Comparing GPS, Log, Survey, and Accelerometry to Measure Physical Activity

Systematic review of best practices for GPS data usage, processing, and linkage in health, exposure science and environmental context research

Global Positioning System (GPS) technology is increasingly used in health research to capture individual mobility and contextual and environmental exposures. However, the tools, techniques and decisions for using GPS data vary from study to study, making comparisons and reproducibility challenging.

OBJECTIVES

The objectives of this systematic review were to (1) identify best practices for GPS data collection and processing; (2) quantify reporting of best practices in published studies; and (3) discuss examples found in reviewed manuscripts that future researchers may employ for reporting GPS data usage, processing and linkage of GPS data in health studies.

DESIGN

A systematic review.

DATA SOURCES

Electronic databases searched (24 October 2023) were PubMed, Scopus and Web of Science (PROSPERO ID: CRD42022322166).

ELIGIBILITY CRITERIA

Included peer-reviewed studies published in English met at least one of the criteria: (1) protocols involving GPS for exposure/context and human health research purposes and containing empirical data; (2) linkage of GPS data to other data intended for research on contextual influences on health; (3) associations between GPS-measured mobility or exposures and health; (4) derived variable methods using GPS data in health research; or (5) comparison of GPS tracking with other methods (eg, travel diary).

DATA EXTRACTION AND SYNTHESIS

We examined 157 manuscripts for reporting of best practices including wear time, sampling frequency, data validity, noise/signal loss and data linkage to assess risk of bias.

RESULTS

We found that 6% of the studies did not disclose the GPS device model used, only 12.1% reported the per cent of GPS data lost by signal loss, only 15.7% reported the per cent of GPS data considered to be noise and only 68.2% reported the inclusion criteria for their data.

CONCLUSIONS

Our recommendations for reporting on GPS usage, processing and linkage may be transferrable to other geospatial devices, with the hope of promoting transparency and reproducibility in this research.

PROSPERO REGISTRATION NUMBER

CRD42022322166.

Motivation for Physical Activity as a Key Determinant of Sedentary Behavior Among Postsecondary Students

It is known that the transition to adulthood represents a critical period of life when acquiring healthy behaviors can influence lifestyle and health throughout adulthood. Given the importance of the consequences of a sedentary lifestyle, identifying influence factors is key to improving healthy behaviors. The objective of this study is to explore the role of postsecondary students' motivation toward physical activity in the association with their screen time and out-of-school physical activity practice. A total of 1522 postsecondary students (90% were aged 17-20 years) recruited from 17 postsecondary institutions completed the self-reported questionnaire during course time. Multivariate linear regression was used to assess the association between motivation to move including additional predictors of behavior such as intention and tendency to self-activate and self-reported screen time and physical activity controlling for age and sex. Motivation including all 3 motivational variables (interest, utility, competence) was negatively associated with screen time, b = -0.498 (95% CI between -0.635 and -0.361) and positively associated with moderate-to-vigorous physical activity, b = 133.986, (95% CI between 102.129 and 165.843). Of the 3 motivational variables, interest had the strongest negative association with screen time, b = -0.434 (95% CI between -0.551 and -0.317), and the strongest positive association with physical activity, b = 113.671, (95% CI between 86.396 and 140.946). These findings indicate that the motivation of postsecondary students toward physical activity significantly influences their behaviors, including screen time and physical activity engagement.

