The Influence of Muscular Action on Bone Strength Via Exercise

Development of musculoskeletal deficits in children with cystic fibrosis in later childhood

Cystic fibrosis (CF) is a genetic condition primarily affecting the respiratory system, with the associated progressive lung damage and loss of function resulting in reduced lifespan. Bone health is also impaired in individuals with CF, leading to much higher fracture risk even in adolescence. However, the development of these deficits during growth and the relative contributions of puberty, body size and muscular loading remain somewhat unexplored. We therefore recruited 25 children with CF (10 girls, mean age 11.3 ± 2.9y) and 147 children without CF (75 girls, mean age 12.4 ± 2.6y). Bone characteristics were assessed using peripheral quantitative computed tomography (pQCT) at 4 % and 66 % distal-proximal tibia. Muscle cross-sectional area (CSA) and density (an indicator of muscle quality) were also assessed at the latter site. Tibial bone microstructure was assessed using high-resolution pQCT (HR-pQCT) at 8 % distal-proximal tibial length. In addition, peak jump power and hop force were measured using jumping mechanography. Group-by-age interactions and group differences in bone and muscle characteristics were examined using multiple linear regression, adjusted for age, sex and pubertal status and in additional models, height and muscle force. In initial models group-by-age interactions were evident for distal tibial total bone mineral content (BMC) and trabecular volumetric bone mineral density (vBMD), with a lower rate of age-related accrual evident in children with CF. In assessments of distal tibial microstructure, similar patterns were observed for trabecular number and thickness, and cortical CSA. In the tibial shaft, group-by-age interactions indicating slower growth in CF were evident for total BMC and cortical CSA, whilst age-independent deficits in CF were observed for several other variables. Peak jump power and hop force also exhibited similar interactions. Group-by-age interactions for bone were partially attenuated at the distal tibia and fully attenuated at the tibial shaft by adjustment for muscle force. These results suggest that bone and muscle deficits in children with CF develop throughout later childhood, independent of differences in pubertal stage and body size. These diverging growth patterns appear to be mediated by differences in muscle function, particularly for bone characteristics in the tibial shaft. Given the high fracture risk in this population from childhood onwards, development of interventions to improve bone health would be of substantial clinical value.

Long-term human spaceflight and inflammaging: Does it promote aging?

Spaceflight and its associated stressors, such as microgravity, radiation exposure, confinement, circadian derailment and disruptive workloads represent an unprecedented type of exposome that is entirely novel from an evolutionary stand point. Within this perspective, we aimed to review the effects of prolonged spaceflight on immune-neuroendocrine systems, brain and brain-gut axis, cardiovascular system and musculoskeletal apparatus, highlighting in particular the similarities with an accelerated aging process. In particular, spaceflight-induced muscle atrophy/sarcopenia and bone loss, vascular and metabolic changes, hyper and hypo reaction of innate and adaptive immune system appear to be modifications shared with the aging process. Most of these modifications are mediated by molecular events that include oxidative and mitochondrial stress, autophagy, DNA damage repair and telomere length alteration, among others, which directly or indirectly converge on the activation of an inflammatory response. According to the inflammaging theory of aging, such an inflammatory response could be a driver of an acceleration of the normal, physiological rate of aging and it is likely that all the systemic modifications in turn lead to an increase of inflammaging in a sort of vicious cycle. The most updated countermeasures to fight these modifications will be also discussed in the light of their possible application not only for astronauts' benefit, but also for older adults on the ground.

Characterising lower-body musculoskeletal morphology and whole-body composition of elite female and male Australian Football players

BACKGROUND

Physical demands and injury rates differ between elite female and male Australian Football (AF) players. To improve understanding of contributing physical factors to these differences, the purpose of this study was to investigate lower-body morphology and whole-body composition of elite footballers competing in the Australian Football League (AFL) and Australian Football League Women's (AFLW).

METHODS

Lower-body morphology and whole-body composition of 23 AFL players and 23 AFLW players were assessed using peripheral Quantitative Computed Tomography and Dual-energy X-ray Absorptiometry at the beginning of pre-season. Differences between cohorts, with sub-analyses of kicking vs. support limbs, and experienced vs. inexperienced player status were assessed using two-sample independent t-tests. Magnitude of differences were assessed using Cohen's d effect sizes.

RESULTS

AFL players had greater absolute (p < 0.001; ES = 3.28) and relative (p < 0.001; ES = 2.29) whole body lean soft-tissue mass, with less absolute (p = 0.004; ES = 0.91) and relative (p < 0.001; ES = 2.29) fat mass than AFLW players. For AFLW players, no significant differences existed between kicking and support limbs with few differences observed between experienced and inexperienced players.

