The Vitamin D is an important vitamin and it is related with the element calcium in the body. The Vitamin D is responsible for the absoprtion of calcium in the body present in the food. In the deficiency or depletion of the Vitamin D in the body is likely to affect the calcium levels. The calcium is the main element present in the bones and the teeth. Calcium helps to build bones. In the condition which involves the depletion of Vitamin D levels the calcium levels will also deplete. This will result in conditions like oesteoporosis, rickets and other bone deformities.
Thus people in the northern climates receiving low sunlight, will likely to receive low Vitamin D and will likely to develop bone related problems due to low calcium levels.
I personally think narrow hand placements are harder for push ups than the wide medium hand placements for push ups. I think that both of the different hand placements uses different muscles, which may be why I feel that the narrow hand placement is harder. Hope I helped!
In addition to protecting your heart and lungs, your ribs also support many of the muscles in your upper body. As a result, breaking a rib can make everyday activities very painful. Given their position in the body, broken ribs are usually left to heal on their own.