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John A. Batsis, Cassandra M. Germain, Elizabeth Vásquez, Alicia J. Zbehlik and Stephen J. Bartels

Objectives:

Physical activity reduces mobility impairments in elders. We examined the association of physical activity on risk of subjective and objective physical function in adults with and at risk for osteoarthritis (OA).

Methods:

Adults aged ≥ 60 years from the longitudinal Osteoarthritis Initiative, a prospective observational study of knee OA, were classified by sex-specific quartiles of Physical Activity Score for the Elderly scores. Using linear mixed models, we assessed 6-year data on self-reported health, gait speed, Late-Life Function and Disability Index (LLFDI) and chair stand.

Results:

Of 2252 subjects, mean age ranged from 66 to 70 years. Within each quartile, physical component (PCS) of the Short Form-12 and gait speed decreased from baseline to follow-up in both sexes (all P < .001), yet the overall changes across PASE quartiles between these 2 time points were no different (P = .40 and .69, males and females, respectively). Decline in PCS occurred in the younger age group, but rates of change between quartiles over time were no different in any outcomes in either sex. LLFDI scores declined in the 70+ age group. Adjusting for knee extensor strength reduced the strength of association.

Conclusions:

Higher physical activity is associated with maintained physical function and is mediated by muscle strength, highlighting the importance of encouraging physical activity in older adults with and at risk for OA.

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Ricardo Drews, Suzete Chiviacowsky and Gabriele Wulf

The present study investigated the effects of different ability conceptions on motor skills learning in 6-, 10-, and 14-year-old children. In each age group, different groups were given either inherent-ability or acquirable-skill instructions before they began practicing a throwing task. Participants were blindfolded and were asked to throw beanbags at a target placed on the floor at a distance of 3 m. All participants performed 40 practice trials and received feedback about the accuracy of their throws after each trial. One day after practice, retention and transfer (greater target distance) tests without instructions or feedback were conducted to assess learning effects. Older participants generally had higher accuracy scores than younger participants. Importantly, instructions emphasizing the learnability of the skill resulted in greater throwing accuracy on the retention test than did those implying an underlying inherent ability. On the transfer test, the same effect was seen for the 14-year-olds, but not for the younger age groups, suggesting that adolescents may be more vulnerable to the threat of their inherent ability being exposed. The present findings demonstrate the importance of ability conceptions for motor learning in children and adolescents. They also add to the mounting evidence of motivational influences on motor skill learning.

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Keijo Häkkinen, Markku Alen, Mauri Kallinen, Mikel Izquierdo, Kirsi Jokelainen, Helka Lassila, Esko Mälkiä, William J. Kraemer and Robert U. Newton

Forty-two healthy men and women in two age groups (40 and 70 years) were examined for muscle cross-sectional area (CSA), maximal voluntary bilateral isometric force, force-time characteristics, maximal concentric 1 RM. and power performance of the leg extensors in a sitting position, squat jump, and standing long-jump. The results suggested that the decline in maximal strength with increasing age is related to the decline in muscle CSA; however, particularly in older women, the force/CSA ratio may also be lowered. Explosive force seems to decrease with increasing age even more than maximal strength. suggesting that muscle atrophy with aging is greater in fast-twitch fibers. The voluntary activation of the agonist and antagonist muscles seems to vary depending on the type of muscle action and/or velocity and time duration of the action in both age groups but to a greater extent in older people. There appears to be an age-related increase in antagonist co activation. especially in dynamic explosive movements.