Human movement patterns of farmers and forest workers from the Thailand-Myanmar border

Background: Human travel patterns play an important role in infectious disease epidemiology and ecology. Movement into geographic spaces with high transmission can lead to increased risk of acquiring infections. Pathogens can also be distributed across the landscape via human travel. Most fine scale studies of human travel patterns have been done in urban settings in wealthy nations. Research into human travel patterns in rural areas of low- and middle-income nations are useful for understanding the human components of epidemiological systems for malaria or other diseases of the rural poor. The goal of this research was to assess the feasibility of using GPS loggers to empirically measure human travel patterns in this setting, as well as to quantify differing travel patterns by age, gender, and seasonality among study participants. Methods: In this pilot study we recruited 50 rural villagers from along the Myanmar-Thailand border to carry GPS loggers for the duration of a year. The GPS loggers were programmed to take a time-stamped reading every 30 minutes. We calculated daily movement ranges and multi-day trips by age and gender. We incorporated remote sensing data to assess patterns of days and nights spent in forested or farm areas, also by age and gender. Results: Our study showed that it is feasible to use GPS devices to measure travel patterns, though we had difficulty recruiting women and management of the project was relatively intensive. We found that older adults traveled farther distances than younger adults and adult males spent more nights in farms or forests. Conclusion: The results of this study suggest that further work along these lines would be feasible in this region. Furthermore, the results from this study are useful for individual-based models of disease transmission and land use.

Flourishing or physical activity?: Identifying temporal precedence in supporting the transition to university

Objective: Flourishing is a mental health indicator that helps students function optimally, which may be important for first-year university students. Physical activity (PA) also contributes to optimal functioning, yet the flourishing and PA relationship has received little attention. The bidirectional relationships between flourishing and meeting moderate-to-vigorous PA (MVPA) guidelines were assessed during the first year of university. Methods: First-year university students completed surveys (September [T1], March [T2]). Reciprocal effects were examined in a cross-lagged path model. Results: Over 40% of the sample was not meeting MVPA guidelines at T1 or T2. Controlling for sex, higher T1 flourishing was associated with higher odds of meeting T2 MVPA guidelines. T1 MVPA did not predict T2 flourishing. Conclusions: The findings provide preliminary evidence that flourishing may support meeting MVPA guidelines for first-year students. Given low rates of meeting guidelines, flourishing and PA could be targeted to foster MVPA, supporting a healthy university transition.

Validity of a Global Positioning System-Based Algorithm and Consumer Wearables for Classifying Active Trips in Children and Adults

OBJECTIVE

To investigate the convergent validity of a global positioning system (GPS)-based and two consumer-based measures with trip logs for classifying pedestrian, cycling, and vehicle trips in children and adults.

METHODS

Participants (N = 34) wore a Qstarz GPS tracker, Fitbit Alta, and Garmin vivosmart 3 on multiple days and logged their outdoor pedestrian, cycling, and vehicle trips. Logged trips were compared with device-measured trips using the Personal Activity Location Measurement System (PALMS) GPS-based algorithms, Fitbit's SmartTrack, and Garmin's Move IQ. Trip- and day-level agreement were tested.

RESULTS

The PALMS identified and correctly classified the mode of 75.6%, 94.5%, and 96.9% of pedestrian, cycling, and vehicle trips (84.5% of active trips, F1 = 0.84 and 0.87) as compared with the log. Fitbit and Garmin identified and correctly classified the mode of 26.8% and 17.8% (22.6% of active trips, F1 = 0.40 and 0.30) and 46.3% and 43.8% (45.2% of active trips, F1 = 0.58 and 0.59) of pedestrian and cycling trips. Garmin was more prone to false positives (false trips not logged). Day-level agreement for PALMS and Garmin versus logs was favorable across trip modes, though PALMS performed best. Fitbit significantly underestimated daily cycling. Results were similar but slightly less favorable for children than adults.

CONCLUSIONS

The PALMS showed good convergent validity in children and adults and were about 50% and 27% more accurate than Fitbit and Garmin (based on F1). Empirically-based recommendations for improving PALMS' pedestrian classification are provided. Since the consumer devices capture both indoor and outdoor walking/running and cycling, they are less appropriate for trip-based research.

