Humerus to Radius Ratio and It S Effect on Stride Length in Canis Lupus Familiaris

Humerus to Radius Ratio and It’s Effect on Stride Length in Canis lupus familiaris

Chelsea Lindwall Saddleback College Biology 3B

Abstract

Canis lupus familiaris, the domesticated dog, is a species with a great amount of variety between breeds. The high amount of variability between breeds makes dogs interesting to study. In this study we are trying to find whether or not the humerus to radius length ratio has any effect on the length of a dog’s trotting stride. Results showed a mean stride length of 51.16cm with an average standard deviation of 0.133 and mean humerus to radius ratio of 0.9628 with an average standard deviation of 7.047. No trend line could be found in the graph indicated by Fig. 1, and therefore stride length is independent of the ratio between the humerus and radius in dogs.

Introduction

Canis lupus familiaris, or the domesticated dog, has evolved from it’s ancestor, the Gray Wolf, to a huge variety of shapes and sizes. Dogs have been selectively bred over thousands of years for specific purposes, including hunting, herding, sled pulling, retrieving, guarding, and general human companionship. All this selective breeding has led to hundreds of distinctly different dog breeds, which when compared look almost like different species rather than types. From color, to fur length, even down to bone structure, every breed is different. This high amount of variability within the canine species makes dogs very interesting to study. (Ostrander, 2007) What all canines do have in common though is a love for running along with a great amount of speed and stamina for their size. The investigator is interested in studying the variations in bone length for different sizes and breeds of dogs, and measuring their effects on the length of stride. Similar studies in horses have shown that the stride length is dependent upon the length of the humerus (Stashak and Adams, 2002) but the investigator would like to know if the stride length is more effected by what may seem like the more obvious variable, the length of the radius, which accounts for a large percentage of a dog’s leg bones. In putting these two bones together in the form of a humerus vs. radius ratio, we can find whether or not the length of stride in dogs is dependent upon either. The objective of this investigation is to discover whether the length of a dog’s trotting stride is mostly dependent upon the length of it’s humerus or the length of it’s radius. From research it is hypothesized that a dog with a radius longer than it’s humerus will have a stride length that is longer than a dog with a shorter humerus or a radius and humerus that are the same length.

Materials and Methods Twenty-five canine participants will be volunteered by friends, family, and clients of the Irvine Pet Complex in Irvine, CA. All will be in good physical condition as supervised by Dr. Harner, DVM, between the ages of 1.5 and 7 years, and weigh between 10kg and 55kg. Humerus length will be taken using a measuring tape by measuring from the point at which the humerus meets the scapula to the point at which the humerus meets the ulna. Radius measurements will be taken by measuring from the point where the humerus and radius meet to the point where the radius meets the metacarpals. Dogs will have their paws dipped in water, and be trotted at a speed of 2.5 m/s on asphalt, and the distance between wet pawprints will be measured. A dog’s trot is a two-beat gait, with the legs moving in diagonal pairs (front left/hind right and front right/hind left), so trotting pawprints appear as two prints diagonally separated by about one or two centimeters, and then another two prints at an average of 50 centimeters away. The larger distance (the stride length) will be measured and the mean of three sets will be taken. The mean distance will be used in final data and calculations.

Results

Mean stride length was 51.16cm with an average standard deviation of 0.133 and mean humerus to radius ratio was 0.9628 with an average standard deviation of 7.047.

Fig.1 This graph shows the mean stride length as it corresponds to the humerus to radius ratio in dogs. The formula for the ratio is humerus/radius so a value closer to zero indicates a humerus that is shorter than the radius, and a value more than one indicates a humerus that is longer than the radius. Discussion

No data trend could be found in the graph indicated by Fig. 1. From this data it can be concluded that the length of a dog’s trotting stride is independent of the ratio between its humerus and radius. Using the data collected I also tried seeing if stride length was simply dependent on the total leg length (the values for the humerus and radius combined), yet there was no visible trend in that data either. In conclusion, I have found that stride length in dogs is independent of the ratio between the humerus and the radius, and therefore must be dependent upon some other factor.

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