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Kaitlin M. Gallagher, Anita N. Vasavada, Leah Fischer and Ethan C. Douglas

A popular posture for using wireless technology is reclined sitting, with the trunk rotated posteriorly to the hips. This position decreases the head’s gravitational moment; however, the head angle relative to the trunk is similar to that of upright sitting when using a tablet in the lap. This study compared cervical extensor musculotendon length changes from neutral among 3 common sitting postures and maximum neck flexion while using a tablet. Twenty-one participants had radiographs taken in neutral, full-flexion, and upright, semireclined, and reclined postures with a tablet in their lap. A biomechanical model was used to calculate subject-specific normalized musculotendon lengths for 27 cervical musculotendon segments. The lower cervical spine was more flexed during reclined sitting, but the skull was more flexed during upright sitting. Normalized musculotendon length increased in the reclined compared with an upright sitting position for the C4-C6/7 (deep) and C2-C6/7 (superficial) multifidi, semispinalis cervicis (C2-C7), and splenius capitis (Skull-C7). The suboccipital (R 2 = .19–.71) and semispinalis capitis segment length changes were significantly correlated with the Skull-C1 angle (0.24–0.51). A semireclined reading position may be an ideal sitting posture to reduce the head’s gravitational moment arm without overstretching the assessed muscles.

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Banu Unver, Kartal Selici, Eda Akbas and Emin Ulas Erdem

The purpose of the study was to investigate the foot posture, ankle muscle strength, range of motion (ROM), and plantar sensation differences among normal weight, overweight, and obese individuals. One hundred and twenty-three individuals (42 normal weight, 40 overweight, and 41 obese) aged between 18 and 50 years participated in the study. Foot posture, ankle muscle strength, ROM, plantar sensation, and foot-related disabilities were evaluated. The relative muscle strength of left plantar flexors and invertors and light touch sensation of the left heel were significantly lower in obese individuals compared with overweight and normal weight (P < .016) individuals. Obese individuals had significantly reduced relative muscle strength of plantar flexors, dorsiflexor, and invertors, plantar flexion and inversion ROM in the left foot; and light touch sensation of the right heel compared with normal weight (P < .016) individuals. Foot Posture Index scores were significantly higher in obese individuals compared with overweight (P < .016) individuals. There were no significant differences in absolute muscle strength, vibration sensation, and foot-related disability scores among the 3 groups (P > .05). Obesity was found to have adverse effects on ankle muscle strength, ROM, and plantar light touch sensation. Vibration sensation was not affected by body mass index, and foot-related disability was not observed in obese adults.

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Caleb D. Johnson and Irene S. Davis

Higher medial–lateral forces have been reported in individuals with stiffer foot arches. However, this was in a small sample of military personnel who ran with a rearfoot strike pattern. Therefore, our purpose was to investigate whether runners, both rearfoot and forefoot strikers, show different associations between medial–lateral forces and arch stiffness. A group of 118 runners (80 rearfoot strikers and 38 forefoot strikers) were recruited. Ground reaction force data were collected during running on an instrumented treadmill. Arch flexibility was assessed as the difference in arch height from sitting to standing positions, and participants were classified into stiff/flexible groups. Group comparisons were performed for the ratio of medial:vertical and lateral:vertical impulses. In rearfoot strikers, runners with stiff arches demonstrated significantly higher medial:vertical impulse ratios (P = .036). Forefoot strikers also demonstrated higher proportions of medial forces; however, the mean difference did not reach statistical significance (P = .084). No differences were detected in the proportion of lateral forces between arch flexibility groups. Consistent with previous findings in military personnel, our results indicate that recreational runners with stiffer arches have a higher proportion of medial forces. Therefore, increasing foot flexibility may increase the ability to attenuate medial forces.