CONCLUSIONS

Greater emphasis on physical development in AFLW players may be required to enable increases in muscle mass and skeletal robustness, to ensure they can tolerate the loads of elite competition.

Development of tibia & fibula bone deficits in children with neurofibromatosis type I - A longitudinal case-control comparison

Neurofibromatosis type 1 (NF1) is associated with lower bone mass and increased risk of fracture. Children with NF1 display faltering growth from mid-childhood. However, to date tibia bone development in children with NF1 across childhood and the role of body size have not been explored. Therefore, we recruited 24 children with NF1 (12 girls, mean age 8.2 ± 1.1y) and 104 children without NF1 (52 girls, mean age 11 ± 1.7y). Tibia and fibula bone characteristics were assessed at 4% and 38% distal-proximal tibia length in all children at baseline using peripheral quantitative computed tomography (pQCT). Longitudinal scans were obtained in 21 children with NF1 (12 girls) over 3.4 ± 0.3y and 71 children without NF1 (34 girls) over 1.1 ± 0.1y, such that at follow-up mean age of both groups (NF1 10.9 ± 1.3y, controls 11.4 ± 1.4y) were similar. Effects of group (NF1/control) on bone outcomes as well as group-by-age interactions, indicating differences in rate of change in bone outcome bone outcomes were assessed via linear mixed effects models with adjustment for sex, age, pubertal status and in additional models with adjustment for height and weight Z-scores. Group (NF1/control)-by-age interactions indicated a slower rate of tibia and fibula bone mass accrual in children with NF1 at all measured sites. These associations were attenuated by 25-50% by adjustment for height and weight Z-scores. At the 4% site, deficits in bone mass at older ages were related to slower trabecular BMD accrual. At the 38% site, group-by-age interactions suggested that bone mass deficits resulted from poorer accrual of cortical CSA and to a lesser extent cortical BMD. Lower limb bone mass deficits evident in children with NF1 appear to be progressive and emerge in mid-childhood. In part, they are related to development of a similar pattern of deficits in longitudinal growth and body weight in NF1. Interventions promoting muscle development or physical activity may be partially effective in attenuating bone mass accrual deficits in this population.

Effects of backhand stroke styles on bone mineral content and density in postmenopausal recreational tennis players: a cross-sectional pilot investigation

Background

One-handed backhand (OB) and two-handed backhand (TB) styles are commonly used in tennis, but only TB generates loadings on the non-dominant arm and a greater extension torque on the rear leg, leading to a greater axial torque involving rotation of the hip and trunk. The current study investigated whether those effects can further affect bone area (BA), bone mineral content (BMC) and density (BMD) in postmenopausal recreational tennis players.

Methods

BA, BMC and BMD of the lumbar spine, hip and distal radius were assessed using dual-energy X-ray absorptiometry in TB, OB, and swimmers’ group as a control (SG) (all participants self-reported for at least 5 years of exercise history, n = 14 per group). Muscular strength was assessed with a hand dynamometer. Among these three groups, the BA, BMC and BMD of distal radius and muscle strength were assessed using one-way ANOVA, and those of the lumbar region and the hip joint were tested by one-way ANCOVA.

Results

TB showed higher BMC and BMD for both lumbar spine and femoral neck than SG (all, p < 0.05). Both OB and TB showed greater BMD inter-trochanter than SG (both, p < 0.05). OB demonstrated greater inter-arm differences in the distal radius, which involved 1/3 distal for BMC and mid-distal radius for BMD compared to the TB and SG (all, p < 0.05). In addition, greater inter-arm asymmetry of grip strength was found in OB compared to TB and SG (both, p < 0.05).

Conclusion

For postmenopausal women, performing two-handed backhand strokes, leads to higher BMC and BMD in the non-dominant arm, the lumbar region, and hips, indicating potential benefit to maintain bone health and strength. Whether this result leads to reducing the risk of osteoporosis needs to be investigated in further research.

Novel instrumented frame for standing exercising of users with complete spinal cord injuries

This paper describes a Functional Electrical Stimulation (FES) standing system for rehabilitation of bone mineral density (BMD) in people with Spinal Cord Injury (SCI). BMD recovery offers an increased quality of life for people with SCI by reducing their risk of fractures. The standing system developed comprises an instrumented frame equipped with force plates and load cells, a motion capture system, and a purpose built 16-channel FES unit. This system can simultaneously record and process a wide range of biomechanical data to produce muscle stimulation which enables users with SCI to safely stand and exercise. An exergame provides visual feedback to the user to assist with upper-body posture control during exercising. To validate the system an alternate weight-shift exercise was used; 3 participants with complete SCI exercised in the system for 1 hour twice-weekly for 6 months. We observed ground reaction forces over 70% of the full body-weight distributed to the supporting leg at each exercising cycle. Exercise performance improved for each participant by an increase of 13.88 percentage points of body-weight in the loading of the supporting leg during the six-month period. Importantly, the observed ground reaction forces are of higher magnitude than other studies which reported positive effects on BMD. This novel instrumentation aims to investigate weight bearing standing therapies aimed at determining the biomechanics of lower limb joint force actions and postural kinematics.

