Non-circular chainrings theoretically enhance cycling performance by increasing effective chainring diameter and varying crank velocity, but research has failed to consistently reproduce the benefits in cycling trials. The aim of this study was (1) to investigate the effect of different chainring shapes on sagittal knee joint moment and sagittal lower limb joint powers and (2) to investigate whether alterations are affected by cadence and workload. Fourteen elite cyclists cycled in six conditions (70, 90 and 110 rpm, each at 180 and 300 W), for 2 min each, using three chainrings of different ovalities (1.0-1.215). Kinematic data and pedal forces were collected. For most conditions, only the chainring with the highest ovality (1.215) was characterised by smaller sagittal knee joint moments, smaller relative sagittal knee joint power contribution and larger relative sagittal hip joint power contribution, which suggests a change from maximising efficiency to maximising power production. Effect sizes increased with higher cadences, but not with higher workload. This study has application for athletes, clinicians and sports equipment industry as a non-circular chainring can change joint-specific power generation and decrease knee joint moment, but certain ovality seems to be necessary to provoke this effect.

3D scanning technology is widely used in medical and clothing applications as well as research projects. This paper presents our experiences with a low-cost hand-held 1 st generation Sense TM 3D scanner (3D Systems Inc., Rock Hill, SC, USA) including free software Sense (V2.2) [1]. The shape of the female torso, including breast tissue volume, was determined using 3D surface scans. Female upper body area implies special requirements for positioning of participant and handling of scanner to gain good scan quality for reliable surface geometry. Lighting, settings and options, advantages and drawbacks of this scanner, including dimensional tolerance and repeatability measurements using mannequin and human body are addressed. Data processing and anonymization issues in the included free software are shown. Dimensional accuracy has to be proven first before using the Sense TM 3D scanner. For this purpose, a rigid plastic mannequin with markups, so-called fiducial points, was used. The distance from incisura jugularis to umbilicus height and nipple distance were measured using manual anthropometry compasses and virtual measurement from the 3D scan. The deviation was 0.1 % and-0.03 %, respectively. Repeatability of measurements was determined calculating average error parameter from 5 scans in standing and supine position (lying on the back) using the alignment procedure in MeshLab (v1.3.4BETA) [2]. Mean average error was 0.26 mm for both standing and supine position using either 4 or 19 pairs of points for alignment. Keeping in mind that the scanner is optimized for human skin and not for plastic surface, which sometimes causes reflections, this deviation can be judged very low. In addition, repeatability measurements were carried out on 3 pilot study participants. Mean average error for all participants and positions was 1.33 mm. Compared to the element size of maximum 3 mm this error is acceptable. Hence, the low-cost Sense TM scanner can be used in research projects dealing with human body geometric measurements.

The definition of 3D Finite Element (FE) volume models of female torso requires geometry information of naked surface and material properties of human tissues. Analog methods determining breast volume by water immersion of breast or plaster casts are still referred to as gold standard [1]. However, the human body surface is nowadays digitized by 3D scanners, which have become handy and affordable in the last years [2,3]. The term segmentation describes the strategy for separating breast tissue region from 3D surface scans of the female thorax. Different segmentation strategies are proposed in literature, either by outline definition [3,4,5,6] or by creating a parametric surface (Coons patch) from boundary curves using fiducial points [1,4]. The volume between breast base (artificial chest wall) and skin surface forms breast volume. In this study, 59 participants (19 to 67 years, bra size 75B to 95G) were scanned with a low-cost hand-held 1 st generation Sense TM 3D scanner (3D Systems Inc., Rock Hill, SC, USA) in two different positions: standing upright on a turntable and lying on the back (supine), both with the palms of their hands resting on the anterior superior iliac spine. The supine position increases the visibility of the inframammary fold, a common problem especially in ptotic breasts [7]. The breast outline was marked with skin marker. From the 3D scan data in *.ply file format containing geometric and color information, triangular elements representing breast tissue and other regions were selected in open source software Blender 2.79b [8]. All selected regions were exported separately as *.stl files for further data processing in FE pre-processor Patran 2014.1 (MSC.Software Corporation, Santa Ana, CA, USA), where breast base was created and breast volume was calculated. Breast volume was compared to bra size and sister size groups, respectively, which usually shows relatively low accordance [9], indicating the importance of application and market specific determination of breast shape and volume.