Short-term bone biochemical response to a single bout of high-impact exercise

Bone response to a single bout of exercise can be observed with biochemical markers of bone formation and resorption. The purpose of this study was to examine the response of bone biochemical markers to a single bout of exhaustive high-impact exercise. 15 physically active young subjects volunteered to participate. The subjects performed continuous bilateral jumping with the ankle plantarflexors at 65 % of maximal ground reaction force (GRF) until exhaustion. Loading was characterized by analyzing the GRF recorded for the duration of the exercise. Venous blood samples were taken at baseline, immediately after, 2h and on day 1 and day 2 after the exercise. Procollagen type I amino terminal propeptide (P1NP, marker of bone formation) and carboxyterminal crosslinked telopeptide (CTx, marker of bone resorption) were analyzed from the blood samples. CTx increased significantly (32 %, p = 0.015) two days after the exercise and there was a tendensy towards increase seen in P1NP (p = 0.053) one day after the exercise. A significant positive correlation (r = 0.49 to 0.69, p &le; 0.038) was observed between change in P1NP from baseline to day 1 and exercise variables (maximal slope of acceleration, body weight (BW) adjusted maximal GRF, BW adjusted GRF exercise intensity and osteogenic index). Based on the two biochemical bone turnover markers, it can be concluded that bone turnover is increased in response to a very<br /

Validity of traditional physical activity intensity calibration methods and the feasibility of self-paced walking and running on individualised calibration of physical activity intensity in children

There are no practical and valid methods for the assessment of individualised physical activity (PA) intensity in observational studies. Therefore, we investigated the validity of commonly used metabolic equivalent of tasks (METs) and predetermined PA intensity classification methods against individualised PA intensity classification in 35 children 7–11-years-of-age. Then, we studied validity of mean amplitude deviation (MAD) measured by accelerometry during self-paced walking and running in assessment of individualised PA intensity. Individualised moderate PA (MPA) was defined as V̇O2 ≥ 40% of V̇O2reserve and V̇O2 3–6 (or alternatively > 4–7) METs as MPA and > 6 (> 7) METs as VPA. Task intensities were classified according to previous calibration studies. MET-categories correctly identified 25.9–83.3% of light PA, 85.9–90.3% of MPA, and 56.7–82.2% of VPA. Task-specific categories correctly classified 53.7% of light PA, 90.6% of MPA, and 57.8% of VPA. MAD during self-paced walking discriminated MVPA from light PA (sensitivity = 67.4, specificity = 88.0) and MAD during self-paced running discriminated VPA from MPA (sensitivity = 78.8, specificity = 79.3). In conclusion, commonly used methods may misclassify PA intensity in children. MAD during self-paced running may provide a novel and practical method for determining individualised VPA intensity in children.Peer reviewe

Exergaming as a viable therapeutic tool to improve static and dynamic balance among older adults and people with idiopathic Parkinson\u27s disease: a systematic review and meta-analysis

The use of virtual reality games (known as &quot;exergaming&quot;) as a neurorehabilitation tool is gaining interest. Therefore, we aim to collate evidence for the effects of exergaming on the balance and postural control of older adults and people with idiopathic Parkinson\u27s disease (IPD). Six electronic databases were searched, from inception to April 2015, to identify relevant studies. Standardized mean differences (SMDs) and 95% confidence intervals (CI) were used to calculate effect sizes between experimental and control groups. I (2) statistics were used to determine levels of heterogeneity. 325 older adults and 56 people with IPD who were assessed across 11&thinsp;-studies. The results showed that exergaming improved static balance (SMD 1.069, 95% CI 0.563-1.576), postural control (SMD 0.826, 95% CI 0.481-1.170), and dynamic balance (SMD -0.808, 95% CI -1.192 to -0.424) in healthy older adults. Two IPD studies showed an improvement in static balance (SMD 0.124, 95% CI -0.581 to 0.828) and postural control (SMD 2.576, 95% CI 1.534-3.599). Our findings suggest that exergaming might be an appropriate therapeutic tool for improving balance and postural control in older adults, but more -large-scale trials are needed to determine if the same is true for people with IPD

