Attentional and visual demands for sprint performance in non-fatigued and fatigued conditions: reliability of a repeated sprint test

Background: Physical performance measures are widely used to assess physical function, providing information about physiological and biomechanical aspects of motor performance. However they do not provide insight into the attentional and visual demands for motor performance. A figure-of-eight sprint test was therefore developed to measure the attentional and visual demands for repeated-sprint performance. The aims of the study were: 1) to assess test-retest reliability of the figure-of-eight sprint test, and 2) to study the attentional and visual demands for sprint performance in a non-fatigued and fatigued condition. Methods: Twenty-seven healthy athletes were included in the study. To determine test-retest reliability, a subgroup of 19 athletes performed the figure-of-eight sprint test twice. The figure-of-eight sprint test consisted of nine 30-second sprints. The sprint test consisted of three test parts: sprinting without any restriction, with an attention-demanding task, and with restricted vision. Increases in sprint times with the attention-demanding task or restricted vision are reflective of the attentional and visual demands for sprinting. Intraclass correlation coefficients (ICCs) and mean difference between test and retest with 95% confidence limits (CL) were used to assess test-retest reliability. Repeated-measures ANOVA were used for comparisons between the sprint times and fatigue measurements of the test parts in both a non-fatigued and fatigued condition. Results: The figure-of-eight sprint test showed good test-retest reliability, with ICCs ranging from 0.75 to 0.94 (95% CL: 0.40-0.98). Zero lay within the 95% CL of the mean differences, indicating that no bias existed between sprint performance at test and retest. Sprint times during the test parts with attention-demanding task (P = 0.01) and restricted vision (P < 0.001) increased significantly compared to the base measurement. Furthermore the sprint times and fatigue measurements increased significantly in fatigued condition. There was a significant interaction effect between test part and level of fatigue (P = 0.03). Conclusions: High ICCs and the absence of systematic variation indicate good test-retest reliability of the figure-of-eight sprint test. The attentional and visual demands for sprint performance, in both a non-fatigued and fatigued condition, can be measured in healthy team-sport athletes with the figure-of-eight sprint test

XML Template (2013) [3.12.2013–5:38pm] [1–11] //blrnas3/cenpro/ApplicationFiles/Journals/SAGE/3B2/JBAJ/Vol00000/130168/APPFile/SG-JBAJ130168.3d (JBA) [PREPRINTER stage] Article

Static versus vacuum cell seeding on high and low porosity ceramic scaffold

The balance between proliferation and transcription of angiogenic factors of mesenchymal stem cells in hypoxia

Bridging large bone defects with mesenchymal stromal cells-seeded scaffolds remains a big challenge in orthopedic surgery, due to the lack of vascularization. Within such a cell-scaffold construct, cells are exposed to ischemic conditions. When human mesenchymal stem cells (hMSCs) encounter hypoxic conditions, they show higher cell proliferation than at ambient oxygen levels. However, when hMSCs are exposed to prolonged ischemia, cell proliferation ceases completely. Exposure of hMSCs to hypoxic conditions is known to result in the transcription of angiogenic factors (AGF), which can promote the development of new blood vessels. In this study, we investigated at which oxygen level hMSC proliferation and the transcription of AGF were optimal. Human bone marrow-derived hMSCs were cultured at 0.1, 1, 2, 3, 4, 5, and 21% oxygen. Cell proliferation over 14 days was assayed using a DNA quantification method. hMSC metabolic activity over 14 days was measured using a MTT test. Quantitative RT-PCR was used to assess mRNA levels of angiogenic factors at the tested oxygen percentages. hMSCs showed the highest cell proliferation rate at 1% oxygen. The highest corrected cell metabolic rate was found at 21% oxygen, followed by 2% oxygen. HIF1 transcription did not increase under hypoxic conditions compared to 21% oxygen conditions. However, transcription of VEGF and ANG-1 was significantly higher at 2% oxygen than at 21% O-2. The optimum oxygen range at which hMSCs proliferated rapidly and angiogenic factors ANG-1 and VEGF simultaneously came to expression was from 1 to 2% oxygen

Static versus vacuum cell seeding on high and low porosity ceramic scaffolds

An adequate cell seeding technique is essential for effective bone regeneration on cell seeded constructs of porous tricalcium phosphates. In previous studies, dynamic cell seeding, in which an external force is applied to seed cells on a biomaterial, resulted in more homogeneous cell seeding in low porosity scaffolds than static seeding. The optimal cell seeding technique for high porosity scaffolds has not been defined yet. Human mesenchymal stem cells were isolated from bone marrow and characterized. The cells were seeded on low porosity (45%) and high porosity (90%) tricalcium phosphate scaffolds using a static and a vacuum seeding technique. LIVE/DEAD (R) staining of the cell-scaffold complexes followed by confocal laser scanning microscopy was used to measure cell proliferation, cell distribution and cell viability one, three and seven days after seeding. Cell proliferation was also quantified using a DNA quantification assay. Neither static nor vacuum seeding resulted in homogeneous cell seeding on both low and high porosity scaffolds. Cell density was lower on the inside than on the outside of the scaffolds. On low porosity scaffolds, the vacuum method yielded the highest numbers of cells compared to the static method. Low porosity scaffolds were seeded most homogeneously using the static seeding method. Seven days after seeding, numbers of adherent cells were comparable for both scaffold types and independent of the cell seeding technique used. In conclusion, on high porosity scaffolds, static seeding results in more homogeneous cell seeding and it is easier to use than a vacuum seeding technique

Attentional and visual demands for sprint performance in non-fatigued and fatigued conditions: reliability of a repeated sprint test

Abstract Background Physical performance measures are widely used to assess physical function, providing information about physiological and biomechanical aspects of motor performance. However they do not provide insight into the attentional and visual demands for motor performance. A figure-of-eight sprint test was therefore developed to measure the attentional and visual demands for repeated-sprint performance. The aims of the study were: 1) to assess test-retest reliability of the figure-of-eight sprint test, and 2) to study the attentional and visual demands for sprint performance in a non-fatigued and fatigued condition. Methods Twenty-seven healthy athletes were included in the study. To determine test-retest reliability, a subgroup of 19 athletes performed the figure-of-eight sprint test twice. The figure-of-eight sprint test consisted of nine 30-second sprints. The sprint test consisted of three test parts: sprinting without any restriction, with an attention-demanding task, and with restricted vision. Increases in sprint times with the attention-demanding task or restricted vision are reflective of the attentional and visual demands for sprinting. Intraclass correlation coefficients (ICCs) and mean difference between test and retest with 95% confidence limits (CL) were used to assess test-retest reliability. Repeated-measures ANOVA were used for comparisons between the sprint times and fatigue measurements of the test parts in both a non-fatigued and fatigued condition. Results The figure-of-eight sprint test showed good test-retest reliability, with ICCs ranging from 0.75 to 0.94 (95% CL: 0.40-0.98). Zero lay within the 95% CL of the mean differences, indicating that no bias existed between sprint performance at test and retest. Sprint times during the test parts with attention-demanding task (P = 0.01) and restricted vision (P Conclusions High ICCs and the absence of systematic variation indicate good test-retest reliability of the figure-of-eight sprint test. The attentional and visual demands for sprint performance, in both a non-fatigued and fatigued condition, can be measured in healthy team-sport athletes with the figure-of-eight sprint test.</p