Motives for competitive sports participation in masters track and field athletes: Impact of sociodemographic factors and competitive background.

OBJECTIVES: Masters athletes due to their lifelong engagement in sport represent a unique group to study motivation for regular physical activity, but there is less scientific data on the sport motives in masters athletes. Therefore, the aim of this study was to evaluate the association of age, sex, education, nationality, competitive background and training amount with sport motives of masters track and field athletes. METHODS: 811 (254 women) athletes aged 35-89 years participated in European Veterans Athletics Championships in the year of 2000. Sport motives were assessed with a questionnaire and categorized into1) well-being, 2) competitive and performance 3) health and fitness motives. RESULTS: Men considered health and fitness motives more important than women (p = 0.022). Over 65-year-old athletes considered health and fitness motives more important than the youngest, 35-49-year age group (p<0.001). Education was not associated with sport motives, while motives varied significantly among different nationalities. Athletes from Nordic Countries considered well-being motives more important than Southern Europeans (p<0.001) or Western Europeans (p<0.05). Athletes from Nordic Countries (p = 0.003), Eastern Europe (p<0.001) and Central Europe (p<0.001) found health and fitness motives more meaningful than athletes from the British Isles. Furthermore, athletes with competitive background before the age of 35 and training amount more than 7.5 h a week found competitive and performance motives more important than athletes without a competitive history (p = 0.002). CONCLUSIONS: These results suggest that age, sex, nationality and former athleticism are associated with sports motives among international level masters track and field athletes. It seems that while for masters athletes with competitive background performance motives dominate, for older adults, particularly for males, health and fitness motives are more important. In addition, when designing the exercise interventions for older adults, different sport motives across countries should be considered.

Age-Related Declines in Lower Limb Muscle Function are Similar in Power and Endurance Athletes of Both Sexes: A Longitudinal Study of Master Athletes.

The age-related decline in muscle function, particularly muscle power, is associated with increased risk of important clinical outcomes. Physical activity is an important determinant of muscle function, and different types of physical activity e.g. power-based versus endurance-based exercise appear to have differential effects on muscle power. Cross-sectional studies suggest that participation in power-based exercise is associated with greater muscle power across adulthood but this has not been investigated longitudinally. We recruited eighty-nine male and female power and endurance master athletes (sprint and distance runners respectively, baseline age 35-90y). Using jumping mechanography, we measured lower limb muscle function during a vertical jump including at least two testing sessions longitudinally over 4.5 ± 2.4y. We examined effects of time, discipline (power/endurance) and sex in addition to two- and three-way interactions using linear mixed-effects models. Peak relative power, relative force and jump height, but not Esslingen Fitness Index (indicating peak power relative to sex and age-matched reference data) declined with time. Peak power, force, height and EFI were greater in power than endurance athletes. There were no sex, discipline or sex*discipline interactions with time for any variable, suggesting that changes were similar over time for athletes of both sexes and disciplines. Advantages in lower limb muscle function in power athletes were maintained with time, in line with previous cross-sectional studies. These results suggest that improvements in lower limb function in less active older individuals following power-based training persist with continued adherence, although this requires further investigation in interventional studies.

Regular Strength and Sprint Training Counteracts Bone Aging: A 10-Year Follow-Up in Male Masters Athletes.