Neuromuscular mechanics and hopping training in elderly

Purpose: The present study examined the effects of repetitive hopping training on muscle activation profiles and fascicle&ndash;tendon interaction in the elderly.Methods: 20 physically active elderly men were randomly assigned for training (TG) and control groups (CG). TG performed supervised bilateral short contact hopping training with progressively increasing training volume. Measurements were performed before the training period (BEF) as well as after 2 weeks (2 W) and 11 weeks (11 W) of training. During measurements, the gastrocnemius medialis&ndash;muscle (GaM) fascicle and its outer Achilles tendon length changes during hopping were examined by ultrasonography together with electromyographic (EMG) activities of calf muscles, kinematics, and kinetics.Results: At 2 W, the ankle joint stiffness was increased by 21.0 &plusmn; 19.3 % and contact time decreased by 9.4 &plusmn; 7.8 % in TG. Thereafter, from 2&ndash;11 W the jumping height increased 56.2 &plusmn; 18.1 % in TG. Simultaneously, tendon forces increased 24.3 &plusmn; 19.0 % but tendon stiffness did not change. GaM fascicles shifted to shorter operating lengths after training without any changes in their length modifications during the contact phase of hopping. Normalized EMG amplitudes during hopping did not change with training.Conclusions: The present study shows that 11 W of hopping training improves the performance of physically active elderly men. This improvement is achieved with shorter GaM operating lengths and, therefore, increased fascicle stiffness and improved tendon utilization after training. Based on these results, hopping training could be recommended for healthy fit elderly to retain and improve rapid force production capacity. &copy; 2014 Springer-Verlag Berlin Heidelber

Priming the Motor Cortex With Anodal Transcranial Direct Current Stimulation Affects the Acute Inhibitory Corticospinal Responses to Strength Training

Synaptic plasticity in the motor cortex (M1) is associated with strength training and can be modified by transcranial direct current stimulation (tDCS). The M1 responses to strength training increase when anodal-tDCS is applied during training due to gating. An additional approach to improve the M1 responses to strength training, which has not been explored, is to use anodal-tDCS to prime the M1 before a bout of strength training. We examined the priming effects of anodal-tDCS of M1 on the acute corticospinal responses to strength training. In a randomized double-blinded cross-over design, changes in isometric strength, corticospinal-excitability and inhibition (assessed as area under the recruitment curve [AURC] using transcranial magnetic stimulation [TMS]) were analysed in 13 adults exposed to 20-min of anodal and sham-tDCS followed by a strength training session of the right elbow-flexors. We observed a significant decrease in isometric elbow-flexor strength immediately following training (11-12%; P < 0.05) which was not different between anodal-tDCS and sham-tDCS. TMS revealed a 24% increase in AURC for corticospinal-excitability following anodal-tDCS and strength training; this increase was not different between conditions. However, there was a 14% reduction in AURC for corticospinal inhibition when anodal-tDCS was applied prior to strength training when compared to sham-tDCS and strength training (all P < 0.05). Priming anodal-tDCS had a limited effect in facilitating corticospinal-excitability following an acute bout of strength training. nterestingly, the interaction of anodal-tDCS and strength training appears to affect the excitability of intracortical inhibitory circuits of the M1 via non-homeostatic mechanisms

MARKERLESS VIDEO-BASED ESTIMATION OF 3D APPROACH VELOCITY IN THE JAVELIN THROW

The purpose of this study was to explore the usefulness of a markerless open-source human pose estimation algorithm, for estimating centre of mass (CoM) velocity in the javelin throw at three discrete time instances: the last right leg touchdown (RLTD), brace leg touchdown (BLTD) and release. Forty throws from four right-handed javelin throwers were simultaneously captured with two high-speed video cameras and a 16-camera marker-based Vicon motion capture system. For horizontal resultant velocity (Velhor), the method demonstrated excellent validity at RLTD, whereas at BLTD and release errors were notable. Based on these findings, CoM Velhor can be estimated using the proposed method with promising accuracy at RLTD. At BLTD and release, using a CoM segment model with arms in more optimized measurement conditions might further improve the accuracy

