Maintaining femoral bone density in adults: how many steps per day are enough?

Association between physical performance and bone mass in community-dwelling postmenopausal Japanese women: The Unzen study

BACKGROUND

Low bone mass is an independent risk factor for osteoporotic fractures. We examined the association between physical performance and bone mass using quantitative ultrasound in community-dwelling postmenopausal Japanese women.

METHODS

We conducted a cross-sectional study on 524 community-dwelling postmenopausal Japanese women who were not being administered osteoporosis medications. Physical performance was assessed on the basis of grip strength, chair stand time, and functional reach. The stiffness index was measured as a quantitative ultrasound parameter for heel bone mass.

RESULTS

Physical performance, assessed by grip strength, chair stand time, and functional reach, and the stiffness index significantly decreased with age (both p<0.001). The multiple linear regression analysis showed that grip strength (p = 0.001), chair stand time (p = 0.004), and functional reach (p = 0.048) were significantly associated with the stiffness index after adjusting for age, body mass index, smoking, drinking, and exercise.

CONCLUSIONS

Physical performance was significantly associated with heel bone mass in community-dwelling postmenopausal Japanese women.

Potential of Neuromuscular Electrical Stimulation as a Bone Loss Countermeasure in Microgravity

INTRODUCTION: For future long-duration spaceflight missions, additional methods of loading the skeleton may be required to supplement exercise to minimize bone loss. Neuromuscular electrical stimulation (NMES) can elicit muscular contractions that create strain on bone. However, the potential effectiveness of NMES on the proximal femur during disuse is not known.METHODS: We measured the maximum isometric force of NMES-induced contractions of the rectus femoris and the hamstrings of 10 subjects (5 male, 5 female), sitting with the hips and knees at 90 degrees of flexion. We employed 2-D biomechanical models of the knee and hip to estimate the hip joint reaction forces, applied these forces to a generic femur finite element analysis model, and qualitatively compared the peak principal strains of the proximal femoral neck to the peak strains modeled in previous studies for other forms of exercise.RESULTS: The average peak tensile/compressive strains were 1380 ± 719 µε/-2179 ± 1130 µε and 573 ± 345 µε/-900 ± 543 µε for the male and female subjects, respectively. While results varied between studies, the strains achieved during NMES generally were comparable to those achieved during walking or stairs, with some individuals matching higher intensity activities.DISCUSSION: This study demonstrated that isometric NMES contractions of the thigh muscles can create strain in the proximal femoral neck similar to that achieved during low impact activities. While NMES alone will unlikely create a sufficient daily strain stimulus to prevent bone loss, it will likely improve the current spaceflight countermeasures by adding more frequent loading throughout the day.Abitante TJ, Bouxsein ML, Duda KR, Newman DJ. Potential of neuromuscular electrical stimulation as a bone loss countermeasure in microgravity. Aerosp Med Hum Perform. 2022; 93(11):774–782.

Changes in physical activity levels and relationship to balance performance, gait speed, and self-rated health in older Swedish women: a longitudinal study

Background and aim

Physical activity levels in older people often decrease and may mean impaired physical functioning leading to an increased fall risk. The aim of this study was to investigate self-reported change in physical activity dose and deterioration in balance performance, gait speed, and self-rated health (SRH) in older women between two time points in a follow-up study.

Methods

A cohort of community-living women, aged 69–79 years (n = 351) were evaluated by questionnaire and clinical tests on balance, gait speed, and SRH at baseline. One hundred and eighty-six women were followed-up by these tests 8.5 years after inclusion. The non-parametric Wilcoxon signed-rank test and Mann–Whitney U test were used for the analysis.

Results

The greatest changes were seen in one-leg standing time (OLST) with eyes closed (− 60%) and eyes open (− 42%). The population was divided into high exercise (HE, n = 49) and low exercise (LE, n = 51) groups. At baseline the HE group had an OLST of 19 s with eyes open and 3 s with eyes closed. In the LE group, these values were 7.3 s and 2 s. At follow-up, differences between HE and LE concerning tandem walk forwards (steps) (HE = 8.5; LE = 2.5) and backwards (HE = 11; LE = 3.5) emerged. The HE group estimated SRH (VAS-scale) 30 mm higher at baseline and 17 mm higher at follow-up than the LE group.

