EXPLORING THE POTENTIAL EFFECTS OF STRENGTH TRAINING ON RUNNING ECONOMY: A SIMULATION STUDY

Strength training can improve running economy (RE) and performance in distance runners. This study investigated the effect of potential adaptations stemming from strength training on RE using simulation. Muscle-tendon unit (MTU) properties (muscle strength and mass, pennation angle, tendon stiffness, fibre composition) of muscle groups were altered within muscle-driven simulations of running at 4.5 and 6.5 m·s-1. Outputs from the muscle-driven simulations were input to an energetics model to determine whole-body metabolic power. Alterations to MTU properties resulted in variable changes (range = 1.4% decrement – 8.9% improvement in RE) to whole-body metabolic power and RE. The findings highlight potential targets for strength training programs aiming to improve RE in distance runners

LOWER BODY MUSCULOTENDON UNIT FUNCTION DURING BOUNDING, HURDLE JUMPING AND RUNNING

To facilitate exercise prescription, this study compared the function of six lower limb musculotendon units during plyometric exercises with running. Fourteen distance runners performed overground running (3.89 m/s), bounding, and hurdle jumps. Computational simulations were used to compare musculotendon unit function, peak powers, and total work. Compared to running, the hurdle jumps had greater gluteus maximus peak power absorption (12.1%; SMD 0.65), and gluteus maximus (15.7%; SMD 0.51) and soleus (16.5%; SMD 0.92) total negative work. Hurdle jumps may be an appropriate exercise when higher eccentric loads of the gluteus maximus and soleus are required. Compared to running, bounding had increased gastrocnemius total negative work (63.8%; SMD 0.81) and may be suitable when eccentric overload of the gastrocnemius is desired

Centromere Protein B Null Mice are Mitotically and Meiotically Normal but Have Lower Body and Testis Weights

CENP-B is a constitutive centromere DNA-binding protein that is conserved in a number of mammalian species and in yeast. Despite this conservation, earlier cytological and indirect experimental studies have provided conflicting evidence concerning the role of this protein in mitosis. The requirement of this protein in meiosis has also not previously been described. To resolve these uncertainties, we used targeted disruption of the Cenpb gene in mouse to study the functional significance of this protein in mitosis and meiosis. Male and female Cenpb null mice have normal body weights at birth and at weaning, but these subsequently lag behind those of the heterozygous and wild-type animals. The weight and sperm content of the testes of Cenpb null mice are also significantly decreased. Otherwise, the animals appear developmentally and reproductively normal. Cytogenetic fluorescence-activated cell sorting and histological analyses of somatic and germline tissues revealed no abnormality. These results indicate that Cenpb is not essential for mitosis or meiosis, although the observed weight reduction raises the possibility that Cenpb deficiency may subtly affect some aspects of centromere assembly and function, and result in reduced rate of cell cycle progression, efficiency of microtubule capture, and/or chromosome movement. A model for a functional redundancy of this protein is presented

The effect of footwear on mechanical behaviour of the human ankle plantar-flexors in forefoot runners

PURPOSE: To compare the ankle plantar-flexor muscle-tendon mechanical behaviour during barefoot and shod forefoot running. METHODS: Thirteen highly trained forefoot runners performed five overground steady-state running trials (4.5 ± 0.5 m(.)s(-1)) while barefoot and shod. Three-dimensional kinematic and ground reaction force data were collected and used as inputs for musculoskeletal modelling. Muscle-tendon behaviour of the ankle plantar-flexors (soleus; medial gastrocnemius; and lateral gastrocnemius) were estimated across the stance phase and compared between barefoot and shod running using a two-way multivariate analysis of variance. RESULTS: During barefoot running peak muscle-tendon unit (MTU) power generation was 16.5% (p = 0.01) higher compared to shod running. Total positive MTU work was 18.5% (p = 0.002) higher during barefoot running compared to shod running. The total sum of tendon elastic strain energy was 8% (p = 0.036) greater during barefoot compared to shod running, however the relative contribution of tendon and muscle fibres to muscle-tendon unit positive work was not different between conditions. CONCLUSION: Barefoot forefoot running demands greater muscle and tendon work than shod forefoot running, but the relative contribution of tendon strain energy to overall muscle-tendon unit work was not greater

