It has been suggested, based on anecdotal evidence, that when shackled broiler chickens struggle, it is due to the discomfort associated with compression of the shank. Birds with larger shanks seem to struggle more violently than birds with smaller shanks. The size of the leg gap is not adjustable. The hypothesis of this study was that males would struggle more than females, as they tend to be larger and have thicker shanks than females. The following data was collected for males and females during a one-minute period when the birds were first shackled: latencies to struggle, numbers of struggling bouts, and total time spent struggling. Each test bird was measured for body weight and circumference of the right shank. The results indicated that male birds were heavier and had larger shanks than females. The males also struggled sooner and longer than females. When the data for males and females was pooled, there was a negative correlation between latency to struggle and shank size and a positive correlation between struggling behaviour and shank size. However, there were no correlations within sex. Body weight was not correlated with any of the struggling behaviour measures. The authors concluded that male broilers may struggle more than females due to the use of shackles that have leg gaps that do not adjust to fit larger shanks.