Conclusion

Greater physical activity seems to be an important predictor for maintaining physical function and SRH in older women.

Wearable multimode sensor with a seamless integrated structure for recognition of different joint motion states with the assistance of a deep learning algorithm

Accurate motion feature extraction and recognition provide critical information for many scientific problems. Herein, a new paradigm for a wearable seamless multimode sensor with the ability to decouple pressure and strain stimuli and recognize the different joint motion states is reported. This wearable sensor is integrated into a unique seamless structure consisting of two main parts (a resistive component and a capacitive component) to decouple the different stimuli by an independent resistance-capacitance sensing mechanism. The sensor exhibits both high strain sensitivity (GF = 7.62, 0-140% strain) under the resistance mechanism and high linear pressure sensitivity (S = 3.4 kPa^-1, 0-14 kPa) under the capacitive mechanism. The sensor can differentiate the motion characteristics of the positions and states of different joints with precise recognition (97.13%) with the assistance of machine learning algorithms. The unique integrated seamless structure is achieved by developing a layer-by-layer casting process that is suitable for large-scale manufacturing. The proposed wearable seamless multimode sensor and the convenient process are expected to contribute significantly to developing essential components in various emerging research fields, including soft robotics, electronic skin, health care, and innovative sports systems applications.

Measuring Daily Compliance With Physical Activity Tracking in Ambulatory Surgery Patients: Comparative Analysis of Five Compliance Criteria

BACKGROUND

Physical activity trackers such as the Fitbit can allow clinicians to monitor the recovery of their patients following surgery. An important issue when analyzing activity tracker data is to determine patients' daily compliance with wearing their assigned device, using an appropriate criterion to determine a valid day of wear. However, it is currently unclear as to how different criteria can affect the reported compliance of patients recovering from ambulatory surgery. Investigating this issue can help to inform the use of activity data by revealing factors that may impact compliance calculations.

OBJECTIVE

This study aimed to understand how using different criteria can affect the reported compliance with activity tracking in ambulatory surgery patients. It also aimed to investigate factors that explain variation between the outcomes of different compliance criteria.

METHODS

A total of 62 patients who were scheduled to undergo total knee arthroplasty (TKA, ie, knee replacement) volunteered to wear a commercial Fitbit Zip activity tracker over an 8-week perioperative period. Patients were asked to wear the Fitbit Zip daily, beginning 2 weeks prior to their surgery and ending 6 weeks after surgery. Of the 62 patients who enrolled in the study, 20 provided Fitbit data and underwent successful surgery. The Fitbit data were analyzed using 5 different daily compliance criteria, which consider patients as compliant with daily tracking if they either register >0 steps in a day, register >500 steps in a day, register at least one step in 10 different hours of the day, register >0 steps in 3 distinct time windows, or register >0 steps in 3 out of 4 six-hour time windows. The criteria were compared in terms of compliance outcomes produced for each patient. Data were explored using heatmaps and line graphs. Linear mixed models were used to identify factors that lead to variation between compliance outcomes across the sample.

RESULTS

The 5 compliance criteria produce different outcomes when applied to the patients' data, with an average 24% difference in reported compliance between the most lenient and strictest criteria. However, the extent to which each patient's reported compliance was impacted by different criteria was not uniform. Some individuals were relatively unaffected, whereas others varied by up to 72%. Wearing the activity tracker as a clip-on device, rather than on the wrist, was associated with greater differences between compliance outcomes at the individual level (P=.004, r=.616). This effect was statistically significant (P<.001) in the first 2 weeks after surgery. There was also a small but significant main effect of age on compliance in the first 2 weeks after surgery (P=.040). Gender and BMI were not associated with differences in individual compliance outcomes. Finally, the analysis revealed that surgery has an impact on patients' compliance, with noticeable reductions in activity following surgery. These reductions affect compliance calculations by discarding greater amounts of data under strict criteria.

