- and vigorous-intensity PA (MVPA) minutes from baseline to the end-of-semester (P <.05), whereas the intervention group showed no changes in MVPA minutes over time. However, the intervention group also showed increased sedentary time and decreased time spent in light-intensity PA during the intervention period. Taken together, the present study found null effects of utilizing the wearable activity tracker in promoting PA in college students suggesting that intervention of primary using the wearable activity tracker as a behavior change strategy may not be effective to increase in PA in this setting.     

A 3D kinematic analysis of breathing patterns in competitive swimmers

Abstract

The purpose of this paper was to understand which differences long-term swimming training can cause on trunk mechanics during breathing and how these differences are related to the years of swimming training. The variations and coordination among trunk compartments were considered as target movement patterns. Video-based plethysmography was utilised for data acquisition and pre-processing. A group of swimmers, who followed a long-term intensive swimming training previously to this study, was compared with a non-swimmer control group. The participants of both groups performed quiet breathing and vital capacity tests. From the compartmental volumes associated with each breathing curves, the relative amplitude and cross-correlation among these volumetric time-varying signals were calculated, in order to analyse the relative partial volume variation and the coordination among trunk compartments involved in respiration. The results of a Mixed-ANOVA test (P ≤ 0.05) revealed higher coefficient of variation (P < 0.001) and correlations among trunk compartments in the swimmers group when vital capacity was performed. Significant linear regression was found between the years of swim training and the coefficients of variation and correlation. The results suggest that after long periods of intensive swim training, athletes might develop specific breathing patterns featuring higher volume variations in the abdominal region and more coordination among compartments involved in forced respiratory tasks such as vital capacity.     

Lower leg and foot contributions to turnout in female pre-professional dancers: A 3D kinematic analysis

Turnout is a central element of classical ballet which involves sustained external rotation of the lower limbs during dance movements. Lower leg and foot compensation mechanisms which are often used to increase turnout have been attributed to the high incidence of lower limb injury in dancers. Evaluation of dancers’ leg posture is needed to provide insight into the lower limb kinematic strategies used to achieve turnout. The primary purpose of this study was to use 3D kinematic analyses to determine the lower leg and foot compensations that are incorporated by female university dancers to accentuate their turnout. Active and passive external tibiofemoral rotation (TFR) was also measured. A moderate-strong negative relationship was observed between hip external rotation (HER) and foot abduction in the three first position conditions. A moderate negative relationship was found between passive TFR and foot abduction in all first position conditions. Our findings suggest dancers are more likely to pronate, than rotate the knee to compensate for limited HER. Dancers with a limited capacity to pronate may force additional rotation via the knee. Ongoing research would benefit from more in-depth analyses of the foot/ankle complex using a multi-segment foot model.     

Lean mass as a total mediator of the influence of muscular fitness on bone health in schoolchildren: a mediation analysis

This report aims to analyse the independent association of lean mass and muscle fitness with bone mineral content (BMC) and bone mineral density (BMD), and to examine whether the relationship between muscle fitness and bone health is mediated by lean mass. Body composition (by dual energy X-ray absorptiometry (DXA)), muscle fitness, physical activity, age and height were measured in 132 schoolchildren (62 boys, aged 8–11 years). Analysis of covariance tested differences in bone-related variables by lean mass and muscle fitness, controlling for different sets of confounders. Linear regression models fitted for mediation analyses examined whether the association between muscle fitness and bone mass was mediated by lean mass. Children with good performance in handgrip and standing long jump had better and worse bone health, respectively. These differences disappeared after controlling for lean mass. Children with high lean mass had higher values in all bone-related variables. In addition, the relationship between muscle fitness and bone mass was fully mediated by lean mass. In conclusion, the relationship between upper-limbs muscle fitness and bone health seems to be dependent on lean mass but not on muscle fitness. Schoolchildren with high lean mass have more BMC and BMD in all regions. Lean mass mediates the association between muscle fitness and bone mass.     