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Eduard Kurz, Christoph Anders, Mario Walther, Philipp Schenk and Hans-Christoph Scholle

To judge a person’s maximum trunk extension performance as either age-appropriate or deconditioned is challenging. The current study aimed at determining age and anthropometrically adjusted maximum voluntary contraction (MVC) of back extensors considering the number and recovery time between trials. Thirty-one younger (20–30 years) and 33 older (50–60 years) healthy males performed five repetitions of maximal isometric trunk extensions in an upright standing position with randomized recovery times ranging between one to five minutes at one minute intervals. Torque values were normalized according to the individual’s upper body mass resulting in upper body torque ratios (UBTR). To evaluate the impact of age, recovery time, and fatigue on UBTR we applied a linear mixed-effects model. Based on surface EMG data muscular fatigue could be excluded for both groups. For all MVC trials, UBTR levels differed significantly between age groups (range of mean values: younger: 2.26–2.28, older: 1.78–1.87, effect size: 1.00) but were independent from recovery time. However, the older males tended to exert higher UBTR values after shorter recovery periods. The study provides normative values of anthropometrically and age-group adjusted maximum back extensor forces. For the investigated groups, only two MVC trials with a recovery time of about one minute seem appropriate.

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Brenda Bruner and Karen Chad

Background:

Overweight and obesity among Aboriginal women is a growing concern, with increasing prevalence rates linked to a sedentary lifestyle. Physical inactivity is a modifiable risk factor for unhealthy body weight; however before addressing health enhancing behaviors, understanding lifestyle practices, attitudes and beliefs are important.

Methods:

A mixed methods approach assessed physical activity (PA) practices (n = 58), and attitudes and beliefs (n = 19) among First Nations women. The Modifiable Activity Questionnaire assessed PA, and a focused ethnography explored attitudes and beliefs.

Results:

Self-reported PA was highest in the youngest age group. Both total and leisure-time PA decreased when house-related activities were not accounted for. Younger participants reported sport-related activities, while older participants reported traditional activities (eg, berry picking, fishing). Participants’ believed PA promoted good health, yet personal (ie, lack of time), community-specific (ie, lack of opportunities/encouragement) and environmental (ie, inclement weather, safety) factors acted as barriers. Age-specific, women-only programs were highlighted as potential enablers.

Conclusions:

The findings highlight the need to assess cultural specific practices, attitudes and beliefs as PA programs that focus on reducing barriers identified in the community and are designed based on expressed interest and preferences may improve leisure-related PA levels among all age groups.

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Larissa Roux, Mike Pratt, I-Min Lee, Terry Bazzarre and David Buchner

Background:

Community-based efforts to promote physical activity (PA) in adults have been found to be cost-effective in general, but it is unknown if this is true in middle-age specifically. Age group-specific economic evaluations could help inform the design and delivery of better and more tailored PA promotion.

Methods:

A Markov model was developed to estimate the cost-effectiveness (CE) of 7 exemplar community-level interventions to promote PA recommended by the Guide to Community Preventive Services, over a 20-year horizon. The CE of these interventions in 25- to 64-year-old adults was compared with their CE in middle-aged adults, aged 50 to 64 years. The robustness of the results was examined through sensitivity analyses.

Results:

Cost/QALY (quality-adjusted life year) of the evaluated interventions in 25- to 64-year-olds ranged from $42,456/QALY to $145,868/QALY. Interventions were more cost-effective in middle-aged adults, with CE ratios 38% to 47% lower than in 25- to 64-year-old adults. Sensitivity analyses showed greater than a 90% probability that the true CE of 4 of the 7 interventions was below $125,000/QALY in adults aged 50 to 64 years.

Conclusion:

The exemplar PA promotion interventions evaluated appeared to be especially cost-effective for middle-aged adults. Prioritizing such efforts to this age group is a good use of societal resources.

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Zoe Rebecca Knowles, Daniel Parnell, Gareth Stratton and Nicola Diane Ridgers

Background:

Qualitative research into the effect of school recess on children’s physical activity is currently limited. This study used a write and draw technique to explore children’s perceptions of physical activity opportunities during recess.

Methods:

299 children age 7−11 years from 3 primary schools were enlisted. Children were grouped into Years 3 & 4 and Years 5 & 6 and completed a write and draw task focusing on likes and dislikes. Pen profiles were used to analyze the data.