CONCLUSIONS

This study suggests that different compliance criteria cannot be used interchangeably to analyze activity data provided by TKA patients. Surgery leads to a temporary reduction in patients' mobility, which affects their reported compliance when strict thresholds are used. Reductions in mobility suggest that the use of lenient compliance criteria, such as >0 steps or windowed approaches, can avoid unnecessary data exclusion over the perioperative period. Encouraging patients to wear the device at their wrist may improve data quality by increasing the likelihood of patients wearing their tracker and ensuring that activity is registered in the 2 weeks after surgery.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03518866; https://clinicaltrials.gov/ct2/show/NCT03518866.

Association between self-reported walking speed and calcaneal stiffness index in postmenopausal Japanese women

BACKGROUND

Osteoporosis and related fractures, a worldwide public health issue of growing concern, is characterized by compromised bone strength and an increased risk of fracture. Here we show an association between self-reported walking speed and bone mass among community-dwelling postmenopausal Japanese women aged 50 years and older. DESIGN; CROSS-SECTIONAL STUDY: Setting and Participants; The survey population included 1008 postmenopausal women 50-92 years of age residing in rural communities.

METHODS

Self-reported walking speed was ascertained by asking the participants: "Is your walking speed faster than others of the same age and sex?" to which participants responded "yes (faster)" or "no (moderate/slower)." Calcaneal stiffness index was measured.

RESULTS

Women with a faster self-reported walking speed were younger and had a lower BMI, higher stiffness index, and higher grip strength than women with a slower walking speed. Multiple linear regression analysis adjusted for age, BMI, grip strength, comorbidity, current smoking, and alcohol drinking status showed a significant association between faster self-reported walking speed and higher calcaneal stiffness index (p <  0.001).

CONCLUSIONS

Our findings suggest that questionnaires of walking speed may be useful for predicting bone mass and that a fast self-reported walking may benefit bone health in postmenopausal women.

Quality over quantity: skeletal loading intensity plays a key role in understanding the relationship between physical activity and bone density in postmenopausal women

OBJECTIVE

Increasing physical activity (PA) is regularly cited as a modifiable target to improve health outcomes and quality of life in the aging population, especially postmenopausal women who exhibit low bone mineral density (BMD) and high fracture risk. In this cross-sectional study, we aimed to quantify real-world PA and its association with BMD in postmenopausal women.

METHODS

Seventy postmenopausal women, aged 46 to 79 years, received a dual-energy X-ray absorptiometry scan measuring total hip BMD and wore bilateral triaxial accelerometers on the ankles for 7 days to measure PA in their free-living environment. Custom step detection and peak vertical ground reaction force estimation algorithms, sensitive to both quantity and intensity of PA, were used to calculate a daily bone density index (BDI) for each participant. Multiple regression was used to quantify the relationship between total hip BMD, age, step counts, and mean BDI over the span of 7 days of data collection.

RESULTS

All participants completed the full 7 days of PA monitoring, totaling more than 7 million detected steps. Participants averaged 14,485 ± 4,334 steps daily with mean peak vertical ground reaction force stepping loads of 675 ± 121 N during daily living. Across the population, total hip BMD was found to be significantly correlated with objective estimates of mean BDI (r = 0.44), as well as participant age (r = 0.285).

CONCLUSION

Despite having higher-than-expected PA, the low stepping loads observed in this cohort, along with half of the participants having low BMD measures, underscores the need for PA intensity to be considered in the management of postmenopausal bone health.

