Anthro leg gestures

From my previous post, here are a few ideas on gestures when it comes to the anthro legs. Firstly I look to draw the curves they create. I've posted before about the elastic energy that digitigrade and ungiligate legs reserve whilst walking, this is effectively why they are configured the way that they are. So simplify this to curves as if the legs were bamboo, bending, curving under strain. So long as you remember that with any stance, the ball of the foot/paw/hoof needs to be in contact with the ground under the bodies center of gravity. Keeping that in mind will help you create that curve and make your characters look more grounded.

Lumbar Support

I've gone back to thinking more about spinal curves when it comes to anthros. This is particularly relevant with tough, heavy types and also very relevant when thinking about how a tail would be structured and function on a biped. I think that the fundamental understanding of what can and can't be done with anthros bipeds certainly concerns the lumbar support system.

Part of the lumbar lordosis support

The human S-curve transfers tension and load down into the pelvis via the sacro-iliac joint. If we are going to retain anthro features such as larger skulls, bigger chest and shoulder like that of Minotaurs, the more weight we are applying to the cervical and thoracic vertebrae, ultimately pulling the torso forward as well as the centre of gravity. This is going to make it harder for this S-curve to hold it's mid-line (shown in red). If the mid-line shifts away from the sacro-iliac joint then weight transmission is less efficient, resulting in muscle groups having to bear the torso's load rather than the spine. 


In humans an important deep structure called the thoracolumbar fascia, which are tough multi-directional connective tissues directly attached to the spinous processes of the lumbar vertebrae. Our erector spinae muscles and latissimus dorsi, as well as our core muscles such as the obliques act to pull the thoracic spine (our chest) backwards and downwards, keeping us held upright. The gluteals as I've mentioned in previous posts are under tone to hold the pelvis from tilting forward, keeping us stood upright. These multiple actions ultimately draw the lumbar spine into lordosis like drawing the string on a bow, the lumbar curve is under a great deal of elastic energy, stored in the thoracolumbar fascia.


Understanding the limits of the lumbar curve is important for anthro characters, who are often portrayed as extra massive, with craning necks and heads. The spinal curves may have to adjust to hold this weight and maintain the mid-line, either through hyperlordosis or even kyphosis.

How the sacro-iliac joint and the lumbar curve would be arranged to structure a tail is a relevant question. It would certainly require changes to the configuration of the pelvis as well as considerations on nerve pathways out of the sacrum.

More on the thoracolumbar fascia:

Stance sketches

Some ideas on digitigrade and ungiligrade legs this week. I'm hoping to have the time this month to complete some 2D animations on walking.

Anthro-grade stance

Been a few weeks from my last post, had a few things on my mind but it's given me time to sketch out more ideas, particularly on the subject of tails and anthro legs.

To keep the anthro 'stoop' we need to change some of the anatomy. Quadriceps shown in green, gluteals in shades of red, hamstrings in purple and the ilio-tibial tract in cream.

Anthro leg anatomy issues really come down to antho characters standing in a constant 'stoop'. I think that this is some sort of visual misnomer in that it's drawn to emulate the shape of an animals leg but with limited consideration on the extent of its impact to the anatomy. 

Holding a stooped position as a human is hard work, it requires a great deal of force from the quadriceps to keep the knee in partial flexion and the gluteals and hamstrings are under stress to hold the femur at an angle. This is because the weight of the torso is placing the centre of gravity too far behind the feet, the pelvis needs to tilt the torso forward to counterbalance this, bringing the centre of gravity back under the torso. That's why if you try squats in the gym, releasing the stress on your glutes can be done by leaning forward. This stoop is very energy inefficient, and clearly will lead to characters walking not only on bent knees but in a bent forward stance.

