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Name: Regis
Status: student
Grade: 9-12
Location: Outside U.S.
Country: USA
Date: March 2009

Question:
Why is the second toe on a human usually longer than the first toe on many humans?



Replies:
There are 5 metatarsal bones in the foot. Attached to each one are the bones of the toes. The 1st Metatarsal is the strongest of the 5, and it is the only one that additionally has two small bones on the bottom of its most distal end, its weight bearing surface. So, being the strongest and also having the two Sesamoid bones assisting in its ability to bear weight, it is believed that there are really six weight bearing points on the ball of the foot with the 1st carrying one third of the weight and the other four each bearing one sixth of the weight on the front of the foot.

Now, since the 1st is the strongest, it need not have evolved to be as long as the others in order to correctly bear its portion of the body during standing or walking. Therefore, the weight bearing parabola of the forefoot is a curve (an arc form from right to left) with the second metatarsal appear to be the most forward of the five, followed by the 1st and third, which are usually about the same length, and then followed by the 4th and then the 5th being the shortest of the five. The toe length will correspond to the length of each metatarsal which explains why the second toe is generally the longest, on average, although not always so.

Now, another result of that anatomy is as follows –

Since the second metatarsal is longer then the 1st, during a walking stride, and in order to more evenly distribute the body weight, one third of the weight of each step is borne by the 1st metatarsal (with two of the six bearing points) and the second metatarsal bears one sixth, resulting in the 1st and 2nd metatarsals together bearing a total of 1/3 of the body’s weight when walking or standing. Now, with the 2nd metatarsal being longer then the 1st, in order for a person to step off in a forward direction in a gait cycle, the foot must position itself to evenly distribute the weight between the 1st and 2nd metatarsal heads so that the gait progression does not result in too much weight being borne by the longest metatarsal, but being split between the 1st and 2nd Metatarsal head weight bearing surfaces. Since they are not the same length. In order to walk forward the foot must turn slightly outward so that the weight can be more evenly distributed between the 1st and 2nd metatarsal heads. In order to do that the foot turns out about 15 degrees in the normal walking pattern so the weight can come off evenly between the 1st and 2nd metatarsal heads in a gait cycle. So therefore, when you watch people walk you will observe that they will out-toe about 15 degrees on each foot, on average.

So in answer to your question, the metatarsal that is the longest will end up with the correspondingly longest appearing toe.

Short question – long answer.

Dr. Kanat



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