Best Practices for Conducting Observational Research to Assess the Relation between Nutrition and Bone: An International Working Group Summary

Diet is a modifiable factor that can affect bone strength and integrity, and the risk of fractures. Currently, a hierarchy of scientific evidence contributes to our understanding of the role of diet on bone health and fracture risk. The strength of evidence is generally based on the type of study conducted, the quality of the methodology employed, the rigor and integrity of the data collected and analysis plan, and the transparency and completeness of the results. Randomized controlled trials (RCTs) are considered to be the gold standard from a clinical research paradigm, but there is a dearth of high-quality diet-related intervention trials with bone as the primary outcome, forcing the use of observational research to inform research and clinical practices. However, for observational research to be of the most utility, standardization and optimization of the study design, accurate and reliable measurement of key variables, and appropriate data analysis and data reporting are paramount. Although there have been recommendations made in relation to RCTs in the field of nutrition, no clear rubric exists for best practices in conducting observational research with regard to nutrition and bone health. Therefore, the purpose of this paper is to describe the best practices and considerations for designing, conducting, analyzing, interpreting, and reporting observational research specifically for understanding the role of nutrition in bone health, amassed by a global panel of scientific experts with strengths in bone, nutrition epidemiology, physical activity, public health, clinical and translational trials, and observational study methods. The global panel of scientific experts represents the leadership and selected participants from the 10th annual International Symposium for the Nutritional Aspects of Osteoporosis. The topics selected and best practices presented reflect expert opinion and areas of scientific expertise of the authors rather than a systematic or comprehensive literature review or professional reporting guidelines.

Bone changes in the lower limbs from participation in an FES rowing exercise program implemented within two years after traumatic spinal cord injury

Objective: To determine the effect of a functional electrical stimulation (FES) rowing program on bone mineral density (BMD) when implemented within two years after SCI.Design: Prospective.Setting: Health Care Facility.Participants: Convenience sample; four adults with recent (<2 years) traumatic, motor complete SCI (C7-T12 AIS A-B).Intervention: A 90-session FES rowing exercise program; participants attended 30-minute FES training sessions approximately three times each week for the duration of their participation.Outcome Measures: BMD in the distal femur and tibia were measured using peripheral Quantitative Computed Tomography (pQCT) at enrollment (T₀) and after 30 (T₁), 60 (T₂), and 90 (T₃) sessions. Bone stimulus was calculated for each rower at each time point using the average number of weekly loading cycles, peak foot reaction force, and bone mineral content from the previous time point. A regression analysis was used to determine the relationship between calculated bone stimulus and change in femoral trabecular BMD between time points.Results: Trabecular BMD in the femur and tibia decreased for all participants in T_0-1, but the rate of loss slowed or reversed between T_1-2, with little-to-no bone loss for most participants during T_2-3. The calculated bone stimulus was significantly correlated with change in femoral trabecular BMD (P = 0.016; R²= 0.458).Conclusion: Consistent participation in an FES rowing program provides sufficient forces and loading cycles to reduce or reverse expected bone loss at the distal femur and tibia, at least temporarily, in some individuals within two years after SCI.Trial Registration: NCT02008149.

Short- and Long-Term Effects of Balance Training on Physical Activity in Older Adults With Osteoporosis: A Randomized Controlled Trial

Background and Purpose:

We have developed a 12-week balance training program for older adults shown to improve fall-related concerns, gait speed, balance performance, and physical function. We hypothesized that this balance training would also contribute to higher habitual physical activity (PA) levels and improved health-related quality of life (HRQoL). The primary aim was to evaluate short- and long-term effects of the balance training program on objectively measured habitual PA in older adults with osteoporosis. Secondary aims were to assess the effects of the balance training on HRQoL, and to study whether any effects on PA were associated with changes in HRQoL, gait speed, balance performance, fall-related concerns, and physical function.

Methods:

A randomized controlled trial with follow-up at 3, 9, and 15 months, including 91 participants with osteoporosis (75.6 ± 5.4 years), compared a balance training group (n = 61) with a control group (n = 30). The primary outcome was effect on habitual PA measured as steps/day, dichotomized into less than 5000 or 5000 or more steps/day. Physical activity was assessed with pedometers (Yamax) and accelerometers (Actigraph), HRQoL with the Short Form-36 (SF-36), gait with a GAITRite walkway, balance performance with Modified-Figure-Eight test and one-leg stance, fall-related concerns with Falls Efficacy Scale International, and physical function with the advanced lower extremity subscale of the questionnaire Late Life Function and Disability Instrument. Statistical methods used were multivariate logistic regression and logistic generalized estimating equation.