Breech presentation is associated with lower adolescent tibial bone strength

We compared bone outcomes in adolescents with breech and cephalic presentation. Tibia bone mineral content, density, periosteal circumference, and cross-sectional moment of inertia were lower in breech presentation, and females with breech presentation had lower hip CSA. These findings suggest that prenatal loading may exert long-lasting influences on skeletal development.

INTRODUCTION

Breech position during pregnancy is associated with reduced range of fetal movement, and with lower limb joint stresses. Breech presentation at birth is associated with lower neonatal bone mineral content (BMC) and area, but it is unknown whether these associations persist into later life.

METHODS

We examined associations between presentation at onset of labor, and tibia and hip bone outcomes at age 17 years in 1971 participants (1062 females) from a UK prospective birth cohort that recruited > 15,000 pregnant women in 1991-1992. Cortical BMC, cross-sectional area (CSA) and bone mineral density (BMD), periosteal circumference, and cross-sectional moment of inertia (CSMI) were measured by peripheral quantitative computed tomography (pQCT) at 50% tibia length. Total hip BMC, bone area, BMD, and CSMI were measured by dual-energy X-ray absorptiometry (DXA).

RESULTS

In models adjusted for sex, age, maternal education, smoking, parity, and age, singleton/multiple births, breech presentation (n = 102) was associated with lower tibial cortical BMC (- 0.14SD, 95% CI - 0.29 to 0.00), CSA (- 0.12SD, - 0.26 to 0.02), BMD (- 0.16SD, - 0.31 to - 0.01), periosteal circumference (- 0.14SD, - 0.27 to - 0.01), and CSMI (- 0.11SD, - 0.24 to 0.01). In females only, breech presentation was associated with lower hip CSA (- 0.24SD, - 0.43 to 0.00) but not with other hip outcomes. Additional adjustment for potential mediators (delivery method, birthweight, gestational age, childhood motor competence and adolescent height and body composition) did not substantially affect associations with either tibia or hip outcomes.

CONCLUSIONS

These findings suggest that prenatal skeletal loading may exert long-lasting influences on skeletal size and strength but require replication.

Mechanical suppression of osteolytic bone metastases in advanced breast cancer patients: a randomised controlled study protocol evaluating safety, feasibility and preliminary efficacy of exercise as a targeted medicine

BACKGROUND

Skeletal metastases present a major challenge for clinicians, representing an advanced and typically incurable stage of cancer. Bone is also the most common location for metastatic breast carcinoma, with skeletal lesions identified in over 80% of patients with advanced breast cancer. Preclinical models have demonstrated the ability of mechanical stimulation to suppress tumour formation and promote skeletal preservation at bone sites with osteolytic lesions, generating modulatory interference of tumour-driven bone remodelling. Preclinical studies have also demonstrated anti-cancer effects through exercise by minimising tumour hypoxia, normalising tumour vasculature and increasing tumoural blood perfusion. This study proposes to explore the promising role of targeted exercise to suppress tumour growth while concomitantly delivering broader health benefits in patients with advanced breast cancer with osteolytic bone metastases.

METHODS

This single-blinded, two-armed, randomised and controlled pilot study aims to establish the safety, feasibility and efficacy of an individually tailored, modular multi-modal exercise programme incorporating spinal isometric training (targeted muscle contraction) in 40 women with advanced breast cancer and stable osteolytic spinal metastases. Participants will be randomly assigned to exercise or usual medical care. The intervention arm will receive a 3-month clinically supervised exercise programme, which if proven to be safe and efficacious will be offered to the control-arm patients following study completion. Primary endpoints (programme feasibility, safety, tolerance and adherence) and secondary endpoints (tumour morphology, serum tumour biomarkers, bone metabolism, inflammation, anthropometry, body composition, bone pain, physical function and patient-reported outcomes) will be measured at baseline and following the intervention.

DISCUSSION

Exercise medicine may positively alter tumour biology through numerous mechanical and non-mechanical mechanisms. This randomised controlled pilot trial will explore the preliminary effects of targeted exercise on tumour morphology and circulating metastatic tumour biomarkers using an osteolytic skeletal metastases model in patients with breast cancer. The study is principally aimed at establishing feasibility and safety. If proven to be safe and feasible, results from this study could have important implications for the delivery of this exercise programme to patients with advanced cancer and sclerotic skeletal metastases or with skeletal lesions present in haematological cancers (such as osteolytic lesions in multiple myeloma), for which future research is recommended.