Musculoskeletal asymmetry in football athletes: A product of limb function over time

Purpose Asymmetrical loading patterns are commonplace in football sports. Our aim was to examine the influence of training age and limb function on lower-body musculoskeletal morphology. Methods Fifty-five elite football athletes were stratified into less experienced (≤3 yr; n = 27) and more experienced (\u3e3 yr; n = 28) groups by training age. All athletes underwent whole-body dual-energy x-ray absorptiometry scans and lower-body peripheral quantitative computed tomography tibial scans on the kicking and support limbs. Results Significant interactions between training age and limb function were evident across all skeletal parameters (F16, 91 = 0.182, P = 0.031, Wilks Λ = 0.969). Asymmetries between limbs were significantly larger in the more experienced players than the less experienced players for tibial mass (P ≤ 0.044, d ≥ 0.50), total cross-sectional area (P ≤ 0.039, d ≥ 0.53), and stress-strain indices (P ≤ 0.050, d ≥ 0.42). No significant asymmetry was evident for total volumetric density. More experienced players also exhibited greater lower-body tibial mass (P ≤ 0.001, d ≥ 1.22), volumetric density (P ≤ 0.009, d ≥ 0.79), cross-sectional area (P ≤ 0.387, d ≥ 0.21), stress-strain indices (P ≤ 0.012, d ≥ 0.69), fracture loads (P ≤ 0.018, d ≥ 0.57), and muscle mass and cross-sectional area (P ≤ 0.016, d ≥ 0.68) than less experienced players. Conclusions Asymmetries were evident in athletes as a product of limb function over time. Chronic exposure to routine high-impact gravitational loads afforded to the support limb preferentially improved bone mass and structure (cross-sectional area and cortex thickness) as potent contributors to bone strength relative to the high-magnitude muscular loads predominantly afforded to the kicking limb. Copyright © 2016 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited

Treatment with soluble activin type IIB-receptor improves bone mass and strength in a mouse model of Duchenne muscular dystrophy

Background: Inhibition of activin/myostatin pathway has emerged as a novel approach to increase muscle mass and bone strength. Duchenne muscular dystrophy (DMD) is a neuromuscular disorder that leads to progressive muscle degeneration and also high incidence of fractures. The aim of our study was to test whether inhibition of activin receptor IIB ligands with or without exercise could improve bone strength in the mdx mouse model for DMD. Methods: Thirty-two mdx mice were divided to running and non-running groups and to receive either PBS control or soluble activin type IIB-receptor (ActRIIB-Fc) once weekly for 7 weeks. Results: Treatment of mdx mice with ActRIIB-Fc resulted in significantly increased body and muscle weights in both sedentary and exercising mice. Femoral mu CT analysis showed increased bone volume and trabecular number (BV/TV +80%, Tb.N +70%, P <0.05) in both ActRIIB-Fc treated groups. Running also resulted in increased bone volume and trabecular number in PBS-treatedmice. However, there was no significant difference in trabecular bone structure or volumetric bone mineral density between the ActRIIB-Fc and ActRIIB-Fc-R indicating that running did not further improve bone structure in ActRIIB-Fc-treated mice. ActRIIB-Fc increased bone mass also in vertebrae (BV/TV +20%, Tb.N +30%, P <0.05) but the effects were more modest. The number of osteoclasts was decreased in histological analysis and the expression of several osteoblast marker genes was increased in ActRIIB-Fc treated mice suggesting decreased bone resorption and increased bone formation in these mice. Increased bone mass in femurs translated into enhanced bone strength in biomechanical testing as the maximum force and stiffness were significantly elevated in ActRIIB-Fc-treated mice. Conclusions: Our results indicate that treatment of mdx mice with the soluble ActRIIB-Fc results in a robust increase in bone mass, without any additive effect by voluntary running. Thus ActRIIB-Fc could be an attractive option in the treatment of musculoskeletal disorders.Peer reviewe