Cross-sectional and interventional studies suggest that high-intensity strength and impact-type training provide a powerful osteogenic stimulus even in old age. However, longitudinal evidence on the ability of high-intensity training to attenuate age-related bone deterioration is currently lacking. This follow-up study assessed the role of continued strength and sprint training on bone aging in 40- to 85-year-old male sprinters (n = 69) with a long-term training background. Peripheral quantitative computed tomography (pQCT)-derived bone structural, strength, and densitometric parameters of the distal tibia and tibia midshaft were assessed at baseline and 10 years later. The groups of well-trained (actively competing, sprint training including strength training ≥2 times/week; n = 36) and less-trained (<2 times/week, no strength training, switched to endurance training; n = 33) athletes were formed according to self-reports at follow-up. Longitudinal changes in bone traits in the two groups were examined using linear mixed models. Over the 10-year period, group-by-time interactions were found for distal tibia total bone mineral content (BMC), trabecular volumetric bone mineral density (vBMD), and compressive strength index, and for mid-tibia cortical cross-sectional area, medullary area, total BMC, and BMC at the anterior and posterior sites (polar mass distribution analysis) (p < 0.05). These interactions reflected maintained (distal tibia) or improved (mid-tibia) bone properties in the well-trained and decreased bone properties in the less-trained athletes over the 10-year period. Depending on the bone variable, the difference in change in favor of the well-trained group ranged from 2% to 5%. The greatest differences were found in distal tibia trabecular vBMD and mid-tibia posterior BMC, which remained significant (p < 0.05) after adjustment for multiple testing. In conclusion, our longitudinal findings indicate that continued strength and sprint training is associated with maintained or even improved tibial properties in middle-aged and older male sprint athletes, suggesting that regular, intensive exercise counteracts bone aging. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Absence of an aging-related increase in fiber type grouping in athletes and non-athletes.

The aging-related loss of muscle mass is thought to be partly attributable to motor neuron loss and motor unit remodeling that result in fiber type grouping. We examined fiber type grouping in 19- to 85-year-old athletes and non-athletes and evaluated to which extent any observed grouping is explained by the fiber type composition of the muscle. Since regular physical activity may stimulate reinnervation, we hypothesized that fiber groups are larger in master athletes than in age-matched non-athletes. Fiber type grouping was assessed in m. vastus lateralis biopsies from 22 young (19-27 years) and 35 healthy older (66-82 years) non-athletes, and 14 young (20-29 years), 51 middle-aged (38-65 years), and 31 older (66-85 years) athletes. An "enclosed fiber" was any muscle fiber of a particular type surrounded by fibers of the same type only. A fiber type group was defined as a group of fibers with at least one enclosed fiber. Only type II fiber cross-sectional area (FCSA) showed an age-related decline that was greater in athletes (P < .001) than in non-athletes (P = .012). There was no significant age-related effect on fiber group size or fiber group number in athletes or non-athletes, and the observed grouping was similar to that expected from the fiber type composition. At face value, these observations do 1) neither show evidence for an age-related loss and remodeling of motor units nor 2) improved reinnervation with regular physical activity, but 3) histological examination may not reveal the full extent of aging-related motor unit remodeling.

Greater maintenance of bone mineral content in male than female athletes and in sprinting and jumping than endurance athletes: a longitudinal study of bone strength in elite masters athletes.

We investigated longitudinal changes in tibia bone strength in master power (jumping and sprinting) and endurance (distance) athletes of both sexes. Bone mass but not cross-sectional moment of inertia was better maintained in power than endurance athletes over time, particularly in men and independent of changes in performance. OBJECTIVE: Assessment of effects of sex and athletic discipline (lower limb power events, e.g. sprint running and jumping versus endurance running events) on longitudinal changes in bone strength in masters athletes. METHODS: We examined tibia and fibula bone properties at distal (4% distal-proximal tibia length) and proximal (66% length) sites using peripheral quantitative computed tomography (pQCT) in seventy-one track and field masters athletes (30 male, 41 female, age at baseline 57.0 ± 12.2 years) in a longitudinal cohort study that included at least two testing sessions over a mean period of 4.2 ± 3.1 years. Effects of time, as well as time × sex and time × discipline interactions on bone parameters and calf muscle cross-sectional area (CSA), were examined. RESULTS: Effects of time were sex and discipline-dependent, even following adjustment for enrolment age, sex and changes in muscle CSA and athletic performance. Male sex and participation in power events was associated with better maintenance of tibia bone mineral content (BMC, an indicator of bone compressive strength) at 4% and 66% sites. In contrast, there was no strong evidence of sex or discipline effects on cross-sectional moment of inertia (CSMI, an indicator of bone bending and torsional strength-P > 0.3 for interactions). Similar sex and discipline-specific changes were also observed in the fibula. CONCLUSIONS: Results suggest that male athletes and those participating in lower limb power-based rather than endurance-based disciplines have better maintenance of bone compressive but not bending and torsional strength.