Results:

Sixty-eight participants completed the short-term follow-up at 3 months, and 53 participants completed the long-term follow-up at 15 months. Per-protocol analysis (n = 68) showed that the odds ratio for having a daily step count of 5000 or more at 3 months was 6.17 (95% confidence interval, 1.23-30.91), P = .027, for the intervention group compared with the control group. The longitudinal analysis (n = 91) showed that the odds ratio for having a daily step count of 5000 or more at 15 months was 2.02 (95% confidence interval, 0.88-4.64), P = .096, for the intervention group compared with the control group. The mental component sum of the SF-36 improved significantly from baseline to 3 months in the intervention group, and the physical component sum improved in both groups, but no statistically significant differences were found between groups. No associations were found between PA and changes in covariates.

Discussion and Conclusions:

The short-term evaluation showed that balance training increased habitual PA in community-dwelling older adults with osteoporosis. A significantly higher proportion of participants in the intervention group reached a level of 5000 or more steps/day, which is important for overall health. This effect was not associated with improvements in HRQoL, gait speed, balance performance, or fall-related concerns, and did not persist through the long-term follow-up. To accomplish a sustained PA change, a prolonged intervention or more support regarding habitual PA may be required, such as reinforcement with personalized behavior change counseling or PA on prescription.

Cardiovascular calcification and subcortical bone demineralization in hypertension

The present study investigated cardiovascular calcification, peripheral bone mineral density (BMD), and lab indices in hypertensive patients aged 55-74 years without severe kidney dysfunction. Cardiovascular calcification was investigated by ultrasound examinations at eight sites: aortic valve, left and right common carotid artery, left and right carotid artery bifurcation, left and right internal carotid artery, and abdominal aorta. The presence/absence of calcification at each site was coded as 1/0, respectively, for the calculation of a cumulative score. Peripheral bone mineral density was assessed by forearm quantitative computed tomography (pQCT) and was defined as low if the T-score was <-1. Lab work-up included plasma creatinine, calcium, phosphorus, parathyroid hormone and 25-(OH) vitamin D measurements. Ninety-one patients were studied. The range was 2-8 for the calcification score and 229-492 mg cm^-3 for bone mineral density. The prevalence of low bone densitometry was 83.5%. The calcification score and bone densitometry were inversely correlated in a non-adjusted analysis (R=-0.297, P=0.004) and in multivariable regression (beta=-0.335, P=0.003). The association was significant for subcortical bone (beta=-0.302, P=0.007) but not for cortical bone or trabecular bone (P⩾0.194 in both cases). The calcification score was associated with a low prevalence of bone densitometry in the non-adjusted analysis (odds ratio=2.53, 95% CI=1.41/4.54, P=0.002) and in the multivariable logistic regression (odds ratio=2.46, 95% CI=1.25/4.81, P=0.009). Cardiovascular calcification was independently associated with peripheral bone densitometry in hypertensive patients. The data support the hypothesis that vascular calcification and low bone densitometry share some determinants in hypertensive patients.

The effect of brisk walking on postural stability, bone mineral density, body weight and composition in women over 50 years with a sedentary occupation: a randomized controlled trial

BACKGROUND

To assess the effect of brisk walking on postural stability, bone mineral density (BMD) and body composition in women over 50 years of age with a sedentary occupation.

METHODS

A 10-week walking intervention based on self-regulated brisk walking (BW) to or from work of 30-35 min at least 5 times per week. The research included a total of 104 women (58 women in intervention group). The mean center of pressure (COP) velocity in medial-lateral and anterior-posterior directions, mean total COP velocity with eyes open and closed, BMD of the distal forearm and the calcaneus, body weight, fat mass, and lean body mass were assessed.

RESULTS

The BW intervention was completed by 76 % of participants. A significant effect (time × group interaction) was confirmed only in the mean COP velocity in the anterior-posterior direction with eyes closed (F = 7.41, P = 0.008). The effect of BW was not confirmed in BMD, body weight, or body composition. The results indicate that the effect of the intervention is influenced by baseline body mass index in body weight, fat mass and visceral adipose tissue.