Human movement patterns of farmers and forest workers from the Thailand-Myanmar border

Background: Human travel patterns play an important role in infectious disease epidemiology and ecology. Movement into geographic spaces with high transmission can lead to increased risk of acquiring infections. Pathogens can also be distributed across the landscape via human travel. Most fine scale studies of human travel patterns have been done in urban settings in wealthy nations. Research into human travel patterns in rural areas of low- and middle-income nations are useful for understanding the human components of epidemiological systems for malaria or other diseases of the rural poor. The goal of this research was to assess the feasibility of using GPS loggers to empirically measure human travel patterns in this setting, as well as to quantify differing travel patterns by age, gender, and seasonality. Methods: In this pilot study we recruited 50 rural villagers from along the Myanmar-Thailand border to carry GPS loggers for the duration of a year. The GPS loggers were programmed to take a time-stamped reading every 30 minutes. We calculated daily movement ranges and multi-day trips by age and gender. We incorporated remote sensing data to assess patterns of days and nights spent in forested or farm areas, also by age and gender. Results: Our study showed that it is feasible to use GPS devices to measure travel patterns, though we had difficulty recruiting women and management of the project was relatively intensive. We found that older adults traveled farther distances than younger adults and adult males spent more nights in farms or forests. Conclusion: The results of this study suggest that further work along these lines would be feasible in this region. Furthermore, the results from this study are useful for individual-based models of disease transmission and land use.

Device-Measured and Self-Reported Active Travel Associations with Cardiovascular Disease Risk Factors in an Ethnically Diverse Sample of Adults

Active travel (AT) provides an opportunity to alleviate the physical inactivity and climate crises contributing to the global chronic disease burden, including cardiovascular diseases (CVD). Though AT shows promising links to reduced CVD risk, prior studies relied on self-reported AT assessment. In the present study, device-measured and self-reported AT were compared across population subgroups and relationships with CVD risk biomarkers were evaluated for both measures. The study recruited an ethnically diverse sample (N = 602, mean age 59 years, 42% Hispanic/Latino ethnicity) from neighborhoods that varied by walkability and food access. AT was assessed using concurrently collected accelerometer and GPS data and self-report data from a validated survey. Relationships with body mass index (BMI), triglycerides, high-density lipoprotein (HDL) cholesterol, blood pressure (BP), and moderate-to-vigorous physical activity (MVPA) were modeled using multivariable linear regression. Devices captured more AT than did self-report. We found differences in AT measures by population subgroups, including race, ethnicity, education, income, vehicle access, and walkability. Men had more accelerometer-measured MVPA, though women self-reported more daily minutes. Both device and survey AT measures were positively associated with total accelerometer-measured MVPA, though the relationship was stronger with device-measured AT. Device-measured AT was associated with lower BMI. No other CVD risk biomarker was associated with either AT measure. No effect modification by Hispanic/Latino ethnicity was detected. Further studies with device-based measures are warranted to better understand the relationship between AT and cardiovascular health.

Nine Months into the COVID-19 Pandemic: A Longitudinal Study Showing Mental Health and Movement Behaviours Are Impaired in UK Students

Initial studies indicated that student mental health was impaired during the early stages of the pandemic and that maintaining/improving physical activity gave some protection from mental illness. However, as the pandemic persists, these data may not reflect current circumstances and may have been confounded by exam stress. Methods: This study used an online survey to assess the changes in, and associations between, mental health and movement behaviours in 255 UK university students from before the COVID-19 pandemic (October 2019) to 9 months following the UK’s first confirmed case (October 2020). Changes in and associations between mental wellbeing, perceived stress, physical activity, and sedentary behaviour were assessed using a mixed model ANOVA; a multiple linear regression model determined the predictive value of variables associated with Δ mental wellbeing. Results: Mental wellbeing and physical activity decreased (45.2 to 42.3 (p < 0.001); 223 to 173 min/week (p < 0.001)), whereas perceived stress and time spent sedentary increased (19.8 to 22.8 (p < 0.001); 66.0 to 71.2 h/week (p = 0.036)). Δ perceived stress, Δ sedentary behaviour and university year accounted for 64.7%, 12.9%, and 10.1% of the variance in Δ mental wellbeing (p < 0.001; p = 0.006; p = 0.035). Conclusion: The COVID-19 pandemic is having a sustained negative impact on student mental health and movement behaviour.