Sprint and Strength Training Modulates Autophagy and Proteostasis in Aging Sprinters.

PURPOSE: Exercise and aging may modulate muscle protein homeostasis and autophagy, but few studies examine highly trained middle-age or older individuals. This study elucidated the effects of a new long-term training stimulus on markers of muscle autophagy and unfolded protein response (UPR) and on sprint running performance in masters sprinters. METHODS: Thirty-two male competitive sprinters (age 40-76 yr) were randomly divided into experimental (EX) and control (CTRL) groups. The EX training program was a combination of heavy and explosive strength and sprint exercises aimed at improving sprint performance. Fifteen and thirteen participants completed the 20-wk intervention period in EX and CTRL, respectively. The latter were told to continue their routine exercises. Key protein markers were analyzed by Western blotting from vastus lateralis (VL) muscle biopsies. The muscle thickness of VL was analyzed by ultrasonography and sprint performance by a 60-m running test. RESULTS: EX induced improvement in 60-m sprint performance when compared with controls (time-group, P = 0.003) without changes in VL muscle thickness. Content of lipidated microtubule-associated protein 1A/1B-light chain 3 (LC3-II) increased in EX (P = 0.022), suggesting increased autophagosome content. In addition, an autophagosome clearance marker sequestosome 1 (p62) decreased in EX (P = 0.006). Markers of UPR selectively modulated with decreases (e.g., ATF4, P = 0.003) and increases (e.g., EIF2α, P = 0.019) observed in EX. CONCLUSIONS: These findings suggest that a new intensive training stimulus that combines strength training with sprint training may increase muscle autophagosome content in a basal state without any evidence of impaired autophagosome clearance in masters sprinters. Simultaneously, the combined training may have a selective effect on the content of UPR signaling components.

Ankle and knee extensor muscle effort during locomotion in young and older athletes: Implications for understanding age-related locomotor decline.

Age-related reduction in muscle force generation capacity is similarly evident across different lower limb muscle groups, yet decline in locomotor performance with age has been shown to depend primarily on reduced ankle extensor muscle function. To better understand why ageing has the largest detrimental effect on ankle joint function during locomotion, we examined maximal ankle and knee extensor force development during a two-leg hopping test in older and young men, and used these forces as a reference to calculate relative operating efforts for the knee and ankle extensors as participants walked, ran and sprinted. We found that, across locomotion modes in both age groups, ankle extensors operated at a greater relative effort compared to knee extensors; however, slightly less pronounced differences between ankle and knee extensor muscle efforts were present among older men, mainly due to a reduction in the ankle extensor force generation during locomotion modes. We consider these findings as evidence that reduced ankle push-off function in older age is driven by a tendency to keep ankle extensor effort during locomotion lower than it would otherwise be, which, in turn, may be an important self-optimisation strategy to prevent locomotor-induced fatigue of ankle extensor muscles.

Dietary acid load and renal function have varying effects on blood acid-base status and exercise performance across age and sex.

Diet composition influences acid-base status of the body. This may become more relevant as renal functional capacity declines with aging. We examined the effects of low (LD) versus high dietary acid load (HD) on blood acid-base status and exercise performance. Participants included 22 adolescents, 33 young adults (YA), and 33 elderly (EL), who followed a 7-day LD and HD in a randomized order. At the end of both diet periods the subjects performed a cycle ergometer test (3 × 10 min at 35%, 55%, 75%, and (except EL) until exhaustion at 100% of maximal oxygen uptake). At the beginning of and after the diet periods, blood samples were collected at rest and after all workloads. Oxygen uptake, respiratory exchange ratio (RER), and heart rate (HR) were monitored during cycling. In YA and EL, bicarbonate (HCO3-) and base excess (BE) decreased over the HD period, and HCO3-, BE, and pH were lower at rest after HD compared with LD. In YA and EL women, HCO3- and BE were lower at submaximal workloads after HD compared with LD. In YA women, the maximal workload was 19% shorter and maximal oxygen uptake, RER, and HR were lower after HD compared with LD. Our data uniquely suggests that better renal function is associated with higher availability of bases, which may diminish exercise-induced acidosis and improve maximal aerobic performance. Differences in glomerular filtration rate between the subject groups likely explains the larger effects of dietary acid load in the elderly compared with younger subjects and in women compared with men.