Australian secondary school principals’, parents’, and students’ attitudes to prescribed school footwear guidelines

Abstract Background Adolescents are often required to wear footwear that adheres to uniform guidelines at secondary school. There is a paucity of literature on factors influencing school footwear choice and what drives the development of school footwear guidelines. The aims of this study were to describe (i) current school footwear guidelines in secondary schools across Australia, (ii) factors that influence footwear choice in secondary school students and their parents, and (iii) principals, parents, and students’ beliefs on factors which contribute to school footwear guidelines. Methods An online survey was distributed to principals, secondary school students (aged 14–19 years) and their parents across Australia. The survey included questions on current school footwear guidelines, factors influencing footwear choice (for students and parents), participants beliefs on the effect footwear has on musculoskeletal health, current and previous lower limb pain, and beliefs on factors that contribute to school footwear guidelines. Parent and student responses to factors that influence their footwear choice were compared using proportional odds logistic regression. Students and parents’ responses to factors influencing footwear guidelines were compared to principal responses using proportional odds logistic regression. Significance was set at an alpha of < 0.05. Results Eighty principals, 153 parents and 120 secondary school students responded to the survey. 96% (77/80) of principals reported that their schools have set guidelines for school footwear. 88% of principals considered comfort to be important when developing school footwear guidelines. Proportional odds logistics regression showed that parents and students were 3.4 and 4.9 times more likely, respectively, than principals to rate comfort as being important when schools develop footwear guidelines. More than 40% of students reported experiencing musculoskeletal pain, and 70% of these students reported the pain to be exacerbated when in their school shoes. Less than a third of participants considered healthcare recommendations important to the development of footwear guidelines. Conclusions Nearly all principals that participated in this survey had set guidelines for school footwear. There is a discord between parents, students, and principals on the importance that factors such as comfort, play in the development of school footwear guidelines

Altered apoptotic profiles in irradiated patients with increased toxicity.

Purpose: A retrospective study of radiation-induced apoptosis in CD4 and CD8 T-lymphocytes, from 12 cancer patients who displayed enhanced toxicity to radiation therapy and 9 ataxia telangiectasia patients, was performed to test for altered response compared to healthy blood-donors and normal cancer patients. Methods and Materials: Three milliliters of heparinized blood from each donor was sent via express post to the Paul Scherrer Institute (PSI) for subsequent examination. The blood was diluted 1:10 in RPMI medium, irradiated with 0-, 2-, or 9-Gy X-rays, and incubated for 48 h. CD4 and CD8 T-lymphocytes were then labeled using FITC-conjugated antibodies, erythrocytes were lysed, and the DNA stained with propidium iodide. Subsequently, cells were analyzed using a Becton Dickinson FACScan flow cytometer. Radiation-induced apoptosis was recognized in leukocytes as reduced DNA content attributed to apoptosis-associated changes in chromatin structure. Apoptosis was confirmed by light microscopy, electron microscopy, and by the use of commercially available apoptosis detection kits (in situ nick translation and Annexin V). Data from hypersensitive individuals were compared to a standard database of 105 healthy blood-donors, and a database of 48 cancer patient blood donors who displayed normal toxicity to radiation therapy. To integrate radiosensitivity results from CD4 and CD8 T-lymphocytes after 2 and 9 Gy, z-score analyses were performed. Results: A cohort of 12 hypersensitive patients was evaluated; 8 showed enhanced early toxicity, 3 showed enhanced late toxicity, and 1 showed both. The cohort displayed less radiation-induced apoptosis (21.8 s) than average age-matched donors. A cohort of 9 ataxia telangiectasia homozygotes displayed even less apoptosis (23.6 s). Conclusion: The leukocyte apoptosis assay appears to be a useful predictor of individuals likely to display increased toxicity to radiation therapy; however, validation of this requires a prospective study. © 1999 Elsevier Science Inc