Changes in Physical Activity among United Kingdom University Students Following the Implementation of Coronavirus Lockdown Measures

Coronavirus disease (COVID-19) and resulting restrictions have significantly impacted physical activity levels. However, objectively measured changes in physical activity levels among UK university students during lockdown are understudied. Using data collected via remote measurement technology from a mobile physical activity tracker, this study aimed to describe the longitudinal trajectories of physical activity following the start of lockdown among students at a large UK university, and to investigate whether these trajectories varied according to age, gender, and ethnicity. Continuous physical activity data for steps walked per week (n = 730) and miles run per week (n = 264) were analysed over the first period of lockdown and subsequent restriction easing using negative binomial mixed models for repeated measures. Throughout the observation period, more steps were walked by males compared to females, and by White groups compared to all other ethnic groups combined. However, there was a gradual increase in the number of steps walked per week following the commencement of lockdown, irrespective of sociodemographic characteristics. For females only, there was a decrease in the number of miles run per week following lockdown. The long-term impact of the pandemic on physical health is unknown, but our results highlight changes in physical activity which could have implications for physical health.

Content validity and methodological considerations in ecological momentary assessment studies on physical activity and sedentary behaviour: a systematic review

Background

Ecological momentary assessment (EMA) is a method of collecting real-time data based on repeated measures and observations that take place in participant’s daily environment. EMA has many advantages over more traditional, retrospective questionnaires. However, EMA faces some challenges to reach its full potential. The aims of this systematic review are to (1) investigate whether and how content validity of the items (i.e. the specific questions that are part of a larger EMA questionnaire) used in EMA studies on physical activity and sedentary behaviour was assessed, and (2) provide an overview of important methodological considerations of EMA in measuring physical activity and sedentary behaviour.

Methods

Thirty papers (twenty unique studies) were systematically reviewed and variables were coded and analysed within the following 4 domains: (1) Content validity, (2) Sampling approach, (3) Data input modalities and (4) Degree of EMA completion.

Results

Only about half of the studies reported the specific items (n = 12) and the source of the items (n = 11). None of the studies specifically assessed the content validity of the items used. Only a minority (n = 5) of the studies reported any training, and one tested the comprehensibility of the EMA items. A wide variability was found in the design and methodology of the EMA. A minority of the studies (n = 7) reported a rationale for the used prompt frequency, time selection, and monitoring period. Retrospective assessment periods varied from ‘now’ to ‘in the last 3.5 hours’. In some studies there was a possibility to delay (n = 6) or deactivate (n = 10) the prompt, and some provided reminders after the first prompt (n = 9).

Conclusions

Almost no EMA studies reported the content validation of the items used. We recommend using the COSMIN checklist (COnsensus-based Standards for the selection of health Measurement INstruments) to report on the content validity of EMA items. Furthermore, as often no rationale was provided for several methodological decisions, the following three recommendations are made. First, provide a rationale for choosing the sampling modalities. Second, to ensure assessment ‘in the moment’, think carefully about the retrospective assessment period, reminders, and deactivation of the prompt. Third, as high completion rates are important for representativeness of the data and generalizability of the findings, report completion rates.

Trial registration

This review is registered in PROSPERO, the International prospective register of systematic reviews (registration number: CRD42017077996).

Information Literacy in Food and Activity Tracking Among Parkrunners, People With Type 2 Diabetes, and People With Irritable Bowel Syndrome: Exploratory Study

BACKGROUND

The tracking, or logging, of food intake and physical activity is increasing among people, and as a result there is increasing evidence of a link to improvement in health and well-being. Crucial to the effective and safe use of logging is a user's information literacy.

OBJECTIVE

The aim of this study was to analyze food and activity tracking from an information literacy perspective.