Declining Physical Performance Associates with Serum FasL, miR-21, and miR-146a in Aging Sprinters.

Aging is associated with systemic inflammation and cellular apoptosis accelerating physiological dysfunctions. Whether physically active way of life affects these associations is unclear. This study measured the levels of serum inflammatory and apoptotic molecules, their change over 10 years, and their associations with physical performance in sprint-trained male athletes. HsCRP, cell counts, HGB, FasL, miR-21, and miR-146a were measured cross-sectionally (n = 67, 18-90 yrs) and serum FasL, miR-21, and miR-146a and their aging-related associations with physical performance were assessed over a 10-year follow-up (n = 49, 50-90 yrs). The cross-sectional study showed positive age correlations for neutrophils and negative for lymphocytes, red blood cells, HGB, FasL, and miR-146a. During the 10-year follow-up, FasL decreased (P = 0.017) and miR-21 (P < 0.001) and miR-146a (P = 0.005) levels increased. When combining the molecule levels, aging, and physical performance, FasL associated with countermovement jump and bench press (P < 0.001), miR-21 and miR-146a with knee flexion (P = 0.023; P < 0.001), and bench press (P = 0.004; P < 0.001) and miR-146a with sprint performance (P < 0.001). The studied serum molecules changed in an age-dependent manner and were associated with declining physical performance. They have potential as biomarkers of aging-related processes influencing the development of physiological dysfunctions. Further research is needed focusing on the origins and targets of circulating microRNAs to clarify their function in various tissues with aging.

Walking and Running Require Greater Effort from the Ankle than the Knee Extensor Muscles.

INTRODUCTION: The knee and ankle extensors as human primary antigravity muscle groups are of utmost importance in a wide range of locomotor activities. Yet, we know surprisingly little about how these muscle groups work, and specifically, how close to their maximal capacities they function across different modes and intensity of locomotion. Therefore, to advance our understanding of locomotor constraints, we determined and compared relative operating efforts of the knee and ankle extensors during walking, running, and sprinting. METHODS: Using an inverse dynamics biomechanical analysis, the muscle forces of the knee and ankle extensors during walking (1.6 m·s), running (4.1 m·s), and sprinting (9.3 m·s) were quantified and then related to maximum forces of the same muscle groups obtained from a reference hopping test that permitted natural elastic limb behavior. RESULTS: During walking, the relative effort of the ankle extensors was almost two times greater compared with the knee extensors (35% ± 6% vs 19% ± 5%, P < 0.001). Changing walking to running decreased the difference in the relative effort between the extensor muscle groups, but still, the ankle extensors operated at a 25% greater level than the knee extensors (84% ± 12% vs 63% ± 17%, P < 0.05). At top speed sprinting, the ankle extensors reached their maximum operating level, whereas the knee extensors still worked well below their limits, showing a 25% lower relative effort compared with the ankle extensors (96% ± 11% vs 72% ± 19%, P < 0.01). CONCLUSIONS: Regardless of the mode of locomotion, humans operate at a much greater relative effort at the ankle than knee extensor muscles. As a consequence, the great demand on ankle extensors may be a key biomechanical factor limiting our locomotor ability and influencing the way we locomote and adapt to accommodate compromised neuromuscular system function.

What Makes a 97-Year-Old Man Cycle 5,000 km a Year?

BACKGROUND: The nature versus nurture debate is one of the oldest issues in the study of longevity, health and successful aging. OBJECTIVE: We present a 97-year-old man (I.K.) as an example of the effects of habitual exercise on the aging process. METHODS: Extensive assessments included medical examinations, interviews, musculoskeletal structure, performance characteristics, cognitive function and gut microbiota composition. RESULTS: I.K. suffers from iatrogenic hypogonadism, prostate cancer, hypothyroidism and a history of deep popliteal thrombosis. Notwithstanding, he cycles up to 5,000 km a year and participates in competitive sports. His musculoskeletal properties, athletic performance, cognitive function and gut microbiota are outstanding. Some traits even exceed those seen in middle-aged men. CONCLUSIONS: His long-term physically and intellectually active lifestyles combined with extensive social interactions have most likely contributed to his exercise capacity, despite his medical history.

