Head-Loads weaken neck muscles.

Women labourers with head loads of paddy nursery

The women carry heavy load on their head.   People living in the farms are accustomed to carry things like food and firewood back to their homes. The mothers carry their babies strapped onto their backs as well as carrying huge loads on their heads. With most load-bearing methods, the heavier the weight, the more energy we need to burn to carry it. Carrying relatively heavy loads is still a regular activity for many women in the rural Tamilnadu. Rural women regularly work in Agriculture operations carry paddy nursery, bananas etc by  head-loads, most often also to transport essential items such as water and firewood. Mostly women are seen carrying items on their heads, while men usually carry loads on their shoulders. As one can imagine, head-supported loads are inheritantly unstable and they need well-developed neck muscles to support the spinal loading. Bodyweight with no additional energy exertion on level ground and that any load above 20% of their body weight incurs a proportional energy cost. For example, carrying 30% of body mass requires a 10% increase in energy - the 'free ride' hypothesis. With heavier loads, the energy increase was only half that of men carrying the same loads on their backs. The neck (cervical spine) is composed of vertebrae that begin in the upper torso and end at the base of the skull. The bony vertebrae along with the ligaments provide stability to the spine. The muscles allow for support and motion. The neck has a significant amount of motion and supports the weight of the head. However, because it is less protected than the rest of the spine, the neck can be vulnerable to injury and disorders that produce pain and restrict motion. For untrained controls that have not had years to strengthen the right muscles and build up spinal bone density, carrying things on their head actually requires more energy than using a backpack. -Govin