The use of 2D and 3D information in a perceptual-cognitive judgement task

Abstract

We examined whether the use of three-dimensional (3D) simulations in an off-field offside decision-making task is beneficial compared to the more widely available two-dimensional (2D) simulations. Thirty-three assistant referees, who were all involved in professional football, participated in the experiment. They assessed 40 offside situations in both 2D and 3D formats using a counterbalanced design. A distinction was made between offside situations near (i.e., 15 m) and far (i.e., 30 m) from the touchline. Subsequently, a frame recognition task was performed in which assistant referees were asked to indicate which of the five pictures represented the previous video scene. A higher response accuracy score was observed under 3D (80.0%) compared to 2D (75.0%) conditions, in particular for the situations near the touchline (3D: 81.8%; 2D: 72.7%). No differences were reported between 2D and 3D in the frame recognition task. Findings suggest that in highly dynamic and complex situations, the visual system can benefit from the availability of 3D information, especially for relatively fine, metric position judgements. In the memory task, in which a mental abstraction had to be made from a dynamic situation to a static snapshot, 3D stereo disparities do not add anything over and beyond 2D simulations. The specific task demands should be taken into account when considering the most appropriate format for testing and training.     

Relationships between cardiorespiratory fitness,inhibition, and math fluency: A cluster analysis

ABSTRACT

This study identified clusters of adolescents who share similar cardiorespiratory fitness levels and analysed the relationships between cardiorespiratory fitness, inhibition, and math fluency in each of the clusters. The subjects were 490 high-school students aged 10–16 years. The mean age was 13.82 years (SD = 1.12). Latent class analysis identified three clusters with high, medium, and low levels of cardiorespiratory fitness. The high-fitness cluster achieved higher scores in inhibition and math fluency than the low-fitness cluster. Path analysis revealed that the influence of cardiorespiratory fitness on inhibition was non-existent in the three clusters. The effect of inhibition on math fluency was positive and significant in all three cardiorespiratory fitness levels. Cardiorespiratory fitness had a direct, positive, and significant effect on math fluency only in the high-fitness cluster. Therefore, a high level of cardiorespiratory fitness is a significant determining factor in the explanation of math fluency. These results indicate that inhibition does not mediate the relationship between cardiorespiratory fitness and math fluency. However, the benefits of cardiorespiratory fitness affect math fluency, which has important implications for the educational environment and the teaching/learning process.     

Lumbar spinal loading during bowling in cricket: a kinetic analysis using a musculoskeletal modelling approach

The objective of the study was to evaluate two types of cricket bowling techniques by comparing the lumbar spinal loading using a musculoskeletal modelling approach. Three-dimensional kinematic data were recorded by a Vicon motion capture system under two cricket bowling conditions: (1) participants bowled at their absolute maximal speeds (max condition), and (2) participants bowled at their absolute maximal speeds while simultaneously forcing their navel down towards their thighs starting just prior to ball release (max-trunk condition). A three-dimensional musculoskeletal model comprised of the pelvis, sacrum, lumbar vertebrae and torso segments, which enabled the motion of the individual lumbar vertebrae in the sagittal, frontal and coronal planes to be actuated by 210 muscle-tendon units, was used to simulate spinal loading based on the recorded kinematic data. The maximal lumbar spine compressive force is 4.89 ± 0.88BW for the max condition and 4.58 ± 0.54BW for the max-trunk condition. Results showed that there was no significant difference between the two techniques in trunk moments and lumbar spine forces. This indicates that the max-trunk technique may not increase lower back injury risks. The method proposed in this study could be served as a tool to evaluate lower back injury risks for cricket bowling as well as other throwing activities.     

身体的关切:体育美学的当代使命

体育运动之美从身之动的主观体验来把握,可分为3种不同水平的审美体验:一是源自运动中肌肉系统产生的并伴随着情感体验的"运动快感";二是建立在第一反射运动快感基础上,源自对技术动作"内模仿"的"运动联想";三是超越于二级反射的感觉共鸣,是一种心灵走出感官与运动意义相融相忘的"身心通感"。只有从身体的外在形态转向对身体感觉与体验的关注,并致力于为身体的各种感觉,尤其是运动感觉在运动中的充分滋养与发展提供美学依据,体育美学才能实现真正意义上的人文关怀。