TRIAL REGISTRATION

anzctr.org.au , ACTRN-12616001368426 . Registered on 4 October 2016.

Later Age at Onset of Independent Walking Is Associated With Lower Bone Strength at Fracture-Prone Sites in Older Men

Later age at onset of independent walking is associated with lower leg bone strength in childhood and adolescence. However, it is unknown whether these associations persist into older age or whether they are evident at axial (central) or upper limb sites. Therefore, we examined walking age obtained at age 2 years and bone outcomes obtained by dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) scans at ages 60 to 64 years in a nationally representative cohort study of British people, the MRC National Survey of Health and Development. It was hypothesized that later walking age would be associated with lower bone strength at all sites. Later independent walking age was associated with lower height-adjusted hip (standardized regression coefficients with 95% confidence interval [CI] -0.179 [-0.251 to -0.107]), spine (-0.157 [-0.232 to -0.082]), and distal radius (-0.159 [-0.245 to -0.073]) bone mineral content (BMC, indicating bone compressive strength) in men (all p < 0.001). Adjustment for covariates partially attenuated these associations, primarily because of lower lean mass and adolescent sporting ability in later walkers. These associations were also evident for a number of hip geometric parameters (including cross-sectional moment of inertia [CSMI], indicating bone bending/torsional strength) assessed by hip structural analysis (HSA) from DXA scans. Similar height-adjusted associations were also observed in women for several hip, spine, and upper limb outcomes, although adjustment for fat or lean mass led to complete attenuation for most outcomes, with the exception of femoral shaft CSMI and spine bone area (BA). In conclusion, later independent walking age appears to have a lifelong association with bone strength across multiple skeletal sites in men. These effects may result from direct effects of early life loading on bone growth and mediation by adult body composition. Results suggest that late walking age may represent a novel risk factor for subsequent low bone strength. Existing interventions effective in hastening walking age may have positive effects on bone across life. © 2017 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Greater tibial bone strength in male tennis players than controls in the absence of greater muscle output

Background/Objective

The greatest forces experienced by bones result from muscular contractions—muscles produce most force in high-velocity eccentric contractions. Bouncing movements, e.g., sprinting or hopping—where such contractions occur—are highly beneficial for lower limb bones. However, there is a growing body of evidence that torsional stresses are highly osteogenic. Sports in which frequent quick turning occurs—hence large torsional stresses can be expected—e.g., tennis, may also improve bone strength even in the absence of large ground reaction and muscle forces.

Methods

To investigate the relative effects of bouncing and turning movements on bones, we recruited 47 older men (mean age 62.4 ± 12.9 years). They were competitive sprinters (representing exposure to bouncing movement), competitive tennis players (turning movements), and inactive controls. Peripheral quantitative computed tomography scans of tibial diaphysis at 66% distal–proximal length were taken; muscle sizes from peripheral quantitative computed tomography and countermovement jump performance were also examined.

Results

Bone strength of tennis players was clearly greater than that of controls (23% greater bone mass; p < 0.001) and similar to that in sprinters. Tennis players' jump relative power and height were 15% and 25% lower than those of sprinters (p < 0.05) and similar to control values, being 2% greater and 6% lower, respectively (p > 0.5). Material eccentricity analysis suggests that torsional stresses may be a significant adaptive stimulus to tibial bone.

Conclusion

Results suggest that sports with quick turning movements are highly osteogenic, even in the absence of greater muscular output. This may be related to the large torsional stresses produced during turning movements.

Imaging of the muscle-bone relationship

Muscle can be assessed by imaging techniques according to its size (as thickness, area, volume, or alternatively, as a mass) and architecture (fiber length and pennation angle), with values used as an anthropometric measure or a surrogate for force production. Similarly, the size of the bone (as area or volume) can be imaged using MRI or pQCT, although typically bone mineral mass is reported. Bone imaging measures of mineral density, size, and geometry can also be combined to calculate bone's structural strength-measures being highly predictive of bone's failure load ex vivo. Imaging of muscle-bone relationships can, hence, be accomplished through a number of approaches by adoption and comparison of these different muscle and bone parameters, dependent on the research question under investigation. These approaches have revealed evidence of direct, mechanical muscle-bone interactions independent of allometric associations. They have led to important information on bone mechanoadaptation and the influence of muscular action on bone, in addition to influences of age, gender, exercise, and disuse on muscle-bone relationships. Such analyses have also produced promising diagnostic tools for clinical use, such as identification of primary, disuse-induced, and secondary osteoporosis and estimation of bone safety factors. Standardization of muscle-bone imaging methods is required to permit more reliable comparisons between studies and differing imaging modes, and in particular to aid adoption of these methods into widespread clinical practice.