METHODS

An online survey was distributed to three communities via parkrun, diabetes.co.uk and the Irritable Bowel Syndrome Network.

RESULTS

The data showed that there were clear differences in the logging practices of the members of the three different communities, as well as differences in motivations for tracking and the extent of sharing of said tracked data. Respondents showed a good understanding of the importance of information accuracy and were confident in their ability to understand tracked data, however, there were differences in the extent to which food and activity data were shared and also a lack of understanding of the potential reuse and sharing of data by third parties.

CONCLUSIONS

Information literacy in this context involves developing awareness of the issues of accurate information recording, and how tracked information can be applied to support specific health goals. Developing awareness of how and when to share data, as well as of data ownership and privacy, are also important aspects of information literacy.

Daily metabolic expenditures: estimates from US, UK and polish time-use data

BACKGROUND

Behaviour has diverse economic, social and health consequences. Linking time spent in different daily activities to energy expenditure (EE) is one way of investigating the health and physiological consequences of behaviour and identifying targets to improve population health and well-being.

METHODS

We estimated behaviour-related EE for respondents to time use surveys (TUS) from three countries: UK 2001, Poland 2012 and US 2003-13. The Harmonised Multinational Time Use Survey (MTUS) activity categories were matched to MET estimates from the 2011 Compendium of Physical Activities. We attach METs values to each successive activity in the TUS, together with both the original UK, Polish and US activity classifications and the 68-category MTUS activity classification. We used TUS estimates of activity durations across 24-h to estimate the Physical Activity Level (PAL) for respondents from the three countries and the average time spent and MET values for different activity categories.

RESULTS

PAL values ranged from 1.59 in the US to 1.74 in Poland. The main sources of daily EE from PA were paid and unpaid work activities. Discretionary PA accounted for only a very small part (~ 3%) of adult daily energy expenditures. Using the harmonised MTUS 68-activity classification reduced the variability of the aggregate PAEE measure by ~ 20%, but the patterns of association between key demographics (age, sex, educational attainment) were unaffected. TUS data were further used to (1) identify sources of daily PA, and (2) assess adherence to physical activity guidelines (PAG) on a single-day basis. Estimated adherence levels were similar to those reported from other TUS as well as frequency based estimates.

CONCLUSIONS

Comparative studies of energy expenditure based on harmonised time use activity categories could provide insight into the relative importance of different activities for energy expenditure across different countries and demographic groups. However, new observational studies combining TUS data with accelerometer, direct observation and other measures of activity intensity are required for more accurate MET assignments to activity categories in TUS.

Mobile Sensing in Environmental Health and Neighborhood Research

Public health research has witnessed a rapid development in the use of location, environmental, behavioral, and biophysical sensors that provide high-resolution objective time-stamped data. This burgeoning field is stimulated by the development of novel multisensor devices that collect data for an increasing number of channels and algorithms that predict relevant dimensions from one or several data channels. Global positioning system (GPS) tracking, which enables geographic momentary assessment, permits researchers to assess multiplace personal exposure areas and the algorithm-based identification of trips and places visited, eventually validated and complemented using a GPS-based mobility survey. These methods open a new space-time perspective that considers the full dynamic of residential and nonresidential momentary exposures; spatially and temporally disaggregates the behavioral and health outcomes, thus replacing them in their immediate environmental context; investigates complex time sequences; explores the interplay among individual, environmental, and situational predictors; performs life-segment analyses considering infraindividual statistical units using case-crossover models; and derives recommendations for just-in-time interventions.

Establishing physical activity in breast cancer: self-report versus activity tracker

PURPOSE

Establishing accurate estimates of physical activity at baseline is essential for interventions assessing the potential benefits of exercise in adults with cancer. This study compares self-reported physical activity with independent data from activity trackers in women with early breast cancer (BC) recruited into a "walking" intervention during chemotherapy.