Which muscles compromise human locomotor performance with age?

Ageing leads to a progressive decline in human locomotor performance. However, it is not known whether this decline results from reduced joint moment and power generation of all lower limb muscle groups or just some of them. To further our understanding of age-related locomotor decline, we compare the amounts of joint moments and powers generated by lower limb muscles during walking (self-selected), running (4 m s(-1)) and sprinting (maximal speed) among young, middle-aged and old adults. We find that age-related deficit in ankle plantarflexor moment and power generation becomes more severe as locomotion change from walking to running to sprinting. As a result, old adults generate more power at the knee and hip extensors than their younger counterparts when walking and running at the same speed. During maximal sprinting, young adults with faster top speeds demonstrate greater moments and powers from the ankle and hip joints, but interestingly, not from the knee joint when compared with the middle-aged and old adults. These findings indicate that propulsive deficit of ankle contributes most to the age-related locomotor decline. In addition, reduced muscular output from the hip rather than from knee limits the sprinting performance in older age.

Tibial and fibular mid-shaft bone traits in young and older sprinters and non-athletic men.

High impact loading is known to prevent some of the age-related bone loss but its effects on the density distribution of cortical bone are relatively unknown. This study examined the effects of age and habitual sprinting on tibial and fibular mid-shaft bone traits (structural, cortical radial and polar bone mineral density distributions). Data from 67 habitual male sprinters aged 19-39 and 65-84 years, and 60 non-athletic men (referents) aged 21-39 and 65-80 years are reported. Tibial and fibular mid-shaft bone traits (strength strain index SSI, cortical density CoD, and polar and radial cortical density distributions) were assessed with peripheral quantitative computed tomography. Analysis of covariance (ANCOVA) adjusted for height and body mass indicated that the sprinters had 21 % greater tibial SSI (P < 0.001) compared to the referents, with no group × age-group interaction (P = 0.54). At the fibula no group difference or group × age-group interaction was identified (P = 0.12-0.81). For tibial radial density distribution ANCOVA indicated no group × radial division (P = 0.50) or group × age-group × division interaction (P = 0.63), whereas an age × radial division interaction was observed (P < 0.001). For polar density distribution, no age-group × polar sector (P = 0.21), group × polar sector (P = 0.46), or group × age-group × polar sector interactions were detected (P = 0.15). Habitual sprint training appears to maintain tibial bone strength, but not radial cortical density distribution into older age. Fibular bone strength appeared unaffected by habitual sprinting.

OGT and OGA expression in postmenopausal skeletal muscle associates with hormone replacement therapy and muscle cross-sectional area.

Protein glycosylation via O-linked N-acetylglucosaminylation (O-GlcNAcylation) is an important post-translational regulatory mechanism mediated by O-GlcNAc transferase (OGT) and responsive to nutrients and stress. OGT attaches an O-GlcNAc moiety to proteins, while O-GlcNAcase (OGA) catalyzes O-GlcNAc removal. In skeletal muscle of experimental animals, prolonged increase in O-GlcNAcylation associates with age and muscle atrophy. Here we examined the effects of hormone replacement therapy (HRT) and power training (PT) on muscle OGT and OGA gene expression in postmenopausal women generally prone to age-related muscle weakness. In addition, the associations of OGT and OGA gene expressions with muscle phenotype were analyzed. Twenty-seven 50-57-year-old women participated in a yearlong randomized placebo-controlled trial: HRT (n=10), PT (n=8) and control (n=9). OGT and OGA mRNA levels were measured from muscle samples obtained at baseline and after one year. Knee extensor muscle cross-sectional area (CSA), knee extension force, running speed and vertical jumping height were measured. During the yearlong intervention, HRT suppressed the aging-associated upregulation of OGT mRNA that occurred in the controls. The effects of PT were similar but weaker. HRT also tended to increase the OGA mRNA level compared to the controls. The change in the ratio of OGT to OGA gene expressions correlated negatively with the change in muscle CSA. Our results suggest that OGT and OGA gene expressions are associated with muscle size during the critical postmenopausal period. HRT and PT influence muscle OGT and OGA gene expression, which may be one of the mechanisms by which HRT and PT prevent aging-related loss of muscle mass.

