Laptop use and muscle activity in adult females: Ground sitting has lower muscular demand than using a chair.

BACKGROUND: With progressing technology in the portable computing field, laptops are now integral for work, home and social settings. Different working postures adopted by laptop users impose different loads on the relevant muscles, which can be associated with musculoskeletal discomfort in the various body regions. Some Arabic and Asian cultures adopted postures are not well investigated, particularly for the 20-30 years age-group. OBJECTIVE: This study compared muscle activity in the cervical spine, arm, and wrist among different laptop workstation setups. METHODS: In this cross-sectional study, 23 healthy female university students (age = 24.2±2.28 years, range 20-26 years) performed a standardized 10 minute typing task in four different laptop workstation setups: DESK, SOFA, GROUND sitting with back support, and laptop table (LAP-Tab). Differences between electromyography (EMG) muscle activity recorded in the trapezius (TR), cervical extensors (CE), deltoid (DEL), and wrist extensors (WE) were determined using one-way repeated ANOVA measures with a post-hoc Bonferroni test. RESULTS: Significantly higher muscle activity was observed respectively in the workstations of DESK > LAP-Tab > SOFA > GROUND. Significant differences were found between WE muscle activity and the three other muscle groups (p < 0.001). There was a significant interaction between workstations and muscle activity (F(9,264) = 3.81, p < 0.001, = 0.11), where the WE and DEL muscles showed respectively higher and lower muscle activity in all setups. CONCLUSION: Muscles showed variable activity in different workstations such that the GROUND workstation provided the minimum load, while the DESK workstation showed the maximum load on the measured muscle groups. These findings require further investigation in different cultural and gender specific groups.

Anthropometric data of an elderly Iranian population provides insights for system design.

BACKGROUND: Anthropometric data should be considered for each major population age category, specifically because of the dimension changes occurring during ageing. In elderly subjects, the physical activities and their capabilities become limited. Therefore anthropometric reference data for equipment and system designs is necessary. OBJECTIVES: The aim of the study was to collect data for the body dimensions of an elderly Iranian population and evaluate the related gender and age correlations. METHODS: Nineteen body dimensions were manually measured on a sample size of 317 subjects (167 male and 150 female) from four provinces of Iran. A pilot preliminary test for assessing test-retest reliability on ten body dimensions using the Intraclass Correlation Coefficient (ICC2 :1)  was performed. Descriptive statistics were reported based on gender and independent samples t-tests to compare the anthropometric dimensions of both genders and age. RESULTS: Results indicated higher dimensions in males, except for hip-breadth (p = 0.87). In all subjects, increasing age corresponded with: decreased standing shoulder height, eye height, and elbow height; and with sitting height and sitting knee height; while hip-breadth increased. Reliability was acceptable (ICC2.1 >0.88). In the elderly, as with adult subjects, there are significant gender differences in body dimensions, and this should be considered in equipment and system design. Furthermore, this study demonstrated both genders differences and the consequences of aging. CONCLUSIONS: From this pilot data, product designers can consider the anthropometric characteristics for elderly Iranian subjects for equipment and system design.