Obesity is a major ergonomic challenge in the warehouse, especially where functions require significant manual labor, according to a report from Humantech, providers of ergonomic program management services.
Blake McGowan, a certified professional ergonomist with Humantech, offers these observations from research on how obesity affects worker performance:
- Increased strength. Obese individuals have 20% higher absolute strength for hand grip and shoulder flexion during sustained isometric exertions (Cavuoto & Nussbaum, 2013).
- Earlier and greater fatigue onset. Strength capabilities decrease greater and faster during repeated force/torque applications in obese individuals (Maffiuletti et al., 2007).
- Increased postural sway. Extremely obese individuals (BMI ≥ 40) have higher postural sway than the non-obese during prolonged standing tasks (Singh et al., 2009).
- Greater postural adjustments to maintain balance. When performing a forward reaching/aiming task, obese individuals primarily reach using the entire body, whereas individuals with a normal BMI mainly reach with elbow extension and shoulder flexion (Berrigan et al., 2006).
- Increased movement time. When performing a forward reaching/aiming task, obese individuals have a longer movement time, which increases as task difficulty increases (Berrigan et al., 2006).
- Reduced reach distance. Extremely obese individuals (BMI ≥ 40) have reduced functional reach capabilities (13" or 323 mm) compared to the non-obese (16" or 402 mm) (Singh et al., 2009).
- Reduced trunk flexion. In the obese individuals, trunk forward flexion motion is restricted in both sitting and standing tasks (Gilleard & Smith, 2007).
- Decreased range of motion (ROM). Obese individuals have significantly reduced ROM for shoulder extensions and adductions, lumbar spine extension and lateral flexions, and knee flexions (Park et al., 2010).
Listed below are four simple design principles and guidelines to address these differences in physical capabilities:
- Keep work close, within 16" (406 mm) from the front of the body;
- Keep it in the comfort zone, between 38" and 47" (0.97 to 1.19 m), or directly in front of the body between the shoulders and the knees;
- Provide appropriate equipment;
- Promote variety at the workstation.
The prevalence of obesity in the United States continues to climb, exceeding 30% in most gender and age groups (CDC, 2011). According to the World Health Organization (WHO), globally, more than 1.4 billion adults were overweight in 2008 and more than half a billion were obese. By 2015, the WHO projects that 2.3 billion adults will be overweight and more than 700 million will be obese.