Comparisons of Muscular Activity in Males and Females While Walking in Restricted Postures

Increasing numbers of females are entering industrial workplaces. In the mining industry in South Africa, for example, this is partly the result of employment equity laws, which have ruled that by 2009 at least 10% of the workforce must be female (Department of Minerals and Energy, 2004). Differences in factors such as anthropometry and strength are evident between males and females. Males are generally taller and heavier than females, and possess a higher percentage of muscle mass and a lower percentage of body fat compared to females (McArdle et al, 2001). Furthermore, males are seen to possess significantly greater absolute strength than females, while females maintain approximately 50% of the upper body strength of males and 70% of the lower body strength of males (McArdle et al, 2001). Gender is also a factor that influences movement patterns during walking and running, and intrinsic characteristics, including skeletal alignment, muscle strength and anthropometric differences, are likely to contribute to this (Chiu and Wang, 2007). As a result, it is expected that responses to manual tasks are likely to differ between males and females.

The purpose of the authors to do this study was to examine differences in muscular activation between males and females while walking in restricted postures. Restricted postures are evident in various industries, including mining, construction and agriculture. These postures are associated with musculoskeletal disorders and lower back pain. Studies generally focus on a male workforce; however, more females are entering industrial workplaces.

Twelve male and 12 female subjects between the ages of 18 and 25 years participated in the study. Subjects walked on a treadmill at a speed of 3.5 km/h for four minutes under conditions of upright walking, and stooped walking under restrictions at 85% and 70% of stature. Electromyographic activity was measured on seven muscles (trapezius, latissimus dorsi, erector Spinae, rectus femoris, biceps femoris, medial gastrocnemius and tibialus anterior). Ratings of Perceived Exertion (RPE) and Body Discomfort were also obtained. The extent of vertical restriction significantly altered levels of muscle activation. Female subjects had significantly lower levels of activation of the medial gastrocnemius than males. Local RPE was greatest under the lowest restriction, and body discomfort of the neck, lower back and hamstrings was evident during restricted walking. Work place design and interventions should consider these consequences.

Hodgskiss, J., & Zschernack, S. (2013). Comparisons of muscular activity in males and females while walking in restricted postures. Ergonomics SA, 25(1), 39-51.