CONCLUSIONS

BW prevents the deterioration of postural stability with eyes closed, which can have a direct effect on reducing the risk of falls under worse spatial orientation and visibility. The presented intervention model is insufficient for weight loss, changes in BMD, or body composition, and its effect should be assessed during a longer period of time.

TRIAL REGISTRATION

German Clinical Trials Register DRKS00007638 , registered March 10, 2015 (retrospectively registered).

"You Have to Keep Moving, Be Active": Perceptions and Experiences of Habitual Physical Activity in Older Women With Osteoporosis

BACKGROUND

Physical activity (PA) is essential for older adults with osteoporosis, and health care professionals play important roles in promoting PA and encouraging patients to make healthy choices. However, many factors influence habitual PA, and there is only limited knowledge about the perceptions and experiences of PA among older women with osteoporosis.

OBJECTIVES

The purpose of this study was to describe perceptions and experiences of PA and the factors that influence habitual PA among older adults with osteoporosis, impaired balance, and fear of falling.

DESIGN

This was a qualitative interview study applying interpretive content analysis with an inductive approach.

METHODS

Informants were a purposeful sample of 18 women, aged 66 to 86 years, with osteoporosis, impaired balance, and fear of falling. Individual, semistructured, face-to-face interviews were recorded, transcribed, condensed, and coded to find subthemes and themes.

RESULTS

The overall theme found was "Physical activity--a tool for staying healthy with osteoporosis." This overall theme comprised 2 main themes interpreting the challenges and possibilities of being physically active with osteoporosis. These themes were not separate but rather linked to each other like 2 sides of the same coin, with factors that could act as both barriers to and facilitators of PA. Personal preferences and osteoporosis-related concerns influenced habitual PA, and individualization was perceived as important.

LIMITATIONS

Some results may be context specific and limit the transferability to people with other cultural or socioeconomic backgrounds.

CONCLUSIONS

The women perceived that PA was an important tool to maintain health with osteoporosis and believed that they had a responsibility to use this tool. They had adapted to disease-specific limitations and developed strategies to overcome challenges and barriers to PA. Lack of PA promotion and conflicting advice about PA from physicians created uncertainty. Encouragement and guidance from physical therapists, individually or in groups, were very important.

Associação de força e nível de atividade física à densidade mineral óssea na pós-menopausa

INTRODUÇÃO: o exercício físico atua melhorando a densidade mineral óssea DMO por gerar deformidades nesse tecido e estimular remodelação.OBJETIVO: verificar a associação entre força muscular e nível de atividade física à densidade mineral óssea DMO utilizando testes de força de bíceps, de sentar e levantar, dinamometria de mãos, história pregressa de atividade física e nível de atividade física, avaliado pelo pedômetro com a DMO em mulheres na pós-menopausa.MÉTODOS: estudo transversal, descritivo que mensurou a densidade mineral óssea pela absorção de dupla energia de raios X DXA da coluna lombar L1-L4, fêmur e antebraços em 62 mulheres saudáveis no pós-menopausa, com média de 56,82 ± 4,02 anos de idade. Foi aplicado questionário para atividade física pregressa e realizada contagem diária de passos pedômetro. A força muscular foi medida pelos testes de dinamometria de mãos, de 30 segundos de bíceps bilateral e de sentar e levantar da cadeira em 30 segundos. Realizou-se registro alimentar de três dias para mensuração da ingestão diária de cálcio e vitamina D.RESULTADOS: os indivíduos apresentaram altos níveis de atividade física, porém baixa ingestão diária de cálcio e vitamina D. Não foi verificada diferença estatisticamente significativa entre força muscular nos dois grupos estudados, com DMO diminuída e DMO normal. O grupo com DMO diminuída apresentou maior número de passos diários e menor peso quando comparado com o grupo com DMO normal. Foram observadas várias correlações positivas de baixa magnitude, embora significantes, entre a densitometria e a força muscular p < 0,50.CONCLUSÃO: os autores descreveram risco cinco vezes e meia maior em mulheres não praticantes de atividade física da adolescência até a idade adulta e de apresentarem redução da DMO em comparação com as mulheres que apresentaram DMO normal.

