The maximal amount of bone mass gained during growth (peak bone mass) is an important determinant of bone mass in later life and thereby an important determinant of fraeiure risk. Although genetic factors appear lo be primary determinants of peak bone mass, environmental factors such as physical activity and nutrition also contribute. In this article, bone growth and maintenance are reviewed, and mechanisms are described whereby physical activity can affect bone mass. Studies addressing the effects of physical activity on bone status in youth are reviewed: Although conclusive data are not yet available, considerable evidence supports the importance of activity, especially activity initiated before puberty. The critical role of energy in bone growth is outlined, and studies assessing the impact of calcium intake during childhood and adolescence are reviewed. Although results of intervention trials are equivocal, other evidence supports a role for calcium intake during growth. Recommendations for physical activity and nutrition, directed lochildren and adolescents, are presented.
Susan I. Barr and Heather A. McKay
Leigh Gabel, Heather M. Macdonald, Lindsay Nettlefold and Heather A. McKay
Purpose: We examined the influence of vigorous physical activity (VPA) bout frequency on bone strength accrual across adolescence, independent of total volume of VPA. Methods: We measured VPA (6 metabolic equivalents; total volume and bout frequency <5 min in duration) annually using waist-worn accelerometers (ActiGraph GT1M) in 309 adolescents (9–20 y at baseline: 99, <13 y; 126, 13–18 y; 84, >18 y) over a maximum of 4 years. We applied finite element analysis to high-resolution peripheral quantitative computed tomography scans of the distal tibia (8% site) to estimate bone strength (failure load; F.Load, Newtons). We fit a mixed effects model with maturity offset (years from age at peak height velocity) as a random effect and sex, ethnicity, tibia length, lean body mass, and VPA (volume and bout frequency) as fixed effects. Results: VPA volume and bout frequency were positively associated with F.Load across adolescence; however, VPA volume did not predict F.Load once VPA bout frequency was included in the model. Participants in the upper quartile of VPA bout frequency (∼33 bouts per day) had 10% (500 N) greater F.Load across adolescence compared with participants in the lowest quartile (∼9 bouts per day; P = .012). Each additional daily bout of VPA was associated with 21 N greater F.Load, independent of total volume of VPA. Conclusion: Frequent VPA should be promoted for optimal bone strength accrual.
Catherine E. Tong, Joanie Sims Gould and Heather A. McKay
Foreign-born older adults (FBOAs) are at risk for negative health transitions in Canada. Physical activity (PA) enhances health, yet we know very little about the PA habits of FBOAs in Canada. We conducted a mixed-method study in English, Cantonese, Mandarin, Punjabi, and Hindi, with 49 South Asian and Chinese FBOAs in Vancouver, Canada. In total, 49 participants completed surveys; of these 49, 46 wore accelerometers and 18 completed in-depth interviews. Participants’ mean daily step count was 7,876 (women: 8,172, men: 7,164, Chinese: 8,291, and South Asian: 7,196). The bulk of their time is spent in light and sedentary activities. PA is principally acquired through walking for errands and work performed in and around the home. This study challenges the assumption that FBOAs are less active than their nonimmigrant peers and confirms the key role of “nonexercise” and low activity, rather than moderate to vigorous, in older adults’ PA acquisition.
Katharine E. Reed, Darren E.R. Warburton, Crystal L. Whitney and Heather A. McKay
Low physical fitness is associated with increased risk of cardiovascular disease (CVD) in adults and a higher incidence of CVD risk factors in children. Our aim was to compare the aerobic performance of Canadian children in 2004 with that of children measured 2 decades ago. We conducted a cross-sectional comparison of 2 data sets: (a) a 2004 cohort (n = 252) and (b) data from Leger’s 1981 cohort (n = 2,151). Performance was assessed using Leger’s 20 m Shuttle Run Test. First, we compared VO2max by cohort (in age and sex subgroups). Second, we used 1981 derived data, to re-create the original distribution curves, then calculated a 1981 equivalent percentile for each 2004 cohort child. We found that aerobic performance was lower at all ages in 2004 compared with 1981 (p < .01). Thus, the 50th percentile for fitness of children in 2004 was equivalent to that of children in the lowest 20% of fitness in 1981. We support the view that the performance of children on aerobic fitness tests is declining.
Dawn C. Mackey, Alexander D. Perkins, Kaitlin Hong Tai, Joanie Sims-Gould and Heather A. McKay
We conducted Men on the Move, a 12-week randomized controlled feasibility trial of a scalable, choice-based, physical activity (PA) and active transportation intervention. Participants were community-dwelling men aged 60 years and older (n = 29 intervention [INT] and n = 29 waitlist control [CON]). Trained activity coaches delivered: (a) one-on-one participant consultations to develop personal action plans for PA and active transportation, (b) monthly group-based motivational meetings, (c) weekly telephone support, (d) complimentary recreation and transit passes, and (e) pedometers and diaries for self-monitoring. Men on the Move demonstrated high rates of recruitment, retention, and intervention adherence. INT chose a variety of group-based and individual PAs and destinations for their personal action plans. At 12 weeks, INT achieved more steps, moderate–vigorous PA, and energy expenditure than CON. INT was also more likely to take transit and meet national guideline levels of PA. At 24 weeks follow-up, INT benefits were sustained for moderate–vigorous PA and energy expenditure.
