Prevalence, Ergonomic Risk Factors, and Functional Impact of Work-Related Musculoskeletal Disorders between Loaders and Measurers in an Informal West African Grain Market Nigeria

In the bustling heart of West Africa, where the air shimmers with heat and the ground is packed with the dust of commerce, a silent physical toll is being paid by thousands of workers. These are the men who move the grain, the unsung engines of the local economy who lift, carry, and measure sacks of food that feed entire regions. For decades, scientists have known that moving heavy objects by hand can damage the human body, causing pain in the back, knees, and shoulders. This damage, known as musculoskeletal disorders, happens when the body is pushed beyond its limits through repetitive strain, awkward positions, or lifting weights that are simply too heavy. While wealthy nations have introduced machines and strict rules to protect workers from these hazards, the vast informal markets of developing countries often operate without such safeguards. Here, the question is not just whether these workers get hurt, but exactly how the specific nature of their daily tasks shapes the pain they feel, and how long they can work before their bodies begin to break down.

A team of researchers recently traveled to the Dawanau International Grains Market in Kano, Nigeria, to answer these questions with precision. They focused on two distinct groups of men working side by side in the same scorching heat: the Loaders and the Measurers. The Loaders are the heavy lifters, tasked with hoisting massive sacks of groundnuts, often weighing up to fifty kilograms, onto their shoulders and carrying them across the market. The Measurers, by contrast, do not carry the heavy loads but instead stand or kneel for hours, bending over to sift, clean, and measure the grain. The researchers wanted to see if these different ways of working led to different kinds of pain, and to find the exact point where a workday becomes too long for the human body to handle safely.

To find the truth, the team spoke with over three hundred men, asking them detailed questions about where they felt pain over the last year and how they spent their days. They used a method that breaks down the body into specific regions, checking for issues in the neck, back, knees, shoulders, and hands. The results painted a stark picture of the physical cost of this labor. Nearly ninety percent of the workers reported suffering from some form of body pain. The most common injuries were in the lower back, followed closely by the neck, knees, and shoulders. However, the story changed when the researchers looked at the two job roles separately. The Loaders, who perform the heavy lifting, suffered significantly more pain in their lower backs and knees, a direct result of the intense pressure placed on their spines and joints while carrying heavy loads. The Measurers, while carrying less weight, reported more pain in their necks and wrists, caused by the constant, stiff bending and twisting required to measure the grain.

The study went deeper than just counting who was in pain; it looked at how the body was being used. The researchers found that the pain was not random. It clustered into two main patterns. One pattern involved the spine and the legs, which suffered under the weight of the heavy sacks. The other pattern involved the arms and shoulders, which were strained by the effort of holding and stabilizing the loads or the repetitive motion of sifting. This confirmed that the specific way a worker moves their body dictates exactly which parts of their body will eventually wear out. The researchers also discovered that age played a role, with older workers experiencing more strain, but the most significant factor was the length of the workday and the posture the workers held.

Perhaps the most critical finding of the study was the discovery of a specific breaking point in time. By analyzing the data, the researchers identified a clear threshold: if a worker spends more than five and a half hours a day performing these heavy manual tasks, their risk of developing severe, multi-site pain increases dramatically. Before this point, the body can often cope, but once a shift crosses the five-and-a-half-hour mark, the cumulative strain becomes too great, leading to a sharp rise in injuries across multiple body parts. This number is not a guess; it is a data-driven limit that suggests when the body's ability to recover is overwhelmed by the demands of the job.

Despite the high levels of pain, with many workers suffering from issues in three or more parts of their bodies simultaneously, very few of them sought help from a doctor. Less than seven percent of the workers had visited a medical professional for their pain. Instead, they relied on over-the-counter painkillers to keep working, prioritizing their daily wages over their long-term health. This lack of medical care highlights a gap where the workers are suffering in silence, unaware that their pain is a sign of a systemic problem that could be managed with better work practices.

The researchers concluded that the solution lies in changing how the work is organized rather than just telling workers to be more careful. They suggested that the market unions, which already have a strong presence, could enforce a rule where workers stop their heavy lifting after five and a half hours. After this limit, a worker could switch to a lighter task, such as measuring or sorting, allowing their muscles to recover while still earning a wage. They also recommended the introduction of simple, low-cost tools like hand trucks to help move the heavy sacks, reducing the need for workers to carry the full weight on their backs. By understanding the specific limits of the human body in this environment, the study offers a clear path to protecting the health of the men who keep the grain moving, ensuring they can work without sacrificing their future well-being.