Differential effects of exercise on tibial shaft marrow density in young female athletes

Context:Increased mechanical loading can promote the preferential differentiation of bone marrow mesenchymal stem cells to osteoblastogenesis, but it is not known whether long-term bone strength-enhancing exercise in humans can reduce marrow adiposity.Objective:Our objective was to examine whether bone marrow density (MaD), as an estimate of marrow adiposity 1) differs between young female athletes with contrasting loading histories and bone strengths and 2) is an independent predictor of bone strength at the weight-bearing tibia.Design:Mid-tibial MaD, cortical area (CoA), total area, medullary area, strength strain index (SSI), and cortical volumetric bone mineral density (vBMD) (total, endocortical, midcortical, and pericortical) was assessed using peripheral quantitative computed tomography in 179 female athletes involved in both impact and nonimpact loading sports and 41 controls aged 17&ndash;40 years.Results:As we have previously reported CoA, total area, and SSI were 16% to 24% greater in the impact group compared with the controls (all P &lt; .001) and 12% to 18% greater than in the nonimpact group (all P &lt; .001). The impact group also had 0.5% higher MaD than the nonimpact and control groups (both P &lt; .05). Regression analysis further showed that midtibial MaD was significantly associated with SSI, CoA, endocortical vBMD, and pericortical vBMD (P &lt; .05) in all women combined, after adjusting for age, bone length, loading groups, medullary area, muscle cross-sectional area, and percent fat.Conclusion:In young female athletes, tibial bone MaD was associated with loading history and was an independent predictor of tibial bone strength. These findings suggest that an exercise-induced increase in bone strength may be mediated via reduced bone marrow adiposity and consequently increased osteoblastogenesis.<br /

Suboptimal bone status for adolescents with low motor competence and developmental coordination disorder - It\u27s sex specific

Background: Australian adolescents with low motor competence (LMC) have higher fracture rates and poorer bone health compared to European normative data, but currently no normative data exists for Australians. Aims: To examine whether there were bone health differences in Australian adolescents with LMC or Developmental Coordination Disorder (DCD) when compared to typically developing age-matched Australian adolescents. Methods and Procedures: Australian adolescents aged 12–18 years with LMC/DCD (n=39; male=27; female=12) and an Australian comparison sample (n=188; boys=101; girls= 87) undertook radial and tibial peripheral Quantitative Computed Tomography (pQCT) scans. Stress Strain Index (SSI (mm3)), Total Bone Area (TBA (mm2)), Muscle Density (MuD [mgcm3]), Muscle Area (MuA [cm2]), Subcutaneous Fat Area (ScFA [cm2]), Cortical Density (CoD [mgcm3]), Cortical Area (CoD [mm2]), cortical concentric ring volumetric densities, Functional Muscle Bone Unit Index (FMBU: (SSI/bone length)) and Robustness Index (SSI/bone length^3), group and sex differences were examined. Outcome and Results: The main finding was a significant sex-x-group interaction for Tibial FMBU (p=.021), Radial MuD (p=.036), and radial ScFA (p=.002). Boys with LMC/DCD had lower tibial FMBU scores, radial MuD and higher ScFA than the typically developing age-matched sample. Conclusion and Implications: Comparisons of bone measures with Australian comparative data are similar to European findings however sex differences were found in the present study. Australian adolescent boys with LMC/DCD had less robust bones compared to their well-coordinated Australian peers, whereas there were no differences between groups for girls. These differences may be due to lower levels of habitual weight–bearing physical activity, which may be more distinct in adolescent boys with LMC/DCD compared to girls