Relationship between ventilatory function and age in master athletes and a sedentary reference population.

Ageing is accompanied with a decline in respiratory function. It is hypothesised that this may be attenuated by high physical activity levels. We performed spirometry in master athletes (71 women; 84 men; 35-86 years) and sedentary people (39 women; 45 men; 24-82 years), and calculated the predicted lung age (PLA). The negative associations of age with forced expiratory volume in 1 s (FEV1; 34 mL·year(-1)) and other ventilatory parameters were similar in controls and master athletes. FEV1pred was 9 % higher (P < 0.005) and PLA 15 % lower (P = 0.013) in athletes than controls. There were no significant differences between endurance and power athletes and sedentary people in maximal inspiratory and expiratory pressure. Neither age-graded performance nor weekly training hours were significantly related to lung age. Life-long exercise does not appear to attenuate the age-related decrease in ventilatory function. The better respiratory function in master athletes than age-matched sedentary people might be due to self-selection and attrition bias.

Bone density, structure and strength, and their determinants in aging sprint athletes.

PURPOSE: This study was undertaken to examine bone properties in masters sprinters of different ages and younger reference subjects. In addition, the association of sport-specific ground reaction force, muscle, training, and hormone characteristics with the bone parameters was evaluated in the athletes. METHODS: Bone densitometric, structural, and strength parameters were assessed by peripheral quantitative computed tomography at the distal and midtibia in 83 male sprinters (40-85 yr) and 19 physically active referents (31-45 yr). Between-group differences were analyzed by ANCOVA with body mass and height as covariates. RESULTS: Bone values were generally greater in athletes than referents, the greatest differences being in bending strength of the tibia shaft as estimated by maximum moment of inertia (Imax). Among athletes, trabecular volumetric bone mineral density of distal tibia was 12% (P < 0.05) lower in the oldest (≥70 yr) versus youngest group, whereas the total bone mineral content, total cross-sectional area, and compressive bone strength index did not differ between the groups. At midtibia, no age group differences were present in the total bone mineral content, total cross-sectional area, cortical wall thickness, cortical volumetric bone mineral density, polar mass distribution, minimum moment of inertia, or maximum moment of inertia. After controlling for age, body mass, and height, most loading-related characteristics, knee extensor muscle thickness, and hormone concentrations correlated with the bone parameters. Multivariate regression models explained 12%-67% (mean, 47.5%) of the variance of the bone parameters. Mechanical power in the eccentric phase of the hopping and body mass were consistently the strongest independent predictors in the models. CONCLUSION: The results suggest that regular sprint training has positive (direction-specific) effects on bone strength and structure in middle- and older-aged athletes. Interindividual differences in bone traits seem to be due to combined effects of exercise loading, body size, and hormonal characteristics.

Differential influence of peripheral and systemic sex steroids on skeletal muscle quality in pre- and postmenopausal women.

Aging is associated with gradual decline of skeletal muscle strength and mass often leading to diminished muscle quality. This phenomenon is known as sarcopenia and affects about 30% of the over 60-year-old population. Androgens act as anabolic agents regulating muscle mass and improving muscle performance. The role of female sex steroids as well as the ability of skeletal muscle tissue to locally produce sex steroids has been less extensively studied. We show that despite the extensive systemic deficit of sex steroid hormones in postmenopausal compared to premenopausal women, the hormone content of skeletal muscle does not follow the same trend. In contrast to the systemic levels, muscle tissue of post- and premenopausal women had similar concentrations of dehydroepiandrosterone and androstenedione, while the concentrations of estradiol and testosterone were significantly higher in muscle of the postmenopausal women. The presence of steroidogenetic enzymes in muscle tissue indicates that the elevated postmenopausal steroid levels in skeletal muscle are because of local steroidogenesis. The circulating sex steroids were associated with better muscle quality while the muscle concentrations reflected the amount of infiltrated fat within muscle tissue. We conclude that systemically delivered and peripherally produced sex steroids have distinct roles in the regulation of neuromuscular characteristics during aging.