There could be a couple of ways to fix this if you wanted to keep the 'dog leg'. Either increase the muscular force the leg can muster (but this still does not change the energy required to hold the leg up, it just means the muscle will be slower to fatigue). Or you shorten the length of the femur. Shortening the distance of the load arm (shown above) makes the stance more energy efficient. This is because the load (the weight of the torso) is now much closer to the pivot (the knee joint), it means that less force is require to lift the load. Much like when using a wheel barrow, this is an example of a second class lever.

Shortening the thigh doesn't solve the problem but it certainly would help.

'A' represents a possible digitigrade stance with a vertical femur. 'B' represents a possible unguligrade stance where the femur is in a stoop. I was not trying to compare digitigrade and unguligrade here, only a vertical femur and one in a stoop.

Taking the stance as a whole it's easier to see that 'B', stood in a stoop with the torso fully upright, would result in the characters centre of gravity being behind it's foot, it's still below the torso but the torso is now more inclined to want to fall backwards because of the stoop, the quadriceps are taking the strain to hold this stance upright.

'A' is digitigrade and the femur is vertical but the knee is still slightly in flexion. If the quadriceps contract too much it will cause the trunk to fall forward. From a balance perspective the centre of gravity is better maintained under the feet of 'A' since the leg is much more vertical but it will of course require a greater level of tone to hold this stance than that of a human plantigrade biped. 

Combining the ideas above:

• shorter thigh
• thigh more vertical than stooped
• larger musculature to lower the fatigue 
• maintains a stance directly under the torso

Is this a more likely anatomically correct look for an antho? One of many configurations for sure!

Standing upright - Part III

In Part I I looked at changes in pelvic configuration from early hominids. It’s useful to note these changes as it helps explain why we are good at being bipedal and conversely, what wouldn't work or work very well. I’ve laid out what I’ve found here in terms of adaptations to the pelvis from quadruped to biped, these can act as our ‘ground rules’ for consideration when designing anthro characters or mechanical walkers.

Points to consider:

• Centre of gravity – bipeds must make sure their centre of gravity doesn't shift drastically from side to side with each step, this is destablising and inefficient.
• A tall pelvis has the effect of lengthening the torso, meaning that the centre of gravity moves higher, further away from the hips. This makes the trunk harder to stabilise.
• The ‘S’ curve of the lumbar vertebra lowers the centre of gravity towards the hips, helping stabilise the torso.
• This lumbar curve also gives the vertebral column the flex needed to withstand the pressure of the torso acting through it, the lower lumbar have widened giving a larger surface area for weight transmission.
• A wider sacrum has evolved to accommodate the wider lower lumbar vertebra. The sacroiliac joint (connecting the sacrum and the pelvis) also has a large surface area for weight transmission from the torso through both sides of the pelvis down to the femoral heads.
• The widened sacrum increases the width of the 'true pelvis', (the space through the centre of the pelvis), facilitating the ability to birth offspring with much larger craniums.
• However, a wider pelvis is a problem. During the support phase of locomotion one leg is off the ground. The weight of the torso is now acting on the femoral head of the standing leg. This is an example of a first class lever (levers that balance weight like a child's see-saw). The femoral head is acting as the pivot and the distance from the pivot to the body weight is called the 'load arm'. The ‘force arm’ on the other side of the pivot is our gluteus medius (an abductor muscle). It contracts to counterbalance the load arm. The wider we make our pelvis the longer we make the load arm, putting more pressure on the femoral head. We need a larger force or longer force arm to increase the mechanical advantage of this lever, otherwise we risk damaging the femoral head or having the hips slump with each step, just like the chimpanzee. In the Lucy skeleton, Australopithecus afarensis, it reveals her long load arm was countered by an increased length in the neck of the femur and a flaring of the iliac crest of the pelvis to place the abductors further from the pivot.
• The bicondylar angle is unique in humans. The femurs converge at the knees, bringing the legs close to the midline. This means the feet pass close to the midline and the centre of gravity is maintained directly underneath the torso. This is energy efficient as it doesn’t create a side to side motion of the hips when we walk.