Physical Activity and Bone: May the Force be with You

Physical activity (PA) is thought to play an important role in preventing bone loss and osteoporosis in older people. However, the type of activity that is most effective in this regard remains unclear. Objectively measured PA using accelerometers is an accurate method for studying relationships between PA and bone and other outcomes. We recently used this approach in the Avon Longitudinal Study of Parents and Children (ALSPAC) to examine relationships between levels of vertical impacts associated with PA and hip bone mineral density (BMD). Interestingly, vertical impacts >4g, though rare, largely accounted for the relationship between habitual levels of PA and BMD in adolescents. However, in a subsequent pilot study where we used the same method to record PA levels in older people, no >4g impacts were observed. Therefore, to the extent that vertical impacts need to exceed a certain threshold in order to be bone protective, such a threshold is likely to be considerably lower in older people as compared with adolescents. Further studies aimed at identifying such a threshold in older people are planned, to provide a basis for selecting exercise regimes in older people which are most likely to be bone protective.

Association between blood lead and walking speed in the National Health and Nutrition Examination Survey (NHANES 1999-2002)

BACKGROUND

Walking speed is a simple and reliable measure of motor function that is negatively associated with adverse health events in older people, including falls, disability, hospital admissions, and mortality. Lead has adverse affects on human health, particularly on the vascular and neurological systems.

OBJECTIVE

We explored the hypothesis that lead is associated with slower walking speed.

METHODS

We used U.S. National Health and Nutrition Examination Survey (NHANES) cross-sectional data from 1999-2002. The time to walk 20 ft (walking speed) was measured among 1,795 men and 1,798 women ≥ 50 years of age. The association between walking speed and quintiles of blood lead concentration was estimated separately in men and women using linear regression models adjusted for age, education, ethnicity, alcohol use, smoking status, height, and waist circumference.

RESULTS

Mean blood lead concentrations and walking speeds were 2.17 μg/dL and 3.31 ft/sec in women, and 3.18 μg/dL and 3.47 ft/sec in men, respectively. Among women, walking speed decreased with increasing quintiles of blood lead, resulting in an estimated mean value that was 0.11 ft/sec slower (95% CI: -0.19, -0.04; p-trend = 0.005) for women with blood lead concentrations in the highest versus lowest quintile. In contrast, lead was not associated with walking speed in men.

CONCLUSION

Blood lead concentration was associated with decreased walking speed in women, but not in men. Our results contribute to the growing evidence that lead exposure, even at low levels, is detrimental to public health.

The role of physical activity in changes in walking mechanics with age

While age-related declines in walking mechanics have been documented, it remains unclear if changes in walking mechanics with age occur as a natural consequence of aging and to what extent these changes are related to a reduction in fitness and physical activity with aging. The study aim was to determine if the walking mechanics of an older (>50) yet highly active population are different from a younger population (<40). Gait mechanics data for 79 middle-aged (50-64 yrs) and 54 older (65-80 yrs) individuals with ≥ 7500 steps/day, based on a 7 day activity monitoring history, and 33 younger adults (ages 18-40) were collected. The older subjects did not reduce self-selected walking speed relative to the younger subjects. However, the walking speed was maintained by increasing cadence while reducing stride-length for middle-aged and older subjects. Middle-aged and older adults had less ankle dorsi-flexion landing at heel-strike and older adults also had less plantar flexion at toe-off. Small decreases in the ankle dorsi-flexion moments (p=0.019, p=0.008) and increases in the hip extension moments (p=0.004, p=0.005) were found for two normalized walking speeds for the middle-aged and older adults compared to the young adults. These results provide quantitative evidence that increased activity with aging can mitigate declines in walking performance and mechanics with age. The high volume of walking activity in the older subjects did not fully prevent changes in gait mechanics, but may have minimized the magnitude of age-related changes on ambulatory function relative to other reports of older inactive subjects.