METHODS

Baseline (pre-intervention) questions inquired about self-reported physical activity-number of walking days/week and minutes/day-in women who were initiating chemotherapy for Stage I-III BC. Activity trackers measured steps per day during the first full week of chemotherapy. Weighted Kappa statistic and Pearson correlation coefficients were used to evaluate agreement and association between self-reported and objectively tracked physical activity levels, respectively. Univariate analyses were conducted to identify variables that may influence congruence between the two measures.

RESULTS

In a sample of 161 women, 77% were white, with mean age 56 years. Agreement between self-reported and objectively tracked physical activity was "fair" (kappa coefficient = 0.31), with most patients (59%) over-reporting their physical activity levels. There was weak correlation between the two measures (r = 0.24); however, correlation was strong in participants who were not married (r = 0.53) and/or living alone (r = 0.69).

CONCLUSIONS

Objective methods for assessing physical activity (activity trackers, accelerometers) should be used as a complement to self-reported measures to establish credible activity levels for intervention studies seeking to increase physical activity and/or measure the impact of increased physical activity in women with breast cancer.

Physical Activity Levels and New Public Transit: A Systematic Review and Meta-analysis

CONTEXT

Physical inactivity is a public health concern as it contributes to the rising burden of noncommunicable diseases. Introducing new public transportation options, such as extending or building new light rail or bus rapid transit stations, could encourage commuters to walk to and from public transit stops, thus increasing their physical activity levels. Despite previous research generally finding positive associations between public transit usage and physical activity levels, few have summarized the association between introducing new public transportation options and different intensities of physical activity. This study aimed to systematically review the current evidence and perform a meta-analysis on this association.

EVIDENCE ACQUISITION

Ten databases were systematically searched for studies published between 1997 and 2017. To ensure comparability, study outcomes were converted to MET hours/week. A random effects meta-analysis and sensitivity analysis were then conducted.

EVIDENCE SYNTHESIS

Nine studies were identified to be included in the systematic review, of which five were eligible for meta-analysis. Pooled results suggest that building new public transit options is associated with a statistically significant increase in light to moderate physical activity levels by 1.76 MET hours/week (95% CI=0.19, 3.32, p=0.03). This is equivalent to increasing walking and other light to moderate physical activity by about 30 minutes per week, relative to baseline. No significant effect was found for the moderate to vigorous physical activity outcome.

CONCLUSIONS

Results show new public transit options can substantially contribute to increasing low- to moderate-intensity exercise levels, which has the potential to improve health on a population scale.

Dose response association of objective physical activity with mental health in a representative national sample of adults: A cross-sectional study

Although higher physical activity (PA) levels are associated with better mental health, previous findings about the shape of the dose–response relationship between PA and mental health are inconsistent. Furthermore, this association may differ according to sedentary levels. We investigated the cross-sectional dose-response associations between objectively measured PA and mental health in a representative national sample of adults. We also examined whether sedentary time modified the PA—mental health associations. Based on 2007–2013 Canadian Health Measures Survey data, PA and sedentary time were measured using accelerometry among 8150 participants, aged 20 to 79 years. Generalized additive models with a smooth function were fitted to examine associations between minutes per day of moderate and vigorous PA (MVPA), light PA (LPA), daily steps (combined or not with sedentary time) and self-rated mental health. A significant curvilinear relationship between average daily minutes of MVPA and mental health was observed, with increasing benefits up to 50 minutes/day. For LPA, a more complex shape (monotonic and curvilinear) was found. For daily steps, inverted U-shaped curve suggested increasing benefits until a plateau between 5 000 and 16 000 steps. The MVPA-LPA combination was significantly associated with mental health but with a complex pattern (p < 0.0005^E-06). The tested PA-sedentary time combinations showed that increasing sedentary time decreased the positive PA-mental health associations. Non-linear dose-response patterns between the PA modalities and self-reported mental health were observed. Optimal doses of daily minutes of MVPA, LPA, MVPA combined with LPA and daily steps are independently associated with better mental health in adults. The results also suggest that PA-mental health associations could be hampered by daily sedentary time.