Effects of diet-induced obesity and voluntary wheel running on the microstructure of the murine distal femur.

BACKGROUND: Obesity and osteoporosis, two possibly related conditions, are rapidly expanding health concerns in modern society. Both of them are associated with sedentary life style and nutrition. To investigate the effects of diet-induced obesity and voluntary physical activity we used high resolution micro-computed tomography (µCT) together with peripheral quantitative computed tomography (pQCT) to examine the microstructure of the distal femoral metaphysis in mice. METHODS: Forty 7-week-old male C57BL/6J mice were assigned to 4 groups: control (C), control + running (CR), high-fat diet (HF), and high-fat diet + running (HFR). After a 21-week intervention, all the mice were sacrificed and the left femur dissected for pQCT and µCT measurements. RESULTS: The mice fed the high-fat diet showed a significant weight gain (over 70% for HF and 60% for HFR), with increased epididymal fat pad mass and impaired insulin sensitivity. These obese mice had significantly higher trabecular connectivity density, volume, number, thickness, area and mass, and smaller trabecular separation. At the whole bone level, they had larger bone circumference and cross-sectional area and higher density-weighted maximal, minimal, and polar moments of inertia. Voluntary wheel running decreased all the cortical bone parameters, but increased the trabecular mineral density, and decreased the pattern factor and structure model index towards a more plate-like structure. CONCLUSIONS: The results suggest that in mice the femur adapts to obesity by improving bone strength both at the whole bone and micro-structural level. Adaptation to running exercise manifests itself in increased trabecular density and improved 3D structure, but in a limited overall bone growth.

Influence of long-term postmenopausal hormone-replacement therapy on estimated structural bone strength: a study in discordant monozygotic twins.

Although postmenopausal hormone-replacement therapy (HRT) is known to prevent fractures, knowledge on the influence of long-term HRT on bone strength and its determinants other than areal bone mineral density is scarce. This study used a genetically controlled design with 24 monozygotic female twin pairs aged 54 to 72 years in which one cotwin was using HRT (mean duration 8 years) and the other had never used HRT. Estimated bone strength, cross-sectional area, volumetric bone mineral density, bone mineral mass, and cross-sectional density and mass distributions were assessed in the tibial shaft, distal tibia, and distal radius with peripheral computed tomography (pQCT). In the tibial shaft, HRT users had 9% [95% confidence interval (CI) 3%-15%] higher estimated bending strength than their nonusing cotwins. Larger cortical area and higher cortical bone mineral density accounted for this difference. The cortex was larger in the HRT users in the endocortical region. In the distal tibia, estimated compressive strength was 24% (95% CI 9%-40%) higher and in the distal radius 26% (95% CI 11%-41%) higher in the HRT users than in their nonusing cotwins owing to higher volumetric bone mineral density. No difference between users and nonusers was observed in total bone cross-sectional area in any measured bone site. The added mineral mass in the HRT users was distributed evenly within and between bone sites. In postmenopausal women, long-term HRT preserves estimated bone strength systemically by preventing bone mineral loss similarly in body weight-loaded and non-weight-loaded bone.

Variability and symmetry of force platform variables in maximum-speed running in young and older athletes.

Eighteen young (23±4 yr) and 25 older (70±4 yr) male sprinters were examined for ground reaction force (GRF) and temporal-spatial variables. The data were collected during maximum-speed phase, and variability and symmetry indices were calculated from a total of 8 steps. There was little variation (CV<6%) in vertical and resultant GRF and kinematic variables, while impact loading had high variability (CV: 10-21%). Overall, the pattern of variability was similar in both groups. Yet, a small but significant age-related increase in CV was evident in horizontal GRFs. There was a variable-specific asymmetry between legs but it was not related to leg dominance. No age differences existed in the symmetry indices. Results indicate that only selected force platform variables are symmetric and repeatable enough so that their use for comparison purposes is appropriate. Data also suggest that aging may increase variability in certain biomechanical measures, whereas symmetry is not affected by age.