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Tyler N. Brown, AuraLea C. Fain, Kayla D. Seymore and Nicholas J. Lobb

This study determined changes in lower limb joint stiffness when running with body-borne load, and whether they differ with stride or sex. Twenty males and 16 females had joint stiffness quantified when running (4.0 m/s) with body-borne load (20, 25, 30, and 35 kg) and 3 stride lengths (preferred or 15% longer and shorter). Lower limb joint stiffness, flexion range of motion (RoM), and peak flexion moment were submitted to a mixed-model analysis of variance. Knee and ankle stiffness increased 19% and 6% with load (P < .001, P = .049), but decreased 8% and 6% as stride lengthened (P = .004, P < .001). Decreased knee RoM (P < .001, 0.9°–2.7°) and increased knee (P = .007, up to 0.12 N.m/kg.m) and ankle (P = .013, up to 0.03 N.m/kg.m) flexion moment may stiffen joints with load. Greater knee (P < .001, 4.7°–5.4°) and ankle (P < .001, 2.6°–7.2°) flexion RoM may increase joint compliance with longer strides. Females exhibited 15% stiffer knee (P = .025) from larger reductions in knee RoM (4.3°–5.4°) with load than males (P < .004). Stiffer lower limb joints may elevate injury risk while running with load, especially for females.

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Nicholas S. Ryan, Paul A. Bruno and John M. Barden

Studies have investigated the reliability and effect of walking speed on stride time variability during walking trials performed on a treadmill. The objective of this study was to investigate the reliability of stride time variability and the effect of walking speed on stride time variability, during continuous, overground walking in healthy young adults. Participants completed: (1) 2 walking trials at their preferred walking speed on 1 day and another trial 2 to 4 days later and (2) 1 trial at their preferred walking speed, 1 trial approximately 20% to 25% faster than their preferred walking speed, and 1 trial approximately 20% to 25% slower than their preferred walking speed on a separate day. Data from a waist-mounted accelerometer were used to determine the consecutive stride times for each trial. The reliability of stride time variability outcomes was generally poor (intraclass correlations: .167–.487). Although some significant differences in stride time variability were found between the preferred walking speed, fast, and slow trials, individual between-trial differences were generally below the estimated minimum difference considered to be a real difference. The development of a protocol to improve the reliability of stride time variability outcomes during continuous, overground walking would be beneficial to improve their application in research and clinical settings.

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Mengyun Luo, Philayrath Phongsavan, Adrian Bauman, Joel Negin, Zhiruo Zhang and Ding Ding

The correlates of physical activity differ across domains. The authors explored the contribution of domain-specific physical activity to total physical activity and examined how different sociodemographic and social capital-related variables are associated with different physical activity domains in older adults, using nationally representative samples from six low- to middle-income countries. Activity at work and home combined plays an important role in contributing to total physical activity, while leisure-time physical activity accounted for an extremely small proportion. Some correlates of physical activity were similar across countries, such as working status and structural social capital, while other associations were country specific. Promoting structural social capital, trust, and perceived safety may confer positive benefits on older adults’ activity.

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Emmanuel Chiebuka Okoye, Christopher Olusanjo Akosile, Fatai Adesina Maruf, Ifeoma Uchenna Onwuakagba and Victoria Chinonye Chukwuma

Objectives: To cross-culturally adapt and validate the Physical Activity Scale for the Elderly (PASE) into Igbo culture. Methods: The English version of the PASE (E-PASE) was translated into Igbo, harmonized, back-translated, subjected to expert panel review, and pretested. The final Igbo version of PASE (I-PASE), the E-PASE, and the International Physical Activity Questionnaire were then administered to consecutively recruited 109 consenting Igbo older adults. Data were analyzed using frequency, percentage, mean, standard deviation, Mann–Whitney U test, Spearman rank-order correlation, and Cronbach’s alpha at .05 level of significance. Results: All items on the E-PASE were retained on the I-PASE but some modifications were made. The I-PASE had poor internal consistency coefficient (α = .66), poor-to-excellent item, and total score known-group validity (ρ = .24–1.00) and moderate convergent validity (ρ = .50). Conclusion: The I-PASE is a valid, reliable, and culturally specific tool for assessing PA among Igbo older adults.