Results:

Results indicated ‘likes’ focused on play, positive social interaction, and games across both age groups but showed an increasing dominance of games with an appreciation for being outdoors with age. ‘Dislikes’ focused on dysfunctional interactions linked with bullying, membership, equipment, and conflict for playground space. Football was a dominant feature across both age groups and ‘likes/dislikes’ that caused conflict and dominated the physically active games undertaken.

Conclusion:

Recess was important for the development of conflict management and social skills and contributed to physical activity engagement. The findings contradict suggestions that time spent in recess should be reduced because of behavioral issues.

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Sarah A. Wyszomierski, April J. Chambers and Rakié Cham

Slips and falls are a serious public health concern in older populations. Reduced muscle strength is associated with increased age and fall incidence. Understanding the relationships between specific joint muscle strength characteristics and propensity to slip is important to identify biomechanical factors responsible for slip-initiated falls and to improve slip/fall prevention programs. Knee corrective moments generated during slipping assist in balance recovery. Therefore, the study goal was to investigate the relationship between knee flexion/extension strength and slip severity. Isometric knee flexion/extension peak torque and rate of torque development (RTD) of the slipping leg were measured in 29 young and 28 older healthy subjects. Motion data were collected for an unexpected slip during self-paced walking. Peak slip velocity (PSV) of the slipping heel served as a slip severity measure. Within-sex and age group regressions relating gait speed-controlled PSV to strength of the slipping leg revealed significant inverse PSV-knee extension peak torque and PSV-knee flexion/extension RTD relationships in young males only. Differences in PSV-strength relationships between sex and age groups may be caused by greater ranges of strength capabilities in young males. In conclusion, the ability to generate higher, more rapid knee flexion/extension muscle moments (greater peak torque/RTD) may assist in recovery from severe slips.

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Hans U. Wessel, Janette F. Strasburger and Brett M. Mitchell

We have developed normal standards for the Bruce exercise (EX) protocol since a review of 875 studies in patients with congenital or acquired heart disease showed that only 5.1% achieved the predicted 50th percentile for EX time of the standards reported by Cumming, Everatt, and Hastman (Am. J Cardiol 41:69, 1978). Our data are based on 160 males and 103 females, age 4–18 years who met the following criteria: trivial or no heart disease, maximal effort, maximal EX heart rate (HR) > 180 beats/min, and normal resting and EX ECG without arrhythmia. The ECG was monitored continuously and HR computed from the ECG and the end of each minute of EX. Comparison with the predicted data of Cumming et al. for each age group by stage showed essentially identical submaximal EX heart rates but slightly lower maximal HR (–2%), which averaged 197 beats per minute in males and females. EX times were on average 15% lower than the predicted 50th percentile for most age groups in males and females. We developed regression equations, which predict exercise time from age and body size or age, body size and 2nd stage exercise heart rate. They better reflect the capabilities of untrained, asymptomatic children and adolescents seen in our laboratory in the 1990s than the Canadian data of 1978.

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Kristin S. Ondrak and Robert G. McMurray

Background:

Researchers have investigated the energy expenditure of tennis practice and match play in adults but not youth.

Methods:

VO2 was recorded for 36 youth, ages 9 to 18, during 10-minute bouts of tennis practice and match play. A GLM was used to compare VO2 between practice and match play and among age groups (9–12 years, 13–15 years, and 16–18 years); also to compare the difference in adult and child-derived MET values (ΔMET).

Results:

VO2 was higher for tennis match play vs. practice (P < .05) and there was a trend for 16 to 18 year olds having lower VO2 than 9 to 12 year olds (P = .055). ΔMET did not differ between settings but varied by age group (P = .004); it was highest in 9- to 12-year-olds and lowest in 16- to 18-year-olds.

Conclusions:

Youth expend more energy while playing a tennis match than practice, regardless of age. Child-derived MET values equaled those of adults once youth reached ages 16 to 18.