Anna M. Chudyk, Meghan Winters, Erin Gorman, Heather A. McKay and Maureen C. Ashe
The authors investigated the use of Google Earth’s Street View option to audit the presence of built environment features that support older adults’ walking. Two raters conducted virtual (Street View) and in-the-field audits of 48 street segments surrounding urban and suburban assisted living sites in metropolitan Vancouver, BC, Canada. The authors determined agreement using absolute agreement. Their findings indicate that Street View may identify the presence of features that promote older adults’ walking, including sidewalks, benches, public washrooms, and destinations. However, Street View may not be as reliable as in-the-field audits to identify details associated with certain items, such as counts of trees or street lights; presence, features, and height of curb cuts; and sidewalk continuity, condition, and slope. Thus, the appropriateness of virtual audits to identify microscale built environment features associated with older adults’ walking largely depends on the purpose of the audits—specifically, whether the measurer seeks to capture highly detailed features of the built environment.
Ronald F. Zernicke, Grant C. Goulet, Peter R. Cavanagh, Benno M. Nigg, James A. Ashton-Miller, Heather A. McKay and Ton van den Bogert
As a field, biomechanics comprises research from the molecular and cellular levels, to tissues, to organs, to organisms and their movements. In the past 50 years, the impact of biomechanics research on society has been amplified dramatically. Here, we provide five brief summaries of exemplar biomechanics results that have had substantial impact on health and our society, namely 1) spaceflight and microgravitational effects on musculoskeletal health; 2) impact forces, soft tissue vibrations, and skeletal muscle tuning affecting human locomotion; 3) childbirth mechanics, injuries, and pelvic floor dysfunction; 4) prescriptive physical activity in childhood to enhance skeletal growth and development to prevent osteoporotic fractures in adulthood and aging; and 5) creative innovations in technology that have transformed the visual arts and entertainment.
Samantha M. Gray, Peggy Chen, Lena Fleig, Paul A. Gardiner, Megan M. McAllister, Joseph H. Puyat, Joanie Sims-Gould, Heather A. McKay, Meghan Winters and Maureen C. Ashe
Background: Physical activity confers many health benefits to older adults, and adopting activity into daily life routines may lead to better uptake. The purpose of this study was to test the effect of a lifestyle intervention to increase daily physical activity in older women through utilitarian walking and use of public transportation. Methods: In total, 25 inactive women with mean age (SD) of 64.1 (4.6) years participated in this pilot randomized controlled trial [intervention (n = 13) and control (n = 12)]. Seven-day travel diaries (trips per week) and the International Physical Activity Questionnaire (minutes per week) were collected at baseline, 3, and 6 months. Results: At 3 months, intervention participants reported 9 walking trips per week and 643.5 minutes per week of active transportation, whereas control participants reported 4 walking trips per week and 49.5 minutes per week of active transportation. Adjusting for baseline values, there were significant group differences favoring Everyday Activity Supports You for walking trips per week [4.6 (0.5 to 9.4); P = .04] and active transportation minutes per week [692.2 (36.1 to 1323.5); P = .05]. At 6 months, significant group differences were observed in walking trips per week [6.1 (1.9 to 11.4); P = .03] favoring the intervention (9 vs 2 trips per week). Conclusion: Given these promising findings, the next step is to test Everyday Activity Supports You model’s effectiveness to promote physical activity in older women within a larger study.
Lena Fleig, Megan M. McAllister, Penny Brasher, Wendy L. Cook, Pierre Guy, Joseph H. Puyat, Karim M. Khan, Heather A. McKay and Maureen C. Ashe
To characterize patterns of sedentary behavior and physical activity in older adults recovering from hip fracture and to determine characteristics associated with activity.
Community-dwelling, Canadian adults (65 years+) who sustained hip fracture wore an accelerometer at the waist for seven days and provided information on quality of life, falls self-efficacy, cognitive functioning, and mobility.
There were 53 older adults (mean age [SD] 79.5 [7.8] years) enrolled in the study; 49 had valid data and demonstrated high levels of sedentary time (median [p10, p90] 591.3 [482.2, 707.2] minutes/day), low levels of light activity (186.6 [72.6, 293.7]), and MVPA (2 [0.1, 27.6]), as well as few daily steps (2467.7 [617.1, 6820.4]). Regression analyses showed that age, gender, gait speed, and time since fracture were associated with outcomes.
Older adults have long periods of sedentary time with minimal activity. Results are a call to action to encourage people to sit less and move more.