Bin the babies! How to teach axes properly.

Here’s a table of principal axis key terms to help teachers of other boards translate my terminology:

Since the introduction of mechanics as a compulsory theme of study in addition to movement analysis in GCSE and A-level PE, many departments and teachers have used jelly babies to teach axes as well as planes. The thinking goes that jelly babies can be skewered with cocktail sticks which, much like a football player, can be pivoted around the cocktail stick axis. On the face of it, this seems like a neat idea. It’s fun, it’s memorable and it involves jelly. What’s not to like? However, jelly babies will always fail to generate the core intuition of axes because they have no joints and no moving parts. So they shouldn’t stand in for a human being as examples of rotational movement, except for a very, very fundamental and generalised introduction (see below).

My blog title is, at best, a little unfair to anyone who has taught axes with jelly babies. It is a bit “clickbaity”. I agree. I do not aim to offend anyone but, rather, to make a point about how high-quality learning is actually stimulated. I encourage every teacher to make your teaching fun, to bring in some crazy activities from time to time but to do so when those activities actually represent the concepts being taught.

 What is an axis in PE? 

In PE, the three principal axes (transverse, longitudinal and sagittal) are generalisations that summarise lots of smaller rotations at joints. Let’s start at the beginning: an axis is an imaginary line around which rotational movement occurs. Despite what we tend to teach in PE lessons, in the human body the axes that actually do the work pass through joints. In fact, we can also state that axes pass through the fulcrum/pivot points of levers (use this idea to interleave learning with your levers lessons).

This statement might raise a few eyebrows. We usually teach the three principal axes as lines passing through the middle of the body, around the navel, and that’s the right model for exam answers, so students need to know it. But these axes are representative: they summarise movement rather than being the movement itself. They are generalisations that stand for lots of smaller rotations at joints, none of which can be represented using jelly babies.

Let’s look at some examples.

Which joints rotate around the transverse axis?

The transverse axis summarises flexion and extension at joints such as the hip, knee, shoulder and elbow, plus plantar flexion and dorsiflexion at the ankle. Running, sprinting and somersaults are classic examples. We'll use a sprinter for this example:

I want you to consider which joint(s) this runner is rotating around as they start their sprint.

And we could go on. But, please, realise that these rotations (all of which are movement in a part circle around a joint) are all rotations that can be summarised and generalised as rotation around the transverse axis. HOWEVER, not one of these movement patterns can be completed by a jelly baby. 

Now we have this clear, take a look at the image below. It is this intuition that we want the learners to develop. Axes are multiple and always pass through joints. In this image, you can see the sprinter's right leg driving. This involves plantar flexion of the right ankle and extension of the right knee. As we view the image, the ankle rotates clockwise around its transverse axis to produce plantar flexion, and the knee rotates anticlockwise around its transverse axis to produce extension. Students need to realise this. Simply saying sprinting is rotation around the (generalised) transverse axis is not intuitive. But if students understand that sprinting involves multiple rotations around multiple transverse axes at multiple joints, they will fully understand the need to generalise these actions. This is what I encourage you to consider: Teaching the concept fully and then generalising rather than teaching the generalised axes (let's say with jelly babies) and not giving the students the chance to intuitively understand the role of joints in rotation. 

This video 👇, as you'll see, is a very quick demo of me performing the process above with my shoulder. I have presented this countless times at the front of classrooms and it is always a memorable moment, if you'll pardon the pun. 

Which joints rotate around the longitudinal axis?

The longitudinal axis summarises rotation at joints such as the spine, hips and shoulders. A skier turning around a gate, a hammer throw and a full twist in trampolining are classic examples. Let’s now take the longitudinal axis and consider a skier rotating around a gate.

I want you to consider which joint(s) this skier is rotating around as they turn the gate.

All of these movement patterns are rotations around longitudinal axes and we use the longitudinal axis to summarise or generalise these movements as a whole. A jelly baby can perform not one of these movements. Hence, bin the babies!

Which joints rotate around the sagittal axis?

The sagittal axis summarises abduction and adduction at joints such as the shoulders and hips. A cartwheel, a goalkeeper’s diving save and a star jump are classic examples. We will use the example of a cartwheel, but you could use a diving goalkeeper’s save or a range of dance moves:

I want you to consider which joint(s) this performer is rotating around as they cartwheel.

In other words, the “rotation around the sagittal axis” is a summary of the following:

• Rotation around the sagittal axis of the left shoulder
• Rotation around the sagittal axis of the right shoulder
• Rotation around the sagittal axis of the left hip
• Rotation around the sagittal axis of the right hip

A jelly baby can never, ever represent this idea and, therefore, is not an appropriate or intuitive teaching tool. 🙁

So should you bin the jelly babies?

By now, you might be a little annoyed with what I’ve written. You probably love that jelly babies lesson. I get it and, let’s be honest, you are doing no harm if the jelly babies come out and play a small part in a lesson on axes. What I am asking for is the teaching of the fundamental principle of axes alongside this or, better, as the main experience when learning axes. Start with real joints moving in real performances, then show students why we generalise.

Want to find out more?

If you’d like to keep building this thread through your mechanics teaching, take a look at the following:

• Our blogs on Teaching Levers in PE (Part 1) and Teaching Levers in PE (Part 2)

• Our PE Teacher Academy platform includes subject knowledge and curriculum courses on teaching planes and axes

• Our free resources page has even more to use in your classroom

Thank you for reading and have a good day.