The relationship between objectively assessed physical activity and bone health in older adults differs by sex and is mediated by lean mass

Relationships between objectively assessed free-living physical activity (PA) and changes in bone health over time are poorly understood in older adults. This study suggests these relationships are sex-specific and that body composition may influence the mechanical loading benefits of PA.

INTRODUCTION

To investigate associations of objectively assessed PA and bone health in community-dwelling older adults.

METHODS

This secondary analysis of a subset of the Tasmanian Older Adult Cohort study included participants with PA assessed utilising ActiGraph GT1M accelerometers over 7 days (N = 209 participants, 53% female; mean ± SD age 64.5 ± 7.2 years). Steps/day and PA intensity were estimated via established thresholds. Bone mineral content (BMC) was acquired at the total hip, lumbar spine, legs and whole body by DXA at baseline and approximately 2.2 years later. Relationships between PA and BMC were assessed by multivariable linear regression analyses adjusted for age, smoking status, height and total lean mass.

RESULTS

Men with above-median total hip BMC completed significantly less steps per day, but there was no significant difference in PA intensity compared with those with below-median BMC. There were no significant differences in PA in women stratified by median BMC. In women, steps/day were positively associated with leg BMC (B = 0.178; P = 0.017), and sedentary behaviour was negatively associated with leg BMC (- 0.165; 0.016) at baseline. After adjustment for confounders including lean mass and height, higher sedentary behaviour at baseline was associated with declines in femoral neck BMC (- 0.286; 0.011) but also with increases in pelvic BMC (0.246; 0.030) in men and increases in total hip BMC (0.215; 0.032) in women, over 2.2 years. No other significant longitudinal associations were observed after adjustment for body composition.

CONCLUSIONS

Associations of accelerometer-determined sedentary behaviour and PA with bone health in older adults differ by sex and anatomical site and are mediated by body composition.

Prescribing Physical Activity for the Prevention and Treatment of Osteoporosis in Older Adults

Osteoporosis is an age-related disease, characterised by low bone mineral density (BMD) and compromised bone geometry and microarchitecture, leading to reduced bone strength. Physical activity (PA) has potential as a therapy for osteoporosis, yet different modalities of PA have varying influences on bone health. This review explores current evidence for the benefits of PA, and targeted exercise regimes for the prevention and treatment of osteoporosis in older adults. In particular, the outcomes of interventions involving resistance training, low- and high-impact weight bearing activities, and whole-body vibration therapy are discussed. Finally, we present recommendations for future research that may maximise the potential of exercise in primary and secondary prevention of osteoporosis in the ageing population.

Volume and social context of physical activity in association with mental health, anxiety and depression among youth

There is growing interest in physical activity (PA) to prevent mental disorders in youth. However, few studies examine the association between PA and mental health. Further, how PA volume and context relate to mental health and mental disorders remains unclear, especially among youth in transition to adulthood. This study examined the cross-sectional associations among PA volume and context, mental health, and symptoms of anxiety and depression in post-secondary students. A total of 1527 post-secondary students (97.4% were age 16-24years) recruited in a CEGEP in Quebec, Canada completed a self-report questionnaire during class-time in October 2013. Multivariate linear regression was used to model the associations between PA volume and context and mental health, anxiety and depression controlling for sex, age and perceived socioeconomic status. Volume of moderate-to-vigorous leisure time PA (MVPA) was positively associated with mental health (β (95% CI)=0.072 (0.045, 0.099)) and inversely associated with symptoms of anxiety (-0.011 (-0.020, -0.001)) and depression (-0.010 (-0.017, -0.003)). Volume including all PA intensities was associated with mental health (0.052 (0.028, 0.076)). After controlling for PA volume, active youth involved in team sports had better mental health than those who engaged in PA individually. PA volume and the social context of PA are independently associated with mental health among youth. MVPA is inversely associated with anxiety and depressive symptoms.